Source Code : Soft HashMap

Java Is Open Source Programming Language You Can Download From Java and Java Libraries From http://www.oracle.com. Click Here to download
We provide this code related to title for you to solve your developing problem easily. Libraries which is import in this program you can download from http://www.oracle.com. Click Here or search from google with Libraries Name you get jar file related it

Soft HashMap

 


/*
 * dbXML - Native XML Database
 * Copyright (C) 1999-2004  The dbXML Group, L.L.C.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * $Id: SoftHashMap.java,v 1.2 2004/02/12 00:17:58 bradford Exp $
 */

import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.AbstractMap;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * SoftHashMap
 */

public final class SoftHashMap extends AbstractMap {
   private Map hash = new HashMap();
   private final ReferenceQueue queue = new ReferenceQueue();

   public SoftHashMap() {
   }

   public Object get(Object key) {
      Object res = null;
      SoftReference sr = (SoftReference)hash.get(key);
      if ( sr != null ) {
         res = sr.get();
         if ( res == null )
            hash.remove(key);
      }
      return res;
   }

   private void processQueue() {
      for ( ;; ) {
         SoftValue sv = (SoftValue)queue.poll();
         if ( sv != null )
            hash.remove(sv.key);
         else
            return;
      }
   }

   public Object put(Object key, Object value) {
      processQueue();
      return hash.put(key, new SoftValue(value, key, queue));
   }

   public Object remove(Object key) {
      processQueue();
      return hash.remove(key);
   }

   public void clear() {
      processQueue();
      hash.clear();
   }

   public int size() {
      processQueue();
      return hash.size();
   }

   public Set entrySet() {
      /** @todo Figure this out */
      throw new UnsupportedOperationException();
   }


   /**
    * SoftValue
    */

   private static class SoftValue extends SoftReference {
      private final Object key;

      private SoftValue(Object k, Object key, ReferenceQueue q) {
         super(k, q);
         this.key = key;
      }
   }
}

   
  

Thank with us