minwin-gcc-5-2/libjava/classpath/java/lang/ref/WeakReference.java

/* java.lang.ref.WeakReference
   Copyright (C) 1999, 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.lang.ref;

/**
 * A weak reference will be cleared, if the object is only weakly
 * reachable.  It is useful for lookup tables, where you aren't
 * interested in an entry, if the key isn't reachable anymore.
 * <code>WeakHashtable</code> is a complete implementation of such a
 * table. <br>
 *
 * It is also useful to make objects unique: You create a set of weak
 * references to those objects, and when you create a new object you
 * look in this set, if the object already exists and return it.  If
 * an object is not referenced anymore, the reference will
 * automatically cleared, and you may remove it from the set. <br>
 *
 * @author Jochen Hoenicke
 * @see java.util.WeakHashMap
 */
public class WeakReference<T>
  extends Reference<T>
{
  /**
   * Create a new weak reference, that is not registered to any queue.
   * @param referent the object we refer to.
   */
  public WeakReference(T referent)
  {
    super(referent);
  }

  /**
   * Create a new weak reference.
   * @param referent the object we refer to.
   * @param q the reference queue to register on.
   * @exception NullPointerException if q is null.
   */
  public WeakReference(T referent, ReferenceQueue<? super T> q)
  {
    super(referent, q);
  }
}