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.
  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 }