java.lang.Objectjava.io.File
All Implemented Interfaces:
Serializable, Comparable
Direct Known Subclasses:
FileSystemRoot
User interfaces and operating systems use system-dependent pathname strings to name files and directories. This class presents an abstract, system-independent view of hierarchical pathnames. An abstract pathname has two components:
"/" for the UNIX root
directory, or "\\\\" for a Microsoft Windows UNC pathname, and
The conversion of a pathname string to or from an abstract pathname is
inherently system-dependent. When an abstract pathname is converted into a
pathname string, each name is separated from the next by a single copy of
the default separator character. The default name-separator
character is defined by the system property file.separator, and
is made available in the public static fields #separator and #separatorChar of this class.
When a pathname string is converted into an abstract pathname, the names
within it may be separated by the default name-separator character or by any
other name-separator character that is supported by the underlying system.
A pathname, whether abstract or in string form, may be either
absolute or relative. An absolute pathname is complete in
that no other information is required in order to locate the file that it
denotes. A relative pathname, in contrast, must be interpreted in terms of
information taken from some other pathname. By default the classes in the
java.io package always resolve relative pathnames against the
current user directory. This directory is named by the system property
user.dir, and is typically the directory in which the Java
virtual machine was invoked.
The parent of an abstract pathname may be obtained by invoking the #getParent method of this class and consists of the pathname's prefix and each name in the pathname's name sequence except for the last. Each directory's absolute pathname is an ancestor of any File object with an absolute abstract pathname which begins with the directory's absolute pathname. For example, the directory denoted by the abstract pathname "/usr" is an ancestor of the directory denoted by the pathname "/usr/local/bin".
The prefix concept is used to handle root directories on UNIX platforms, and drive specifiers, root directories and UNC pathnames on Microsoft Windows platforms, as follows:
"/". Relative pathnames have no prefix. The abstract pathname
denoting the root directory has the prefix "/" and an empty
name sequence.
":" and
possibly followed by "\\" if the pathname is absolute. The
prefix of a UNC pathname is "\\\\"; the hostname and the share
name are the first two names in the name sequence. A relative pathname that
does not specify a drive has no prefix.
Instances of this class may or may not denote an actual file-system object such as a file or a directory. If it does denote such an object then that object resides in a partition. A partition is an operating system-specific portion of storage for a file system. A single storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may contain multiple partitions. The object, if any, will reside on the partition named by some ancestor of the absolute form of this pathname.
A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions. The file system may have multiple sets of access permissions on a single object. For example, one set may apply to the object's owner, and another may apply to all other users. The access permissions on an object may cause some methods in this class to fail.
Instances of the File class are immutable; that is, once
created, the abstract pathname represented by a File object
will never change.
unascribed - JDK1.0 - | Field Summary | ||
|---|---|---|
| public static final char | separatorChar | The system-dependent default name-separator character. This field is
initialized to contain the first character of the value of the system
property file.separator. On UNIX systems the value of this
field is '/'; on Microsoft Windows systems it is '\\'.
|
| public static final String | separator | The system-dependent default name-separator character, represented as a
string for convenience. This string contains a single character, namely
#separatorChar . |
| public static final char | pathSeparatorChar | The system-dependent path-separator character. This field is
initialized to contain the first character of the value of the system
property path.separator. This character is used to
separate filenames in a sequence of files given as a path list.
On UNIX systems, this character is ':'; on Microsoft Windows systems it
is ';'.
|
| public static final String | pathSeparator | The system-dependent path-separator character, represented as a string
for convenience. This string contains a single character, namely
#pathSeparatorChar . |
| Constructor: |
|---|
File instance by converting the given
pathname string into an abstract pathname. If the given string is
the empty string, then the result is the empty abstract pathname.
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The exact form of a file: URI is system-dependent, hence the transformation performed by this constructor is also system-dependent. For a given abstract pathname f it is guaranteed that new File( f.toURI ()).equals( f.getAbsoluteFile ())so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. This relationship typically does not hold, however, when a file: URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system.
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File instance from a parent pathname string
and a child pathname string.
If Otherwise the
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File instance from a parent abstract
pathname and a child pathname string.
If Otherwise the
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| Method from java.io.File Summary: |
|---|
| canExecute, canRead, canWrite, compareTo, createNewFile, createTempFile, createTempFile, delete, deleteOnExit, equals, exists, getAbsoluteFile, getAbsolutePath, getCanonicalFile, getCanonicalPath, getFreeSpace, getName, getParent, getParentFile, getPath, getPrefixLength, getTotalSpace, getUsableSpace, hashCode, isAbsolute, isDirectory, isFile, isHidden, lastModified, length, list, list, listFiles, listFiles, listFiles, listRoots, mkdir, mkdirs, renameTo, setExecutable, setExecutable, setLastModified, setReadOnly, setReadable, setReadable, setWritable, setWritable, toString, toURI, toURL |
| Methods from java.lang.Object: |
|---|
| clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Method from java.io.File Detail: |
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Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead. |
java.lang.String, java.io.File)
createTempFile(prefix, suffix, null) . |
Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name. If this method returns successfully then it is guaranteed that: #deleteOnExit method.
The To create the new file, the prefix and the suffix may first be
adjusted to fit the limitations of the underlying platform. If the
prefix is too long then it will be truncated, but its first three
characters will always be preserved. If the suffix is too long then it
too will be truncated, but if it begins with a period character
( If the |
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Once deletion has been requested, it is not possible to cancel the request. This method should therefore be used with care. Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead. |
true if and only if the argument is not
null and is an abstract pathname that denotes the same file
or directory as this abstract pathname. Whether or not two abstract
pathnames are equal depends upon the underlying system. On UNIX
systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows
systems it is not. |
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new File(this.#getAbsolutePath ). |
If this abstract pathname is already absolute, then the pathname
string is simply returned as if by the |
new File(this.#getCanonicalPath ). |
A canonical pathname is both absolute and unique. The precise definition of canonical form is system-dependent. This method first converts this pathname to absolute form if necessary, as if by invoking the #getAbsolutePath method, and then maps it to its unique form in a system-dependent way. This typically involves removing redundant names such as "." and ".." from the pathname, resolving symbolic links (on UNIX platforms), and converting drive letters to a standard case (on Microsoft Windows platforms). Every pathname that denotes an existing file or directory has a unique canonical form. Every pathname that denotes a nonexistent file or directory also has a unique canonical form. The canonical form of the pathname of a nonexistent file or directory may be different from the canonical form of the same pathname after the file or directory is created. Similarly, the canonical form of the pathname of an existing file or directory may be different from the canonical form of the same pathname after the file or directory is deleted. |
The returned number of unallocated bytes is a hint, but not a guarantee, that it is possible to use most or any of these bytes. The number of unallocated bytes is most likely to be accurate immediately after this call. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this virtual machine. This method makes no guarantee that write operations to this file system will succeed. |
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null if this pathname does not name a parent directory.
The parent of an abstract pathname consists of the pathname's prefix, if any, and each name in the pathname's name sequence except for the last. If the name sequence is empty then the pathname does not name a parent directory. |
null if this pathname does not name a parent
directory.
The parent of an abstract pathname consists of the pathname's prefix, if any, and each name in the pathname's name sequence except for the last. If the name sequence is empty then the pathname does not name a parent directory. |
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The returned number of available bytes is a hint, but not a guarantee, that it is possible to use most or any of these bytes. The number of unallocated bytes is most likely to be accurate immediately after this call. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this virtual machine. This method makes no guarantee that write operations to this file system will succeed. |
1234321. On Microsoft Windows systems, the hash
code is equal to the exclusive or of the hash code of
its pathname string converted to lower case and the decimal
value 1234321. Locale is not taken into account on
lowercasing the pathname string. |
"/". On Microsoft Windows systems, a
pathname is absolute if its prefix is a drive specifier followed by
"\\", or if its prefix is "\\\\". |
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'.'). On Microsoft Windows systems, a file is
considered to be hidden if it has been marked as such in the filesystem. |
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If this abstract pathname does not denote a directory, then this method returns {@code null}. Otherwise an array of strings is returned, one for each file or directory in the directory. Names denoting the directory itself and the directory's parent directory are not included in the result. Each string is a file name rather than a complete path. There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order. |
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If this abstract pathname does not denote a directory, then this method returns {@code null}. Otherwise an array of {@code File} objects is returned, one for each file or directory in the directory. Pathnames denoting the directory itself and the directory's parent directory are not included in the result. Each resulting abstract pathname is constructed from this abstract pathname using the File(File, String) constructor. Therefore if this pathname is absolute then each resulting pathname is absolute; if this pathname is relative then each resulting pathname will be relative to the same directory. There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order. |
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A particular Java platform may support zero or more hierarchically-organized file systems. Each file system has a {@code root} directory from which all other files in that file system can be reached. Windows platforms, for example, have a root directory for each active drive; UNIX platforms have a single root directory, namely {@code "/"}. The set of available filesystem roots is affected by various system-level operations such as the insertion or ejection of removable media and the disconnecting or unmounting of physical or virtual disk drives. This method returns an array of {@code File} objects that denote the root directories of the available filesystem roots. It is guaranteed that the canonical pathname of any file physically present on the local machine will begin with one of the roots returned by this method. The canonical pathname of a file that resides on some other machine and is accessed via a remote-filesystem protocol such as SMB or NFS may or may not begin with one of the roots returned by this method. If the pathname of a remote file is syntactically indistinguishable from the pathname of a local file then it will begin with one of the roots returned by this method. Thus, for example, {@code File} objects denoting the root directories of the mapped network drives of a Windows platform will be returned by this method, while {@code File} objects containing UNC pathnames will not be returned by this method. Unlike most methods in this class, this method does not throw security exceptions. If a security manager exists and its SecurityManager#checkRead(String) method denies read access to a particular root directory, then that directory will not appear in the result. |
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Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful. |
An invocation of this method of the form file.setExcutable(arg) behaves in exactly the same way as the invocation file.setExecutable(arg, true) |
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All platforms support file-modification times to the nearest second,
but some provide more precision. The argument will be truncated to fit
the supported precision. If the operation succeeds and no intervening
operations on the file take place, then the next invocation of the
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An invocation of this method of the form file.setReadable(arg) behaves in exactly the same way as the invocation file.setReadable(arg, true) |
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An invocation of this method of the form file.setWritable(arg) behaves in exactly the same way as the invocation file.setWritable(arg, true) |
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#getPath method. |
The exact form of the URI is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URI will end with a slash. For a given abstract pathname f, it is guaranteed that new File ( f.toURI()).equals( f.getAbsoluteFile ())so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. Due to the system-dependent nature of abstract pathnames, however, this relationship typically does not hold when a file: URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system. |
Deprecated! This - method does not automatically escape characters that
are illegal in URLs. It is recommended that new code convert an
abstract pathname into a URL by first converting it into a URI, via the
toURI method, and then converting the URI into a URL
via the URI.toURL method.
file: URL. The
exact form of the URL is system-dependent. If it can be determined that
the file denoted by this abstract pathname is a directory, then the
resulting URL will end with a slash. |