J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2000-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 < 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 | } |