Mutex: Difference between revisions

Java also has the synchronized keyword, which allows almost any object to be used to enforce mutual exclusion.

<lang java>public class Main {

static Object mutex = new Object();

static int i = 0;

public void addAndPrint()

{

System.out.print("" + i + " + 1 = ");

i++;

System.out.println("" + i);

}

public void subAndPrint()

{

System.out.print("" + i + " - 1 = ");

i--;

System.out.println("" + i);

}

public static void main(String[] args){

final Main m = new Main();

new Thread() {

public void run()

{

while (true) { synchronized(m.mutex) { m.addAndPrint(); } }

}

}.start();

new Thread() {

public void run()

{

while (true) { synchronized(m.mutex) { m.subAndPrint(); } }

}

}.start();

}

}</lang>

The "synchronized" keyword actually is a form of [[monitor]], which was a later-proposed solution to the same problems that mutexes and semaphores were designed to solve. More about synchronization may be found on Sun's website - http://java.sun.com/docs/books/tutorial/essential/concurrency/sync.html , and more about monitors may be found in any decent operating systems textbook.