Thread only running correctly if there is a System.out.println() inside the while true loop

Question

Basicly, I\'m making a game which to update the players position, it uses this thread:

@Override
public void run() {
    while(true) {
        System.out.pri         


        

Answer 1

You didn't post the code to updatePos. But at a minimum, you need to make that method, as well as keyPressed (and anything else that uses x and/or y) synchronized.

Alternatively you can make both x and y volatile, but then x and y could get updated out of lockstep.

But without any memory synchronisation, changes from one thread are not guaranteed to be observable from another thread.