01: /*
02: * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved.
03: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
04: *
05: * This code is free software; you can redistribute it and/or modify it
06: * under the terms of the GNU General Public License version 2 only, as
07: * published by the Free Software Foundation. Sun designates this
08: * particular file as subject to the "Classpath" exception as provided
09: * 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: }
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