01: /*
02: * hgcommons 7
03: * Hammurapi Group Common Library
04: * Copyright (C) 2003 Hammurapi Group
05: *
06: * This program is free software; you can redistribute it and/or
07: * modify it under the terms of the GNU Lesser General Public
08: * License as published by the Free Software Foundation; either
09: * version 2 of the License, or (at your option) any later version.
10: *
11: * This program is distributed in the hope that it will be useful,
12: * but WITHOUT ANY WARRANTY; without even the implied warranty of
13: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14: * Lesser General Public License for more details.
15: *
16: * You should have received a copy of the GNU Lesser General Public
17: * License along with this library; if not, write to the Free Software
18: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19: *
20: * URL: http://www.hammurapi.biz/hammurapi-biz/ef/xmenu/hammurapi-group/products/products/hgcommons/index.html
21: * e-Mail: support@hammurapi.biz
22: */
23: package biz.hammurapi.cache;
24:
25: import java.lang.ref.Reference;
26: import java.lang.ref.SoftReference;
27: import java.util.HashMap;
28: import java.util.Map;
29:
30: /**
31: * Map with soft-referenced values.
32: * @author Pavel Vlasov
33: * @revision $Revision$
34: */
35: public class SoftHashMap extends HashMap {
36: private Object nullMarker = new Object();
37:
38: /**
39: *
40: */
41: private static final long serialVersionUID = 4095082501213777588L;
42:
43: public SoftHashMap() {
44: super ();
45: }
46:
47: public SoftHashMap(int initialCapacity) {
48: super (initialCapacity);
49: }
50:
51: public SoftHashMap(int initialCapacity, float loadFactor) {
52: super (initialCapacity, loadFactor);
53: }
54:
55: public SoftHashMap(Map m) {
56: super (m);
57: }
58:
59: public Object put(Object key, Object value) {
60: return super .put(key, new SoftReference(
61: value == null ? nullMarker : value));
62: }
63:
64: public Object get(Object key) {
65: Reference ref = (Reference) super .get(key);
66: if (ref == null) {
67: return null;
68: }
69:
70: Object value = ref.get();
71: if (value == null) {
72: remove(key);
73: }
74: return value == nullMarker ? null : value;
75: }
76:
77: }
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