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 }