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

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