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Lock Mechanism ?  RSS feed

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class ThreadA {
public static void main(String [] args) {
ThreadB b = new ThreadB();
synchronized(b) {
try {
System.out.println("Waiting for b to complete...");
} catch (InterruptedException e) {}
System.out.println("Total is: " + b.total);
class ThreadB extends Thread {
int total;
public void run() {
synchronized(this) {
for(int i=0;i<100;i++) {
total += i;

Can somebody please explain the lock mechanism in the above code ?

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check the following code (your code) with comments.
Please read the comments in the numerated order (1-2-3-4-5-6-7)

In other words, the synchronize ensure that only a single thread can synchronize and execute inside the block.
The "wait" will make the thread wait until the other thread notify it, and also release the "lock" on the synchronized object.
You cannot "wait" or "notify" outside of a synchronized block.

Anyone else feel free to provide more or better details, it is not too easy to describe

[ January 22, 2008: Message edited by: Alex Belisle Turcot ]
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