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/*
* 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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