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The source code

/*
 *                 Sun Public License Notice
 *
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 *
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2003 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.editor;

import java.util.ArrayList;
import java.util.List;
import javax.swing.text.Segment;

/**
 * SegmentCache caches {@link javax.swing.text.Segment} instances
 * to allow reusing of them.
 * 
 *   Segment segment = segmentCache.getSegment();
 *   try {
 *       ... // use the segment
 *   } finally {
 *      segmentCache.releaseSegment(segment);
 *   }
 * 
* *
There is one shared instance of the segment cache * provided by the {@link #getSharedInstance()}. *
As the whole mechanism of obtaining/freeing of the segments * depends on the proper behavior of the clients * it's recommended that the individual SegmentCache instances * should be used and be e.g. package-private. */ public class SegmentCache { private static final SegmentCache SHARED = new SegmentCache(); /** * @return shared cache instance. */ public static SegmentCache getSharedInstance() { return SHARED; } /** Free segments. */ private List freeSegments; /** * Constructs SegmentCache instance. */ public SegmentCache() { freeSegments = new ArrayList(); } /** * Returns a free {@link javax.swing.text.Segment}. When done, the segment * should be recycled by invoking {@link #releaseSegment()}. */ public synchronized Segment getSegment() { int size = freeSegments.size(); return (size > 0) ? (Segment)freeSegments.remove(size - 1) : new CachedSegment(); } /** * Releases a shared Segment. *
The shared segment must NOT be used after it's released. *
The shared segment must NOT be released more than once like this: *
     *   segmentCache.releaseSegment(segment);
     *   segmentCache.releaseSegment(segment);
     * 
*
Only the segments obtained from {@link #getSegment()} * can be released. * @param segment segment to be released. */ public synchronized void releaseSegment(Segment segment) { if (segment instanceof CachedSegment) { segment.array = null; segment.count = 0; freeSegments.add(segment); } else { // not instance obtained by getSegment() throw new IllegalStateException( segment + " was not obtained from segment cache"); // NOI18N } } /** * CachedSegment is used as a tagging class to determine if * a Segment being released was returned by {@link #getSegment()} */ private static class CachedSegment extends Segment { } }
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