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1 /*
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2 Copyright (c) 2008 Franklin Schmidt <fschmidt@gmail.com>
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3
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4 Permission is hereby granted, free of charge, to any person obtaining a copy
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5 of this software and associated documentation files (the "Software"), to deal
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6 in the Software without restriction, including without limitation the rights
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7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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8 copies of the Software, and to permit persons to whom the Software is
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9 furnished to do so, subject to the following conditions:
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10
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11 The above copyright notice and this permission notice shall be included in
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12 all copies or substantial portions of the Software.
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13
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14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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20 THE SOFTWARE.
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21 */
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22
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23 package fschmidt.db.util;
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24
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25 import java.util.Map;
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26 import java.util.HashMap;
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27
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28
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29 public final class Unique<T> {
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30
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31 private static class Val<T> {
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32 T o;
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33 int count;
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34 }
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35
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36 private Map<T,Val<T>> map = new HashMap<T,Val<T>>();
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37
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38 public synchronized T get(T o) {
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39 Val<T> v = map.get(o);
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40 if( v == null ) {
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41 v = new Val<T>();
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42 v.o = o;
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43 map.put(o,v);
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44 }
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45 v.count++;
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46 return v.o;
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47 }
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48
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49 public synchronized void free(T o) {
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50 Val<T> v = map.get(o);
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51 if (v==null) return;
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52 if( --v.count == 0 )
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53 map.remove(o);
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54 }
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55 }
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56
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