Home » openjdk-7 » java » util » [javadoc | source]

    1   /*
    2    * Copyright (c) 2000, 2006, 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.util;
   27   
   28   /**
   29    * Marker interface used by <tt>List</tt> implementations to indicate that
   30    * they support fast (generally constant time) random access.  The primary
   31    * purpose of this interface is to allow generic algorithms to alter their
   32    * behavior to provide good performance when applied to either random or
   33    * sequential access lists.
   34    *
   35    * <p>The best algorithms for manipulating random access lists (such as
   36    * <tt>ArrayList</tt>) can produce quadratic behavior when applied to
   37    * sequential access lists (such as <tt>LinkedList</tt>).  Generic list
   38    * algorithms are encouraged to check whether the given list is an
   39    * <tt>instanceof</tt> this interface before applying an algorithm that would
   40    * provide poor performance if it were applied to a sequential access list,
   41    * and to alter their behavior if necessary to guarantee acceptable
   42    * performance.
   43    *
   44    * <p>It is recognized that the distinction between random and sequential
   45    * access is often fuzzy.  For example, some <tt>List</tt> implementations
   46    * provide asymptotically linear access times if they get huge, but constant
   47    * access times in practice.  Such a <tt>List</tt> implementation
   48    * should generally implement this interface.  As a rule of thumb, a
   49    * <tt>List</tt> implementation should implement this interface if,
   50    * for typical instances of the class, this loop:
   51    * <pre>
   52    *     for (int i=0, n=list.size(); i &lt; n; i++)
   53    *         list.get(i);
   54    * </pre>
   55    * runs faster than this loop:
   56    * <pre>
   57    *     for (Iterator i=list.iterator(); i.hasNext(); )
   58    *         i.next();
   59    * </pre>
   60    *
   61    * <p>This interface is a member of the
   62    * <a href="{@docRoot}/../technotes/guides/collections/index.html">
   63    * Java Collections Framework</a>.
   64    *
   65    * @since 1.4
   66    */
   67   public interface RandomAccess {
   68   }

Home » openjdk-7 » java » util » [javadoc | source]