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| 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 < 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 | } | ||