1 /*

     2  * Copyright (c) 2003, 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.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 /*

    25  * @bug     4530538

    26  * @summary A semaphore utility class.

    27  * @author  Mandy Chung

    28  */

    29 

    30 public class Semaphore {

    31     private Object go = new Object();

    32     private int semaCount;

    33     private int waiters = 0;

    34 

    35     public Semaphore() {

    36         semaCount = 0;

    37     }

    38 

    39     public Semaphore(int initialCount) {

    40         semaCount = initialCount;

    41     }

    42 

    43     public void semaP() {

    44         synchronized (go) {

    45             waiters++;

    46             while (semaCount == 0) {

    47                 try {

    48                     go.wait();

    49                 } catch (InterruptedException e) {

    50                     e.printStackTrace();

    51                     throw new InternalError();

    52                 }

    53             }

    54             semaCount--;

    55             waiters--;

    56         }

    57     }

    58     public void semaV() {

    59         synchronized (go) {

    60             semaCount++;

    61             go.notify();

    62         }

    63     }

    64 

    65     public int getWaiterCount() {

    66         synchronized (go) {

    67             return waiters;

    68         }

    69     }

    70 

    71     public Object getLock() {

    72         return go;

    73     }

    74 }