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 Barrier utility class.
27 * @author  Mandy Chung
28 */
29
30public class Barrier {
31    private Object go = new Object();
32    private int count;
33    private int waiters = 0;
34
35    public Barrier(int count) {
36        if (count <= 0) {
37            throw new IllegalArgumentException();
38        }
39        this.count = count;
40    }
41
42    public void set(int count) {
43        if (waiters != 0) {
44            throw new IllegalArgumentException();
45        }
46        this.count = count;
47        this.waiters = 0;
48    }
49
50    public void await() {
51        synchronized (go) {
52            waiters++;
53            while (count > 0) {
54                try {
55                    go.wait();
56                } catch (InterruptedException e) {
57                    e.printStackTrace();
58                    throw new InternalError();
59                }
60            }
61            waiters--;
62        }
63    }
64    public void signal() {
65        synchronized (go) {
66            count--;
67            go.notifyAll();
68        }
69    }
70
71    public int getWaiterCount() {
72        synchronized (go) {
73            return waiters;
74        }
75    }
76}
77