132 lines
5.9 KiB
HTML
132 lines
5.9 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE html
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html lang="en-us" xml:lang="en-us">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="security" content="public" />
|
|
<meta name="Robots" content="index,follow" />
|
|
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
|
|
<meta name="DC.Type" content="reference" />
|
|
<meta name="DC.Title" content="Example: Use mutexes in Java" />
|
|
<meta name="abstract" content="This example shows a Java program creating a critical section of code. In Java, any object or array can function similarly to a mutual exclusion (mutex) using the synchronized keyword on a block of code or a method." />
|
|
<meta name="description" content="This example shows a Java program creating a critical section of code. In Java, any object or array can function similarly to a mutual exclusion (mutex) using the synchronized keyword on a block of code or a method." />
|
|
<meta name="DC.Relation" scheme="URI" content="rzahwmutco.htm" />
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Format" content="XHTML" />
|
|
<meta name="DC.Identifier" content="rzahwex4-ex4rx" />
|
|
<meta name="DC.Language" content="en-us" />
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
|
<!-- US Government Users Restricted Rights -->
|
|
<!-- Use, duplication or disclosure restricted by -->
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
|
<title>Example: Use mutexes in Java</title>
|
|
</head>
|
|
<body id="rzahwex4-ex4rx"><a name="rzahwex4-ex4rx"><!-- --></a>
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
|
<h1 class="topictitle1">Example: Use mutexes in Java</h1>
|
|
<div><p>This example shows a Java™ program creating a critical section
|
|
of code. In Java, any object or array can function similarly to
|
|
a mutual exclusion (mutex) using the synchronized keyword on a block of code
|
|
or a method.</p>
|
|
<div class="section"><div class="note"><span class="notetitle">Note:</span> By using the code examples, you agree to the terms of the <a href="codedisclaimer.htm">Code license and disclaimer information</a>.</div>
|
|
</div>
|
|
<div class="example"> <pre>/*
|
|
FileName: ATEST16.java
|
|
The output of this example is as follows:
|
|
Entered the testcase
|
|
Synchronize to prevent access to shared data
|
|
Create/start the thread
|
|
Thread Thread-1: Entered
|
|
Thread Thread-2: Entered
|
|
Wait a bit until we're 'done' with the shared data
|
|
Thread Thread-3: Entered
|
|
Unlock shared data
|
|
Thread Thread-1: Start critical section, in synchronized block
|
|
Thread Thread-1: End critical section, leave synchronized block
|
|
Thread Thread-2: Start critical section, in synchronized block
|
|
Thread Thread-2: End critical section, leave synchronized block
|
|
Thread Thread-3: Start critical section, in synchronized block
|
|
Thread Thread-3: End critical section, leave synchronized block
|
|
Wait for the threads to complete
|
|
Testcase completed
|
|
*/
|
|
import java.lang.*;
|
|
|
|
|
|
public class ATEST16 {
|
|
public final static int NUMTHREADS = 3;
|
|
public static int sharedData = 0;
|
|
public static int sharedData2 = 0;
|
|
/* Any real java object or array would suit for synchronization */
|
|
/* We invent one here since we have two unique data items to synchronize */
|
|
/* An in this simple example, they're not in an object */
|
|
static class theLock extends Object {
|
|
}
|
|
static public theLock lockObject = new theLock();
|
|
|
|
static class theThread extends Thread {
|
|
public void run() {
|
|
System.out.print("Thread " + getName() + ": Entered\n");
|
|
synchronized (lockObject) {
|
|
/********** Critical Section *******************/
|
|
System.out.print("Thread " + getName() +
|
|
": Start critical section, in synchronized block\n");
|
|
++sharedData; --sharedData2;
|
|
System.out.print("Thread " + getName() +
|
|
": End critical section, leave synchronized block\n");
|
|
/********** Critical Section *******************/
|
|
}
|
|
}
|
|
}
|
|
|
|
public static void main(String argv[]) {
|
|
theThread threads[] = new theThread[NUMTHREADS];
|
|
System.out.print("Entered the testcase\n");
|
|
|
|
System.out.print("Synchronize to prevent access to shared data\n");
|
|
synchronized (lockObject) {
|
|
|
|
System.out.print("Create/start the thread\n");
|
|
for (int i=0; i<NUMTHREADS; ++i) {
|
|
threads[i] = new theThread();
|
|
threads[i].start();
|
|
}
|
|
|
|
System.out.print("Wait a bit until we're 'done' with the shared data\n");
|
|
try {
|
|
Thread.sleep(3000);
|
|
}
|
|
catch (InterruptedException e) {
|
|
System.out.print("sleep interrupted\n");
|
|
}
|
|
System.out.print("Unlock shared data\n");
|
|
}
|
|
|
|
System.out.print("Wait for the threads to complete\n");
|
|
for(int i=0; i <NUMTHREADS; ++i) {
|
|
threads[i].join();
|
|
}
|
|
catch (InterruptedException e) {
|
|
System.out.print("Join interrupted\n");
|
|
}
|
|
}
|
|
|
|
System.out.print("Testcase completed\n");
|
|
System.exit(0);
|
|
}
|
|
|
|
}
|
|
</pre>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahwmutco.htm" title="A mutual exclusion (mutex) is used cooperatively between threads to ensure that only one of the cooperating threads is allowed to access the data or run certain application code at a time.">Mutexes and threads</a></div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html> |