01: /*
02: Copyright 2004 Philip Jacob <phil@whirlycott.com>
03: Seth Fitzsimmons <seth@note.amherst.edu>
04:
05: Licensed under the Apache License, Version 2.0 (the "License");
06: you may not use this file except in compliance with the License.
07: You may obtain a copy of the License at
08:
09: http://www.apache.org/licenses/LICENSE-2.0
10:
11: Unless required by applicable law or agreed to in writing, software
12: distributed under the License is distributed on an "AS IS" BASIS,
13: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14: See the License for the specific language governing permissions and
15: limitations under the License.
16: */
17:
18: package com.whirlycott.cache.policy;
19:
20: import java.util.Comparator;
21: import java.util.Map;
22:
23: import com.whirlycott.cache.Item;
24:
25: /**
26: * A comparison function, used by LRUMaintenancePolicy, which determines whether one Item has been used more recently
27: * than a second Item, using said Items' used properties.
28: *
29: * @author Seth Fitzsimmons
30: */
31: public class UsedComparator implements Comparator<Map.Entry> {
32:
33: /**
34: * Compares two Item objects based on their relative last-used time.
35: */
36: public int compare(final Map.Entry o1, final Map.Entry o2) {
37: int retval = 0;
38:
39: final Item lh = (Item) o1.getValue();
40: final Item rh = (Item) o2.getValue();
41:
42: if (lh != null && rh != null) {
43:
44: if (lh.getUsed() < rh.getUsed()) {
45: retval = -1;
46: }
47:
48: if (lh.getUsed() > rh.getUsed()) {
49: retval = 1;
50: }
51: }
52:
53: return retval;
54: }
55: }
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