Save This Page
Home » openjdk-7 » java » io » [javadoc | source]
    1   /*
    2    * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.io;
   27   
   28   import java.net.URI;
   29   import java.net.URL;
   30   import java.net.MalformedURLException;
   31   import java.net.URISyntaxException;
   32   import java.util.List;
   33   import java.util.ArrayList;
   34   import java.security.AccessController;
   35   import java.security.SecureRandom;
   36   import java.nio.file.Path;
   37   import java.nio.file.FileSystems;
   38   import sun.security.action.GetPropertyAction;
   39   
   40   /**
   41    * An abstract representation of file and directory pathnames.
   42    *
   43    * <p> User interfaces and operating systems use system-dependent <em>pathname
   44    * strings</em> to name files and directories.  This class presents an
   45    * abstract, system-independent view of hierarchical pathnames.  An
   46    * <em>abstract pathname</em> has two components:
   47    *
   48    * <ol>
   49    * <li> An optional system-dependent <em>prefix</em> string,
   50    *      such as a disk-drive specifier, <code>"/"</code>&nbsp;for the UNIX root
   51    *      directory, or <code>"\\\\"</code>&nbsp;for a Microsoft Windows UNC pathname, and
   52    * <li> A sequence of zero or more string <em>names</em>.
   53    * </ol>
   54    *
   55    * The first name in an abstract pathname may be a directory name or, in the
   56    * case of Microsoft Windows UNC pathnames, a hostname.  Each subsequent name
   57    * in an abstract pathname denotes a directory; the last name may denote
   58    * either a directory or a file.  The <em>empty</em> abstract pathname has no
   59    * prefix and an empty name sequence.
   60    *
   61    * <p> The conversion of a pathname string to or from an abstract pathname is
   62    * inherently system-dependent.  When an abstract pathname is converted into a
   63    * pathname string, each name is separated from the next by a single copy of
   64    * the default <em>separator character</em>.  The default name-separator
   65    * character is defined by the system property <code>file.separator</code>, and
   66    * is made available in the public static fields <code>{@link
   67    * #separator}</code> and <code>{@link #separatorChar}</code> of this class.
   68    * When a pathname string is converted into an abstract pathname, the names
   69    * within it may be separated by the default name-separator character or by any
   70    * other name-separator character that is supported by the underlying system.
   71    *
   72    * <p> A pathname, whether abstract or in string form, may be either
   73    * <em>absolute</em> or <em>relative</em>.  An absolute pathname is complete in
   74    * that no other information is required in order to locate the file that it
   75    * denotes.  A relative pathname, in contrast, must be interpreted in terms of
   76    * information taken from some other pathname.  By default the classes in the
   77    * <code>java.io</code> package always resolve relative pathnames against the
   78    * current user directory.  This directory is named by the system property
   79    * <code>user.dir</code>, and is typically the directory in which the Java
   80    * virtual machine was invoked.
   81    *
   82    * <p> The <em>parent</em> of an abstract pathname may be obtained by invoking
   83    * the {@link #getParent} method of this class and consists of the pathname's
   84    * prefix and each name in the pathname's name sequence except for the last.
   85    * Each directory's absolute pathname is an ancestor of any <tt>File</tt>
   86    * object with an absolute abstract pathname which begins with the directory's
   87    * absolute pathname.  For example, the directory denoted by the abstract
   88    * pathname <tt>"/usr"</tt> is an ancestor of the directory denoted by the
   89    * pathname <tt>"/usr/local/bin"</tt>.
   90    *
   91    * <p> The prefix concept is used to handle root directories on UNIX platforms,
   92    * and drive specifiers, root directories and UNC pathnames on Microsoft Windows platforms,
   93    * as follows:
   94    *
   95    * <ul>
   96    *
   97    * <li> For UNIX platforms, the prefix of an absolute pathname is always
   98    * <code>"/"</code>.  Relative pathnames have no prefix.  The abstract pathname
   99    * denoting the root directory has the prefix <code>"/"</code> and an empty
  100    * name sequence.
  101    *
  102    * <li> For Microsoft Windows platforms, the prefix of a pathname that contains a drive
  103    * specifier consists of the drive letter followed by <code>":"</code> and
  104    * possibly followed by <code>"\\"</code> if the pathname is absolute.  The
  105    * prefix of a UNC pathname is <code>"\\\\"</code>; the hostname and the share
  106    * name are the first two names in the name sequence.  A relative pathname that
  107    * does not specify a drive has no prefix.
  108    *
  109    * </ul>
  110    *
  111    * <p> Instances of this class may or may not denote an actual file-system
  112    * object such as a file or a directory.  If it does denote such an object
  113    * then that object resides in a <i>partition</i>.  A partition is an
  114    * operating system-specific portion of storage for a file system.  A single
  115    * storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may
  116    * contain multiple partitions.  The object, if any, will reside on the
  117    * partition <a name="partName">named</a> by some ancestor of the absolute
  118    * form of this pathname.
  119    *
  120    * <p> A file system may implement restrictions to certain operations on the
  121    * actual file-system object, such as reading, writing, and executing.  These
  122    * restrictions are collectively known as <i>access permissions</i>.  The file
  123    * system may have multiple sets of access permissions on a single object.
  124    * For example, one set may apply to the object's <i>owner</i>, and another
  125    * may apply to all other users.  The access permissions on an object may
  126    * cause some methods in this class to fail.
  127    *
  128    * <p> Instances of the <code>File</code> class are immutable; that is, once
  129    * created, the abstract pathname represented by a <code>File</code> object
  130    * will never change.
  131    *
  132    * <h4>Interoperability with {@code java.nio.file} package</h4>
  133    *
  134    * <p> The <a href="../../java/nio/file/package-summary.html">{@code java.nio.file}</a>
  135    * package defines interfaces and classes for the Java virtual machine to access
  136    * files, file attributes, and file systems. This API may be used to overcome
  137    * many of the limitations of the {@code java.io.File} class.
  138    * The {@link #toPath toPath} method may be used to obtain a {@link
  139    * Path} that uses the abstract path represented by a {@code File} object to
  140    * locate a file. The resulting {@code Path} may be used with the {@link
  141    * java.nio.file.Files} class to provide more efficient and extensive access to
  142    * additional file operations, file attributes, and I/O exceptions to help
  143    * diagnose errors when an operation on a file fails.
  144    *
  145    * @author  unascribed
  146    * @since   JDK1.0
  147    */
  148   
  149   public class File
  150       implements Serializable, Comparable<File>
  151   {
  152   
  153       /**
  154        * The FileSystem object representing the platform's local file system.
  155        */
  156       static private FileSystem fs = FileSystem.getFileSystem();
  157   
  158       /**
  159        * This abstract pathname's normalized pathname string.  A normalized
  160        * pathname string uses the default name-separator character and does not
  161        * contain any duplicate or redundant separators.
  162        *
  163        * @serial
  164        */
  165       private String path;
  166   
  167       /**
  168        * The length of this abstract pathname's prefix, or zero if it has no
  169        * prefix.
  170        */
  171       private transient int prefixLength;
  172   
  173       /**
  174        * Returns the length of this abstract pathname's prefix.
  175        * For use by FileSystem classes.
  176        */
  177       int getPrefixLength() {
  178           return prefixLength;
  179       }
  180   
  181       /**
  182        * The system-dependent default name-separator character.  This field is
  183        * initialized to contain the first character of the value of the system
  184        * property <code>file.separator</code>.  On UNIX systems the value of this
  185        * field is <code>'/'</code>; on Microsoft Windows systems it is <code>'\\'</code>.
  186        *
  187        * @see     java.lang.System#getProperty(java.lang.String)
  188        */
  189       public static final char separatorChar = fs.getSeparator();
  190   
  191       /**
  192        * The system-dependent default name-separator character, represented as a
  193        * string for convenience.  This string contains a single character, namely
  194        * <code>{@link #separatorChar}</code>.
  195        */
  196       public static final String separator = "" + separatorChar;
  197   
  198       /**
  199        * The system-dependent path-separator character.  This field is
  200        * initialized to contain the first character of the value of the system
  201        * property <code>path.separator</code>.  This character is used to
  202        * separate filenames in a sequence of files given as a <em>path list</em>.
  203        * On UNIX systems, this character is <code>':'</code>; on Microsoft Windows systems it
  204        * is <code>';'</code>.
  205        *
  206        * @see     java.lang.System#getProperty(java.lang.String)
  207        */
  208       public static final char pathSeparatorChar = fs.getPathSeparator();
  209   
  210       /**
  211        * The system-dependent path-separator character, represented as a string
  212        * for convenience.  This string contains a single character, namely
  213        * <code>{@link #pathSeparatorChar}</code>.
  214        */
  215       public static final String pathSeparator = "" + pathSeparatorChar;
  216   
  217   
  218       /* -- Constructors -- */
  219   
  220       /**
  221        * Internal constructor for already-normalized pathname strings.
  222        */
  223       private File(String pathname, int prefixLength) {
  224           this.path = pathname;
  225           this.prefixLength = prefixLength;
  226       }
  227   
  228       /**
  229        * Internal constructor for already-normalized pathname strings.
  230        * The parameter order is used to disambiguate this method from the
  231        * public(File, String) constructor.
  232        */
  233       private File(String child, File parent) {
  234           assert parent.path != null;
  235           assert (!parent.path.equals(""));
  236           this.path = fs.resolve(parent.path, child);
  237           this.prefixLength = parent.prefixLength;
  238       }
  239   
  240       /**
  241        * Creates a new <code>File</code> instance by converting the given
  242        * pathname string into an abstract pathname.  If the given string is
  243        * the empty string, then the result is the empty abstract pathname.
  244        *
  245        * @param   pathname  A pathname string
  246        * @throws  NullPointerException
  247        *          If the <code>pathname</code> argument is <code>null</code>
  248        */
  249       public File(String pathname) {
  250           if (pathname == null) {
  251               throw new NullPointerException();
  252           }
  253           this.path = fs.normalize(pathname);
  254           this.prefixLength = fs.prefixLength(this.path);
  255       }
  256   
  257       /* Note: The two-argument File constructors do not interpret an empty
  258          parent abstract pathname as the current user directory.  An empty parent
  259          instead causes the child to be resolved against the system-dependent
  260          directory defined by the FileSystem.getDefaultParent method.  On Unix
  261          this default is "/", while on Microsoft Windows it is "\\".  This is required for
  262          compatibility with the original behavior of this class. */
  263   
  264       /**
  265        * Creates a new <code>File</code> instance from a parent pathname string
  266        * and a child pathname string.
  267        *
  268        * <p> If <code>parent</code> is <code>null</code> then the new
  269        * <code>File</code> instance is created as if by invoking the
  270        * single-argument <code>File</code> constructor on the given
  271        * <code>child</code> pathname string.
  272        *
  273        * <p> Otherwise the <code>parent</code> pathname string is taken to denote
  274        * a directory, and the <code>child</code> pathname string is taken to
  275        * denote either a directory or a file.  If the <code>child</code> pathname
  276        * string is absolute then it is converted into a relative pathname in a
  277        * system-dependent way.  If <code>parent</code> is the empty string then
  278        * the new <code>File</code> instance is created by converting
  279        * <code>child</code> into an abstract pathname and resolving the result
  280        * against a system-dependent default directory.  Otherwise each pathname
  281        * string is converted into an abstract pathname and the child abstract
  282        * pathname is resolved against the parent.
  283        *
  284        * @param   parent  The parent pathname string
  285        * @param   child   The child pathname string
  286        * @throws  NullPointerException
  287        *          If <code>child</code> is <code>null</code>
  288        */
  289       public File(String parent, String child) {
  290           if (child == null) {
  291               throw new NullPointerException();
  292           }
  293           if (parent != null) {
  294               if (parent.equals("")) {
  295                   this.path = fs.resolve(fs.getDefaultParent(),
  296                                          fs.normalize(child));
  297               } else {
  298                   this.path = fs.resolve(fs.normalize(parent),
  299                                          fs.normalize(child));
  300               }
  301           } else {
  302               this.path = fs.normalize(child);
  303           }
  304           this.prefixLength = fs.prefixLength(this.path);
  305       }
  306   
  307       /**
  308        * Creates a new <code>File</code> instance from a parent abstract
  309        * pathname and a child pathname string.
  310        *
  311        * <p> If <code>parent</code> is <code>null</code> then the new
  312        * <code>File</code> instance is created as if by invoking the
  313        * single-argument <code>File</code> constructor on the given
  314        * <code>child</code> pathname string.
  315        *
  316        * <p> Otherwise the <code>parent</code> abstract pathname is taken to
  317        * denote a directory, and the <code>child</code> pathname string is taken
  318        * to denote either a directory or a file.  If the <code>child</code>
  319        * pathname string is absolute then it is converted into a relative
  320        * pathname in a system-dependent way.  If <code>parent</code> is the empty
  321        * abstract pathname then the new <code>File</code> instance is created by
  322        * converting <code>child</code> into an abstract pathname and resolving
  323        * the result against a system-dependent default directory.  Otherwise each
  324        * pathname string is converted into an abstract pathname and the child
  325        * abstract pathname is resolved against the parent.
  326        *
  327        * @param   parent  The parent abstract pathname
  328        * @param   child   The child pathname string
  329        * @throws  NullPointerException
  330        *          If <code>child</code> is <code>null</code>
  331        */
  332       public File(File parent, String child) {
  333           if (child == null) {
  334               throw new NullPointerException();
  335           }
  336           if (parent != null) {
  337               if (parent.path.equals("")) {
  338                   this.path = fs.resolve(fs.getDefaultParent(),
  339                                          fs.normalize(child));
  340               } else {
  341                   this.path = fs.resolve(parent.path,
  342                                          fs.normalize(child));
  343               }
  344           } else {
  345               this.path = fs.normalize(child);
  346           }
  347           this.prefixLength = fs.prefixLength(this.path);
  348       }
  349   
  350       /**
  351        * Creates a new <tt>File</tt> instance by converting the given
  352        * <tt>file:</tt> URI into an abstract pathname.
  353        *
  354        * <p> The exact form of a <tt>file:</tt> URI is system-dependent, hence
  355        * the transformation performed by this constructor is also
  356        * system-dependent.
  357        *
  358        * <p> For a given abstract pathname <i>f</i> it is guaranteed that
  359        *
  360        * <blockquote><tt>
  361        * new File(</tt><i>&nbsp;f</i><tt>.{@link #toURI() toURI}()).equals(</tt><i>&nbsp;f</i><tt>.{@link #getAbsoluteFile() getAbsoluteFile}())
  362        * </tt></blockquote>
  363        *
  364        * so long as the original abstract pathname, the URI, and the new abstract
  365        * pathname are all created in (possibly different invocations of) the same
  366        * Java virtual machine.  This relationship typically does not hold,
  367        * however, when a <tt>file:</tt> URI that is created in a virtual machine
  368        * on one operating system is converted into an abstract pathname in a
  369        * virtual machine on a different operating system.
  370        *
  371        * @param  uri
  372        *         An absolute, hierarchical URI with a scheme equal to
  373        *         <tt>"file"</tt>, a non-empty path component, and undefined
  374        *         authority, query, and fragment components
  375        *
  376        * @throws  NullPointerException
  377        *          If <tt>uri</tt> is <tt>null</tt>
  378        *
  379        * @throws  IllegalArgumentException
  380        *          If the preconditions on the parameter do not hold
  381        *
  382        * @see #toURI()
  383        * @see java.net.URI
  384        * @since 1.4
  385        */
  386       public File(URI uri) {
  387   
  388           // Check our many preconditions
  389           if (!uri.isAbsolute())
  390               throw new IllegalArgumentException("URI is not absolute");
  391           if (uri.isOpaque())
  392               throw new IllegalArgumentException("URI is not hierarchical");
  393           String scheme = uri.getScheme();
  394           if ((scheme == null) || !scheme.equalsIgnoreCase("file"))
  395               throw new IllegalArgumentException("URI scheme is not \"file\"");
  396           if (uri.getAuthority() != null)
  397               throw new IllegalArgumentException("URI has an authority component");
  398           if (uri.getFragment() != null)
  399               throw new IllegalArgumentException("URI has a fragment component");
  400           if (uri.getQuery() != null)
  401               throw new IllegalArgumentException("URI has a query component");
  402           String p = uri.getPath();
  403           if (p.equals(""))
  404               throw new IllegalArgumentException("URI path component is empty");
  405   
  406           // Okay, now initialize
  407           p = fs.fromURIPath(p);
  408           if (File.separatorChar != '/')
  409               p = p.replace('/', File.separatorChar);
  410           this.path = fs.normalize(p);
  411           this.prefixLength = fs.prefixLength(this.path);
  412       }
  413   
  414   
  415       /* -- Path-component accessors -- */
  416   
  417       /**
  418        * Returns the name of the file or directory denoted by this abstract
  419        * pathname.  This is just the last name in the pathname's name
  420        * sequence.  If the pathname's name sequence is empty, then the empty
  421        * string is returned.
  422        *
  423        * @return  The name of the file or directory denoted by this abstract
  424        *          pathname, or the empty string if this pathname's name sequence
  425        *          is empty
  426        */
  427       public String getName() {
  428           int index = path.lastIndexOf(separatorChar);
  429           if (index < prefixLength) return path.substring(prefixLength);
  430           return path.substring(index + 1);
  431       }
  432   
  433       /**
  434        * Returns the pathname string of this abstract pathname's parent, or
  435        * <code>null</code> if this pathname does not name a parent directory.
  436        *
  437        * <p> The <em>parent</em> of an abstract pathname consists of the
  438        * pathname's prefix, if any, and each name in the pathname's name
  439        * sequence except for the last.  If the name sequence is empty then
  440        * the pathname does not name a parent directory.
  441        *
  442        * @return  The pathname string of the parent directory named by this
  443        *          abstract pathname, or <code>null</code> if this pathname
  444        *          does not name a parent
  445        */
  446       public String getParent() {
  447           int index = path.lastIndexOf(separatorChar);
  448           if (index < prefixLength) {
  449               if ((prefixLength > 0) && (path.length() > prefixLength))
  450                   return path.substring(0, prefixLength);
  451               return null;
  452           }
  453           return path.substring(0, index);
  454       }
  455   
  456       /**
  457        * Returns the abstract pathname of this abstract pathname's parent,
  458        * or <code>null</code> if this pathname does not name a parent
  459        * directory.
  460        *
  461        * <p> The <em>parent</em> of an abstract pathname consists of the
  462        * pathname's prefix, if any, and each name in the pathname's name
  463        * sequence except for the last.  If the name sequence is empty then
  464        * the pathname does not name a parent directory.
  465        *
  466        * @return  The abstract pathname of the parent directory named by this
  467        *          abstract pathname, or <code>null</code> if this pathname
  468        *          does not name a parent
  469        *
  470        * @since 1.2
  471        */
  472       public File getParentFile() {
  473           String p = this.getParent();
  474           if (p == null) return null;
  475           return new File(p, this.prefixLength);
  476       }
  477   
  478       /**
  479        * Converts this abstract pathname into a pathname string.  The resulting
  480        * string uses the {@link #separator default name-separator character} to
  481        * separate the names in the name sequence.
  482        *
  483        * @return  The string form of this abstract pathname
  484        */
  485       public String getPath() {
  486           return path;
  487       }
  488   
  489   
  490       /* -- Path operations -- */
  491   
  492       /**
  493        * Tests whether this abstract pathname is absolute.  The definition of
  494        * absolute pathname is system dependent.  On UNIX systems, a pathname is
  495        * absolute if its prefix is <code>"/"</code>.  On Microsoft Windows systems, a
  496        * pathname is absolute if its prefix is a drive specifier followed by
  497        * <code>"\\"</code>, or if its prefix is <code>"\\\\"</code>.
  498        *
  499        * @return  <code>true</code> if this abstract pathname is absolute,
  500        *          <code>false</code> otherwise
  501        */
  502       public boolean isAbsolute() {
  503           return fs.isAbsolute(this);
  504       }
  505   
  506       /**
  507        * Returns the absolute pathname string of this abstract pathname.
  508        *
  509        * <p> If this abstract pathname is already absolute, then the pathname
  510        * string is simply returned as if by the <code>{@link #getPath}</code>
  511        * method.  If this abstract pathname is the empty abstract pathname then
  512        * the pathname string of the current user directory, which is named by the
  513        * system property <code>user.dir</code>, is returned.  Otherwise this
  514        * pathname is resolved in a system-dependent way.  On UNIX systems, a
  515        * relative pathname is made absolute by resolving it against the current
  516        * user directory.  On Microsoft Windows systems, a relative pathname is made absolute
  517        * by resolving it against the current directory of the drive named by the
  518        * pathname, if any; if not, it is resolved against the current user
  519        * directory.
  520        *
  521        * @return  The absolute pathname string denoting the same file or
  522        *          directory as this abstract pathname
  523        *
  524        * @throws  SecurityException
  525        *          If a required system property value cannot be accessed.
  526        *
  527        * @see     java.io.File#isAbsolute()
  528        */
  529       public String getAbsolutePath() {
  530           return fs.resolve(this);
  531       }
  532   
  533       /**
  534        * Returns the absolute form of this abstract pathname.  Equivalent to
  535        * <code>new&nbsp;File(this.{@link #getAbsolutePath})</code>.
  536        *
  537        * @return  The absolute abstract pathname denoting the same file or
  538        *          directory as this abstract pathname
  539        *
  540        * @throws  SecurityException
  541        *          If a required system property value cannot be accessed.
  542        *
  543        * @since 1.2
  544        */
  545       public File getAbsoluteFile() {
  546           String absPath = getAbsolutePath();
  547           return new File(absPath, fs.prefixLength(absPath));
  548       }
  549   
  550       /**
  551        * Returns the canonical pathname string of this abstract pathname.
  552        *
  553        * <p> A canonical pathname is both absolute and unique.  The precise
  554        * definition of canonical form is system-dependent.  This method first
  555        * converts this pathname to absolute form if necessary, as if by invoking the
  556        * {@link #getAbsolutePath} method, and then maps it to its unique form in a
  557        * system-dependent way.  This typically involves removing redundant names
  558        * such as <tt>"."</tt> and <tt>".."</tt> from the pathname, resolving
  559        * symbolic links (on UNIX platforms), and converting drive letters to a
  560        * standard case (on Microsoft Windows platforms).
  561        *
  562        * <p> Every pathname that denotes an existing file or directory has a
  563        * unique canonical form.  Every pathname that denotes a nonexistent file
  564        * or directory also has a unique canonical form.  The canonical form of
  565        * the pathname of a nonexistent file or directory may be different from
  566        * the canonical form of the same pathname after the file or directory is
  567        * created.  Similarly, the canonical form of the pathname of an existing
  568        * file or directory may be different from the canonical form of the same
  569        * pathname after the file or directory is deleted.
  570        *
  571        * @return  The canonical pathname string denoting the same file or
  572        *          directory as this abstract pathname
  573        *
  574        * @throws  IOException
  575        *          If an I/O error occurs, which is possible because the
  576        *          construction of the canonical pathname may require
  577        *          filesystem queries
  578        *
  579        * @throws  SecurityException
  580        *          If a required system property value cannot be accessed, or
  581        *          if a security manager exists and its <code>{@link
  582        *          java.lang.SecurityManager#checkRead}</code> method denies
  583        *          read access to the file
  584        *
  585        * @since   JDK1.1
  586        * @see     Path#toRealPath
  587        */
  588       public String getCanonicalPath() throws IOException {
  589           return fs.canonicalize(fs.resolve(this));
  590       }
  591   
  592       /**
  593        * Returns the canonical form of this abstract pathname.  Equivalent to
  594        * <code>new&nbsp;File(this.{@link #getCanonicalPath})</code>.
  595        *
  596        * @return  The canonical pathname string denoting the same file or
  597        *          directory as this abstract pathname
  598        *
  599        * @throws  IOException
  600        *          If an I/O error occurs, which is possible because the
  601        *          construction of the canonical pathname may require
  602        *          filesystem queries
  603        *
  604        * @throws  SecurityException
  605        *          If a required system property value cannot be accessed, or
  606        *          if a security manager exists and its <code>{@link
  607        *          java.lang.SecurityManager#checkRead}</code> method denies
  608        *          read access to the file
  609        *
  610        * @since 1.2
  611        * @see     Path#toRealPath
  612        */
  613       public File getCanonicalFile() throws IOException {
  614           String canonPath = getCanonicalPath();
  615           return new File(canonPath, fs.prefixLength(canonPath));
  616       }
  617   
  618       private static String slashify(String path, boolean isDirectory) {
  619           String p = path;
  620           if (File.separatorChar != '/')
  621               p = p.replace(File.separatorChar, '/');
  622           if (!p.startsWith("/"))
  623               p = "/" + p;
  624           if (!p.endsWith("/") && isDirectory)
  625               p = p + "/";
  626           return p;
  627       }
  628   
  629       /**
  630        * Converts this abstract pathname into a <code>file:</code> URL.  The
  631        * exact form of the URL is system-dependent.  If it can be determined that
  632        * the file denoted by this abstract pathname is a directory, then the
  633        * resulting URL will end with a slash.
  634        *
  635        * @return  A URL object representing the equivalent file URL
  636        *
  637        * @throws  MalformedURLException
  638        *          If the path cannot be parsed as a URL
  639        *
  640        * @see     #toURI()
  641        * @see     java.net.URI
  642        * @see     java.net.URI#toURL()
  643        * @see     java.net.URL
  644        * @since   1.2
  645        *
  646        * @deprecated This method does not automatically escape characters that
  647        * are illegal in URLs.  It is recommended that new code convert an
  648        * abstract pathname into a URL by first converting it into a URI, via the
  649        * {@link #toURI() toURI} method, and then converting the URI into a URL
  650        * via the {@link java.net.URI#toURL() URI.toURL} method.
  651        */
  652       @Deprecated
  653       public URL toURL() throws MalformedURLException {
  654           return new URL("file", "", slashify(getAbsolutePath(), isDirectory()));
  655       }
  656   
  657       /**
  658        * Constructs a <tt>file:</tt> URI that represents this abstract pathname.
  659        *
  660        * <p> The exact form of the URI is system-dependent.  If it can be
  661        * determined that the file denoted by this abstract pathname is a
  662        * directory, then the resulting URI will end with a slash.
  663        *
  664        * <p> For a given abstract pathname <i>f</i>, it is guaranteed that
  665        *
  666        * <blockquote><tt>
  667        * new {@link #File(java.net.URI) File}(</tt><i>&nbsp;f</i><tt>.toURI()).equals(</tt><i>&nbsp;f</i><tt>.{@link #getAbsoluteFile() getAbsoluteFile}())
  668        * </tt></blockquote>
  669        *
  670        * so long as the original abstract pathname, the URI, and the new abstract
  671        * pathname are all created in (possibly different invocations of) the same
  672        * Java virtual machine.  Due to the system-dependent nature of abstract
  673        * pathnames, however, this relationship typically does not hold when a
  674        * <tt>file:</tt> URI that is created in a virtual machine on one operating
  675        * system is converted into an abstract pathname in a virtual machine on a
  676        * different operating system.
  677        *
  678        * <p> Note that when this abstract pathname represents a UNC pathname then
  679        * all components of the UNC (including the server name component) are encoded
  680        * in the {@code URI} path. The authority component is undefined, meaning
  681        * that it is represented as {@code null}. The {@link Path} class defines the
  682        * {@link Path#toUri toUri} method to encode the server name in the authority
  683        * component of the resulting {@code URI}. The {@link #toPath toPath} method
  684        * may be used to obtain a {@code Path} representing this abstract pathname.
  685        *
  686        * @return  An absolute, hierarchical URI with a scheme equal to
  687        *          <tt>"file"</tt>, a path representing this abstract pathname,
  688        *          and undefined authority, query, and fragment components
  689        * @throws SecurityException If a required system property value cannot
  690        * be accessed.
  691        *
  692        * @see #File(java.net.URI)
  693        * @see java.net.URI
  694        * @see java.net.URI#toURL()
  695        * @since 1.4
  696        */
  697       public URI toURI() {
  698           try {
  699               File f = getAbsoluteFile();
  700               String sp = slashify(f.getPath(), f.isDirectory());
  701               if (sp.startsWith("//"))
  702                   sp = "//" + sp;
  703               return new URI("file", null, sp, null);
  704           } catch (URISyntaxException x) {
  705               throw new Error(x);         // Can't happen
  706           }
  707       }
  708   
  709   
  710       /* -- Attribute accessors -- */
  711   
  712       /**
  713        * Tests whether the application can read the file denoted by this
  714        * abstract pathname.
  715        *
  716        * @return  <code>true</code> if and only if the file specified by this
  717        *          abstract pathname exists <em>and</em> can be read by the
  718        *          application; <code>false</code> otherwise
  719        *
  720        * @throws  SecurityException
  721        *          If a security manager exists and its <code>{@link
  722        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  723        *          method denies read access to the file
  724        */
  725       public boolean canRead() {
  726           SecurityManager security = System.getSecurityManager();
  727           if (security != null) {
  728               security.checkRead(path);
  729           }
  730           return fs.checkAccess(this, FileSystem.ACCESS_READ);
  731       }
  732   
  733       /**
  734        * Tests whether the application can modify the file denoted by this
  735        * abstract pathname.
  736        *
  737        * @return  <code>true</code> if and only if the file system actually
  738        *          contains a file denoted by this abstract pathname <em>and</em>
  739        *          the application is allowed to write to the file;
  740        *          <code>false</code> otherwise.
  741        *
  742        * @throws  SecurityException
  743        *          If a security manager exists and its <code>{@link
  744        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
  745        *          method denies write access to the file
  746        */
  747       public boolean canWrite() {
  748           SecurityManager security = System.getSecurityManager();
  749           if (security != null) {
  750               security.checkWrite(path);
  751           }
  752           return fs.checkAccess(this, FileSystem.ACCESS_WRITE);
  753       }
  754   
  755       /**
  756        * Tests whether the file or directory denoted by this abstract pathname
  757        * exists.
  758        *
  759        * @return  <code>true</code> if and only if the file or directory denoted
  760        *          by this abstract pathname exists; <code>false</code> otherwise
  761        *
  762        * @throws  SecurityException
  763        *          If a security manager exists and its <code>{@link
  764        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  765        *          method denies read access to the file or directory
  766        */
  767       public boolean exists() {
  768           SecurityManager security = System.getSecurityManager();
  769           if (security != null) {
  770               security.checkRead(path);
  771           }
  772           return ((fs.getBooleanAttributes(this) & FileSystem.BA_EXISTS) != 0);
  773       }
  774   
  775       /**
  776        * Tests whether the file denoted by this abstract pathname is a
  777        * directory.
  778        *
  779        * <p> Where it is required to distinguish an I/O exception from the case
  780        * that the file is not a directory, or where several attributes of the
  781        * same file are required at the same time, then the {@link
  782        * java.nio.file.Files#readAttributes(Path,Class,LinkOption[])
  783        * Files.readAttributes} method may be used.
  784        *
  785        * @return <code>true</code> if and only if the file denoted by this
  786        *          abstract pathname exists <em>and</em> is a directory;
  787        *          <code>false</code> otherwise
  788        *
  789        * @throws  SecurityException
  790        *          If a security manager exists and its <code>{@link
  791        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  792        *          method denies read access to the file
  793        */
  794       public boolean isDirectory() {
  795           SecurityManager security = System.getSecurityManager();
  796           if (security != null) {
  797               security.checkRead(path);
  798           }
  799           return ((fs.getBooleanAttributes(this) & FileSystem.BA_DIRECTORY)
  800                   != 0);
  801       }
  802   
  803       /**
  804        * Tests whether the file denoted by this abstract pathname is a normal
  805        * file.  A file is <em>normal</em> if it is not a directory and, in
  806        * addition, satisfies other system-dependent criteria.  Any non-directory
  807        * file created by a Java application is guaranteed to be a normal file.
  808        *
  809        * <p> Where it is required to distinguish an I/O exception from the case
  810        * that the file is not a normal file, or where several attributes of the
  811        * same file are required at the same time, then the {@link
  812        * java.nio.file.Files#readAttributes(Path,Class,LinkOption[])
  813        * Files.readAttributes} method may be used.
  814        *
  815        * @return  <code>true</code> if and only if the file denoted by this
  816        *          abstract pathname exists <em>and</em> is a normal file;
  817        *          <code>false</code> otherwise
  818        *
  819        * @throws  SecurityException
  820        *          If a security manager exists and its <code>{@link
  821        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  822        *          method denies read access to the file
  823        */
  824       public boolean isFile() {
  825           SecurityManager security = System.getSecurityManager();
  826           if (security != null) {
  827               security.checkRead(path);
  828           }
  829           return ((fs.getBooleanAttributes(this) & FileSystem.BA_REGULAR) != 0);
  830       }
  831   
  832       /**
  833        * Tests whether the file named by this abstract pathname is a hidden
  834        * file.  The exact definition of <em>hidden</em> is system-dependent.  On
  835        * UNIX systems, a file is considered to be hidden if its name begins with
  836        * a period character (<code>'.'</code>).  On Microsoft Windows systems, a file is
  837        * considered to be hidden if it has been marked as such in the filesystem.
  838        *
  839        * @return  <code>true</code> if and only if the file denoted by this
  840        *          abstract pathname is hidden according to the conventions of the
  841        *          underlying platform
  842        *
  843        * @throws  SecurityException
  844        *          If a security manager exists and its <code>{@link
  845        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  846        *          method denies read access to the file
  847        *
  848        * @since 1.2
  849        */
  850       public boolean isHidden() {
  851           SecurityManager security = System.getSecurityManager();
  852           if (security != null) {
  853               security.checkRead(path);
  854           }
  855           return ((fs.getBooleanAttributes(this) & FileSystem.BA_HIDDEN) != 0);
  856       }
  857   
  858       /**
  859        * Returns the time that the file denoted by this abstract pathname was
  860        * last modified.
  861        *
  862        * <p> Where it is required to distinguish an I/O exception from the case
  863        * where {@code 0L} is returned, or where several attributes of the
  864        * same file are required at the same time, or where the time of last
  865        * access or the creation time are required, then the {@link
  866        * java.nio.file.Files#readAttributes(Path,Class,LinkOption[])
  867        * Files.readAttributes} method may be used.
  868        *
  869        * @return  A <code>long</code> value representing the time the file was
  870        *          last modified, measured in milliseconds since the epoch
  871        *          (00:00:00 GMT, January 1, 1970), or <code>0L</code> if the
  872        *          file does not exist or if an I/O error occurs
  873        *
  874        * @throws  SecurityException
  875        *          If a security manager exists and its <code>{@link
  876        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  877        *          method denies read access to the file
  878        */
  879       public long lastModified() {
  880           SecurityManager security = System.getSecurityManager();
  881           if (security != null) {
  882               security.checkRead(path);
  883           }
  884           return fs.getLastModifiedTime(this);
  885       }
  886   
  887       /**
  888        * Returns the length of the file denoted by this abstract pathname.
  889        * The return value is unspecified if this pathname denotes a directory.
  890        *
  891        * <p> Where it is required to distinguish an I/O exception from the case
  892        * that {@code 0L} is returned, or where several attributes of the same file
  893        * are required at the same time, then the {@link
  894        * java.nio.file.Files#readAttributes(Path,Class,LinkOption[])
  895        * Files.readAttributes} method may be used.
  896        *
  897        * @return  The length, in bytes, of the file denoted by this abstract
  898        *          pathname, or <code>0L</code> if the file does not exist.  Some
  899        *          operating systems may return <code>0L</code> for pathnames
  900        *          denoting system-dependent entities such as devices or pipes.
  901        *
  902        * @throws  SecurityException
  903        *          If a security manager exists and its <code>{@link
  904        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
  905        *          method denies read access to the file
  906        */
  907       public long length() {
  908           SecurityManager security = System.getSecurityManager();
  909           if (security != null) {
  910               security.checkRead(path);
  911           }
  912           return fs.getLength(this);
  913       }
  914   
  915   
  916       /* -- File operations -- */
  917   
  918       /**
  919        * Atomically creates a new, empty file named by this abstract pathname if
  920        * and only if a file with this name does not yet exist.  The check for the
  921        * existence of the file and the creation of the file if it does not exist
  922        * are a single operation that is atomic with respect to all other
  923        * filesystem activities that might affect the file.
  924        * <P>
  925        * Note: this method should <i>not</i> be used for file-locking, as
  926        * the resulting protocol cannot be made to work reliably. The
  927        * {@link java.nio.channels.FileLock FileLock}
  928        * facility should be used instead.
  929        *
  930        * @return  <code>true</code> if the named file does not exist and was
  931        *          successfully created; <code>false</code> if the named file
  932        *          already exists
  933        *
  934        * @throws  IOException
  935        *          If an I/O error occurred
  936        *
  937        * @throws  SecurityException
  938        *          If a security manager exists and its <code>{@link
  939        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
  940        *          method denies write access to the file
  941        *
  942        * @since 1.2
  943        */
  944       public boolean createNewFile() throws IOException {
  945           SecurityManager security = System.getSecurityManager();
  946           if (security != null) security.checkWrite(path);
  947           return fs.createFileExclusively(path);
  948       }
  949   
  950       /**
  951        * Deletes the file or directory denoted by this abstract pathname.  If
  952        * this pathname denotes a directory, then the directory must be empty in
  953        * order to be deleted.
  954        *
  955        * <p> Note that the {@link java.nio.file.Files} class defines the {@link
  956        * java.nio.file.Files#delete(Path) delete} method to throw an {@link IOException}
  957        * when a file cannot be deleted. This is useful for error reporting and to
  958        * diagnose why a file cannot be deleted.
  959        *
  960        * @return  <code>true</code> if and only if the file or directory is
  961        *          successfully deleted; <code>false</code> otherwise
  962        *
  963        * @throws  SecurityException
  964        *          If a security manager exists and its <code>{@link
  965        *          java.lang.SecurityManager#checkDelete}</code> method denies
  966        *          delete access to the file
  967        */
  968       public boolean delete() {
  969           SecurityManager security = System.getSecurityManager();
  970           if (security != null) {
  971               security.checkDelete(path);
  972           }
  973           return fs.delete(this);
  974       }
  975   
  976       /**
  977        * Requests that the file or directory denoted by this abstract
  978        * pathname be deleted when the virtual machine terminates.
  979        * Files (or directories) are deleted in the reverse order that
  980        * they are registered. Invoking this method to delete a file or
  981        * directory that is already registered for deletion has no effect.
  982        * Deletion will be attempted only for normal termination of the
  983        * virtual machine, as defined by the Java Language Specification.
  984        *
  985        * <p> Once deletion has been requested, it is not possible to cancel the
  986        * request.  This method should therefore be used with care.
  987        *
  988        * <P>
  989        * Note: this method should <i>not</i> be used for file-locking, as
  990        * the resulting protocol cannot be made to work reliably. The
  991        * {@link java.nio.channels.FileLock FileLock}
  992        * facility should be used instead.
  993        *
  994        * @throws  SecurityException
  995        *          If a security manager exists and its <code>{@link
  996        *          java.lang.SecurityManager#checkDelete}</code> method denies
  997        *          delete access to the file
  998        *
  999        * @see #delete
 1000        *
 1001        * @since 1.2
 1002        */
 1003       public void deleteOnExit() {
 1004           SecurityManager security = System.getSecurityManager();
 1005           if (security != null) {
 1006               security.checkDelete(path);
 1007           }
 1008           DeleteOnExitHook.add(path);
 1009       }
 1010   
 1011       /**
 1012        * Returns an array of strings naming the files and directories in the
 1013        * directory denoted by this abstract pathname.
 1014        *
 1015        * <p> If this abstract pathname does not denote a directory, then this
 1016        * method returns {@code null}.  Otherwise an array of strings is
 1017        * returned, one for each file or directory in the directory.  Names
 1018        * denoting the directory itself and the directory's parent directory are
 1019        * not included in the result.  Each string is a file name rather than a
 1020        * complete path.
 1021        *
 1022        * <p> There is no guarantee that the name strings in the resulting array
 1023        * will appear in any specific order; they are not, in particular,
 1024        * guaranteed to appear in alphabetical order.
 1025        *
 1026        * <p> Note that the {@link java.nio.file.Files} class defines the {@link
 1027        * java.nio.file.Files#newDirectoryStream(Path) newDirectoryStream} method to
 1028        * open a directory and iterate over the names of the files in the directory.
 1029        * This may use less resources when working with very large directories, and
 1030        * may be more responsive when working with remote directories.
 1031        *
 1032        * @return  An array of strings naming the files and directories in the
 1033        *          directory denoted by this abstract pathname.  The array will be
 1034        *          empty if the directory is empty.  Returns {@code null} if
 1035        *          this abstract pathname does not denote a directory, or if an
 1036        *          I/O error occurs.
 1037        *
 1038        * @throws  SecurityException
 1039        *          If a security manager exists and its {@link
 1040        *          SecurityManager#checkRead(String)} method denies read access to
 1041        *          the directory
 1042        */
 1043       public String[] list() {
 1044           SecurityManager security = System.getSecurityManager();
 1045           if (security != null) {
 1046               security.checkRead(path);
 1047           }
 1048           return fs.list(this);
 1049       }
 1050   
 1051       /**
 1052        * Returns an array of strings naming the files and directories in the
 1053        * directory denoted by this abstract pathname that satisfy the specified
 1054        * filter.  The behavior of this method is the same as that of the
 1055        * {@link #list()} method, except that the strings in the returned array
 1056        * must satisfy the filter.  If the given {@code filter} is {@code null}
 1057        * then all names are accepted.  Otherwise, a name satisfies the filter if
 1058        * and only if the value {@code true} results when the {@link
 1059        * FilenameFilter#accept FilenameFilter.accept(File,&nbsp;String)} method
 1060        * of the filter is invoked on this abstract pathname and the name of a
 1061        * file or directory in the directory that it denotes.
 1062        *
 1063        * @param  filter
 1064        *         A filename filter
 1065        *
 1066        * @return  An array of strings naming the files and directories in the
 1067        *          directory denoted by this abstract pathname that were accepted
 1068        *          by the given {@code filter}.  The array will be empty if the
 1069        *          directory is empty or if no names were accepted by the filter.
 1070        *          Returns {@code null} if this abstract pathname does not denote
 1071        *          a directory, or if an I/O error occurs.
 1072        *
 1073        * @throws  SecurityException
 1074        *          If a security manager exists and its {@link
 1075        *          SecurityManager#checkRead(String)} method denies read access to
 1076        *          the directory
 1077        *
 1078        * @see java.nio.file.Files#newDirectoryStream(Path,String)
 1079        */
 1080       public String[] list(FilenameFilter filter) {
 1081           String names[] = list();
 1082           if ((names == null) || (filter == null)) {
 1083               return names;
 1084           }
 1085           List<String> v = new ArrayList<>();
 1086           for (int i = 0 ; i < names.length ; i++) {
 1087               if (filter.accept(this, names[i])) {
 1088                   v.add(names[i]);
 1089               }
 1090           }
 1091           return v.toArray(new String[v.size()]);
 1092       }
 1093   
 1094       /**
 1095        * Returns an array of abstract pathnames denoting the files in the
 1096        * directory denoted by this abstract pathname.
 1097        *
 1098        * <p> If this abstract pathname does not denote a directory, then this
 1099        * method returns {@code null}.  Otherwise an array of {@code File} objects
 1100        * is returned, one for each file or directory in the directory.  Pathnames
 1101        * denoting the directory itself and the directory's parent directory are
 1102        * not included in the result.  Each resulting abstract pathname is
 1103        * constructed from this abstract pathname using the {@link #File(File,
 1104        * String) File(File,&nbsp;String)} constructor.  Therefore if this
 1105        * pathname is absolute then each resulting pathname is absolute; if this
 1106        * pathname is relative then each resulting pathname will be relative to
 1107        * the same directory.
 1108        *
 1109        * <p> There is no guarantee that the name strings in the resulting array
 1110        * will appear in any specific order; they are not, in particular,
 1111        * guaranteed to appear in alphabetical order.
 1112        *
 1113        * <p> Note that the {@link java.nio.file.Files} class defines the {@link
 1114        * java.nio.file.Files#newDirectoryStream(Path) newDirectoryStream} method
 1115        * to open a directory and iterate over the names of the files in the
 1116        * directory. This may use less resources when working with very large
 1117        * directories.
 1118        *
 1119        * @return  An array of abstract pathnames denoting the files and
 1120        *          directories in the directory denoted by this abstract pathname.
 1121        *          The array will be empty if the directory is empty.  Returns
 1122        *          {@code null} if this abstract pathname does not denote a
 1123        *          directory, or if an I/O error occurs.
 1124        *
 1125        * @throws  SecurityException
 1126        *          If a security manager exists and its {@link
 1127        *          SecurityManager#checkRead(String)} method denies read access to
 1128        *          the directory
 1129        *
 1130        * @since  1.2
 1131        */
 1132       public File[] listFiles() {
 1133           String[] ss = list();
 1134           if (ss == null) return null;
 1135           int n = ss.length;
 1136           File[] fs = new File[n];
 1137           for (int i = 0; i < n; i++) {
 1138               fs[i] = new File(ss[i], this);
 1139           }
 1140           return fs;
 1141       }
 1142   
 1143       /**
 1144        * Returns an array of abstract pathnames denoting the files and
 1145        * directories in the directory denoted by this abstract pathname that
 1146        * satisfy the specified filter.  The behavior of this method is the same
 1147        * as that of the {@link #listFiles()} method, except that the pathnames in
 1148        * the returned array must satisfy the filter.  If the given {@code filter}
 1149        * is {@code null} then all pathnames are accepted.  Otherwise, a pathname
 1150        * satisfies the filter if and only if the value {@code true} results when
 1151        * the {@link FilenameFilter#accept
 1152        * FilenameFilter.accept(File,&nbsp;String)} method of the filter is
 1153        * invoked on this abstract pathname and the name of a file or directory in
 1154        * the directory that it denotes.
 1155        *
 1156        * @param  filter
 1157        *         A filename filter
 1158        *
 1159        * @return  An array of abstract pathnames denoting the files and
 1160        *          directories in the directory denoted by this abstract pathname.
 1161        *          The array will be empty if the directory is empty.  Returns
 1162        *          {@code null} if this abstract pathname does not denote a
 1163        *          directory, or if an I/O error occurs.
 1164        *
 1165        * @throws  SecurityException
 1166        *          If a security manager exists and its {@link
 1167        *          SecurityManager#checkRead(String)} method denies read access to
 1168        *          the directory
 1169        *
 1170        * @since  1.2
 1171        * @see java.nio.file.Files#newDirectoryStream(Path,String)
 1172        */
 1173       public File[] listFiles(FilenameFilter filter) {
 1174           String ss[] = list();
 1175           if (ss == null) return null;
 1176           ArrayList<File> files = new ArrayList<>();
 1177           for (String s : ss)
 1178               if ((filter == null) || filter.accept(this, s))
 1179                   files.add(new File(s, this));
 1180           return files.toArray(new File[files.size()]);
 1181       }
 1182   
 1183       /**
 1184        * Returns an array of abstract pathnames denoting the files and
 1185        * directories in the directory denoted by this abstract pathname that
 1186        * satisfy the specified filter.  The behavior of this method is the same
 1187        * as that of the {@link #listFiles()} method, except that the pathnames in
 1188        * the returned array must satisfy the filter.  If the given {@code filter}
 1189        * is {@code null} then all pathnames are accepted.  Otherwise, a pathname
 1190        * satisfies the filter if and only if the value {@code true} results when
 1191        * the {@link FileFilter#accept FileFilter.accept(File)} method of the
 1192        * filter is invoked on the pathname.
 1193        *
 1194        * @param  filter
 1195        *         A file filter
 1196        *
 1197        * @return  An array of abstract pathnames denoting the files and
 1198        *          directories in the directory denoted by this abstract pathname.
 1199        *          The array will be empty if the directory is empty.  Returns
 1200        *          {@code null} if this abstract pathname does not denote a
 1201        *          directory, or if an I/O error occurs.
 1202        *
 1203        * @throws  SecurityException
 1204        *          If a security manager exists and its {@link
 1205        *          SecurityManager#checkRead(String)} method denies read access to
 1206        *          the directory
 1207        *
 1208        * @since  1.2
 1209        * @see java.nio.file.Files#newDirectoryStream(Path,java.nio.file.DirectoryStream.Filter)
 1210        */
 1211       public File[] listFiles(FileFilter filter) {
 1212           String ss[] = list();
 1213           if (ss == null) return null;
 1214           ArrayList<File> files = new ArrayList<>();
 1215           for (String s : ss) {
 1216               File f = new File(s, this);
 1217               if ((filter == null) || filter.accept(f))
 1218                   files.add(f);
 1219           }
 1220           return files.toArray(new File[files.size()]);
 1221       }
 1222   
 1223       /**
 1224        * Creates the directory named by this abstract pathname.
 1225        *
 1226        * @return  <code>true</code> if and only if the directory was
 1227        *          created; <code>false</code> otherwise
 1228        *
 1229        * @throws  SecurityException
 1230        *          If a security manager exists and its <code>{@link
 1231        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1232        *          method does not permit the named directory to be created
 1233        */
 1234       public boolean mkdir() {
 1235           SecurityManager security = System.getSecurityManager();
 1236           if (security != null) {
 1237               security.checkWrite(path);
 1238           }
 1239           return fs.createDirectory(this);
 1240       }
 1241   
 1242       /**
 1243        * Creates the directory named by this abstract pathname, including any
 1244        * necessary but nonexistent parent directories.  Note that if this
 1245        * operation fails it may have succeeded in creating some of the necessary
 1246        * parent directories.
 1247        *
 1248        * @return  <code>true</code> if and only if the directory was created,
 1249        *          along with all necessary parent directories; <code>false</code>
 1250        *          otherwise
 1251        *
 1252        * @throws  SecurityException
 1253        *          If a security manager exists and its <code>{@link
 1254        *          java.lang.SecurityManager#checkRead(java.lang.String)}</code>
 1255        *          method does not permit verification of the existence of the
 1256        *          named directory and all necessary parent directories; or if
 1257        *          the <code>{@link
 1258        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1259        *          method does not permit the named directory and all necessary
 1260        *          parent directories to be created
 1261        */
 1262       public boolean mkdirs() {
 1263           if (exists()) {
 1264               return false;
 1265           }
 1266           if (mkdir()) {
 1267               return true;
 1268           }
 1269           File canonFile = null;
 1270           try {
 1271               canonFile = getCanonicalFile();
 1272           } catch (IOException e) {
 1273               return false;
 1274           }
 1275   
 1276           File parent = canonFile.getParentFile();
 1277           return (parent != null && (parent.mkdirs() || parent.exists()) &&
 1278                   canonFile.mkdir());
 1279       }
 1280   
 1281       /**
 1282        * Renames the file denoted by this abstract pathname.
 1283        *
 1284        * <p> Many aspects of the behavior of this method are inherently
 1285        * platform-dependent: The rename operation might not be able to move a
 1286        * file from one filesystem to another, it might not be atomic, and it
 1287        * might not succeed if a file with the destination abstract pathname
 1288        * already exists.  The return value should always be checked to make sure
 1289        * that the rename operation was successful.
 1290        *
 1291        * <p> Note that the {@link java.nio.file.Files} class defines the {@link
 1292        * java.nio.file.Files#move move} method to move or rename a file in a
 1293        * platform independent manner.
 1294        *
 1295        * @param  dest  The new abstract pathname for the named file
 1296        *
 1297        * @return  <code>true</code> if and only if the renaming succeeded;
 1298        *          <code>false</code> otherwise
 1299        *
 1300        * @throws  SecurityException
 1301        *          If a security manager exists and its <code>{@link
 1302        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1303        *          method denies write access to either the old or new pathnames
 1304        *
 1305        * @throws  NullPointerException
 1306        *          If parameter <code>dest</code> is <code>null</code>
 1307        */
 1308       public boolean renameTo(File dest) {
 1309           SecurityManager security = System.getSecurityManager();
 1310           if (security != null) {
 1311               security.checkWrite(path);
 1312               security.checkWrite(dest.path);
 1313           }
 1314           return fs.rename(this, dest);
 1315       }
 1316   
 1317       /**
 1318        * Sets the last-modified time of the file or directory named by this
 1319        * abstract pathname.
 1320        *
 1321        * <p> All platforms support file-modification times to the nearest second,
 1322        * but some provide more precision.  The argument will be truncated to fit
 1323        * the supported precision.  If the operation succeeds and no intervening
 1324        * operations on the file take place, then the next invocation of the
 1325        * <code>{@link #lastModified}</code> method will return the (possibly
 1326        * truncated) <code>time</code> argument that was passed to this method.
 1327        *
 1328        * @param  time  The new last-modified time, measured in milliseconds since
 1329        *               the epoch (00:00:00 GMT, January 1, 1970)
 1330        *
 1331        * @return <code>true</code> if and only if the operation succeeded;
 1332        *          <code>false</code> otherwise
 1333        *
 1334        * @throws  IllegalArgumentException  If the argument is negative
 1335        *
 1336        * @throws  SecurityException
 1337        *          If a security manager exists and its <code>{@link
 1338        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1339        *          method denies write access to the named file
 1340        *
 1341        * @since 1.2
 1342        */
 1343       public boolean setLastModified(long time) {
 1344           if (time < 0) throw new IllegalArgumentException("Negative time");
 1345           SecurityManager security = System.getSecurityManager();
 1346           if (security != null) {
 1347               security.checkWrite(path);
 1348           }
 1349           return fs.setLastModifiedTime(this, time);
 1350       }
 1351   
 1352       /**
 1353        * Marks the file or directory named by this abstract pathname so that
 1354        * only read operations are allowed.  After invoking this method the file
 1355        * or directory is guaranteed not to change until it is either deleted or
 1356        * marked to allow write access.  Whether or not a read-only file or
 1357        * directory may be deleted depends upon the underlying system.
 1358        *
 1359        * @return <code>true</code> if and only if the operation succeeded;
 1360        *          <code>false</code> otherwise
 1361        *
 1362        * @throws  SecurityException
 1363        *          If a security manager exists and its <code>{@link
 1364        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1365        *          method denies write access to the named file
 1366        *
 1367        * @since 1.2
 1368        */
 1369       public boolean setReadOnly() {
 1370           SecurityManager security = System.getSecurityManager();
 1371           if (security != null) {
 1372               security.checkWrite(path);
 1373           }
 1374           return fs.setReadOnly(this);
 1375       }
 1376   
 1377       /**
 1378        * Sets the owner's or everybody's write permission for this abstract
 1379        * pathname.
 1380        *
 1381        * <p> The {@link java.nio.file.Files} class defines methods that operate on
 1382        * file attributes including file permissions. This may be used when finer
 1383        * manipulation of file permissions is required.
 1384        *
 1385        * @param   writable
 1386        *          If <code>true</code>, sets the access permission to allow write
 1387        *          operations; if <code>false</code> to disallow write operations
 1388        *
 1389        * @param   ownerOnly
 1390        *          If <code>true</code>, the write permission applies only to the
 1391        *          owner's write permission; otherwise, it applies to everybody.  If
 1392        *          the underlying file system can not distinguish the owner's write
 1393        *          permission from that of others, then the permission will apply to
 1394        *          everybody, regardless of this value.
 1395        *
 1396        * @return  <code>true</code> if and only if the operation succeeded. The
 1397        *          operation will fail if the user does not have permission to change
 1398        *          the access permissions of this abstract pathname.
 1399        *
 1400        * @throws  SecurityException
 1401        *          If a security manager exists and its <code>{@link
 1402        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1403        *          method denies write access to the named file
 1404        *
 1405        * @since 1.6
 1406        */
 1407       public boolean setWritable(boolean writable, boolean ownerOnly) {
 1408           SecurityManager security = System.getSecurityManager();
 1409           if (security != null) {
 1410               security.checkWrite(path);
 1411           }
 1412           return fs.setPermission(this, FileSystem.ACCESS_WRITE, writable, ownerOnly);
 1413       }
 1414   
 1415       /**
 1416        * A convenience method to set the owner's write permission for this abstract
 1417        * pathname.
 1418        *
 1419        * <p> An invocation of this method of the form <tt>file.setWritable(arg)</tt>
 1420        * behaves in exactly the same way as the invocation
 1421        *
 1422        * <pre>
 1423        *     file.setWritable(arg, true) </pre>
 1424        *
 1425        * @param   writable
 1426        *          If <code>true</code>, sets the access permission to allow write
 1427        *          operations; if <code>false</code> to disallow write operations
 1428        *
 1429        * @return  <code>true</code> if and only if the operation succeeded.  The
 1430        *          operation will fail if the user does not have permission to
 1431        *          change the access permissions of this abstract pathname.
 1432        *
 1433        * @throws  SecurityException
 1434        *          If a security manager exists and its <code>{@link
 1435        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1436        *          method denies write access to the file
 1437        *
 1438        * @since 1.6
 1439        */
 1440       public boolean setWritable(boolean writable) {
 1441           return setWritable(writable, true);
 1442       }
 1443   
 1444       /**
 1445        * Sets the owner's or everybody's read permission for this abstract
 1446        * pathname.
 1447        *
 1448        * <p> The {@link java.nio.file.Files} class defines methods that operate on
 1449        * file attributes including file permissions. This may be used when finer
 1450        * manipulation of file permissions is required.
 1451        *
 1452        * @param   readable
 1453        *          If <code>true</code>, sets the access permission to allow read
 1454        *          operations; if <code>false</code> to disallow read operations
 1455        *
 1456        * @param   ownerOnly
 1457        *          If <code>true</code>, the read permission applies only to the
 1458        *          owner's read permission; otherwise, it applies to everybody.  If
 1459        *          the underlying file system can not distinguish the owner's read
 1460        *          permission from that of others, then the permission will apply to
 1461        *          everybody, regardless of this value.
 1462        *
 1463        * @return  <code>true</code> if and only if the operation succeeded.  The
 1464        *          operation will fail if the user does not have permission to
 1465        *          change the access permissions of this abstract pathname.  If
 1466        *          <code>readable</code> is <code>false</code> and the underlying
 1467        *          file system does not implement a read permission, then the
 1468        *          operation will fail.
 1469        *
 1470        * @throws  SecurityException
 1471        *          If a security manager exists and its <code>{@link
 1472        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1473        *          method denies write access to the file
 1474        *
 1475        * @since 1.6
 1476        */
 1477       public boolean setReadable(boolean readable, boolean ownerOnly) {
 1478           SecurityManager security = System.getSecurityManager();
 1479           if (security != null) {
 1480               security.checkWrite(path);
 1481           }
 1482           return fs.setPermission(this, FileSystem.ACCESS_READ, readable, ownerOnly);
 1483       }
 1484   
 1485       /**
 1486        * A convenience method to set the owner's read permission for this abstract
 1487        * pathname.
 1488        *
 1489        * <p>An invocation of this method of the form <tt>file.setReadable(arg)</tt>
 1490        * behaves in exactly the same way as the invocation
 1491        *
 1492        * <pre>
 1493        *     file.setReadable(arg, true) </pre>
 1494        *
 1495        * @param  readable
 1496        *          If <code>true</code>, sets the access permission to allow read
 1497        *          operations; if <code>false</code> to disallow read operations
 1498        *
 1499        * @return  <code>true</code> if and only if the operation succeeded.  The
 1500        *          operation will fail if the user does not have permission to
 1501        *          change the access permissions of this abstract pathname.  If
 1502        *          <code>readable</code> is <code>false</code> and the underlying
 1503        *          file system does not implement a read permission, then the
 1504        *          operation will fail.
 1505        *
 1506        * @throws  SecurityException
 1507        *          If a security manager exists and its <code>{@link
 1508        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1509        *          method denies write access to the file
 1510        *
 1511        * @since 1.6
 1512        */
 1513       public boolean setReadable(boolean readable) {
 1514           return setReadable(readable, true);
 1515       }
 1516   
 1517       /**
 1518        * Sets the owner's or everybody's execute permission for this abstract
 1519        * pathname.
 1520        *
 1521        * <p> The {@link java.nio.file.Files} class defines methods that operate on
 1522        * file attributes including file permissions. This may be used when finer
 1523        * manipulation of file permissions is required.
 1524        *
 1525        * @param   executable
 1526        *          If <code>true</code>, sets the access permission to allow execute
 1527        *          operations; if <code>false</code> to disallow execute operations
 1528        *
 1529        * @param   ownerOnly
 1530        *          If <code>true</code>, the execute permission applies only to the
 1531        *          owner's execute permission; otherwise, it applies to everybody.
 1532        *          If the underlying file system can not distinguish the owner's
 1533        *          execute permission from that of others, then the permission will
 1534        *          apply to everybody, regardless of this value.
 1535        *
 1536        * @return  <code>true</code> if and only if the operation succeeded.  The
 1537        *          operation will fail if the user does not have permission to
 1538        *          change the access permissions of this abstract pathname.  If
 1539        *          <code>executable</code> is <code>false</code> and the underlying
 1540        *          file system does not implement an execute permission, then the
 1541        *          operation will fail.
 1542        *
 1543        * @throws  SecurityException
 1544        *          If a security manager exists and its <code>{@link
 1545        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1546        *          method denies write access to the file
 1547        *
 1548        * @since 1.6
 1549        */
 1550       public boolean setExecutable(boolean executable, boolean ownerOnly) {
 1551           SecurityManager security = System.getSecurityManager();
 1552           if (security != null) {
 1553               security.checkWrite(path);
 1554           }
 1555           return fs.setPermission(this, FileSystem.ACCESS_EXECUTE, executable, ownerOnly);
 1556       }
 1557   
 1558       /**
 1559        * A convenience method to set the owner's execute permission for this abstract
 1560        * pathname.
 1561        *
 1562        * <p>An invocation of this method of the form <tt>file.setExcutable(arg)</tt>
 1563        * behaves in exactly the same way as the invocation
 1564        *
 1565        * <pre>
 1566        *     file.setExecutable(arg, true) </pre>
 1567        *
 1568        * @param   executable
 1569        *          If <code>true</code>, sets the access permission to allow execute
 1570        *          operations; if <code>false</code> to disallow execute operations
 1571        *
 1572        * @return   <code>true</code> if and only if the operation succeeded.  The
 1573        *           operation will fail if the user does not have permission to
 1574        *           change the access permissions of this abstract pathname.  If
 1575        *           <code>executable</code> is <code>false</code> and the underlying
 1576        *           file system does not implement an excute permission, then the
 1577        *           operation will fail.
 1578        *
 1579        * @throws  SecurityException
 1580        *          If a security manager exists and its <code>{@link
 1581        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1582        *          method denies write access to the file
 1583        *
 1584        * @since 1.6
 1585        */
 1586       public boolean setExecutable(boolean executable) {
 1587           return setExecutable(executable, true);
 1588       }
 1589   
 1590       /**
 1591        * Tests whether the application can execute the file denoted by this
 1592        * abstract pathname.
 1593        *
 1594        * @return  <code>true</code> if and only if the abstract pathname exists
 1595        *          <em>and</em> the application is allowed to execute the file
 1596        *
 1597        * @throws  SecurityException
 1598        *          If a security manager exists and its <code>{@link
 1599        *          java.lang.SecurityManager#checkExec(java.lang.String)}</code>
 1600        *          method denies execute access to the file
 1601        *
 1602        * @since 1.6
 1603        */
 1604       public boolean canExecute() {
 1605           SecurityManager security = System.getSecurityManager();
 1606           if (security != null) {
 1607               security.checkExec(path);
 1608           }
 1609           return fs.checkAccess(this, FileSystem.ACCESS_EXECUTE);
 1610       }
 1611   
 1612   
 1613       /* -- Filesystem interface -- */
 1614   
 1615       /**
 1616        * List the available filesystem roots.
 1617        *
 1618        * <p> A particular Java platform may support zero or more
 1619        * hierarchically-organized file systems.  Each file system has a
 1620        * {@code root} directory from which all other files in that file system
 1621        * can be reached.  Windows platforms, for example, have a root directory
 1622        * for each active drive; UNIX platforms have a single root directory,
 1623        * namely {@code "/"}.  The set of available filesystem roots is affected
 1624        * by various system-level operations such as the insertion or ejection of
 1625        * removable media and the disconnecting or unmounting of physical or
 1626        * virtual disk drives.
 1627        *
 1628        * <p> This method returns an array of {@code File} objects that denote the
 1629        * root directories of the available filesystem roots.  It is guaranteed
 1630        * that the canonical pathname of any file physically present on the local
 1631        * machine will begin with one of the roots returned by this method.
 1632        *
 1633        * <p> The canonical pathname of a file that resides on some other machine
 1634        * and is accessed via a remote-filesystem protocol such as SMB or NFS may
 1635        * or may not begin with one of the roots returned by this method.  If the
 1636        * pathname of a remote file is syntactically indistinguishable from the
 1637        * pathname of a local file then it will begin with one of the roots
 1638        * returned by this method.  Thus, for example, {@code File} objects
 1639        * denoting the root directories of the mapped network drives of a Windows
 1640        * platform will be returned by this method, while {@code File} objects
 1641        * containing UNC pathnames will not be returned by this method.
 1642        *
 1643        * <p> Unlike most methods in this class, this method does not throw
 1644        * security exceptions.  If a security manager exists and its {@link
 1645        * SecurityManager#checkRead(String)} method denies read access to a
 1646        * particular root directory, then that directory will not appear in the
 1647        * result.
 1648        *
 1649        * @return  An array of {@code File} objects denoting the available
 1650        *          filesystem roots, or {@code null} if the set of roots could not
 1651        *          be determined.  The array will be empty if there are no
 1652        *          filesystem roots.
 1653        *
 1654        * @since  1.2
 1655        * @see java.nio.file.FileStore
 1656        */
 1657       public static File[] listRoots() {
 1658           return fs.listRoots();
 1659       }
 1660   
 1661   
 1662       /* -- Disk usage -- */
 1663   
 1664       /**
 1665        * Returns the size of the partition <a href="#partName">named</a> by this
 1666        * abstract pathname.
 1667        *
 1668        * @return  The size, in bytes, of the partition or <tt>0L</tt> if this
 1669        *          abstract pathname does not name a partition
 1670        *
 1671        * @throws  SecurityException
 1672        *          If a security manager has been installed and it denies
 1673        *          {@link RuntimePermission}<tt>("getFileSystemAttributes")</tt>
 1674        *          or its {@link SecurityManager#checkRead(String)} method denies
 1675        *          read access to the file named by this abstract pathname
 1676        *
 1677        * @since  1.6
 1678        */
 1679       public long getTotalSpace() {
 1680           SecurityManager sm = System.getSecurityManager();
 1681           if (sm != null) {
 1682               sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
 1683               sm.checkRead(path);
 1684           }
 1685           return fs.getSpace(this, FileSystem.SPACE_TOTAL);
 1686       }
 1687   
 1688       /**
 1689        * Returns the number of unallocated bytes in the partition <a
 1690        * href="#partName">named</a> by this abstract path name.
 1691        *
 1692        * <p> The returned number of unallocated bytes is a hint, but not
 1693        * a guarantee, that it is possible to use most or any of these
 1694        * bytes.  The number of unallocated bytes is most likely to be
 1695        * accurate immediately after this call.  It is likely to be made
 1696        * inaccurate by any external I/O operations including those made
 1697        * on the system outside of this virtual machine.  This method
 1698        * makes no guarantee that write operations to this file system
 1699        * will succeed.
 1700        *
 1701        * @return  The number of unallocated bytes on the partition <tt>0L</tt>
 1702        *          if the abstract pathname does not name a partition.  This
 1703        *          value will be less than or equal to the total file system size
 1704        *          returned by {@link #getTotalSpace}.
 1705        *
 1706        * @throws  SecurityException
 1707        *          If a security manager has been installed and it denies
 1708        *          {@link RuntimePermission}<tt>("getFileSystemAttributes")</tt>
 1709        *          or its {@link SecurityManager#checkRead(String)} method denies
 1710        *          read access to the file named by this abstract pathname
 1711        *
 1712        * @since  1.6
 1713        */
 1714       public long getFreeSpace() {
 1715           SecurityManager sm = System.getSecurityManager();
 1716           if (sm != null) {
 1717               sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
 1718               sm.checkRead(path);
 1719           }
 1720           return fs.getSpace(this, FileSystem.SPACE_FREE);
 1721       }
 1722   
 1723       /**
 1724        * Returns the number of bytes available to this virtual machine on the
 1725        * partition <a href="#partName">named</a> by this abstract pathname.  When
 1726        * possible, this method checks for write permissions and other operating
 1727        * system restrictions and will therefore usually provide a more accurate
 1728        * estimate of how much new data can actually be written than {@link
 1729        * #getFreeSpace}.
 1730        *
 1731        * <p> The returned number of available bytes is a hint, but not a
 1732        * guarantee, that it is possible to use most or any of these bytes.  The
 1733        * number of unallocated bytes is most likely to be accurate immediately
 1734        * after this call.  It is likely to be made inaccurate by any external
 1735        * I/O operations including those made on the system outside of this
 1736        * virtual machine.  This method makes no guarantee that write operations
 1737        * to this file system will succeed.
 1738        *
 1739        * @return  The number of available bytes on the partition or <tt>0L</tt>
 1740        *          if the abstract pathname does not name a partition.  On
 1741        *          systems where this information is not available, this method
 1742        *          will be equivalent to a call to {@link #getFreeSpace}.
 1743        *
 1744        * @throws  SecurityException
 1745        *          If a security manager has been installed and it denies
 1746        *          {@link RuntimePermission}<tt>("getFileSystemAttributes")</tt>
 1747        *          or its {@link SecurityManager#checkRead(String)} method denies
 1748        *          read access to the file named by this abstract pathname
 1749        *
 1750        * @since  1.6
 1751        */
 1752       public long getUsableSpace() {
 1753           SecurityManager sm = System.getSecurityManager();
 1754           if (sm != null) {
 1755               sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
 1756               sm.checkRead(path);
 1757           }
 1758           return fs.getSpace(this, FileSystem.SPACE_USABLE);
 1759       }
 1760   
 1761       /* -- Temporary files -- */
 1762   
 1763       private static class TempDirectory {
 1764           private TempDirectory() { }
 1765   
 1766           // temporary directory location
 1767           private static final File tmpdir = new File(fs.normalize(AccessController
 1768               .doPrivileged(new GetPropertyAction("java.io.tmpdir"))));
 1769           static File location() {
 1770               return tmpdir;
 1771           }
 1772   
 1773           // file name generation
 1774           private static final SecureRandom random = new SecureRandom();
 1775           static File generateFile(String prefix, String suffix, File dir) {
 1776               long n = random.nextLong();
 1777               if (n == Long.MIN_VALUE) {
 1778                   n = 0;      // corner case
 1779               } else {
 1780                   n = Math.abs(n);
 1781               }
 1782               return new File(dir, prefix + Long.toString(n) + suffix);
 1783           }
 1784       }
 1785   
 1786       /**
 1787        * <p> Creates a new empty file in the specified directory, using the
 1788        * given prefix and suffix strings to generate its name.  If this method
 1789        * returns successfully then it is guaranteed that:
 1790        *
 1791        * <ol>
 1792        * <li> The file denoted by the returned abstract pathname did not exist
 1793        *      before this method was invoked, and
 1794        * <li> Neither this method nor any of its variants will return the same
 1795        *      abstract pathname again in the current invocation of the virtual
 1796        *      machine.
 1797        * </ol>
 1798        *
 1799        * This method provides only part of a temporary-file facility.  To arrange
 1800        * for a file created by this method to be deleted automatically, use the
 1801        * <code>{@link #deleteOnExit}</code> method.
 1802        *
 1803        * <p> The <code>prefix</code> argument must be at least three characters
 1804        * long.  It is recommended that the prefix be a short, meaningful string
 1805        * such as <code>"hjb"</code> or <code>"mail"</code>.  The
 1806        * <code>suffix</code> argument may be <code>null</code>, in which case the
 1807        * suffix <code>".tmp"</code> will be used.
 1808        *
 1809        * <p> To create the new file, the prefix and the suffix may first be
 1810        * adjusted to fit the limitations of the underlying platform.  If the
 1811        * prefix is too long then it will be truncated, but its first three
 1812        * characters will always be preserved.  If the suffix is too long then it
 1813        * too will be truncated, but if it begins with a period character
 1814        * (<code>'.'</code>) then the period and the first three characters
 1815        * following it will always be preserved.  Once these adjustments have been
 1816        * made the name of the new file will be generated by concatenating the
 1817        * prefix, five or more internally-generated characters, and the suffix.
 1818        *
 1819        * <p> If the <code>directory</code> argument is <code>null</code> then the
 1820        * system-dependent default temporary-file directory will be used.  The
 1821        * default temporary-file directory is specified by the system property
 1822        * <code>java.io.tmpdir</code>.  On UNIX systems the default value of this
 1823        * property is typically <code>"/tmp"</code> or <code>"/var/tmp"</code>; on
 1824        * Microsoft Windows systems it is typically <code>"C:\\WINNT\\TEMP"</code>.  A different
 1825        * value may be given to this system property when the Java virtual machine
 1826        * is invoked, but programmatic changes to this property are not guaranteed
 1827        * to have any effect upon the temporary directory used by this method.
 1828        *
 1829        * @param  prefix     The prefix string to be used in generating the file's
 1830        *                    name; must be at least three characters long
 1831        *
 1832        * @param  suffix     The suffix string to be used in generating the file's
 1833        *                    name; may be <code>null</code>, in which case the
 1834        *                    suffix <code>".tmp"</code> will be used
 1835        *
 1836        * @param  directory  The directory in which the file is to be created, or
 1837        *                    <code>null</code> if the default temporary-file
 1838        *                    directory is to be used
 1839        *
 1840        * @return  An abstract pathname denoting a newly-created empty file
 1841        *
 1842        * @throws  IllegalArgumentException
 1843        *          If the <code>prefix</code> argument contains fewer than three
 1844        *          characters
 1845        *
 1846        * @throws  IOException  If a file could not be created
 1847        *
 1848        * @throws  SecurityException
 1849        *          If a security manager exists and its <code>{@link
 1850        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1851        *          method does not allow a file to be created
 1852        *
 1853        * @since 1.2
 1854        */
 1855       public static File createTempFile(String prefix, String suffix,
 1856                                         File directory)
 1857           throws IOException
 1858       {
 1859           if (prefix.length() < 3)
 1860               throw new IllegalArgumentException("Prefix string too short");
 1861           if (suffix == null)
 1862               suffix = ".tmp";
 1863   
 1864           File tmpdir = (directory != null) ? directory : TempDirectory.location();
 1865           SecurityManager sm = System.getSecurityManager();
 1866           File f;
 1867           do {
 1868               f = TempDirectory.generateFile(prefix, suffix, tmpdir);
 1869               if (sm != null) {
 1870                   try {
 1871                       sm.checkWrite(f.getPath());
 1872                   } catch (SecurityException se) {
 1873                       // don't reveal temporary directory location
 1874                       if (directory == null)
 1875                           throw new SecurityException("Unable to create temporary file");
 1876                       throw se;
 1877                   }
 1878               }
 1879           } while (!fs.createFileExclusively(f.getPath()));
 1880           return f;
 1881       }
 1882   
 1883       /**
 1884        * Creates an empty file in the default temporary-file directory, using
 1885        * the given prefix and suffix to generate its name. Invoking this method
 1886        * is equivalent to invoking <code>{@link #createTempFile(java.lang.String,
 1887        * java.lang.String, java.io.File)
 1888        * createTempFile(prefix,&nbsp;suffix,&nbsp;null)}</code>.
 1889        *
 1890        * <p> The {@link
 1891        * java.nio.file.Files#createTempFile(String,String,java.nio.file.attribute.FileAttribute[])
 1892        * Files.createTempFile} method provides an alternative method to create an
 1893        * empty file in the temporary-file directory. Files created by that method
 1894        * may have more restrictive access permissions to files created by this
 1895        * method and so may be more suited to security-sensitive applications.
 1896        *
 1897        * @param  prefix     The prefix string to be used in generating the file's
 1898        *                    name; must be at least three characters long
 1899        *
 1900        * @param  suffix     The suffix string to be used in generating the file's
 1901        *                    name; may be <code>null</code>, in which case the
 1902        *                    suffix <code>".tmp"</code> will be used
 1903        *
 1904        * @return  An abstract pathname denoting a newly-created empty file
 1905        *
 1906        * @throws  IllegalArgumentException
 1907        *          If the <code>prefix</code> argument contains fewer than three
 1908        *          characters
 1909        *
 1910        * @throws  IOException  If a file could not be created
 1911        *
 1912        * @throws  SecurityException
 1913        *          If a security manager exists and its <code>{@link
 1914        *          java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
 1915        *          method does not allow a file to be created
 1916        *
 1917        * @since 1.2
 1918        * @see java.nio.file.Files#createTempDirectory(String,FileAttribute[])
 1919        */
 1920       public static File createTempFile(String prefix, String suffix)
 1921           throws IOException
 1922       {
 1923           return createTempFile(prefix, suffix, null);
 1924       }
 1925   
 1926       /* -- Basic infrastructure -- */
 1927   
 1928       /**
 1929        * Compares two abstract pathnames lexicographically.  The ordering
 1930        * defined by this method depends upon the underlying system.  On UNIX
 1931        * systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows
 1932        * systems it is not.
 1933        *
 1934        * @param   pathname  The abstract pathname to be compared to this abstract
 1935        *                    pathname
 1936        *
 1937        * @return  Zero if the argument is equal to this abstract pathname, a
 1938        *          value less than zero if this abstract pathname is
 1939        *          lexicographically less than the argument, or a value greater
 1940        *          than zero if this abstract pathname is lexicographically
 1941        *          greater than the argument
 1942        *
 1943        * @since   1.2
 1944        */
 1945       public int compareTo(File pathname) {
 1946           return fs.compare(this, pathname);
 1947       }
 1948   
 1949       /**
 1950        * Tests this abstract pathname for equality with the given object.
 1951        * Returns <code>true</code> if and only if the argument is not
 1952        * <code>null</code> and is an abstract pathname that denotes the same file
 1953        * or directory as this abstract pathname.  Whether or not two abstract
 1954        * pathnames are equal depends upon the underlying system.  On UNIX
 1955        * systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows
 1956        * systems it is not.
 1957        *
 1958        * @param   obj   The object to be compared with this abstract pathname
 1959        *
 1960        * @return  <code>true</code> if and only if the objects are the same;
 1961        *          <code>false</code> otherwise
 1962        */
 1963       public boolean equals(Object obj) {
 1964           if ((obj != null) && (obj instanceof File)) {
 1965               return compareTo((File)obj) == 0;
 1966           }
 1967           return false;
 1968       }
 1969   
 1970       /**
 1971        * Computes a hash code for this abstract pathname.  Because equality of
 1972        * abstract pathnames is inherently system-dependent, so is the computation
 1973        * of their hash codes.  On UNIX systems, the hash code of an abstract
 1974        * pathname is equal to the exclusive <em>or</em> of the hash code
 1975        * of its pathname string and the decimal value
 1976        * <code>1234321</code>.  On Microsoft Windows systems, the hash
 1977        * code is equal to the exclusive <em>or</em> of the hash code of
 1978        * its pathname string converted to lower case and the decimal
 1979        * value <code>1234321</code>.  Locale is not taken into account on
 1980        * lowercasing the pathname string.
 1981        *
 1982        * @return  A hash code for this abstract pathname
 1983        */
 1984       public int hashCode() {
 1985           return fs.hashCode(this);
 1986       }
 1987   
 1988       /**
 1989        * Returns the pathname string of this abstract pathname.  This is just the
 1990        * string returned by the <code>{@link #getPath}</code> method.
 1991        *
 1992        * @return  The string form of this abstract pathname
 1993        */
 1994       public String toString() {
 1995           return getPath();
 1996       }
 1997   
 1998       /**
 1999        * WriteObject is called to save this filename.
 2000        * The separator character is saved also so it can be replaced
 2001        * in case the path is reconstituted on a different host type.
 2002        * <p>
 2003        * @serialData  Default fields followed by separator character.
 2004        */
 2005       private synchronized void writeObject(java.io.ObjectOutputStream s)
 2006           throws IOException
 2007       {
 2008           s.defaultWriteObject();
 2009           s.writeChar(this.separatorChar); // Add the separator character
 2010       }
 2011   
 2012       /**
 2013        * readObject is called to restore this filename.
 2014        * The original separator character is read.  If it is different
 2015        * than the separator character on this system, then the old separator
 2016        * is replaced by the local separator.
 2017        */
 2018       private synchronized void readObject(java.io.ObjectInputStream s)
 2019            throws IOException, ClassNotFoundException
 2020       {
 2021           ObjectInputStream.GetField fields = s.readFields();
 2022           String pathField = (String)fields.get("path", null);
 2023           char sep = s.readChar(); // read the previous separator char
 2024           if (sep != separatorChar)
 2025               pathField = pathField.replace(sep, separatorChar);
 2026           this.path = fs.normalize(pathField);
 2027           this.prefixLength = fs.prefixLength(this.path);
 2028       }
 2029   
 2030       /** use serialVersionUID from JDK 1.0.2 for interoperability */
 2031       private static final long serialVersionUID = 301077366599181567L;
 2032   
 2033       // -- Integration with java.nio.file --
 2034   
 2035       private volatile transient Path filePath;
 2036   
 2037       /**
 2038        * Returns a {@link Path java.nio.file.Path} object constructed from the
 2039        * this abstract path. The resulting {@code Path} is associated with the
 2040        * {@link java.nio.file.FileSystems#getDefault default-filesystem}.
 2041        *
 2042        * <p> The first invocation of this method works as if invoking it were
 2043        * equivalent to evaluating the expression:
 2044        * <blockquote><pre>
 2045        * {@link java.nio.file.FileSystems#getDefault FileSystems.getDefault}().{@link
 2046        * java.nio.file.FileSystem#getPath getPath}(this.{@link #getPath getPath}());
 2047        * </pre></blockquote>
 2048        * Subsequent invocations of this method return the same {@code Path}.
 2049        *
 2050        * <p> If this abstract pathname is the empty abstract pathname then this
 2051        * method returns a {@code Path} that may be used to access the current
 2052        * user directory.
 2053        *
 2054        * @return  a {@code Path} constructed from this abstract path
 2055        *
 2056        * @throws  java.nio.file.InvalidPathException
 2057        *          if a {@code Path} object cannot be constructed from the abstract
 2058        *          path (see {@link java.nio.file.FileSystem#getPath FileSystem.getPath})
 2059        *
 2060        * @since   1.7
 2061        * @see Path#toFile
 2062        */
 2063       public Path toPath() {
 2064           Path result = filePath;
 2065           if (result == null) {
 2066               synchronized (this) {
 2067                   result = filePath;
 2068                   if (result == null) {
 2069                       result = FileSystems.getDefault().getPath(path);
 2070                       filePath = result;
 2071                   }
 2072               }
 2073           }
 2074           return result;
 2075       }
 2076   }

Save This Page
Home » openjdk-7 » java » io » [javadoc | source]