1 /* |
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2 * Copyright (c) 1994, 2005, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package sun.misc; |
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27 |
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28 /** |
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29 * ConditionLock is a Lock with a built in state variable. This class |
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30 * provides the ability to wait for the state variable to be set to a |
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31 * desired value and then acquire the lock.<p> |
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32 * |
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33 * The lockWhen() and unlockWith() methods can be safely intermixed |
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34 * with the lock() and unlock() methods. However if there is a thread |
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35 * waiting for the state variable to become a particular value and you |
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36 * simply call Unlock(), that thread will not be able to acquire the |
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37 * lock until the state variable equals its desired value. |
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38 * |
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39 * @author Peter King |
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40 */ |
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41 public final |
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42 class ConditionLock extends Lock { |
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43 private int state = 0; |
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44 |
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45 /** |
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46 * Creates a ConditionLock. |
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47 */ |
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48 public ConditionLock () { |
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49 } |
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50 |
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51 /** |
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52 * Creates a ConditionLock in an initialState. |
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53 */ |
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54 public ConditionLock (int initialState) { |
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55 state = initialState; |
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56 } |
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57 |
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58 /** |
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59 * Acquires the lock when the state variable equals the desired state. |
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60 * |
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61 * @param desiredState the desired state |
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62 * @exception java.lang.InterruptedException if any thread has |
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63 * interrupted this thread. |
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64 */ |
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65 public synchronized void lockWhen(int desiredState) |
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66 throws InterruptedException |
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67 { |
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68 while (state != desiredState) { |
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69 wait(); |
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70 } |
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71 lock(); |
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72 } |
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73 |
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74 /** |
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75 * Releases the lock, and sets the state to a new value. |
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76 * @param newState the new state |
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77 */ |
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78 public synchronized void unlockWith(int newState) { |
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79 state = newState; |
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80 unlock(); |
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81 } |
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82 } |
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