1 /*
   2  * Copyright (c) 2001, 2008, 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 package javax.swing.text;
  26 
  27 import java.util.ArrayList;
  28 import java.util.List;
  29 
  30 /**
  31  * SegmentCache caches <code>Segment</code>s to avoid continually creating
  32  * and destroying of <code>Segment</code>s. A common use of this class would
  33  * be:
  34  * <pre>
  35  *   Segment segment = segmentCache.getSegment();
  36  *   // do something with segment
  37  *   ...
  38  *   segmentCache.releaseSegment(segment);
  39  * </pre>
  40  *
  41  */
  42 class SegmentCache {
  43     /**
  44      * A global cache.
  45      */
  46     private static SegmentCache sharedCache = new SegmentCache();
  47 
  48     /**
  49      * A list of the currently unused Segments.
  50      */
  51     private List<Segment> segments;
  52 
  53 
  54     /**
  55      * Returns the shared SegmentCache.
  56      */
  57     public static SegmentCache getSharedInstance() {
  58         return sharedCache;
  59     }
  60 
  61     /**
  62      * A convenience method to get a Segment from the shared
  63      * <code>SegmentCache</code>.
  64      */
  65     public static Segment getSharedSegment() {
  66         return getSharedInstance().getSegment();
  67     }
  68 
  69     /**
  70      * A convenience method to release a Segment to the shared
  71      * <code>SegmentCache</code>.
  72      */
  73     public static void releaseSharedSegment(Segment segment) {
  74         getSharedInstance().releaseSegment(segment);
  75     }
  76 
  77 
  78 
  79     /**
  80      * Creates and returns a SegmentCache.
  81      */
  82     public SegmentCache() {
  83         segments = new ArrayList<Segment>(11);
  84     }
  85 
  86     /**
  87      * Returns a <code>Segment</code>. When done, the <code>Segment</code>
  88      * should be recycled by invoking <code>releaseSegment</code>.
  89      */
  90     public Segment getSegment() {
  91         synchronized(this) {
  92             int size = segments.size();
  93 
  94             if (size > 0) {
  95                 return segments.remove(size - 1);
  96             }
  97         }
  98         return new CachedSegment();
  99     }
 100 
 101     /**
 102      * Releases a Segment. You should not use a Segment after you release it,
 103      * and you should NEVER release the same Segment more than once, eg:
 104      * <pre>
 105      *   segmentCache.releaseSegment(segment);
 106      *   segmentCache.releaseSegment(segment);
 107      * </pre>
 108      * Will likely result in very bad things happening!
 109      */
 110     public void releaseSegment(Segment segment) {
 111         if (segment instanceof CachedSegment) {
 112             synchronized(this) {
 113                 segment.array = null;
 114                 segment.count = 0;
 115                 segments.add(segment);
 116             }
 117         }
 118     }
 119 
 120 
 121     /**
 122      * CachedSegment is used as a tagging interface to determine if
 123      * a Segment can successfully be shared.
 124      */
 125     private static class CachedSegment extends Segment {
 126     }
 127 }
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