01: /*
02: * Copyright (c) 1998-2002 Carnegie Mellon University. All rights
03: * reserved.
04: *
05: * Redistribution and use in source and binary forms, with or without
06: * modification, are permitted provided that the following conditions
07: * are met:
08: *
09: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: *
12: * 2. Redistributions in binary form must reproduce the above copyright
13: * notice, this list of conditions and the following disclaimer in
14: * the documentation and/or other materials provided with the
15: * distribution.
16: *
17: * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND
18: * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
19: * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20: * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
21: * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28: *
29: */
30:
31: package rcm.util;
32:
33: import java.util.Hashtable;
34:
35: /**
36: * Subclass of Hashtable that supports merging the existing object
37: * stored in the hashtable with a new object.
38: */
39: public abstract class MergingHashtable extends Hashtable {
40:
41: public Object add(Object key, Object value) {
42: Object curr = get(key);
43: if (curr != null)
44: value = merge(curr, value);
45: return put(key, value);
46: }
47:
48: protected abstract Object merge(Object current, Object addition);
49:
50: }
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