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1   /*
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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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9    * by Oracle in the LICENSE file that accompanied this code.
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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).
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17   * You should have received a copy of the GNU General Public License version
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19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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  }