001 /* 002 * Copyright (C) 2008-2010 by Holger Arndt 003 * 004 * This file is part of the Universal Java Matrix Package (UJMP). 005 * See the NOTICE file distributed with this work for additional 006 * information regarding copyright ownership and licensing. 007 * 008 * UJMP is free software; you can redistribute it and/or modify 009 * it under the terms of the GNU Lesser General Public License as 010 * published by the Free Software Foundation; either version 2 011 * of the License, or (at your option) any later version. 012 * 013 * UJMP is distributed in the hope that it will be useful, 014 * but WITHOUT ANY WARRANTY; without even the implied warranty of 015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 016 * GNU Lesser General Public License for more details. 017 * 018 * You should have received a copy of the GNU Lesser General Public 019 * License along with UJMP; if not, write to the 020 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, 021 * Boston, MA 02110-1301 USA 022 */ 023 024 package org.ujmp.core.collections; 025 026 import java.lang.ref.SoftReference; 027 import java.util.HashMap; 028 import java.util.Map; 029 import java.util.Set; 030 031 public class SoftHashMap<K, V> extends AbstractMap<K, V> { 032 private static final long serialVersionUID = 6784629567536455622L; 033 034 private transient Map<K, SoftReference<V>> map = null; 035 036 public SoftHashMap() { 037 } 038 039 public SoftHashMap(Map<? extends K, ? extends V> map) { 040 this(); 041 putAll(map); 042 } 043 044 private Map<K, SoftReference<V>> getMap() { 045 if (map == null) { 046 map = new HashMap<K, SoftReference<V>>(); 047 } 048 return map; 049 } 050 051 public void clear() { 052 getMap().clear(); 053 } 054 055 public V get(Object key) { 056 SoftReference<V> v = getMap().get(key); 057 return v == null ? null : v.get(); 058 } 059 060 public Set<K> keySet() { 061 return getMap().keySet(); 062 } 063 064 public V put(K key, V value) { 065 do { 066 try { 067 SoftReference<V> v = getMap().put(key, new SoftReference<V>(value)); 068 return v == null ? null : v.get(); 069 } catch (OutOfMemoryError e) { 070 getMap().remove(getMap().keySet().iterator().next()); 071 } 072 } while (!getMap().isEmpty()); 073 throw new OutOfMemoryError("removing all entries from Map could not avoid OutOfMemoryError"); 074 } 075 076 public V remove(Object key) { 077 SoftReference<V> v = getMap().remove(key); 078 return v == null ? null : v.get(); 079 } 080 081 public int size() { 082 return getMap().size(); 083 } 084 085 }