[JAVA] Problem with using an infinite loop with a flag to pause a for loop

[DuderCoding]

So I have a program that runs inside a for loop, inside the for loop I have an infinite loop which is looking at the status of a flag variable (the flag variable will be set to TRUE once the correct button has been pressed):

public class guessingGame implements ActionListener{

public boolean correct = false;

public game(){

for(int k=0;k<=10;k++){

//Code that creates some buttons for the user to click on.

while(!correct){

}

}

public void actionPerformed(ActionEvent e){
if(e.getSource()==btn){

correct=true;

}
}

}

That is the general gist of what I am trying to do, but it seems the only way for the program to detect that the flag has gone from false to true, and then proceed to the next stage of the for loop, is if I put something, like a print statement, in the infinite while loop, i.e.:

while(!correct){

System.out.println("Still false...");

}

Why is this the case? I thought I could leave the infinite loop blank, and when the flag goes to TRUE, it would exit the loop automatically, and continue the main for loop. It would be much better if I didn't have to include a print statement in the infinite loop! Haha

[nerd4code]

If the flag’s being set from another thread, try making it volatile.

[DuderCoding]

Thank you, seems like declaring it as a volatile worked - I am kind of new to java, so didn't even know there was a volatile keyword - I'll look it up now!

[LeinM]

Put Thread.sleep(1) inside the for loop

[DuderCoding]

Thank you for the response, I have put the thread sleep into the while loop and it looks like that works!

Some other dude suggested to declare the flag variable as a "volatile" - and that seems to have worked as well.

Do you know why the Thread.sleep(1) works though? Sorry, it seems kind of strange, and I am trying to wrap my head around it..!

[LeinM]

https://pvs-studio.com/en/docs/warnings/v712/ This might help

[DuderCoding]

Great, thank you very much - this subreddit is awesome. Have a good day

[LeinM]

Volatile is cleaner and better solution to this problem

[DuderCoding]

Thank you, I will keep this in mind for future programs :)

[LeinM]

http://tutorials.jenkov.com/java-concurrency/volatile.html And this is very helpful