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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 | +} | |