CODEWITHSUNDEEP
javamultithreadingswing
skystar7
skystar7

Reputation: 4597

strange behaviour of javax.swing.Timer

in main if the following code is used 

Timer timer = new Timer(200, new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("boo");
    }
});

timer.start();
Thread.sleep(3000);

boo will be printed every 200 milliseconds as expected.

While

Timer timer = new Timer(200, new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("boo");
    }
});

timer.start();

nothing will be output!

Upvotes: 0

Views: 217

Answers (4)

mKorbel
mKorbel

Reputation: 109823

1) this code wokrs and in all cases is correct 

Timer timer = new Timer(200, new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("boo");
    }
});    
timer.start();

you have to check if javax.swing.Timer#setRepeats() have true value (default value), if isn't changed, otherwise you have a code that block Event Dispatch Thread, thenafter Swing's Timer too,

2) don't use Thread.sleep(int) during EDT, and untill Sleep ended caused this code block for EDT,

Upvotes: 1

Jesper
Jesper

Reputation: 206996

Is that the complete program (is that the only code in your main method)? If yes, then in the second case the program ends before the timer goes off, so it won't print anything, because the program is finished almost immediately.

Upvotes: 1

Amir Afghani
Amir Afghani

Reputation: 38561

Could it be that the Thread.sleep is on the main thread and that the reason nothing is printed in the second case is that the main thread goes away and the program exits?

Upvotes: 1

Ernest Friedman-Hill
Ernest Friedman-Hill

Reputation: 81724

Presumably the code you're showing is in main(). When main() returns, the program exits before the timer thread has a chance to get going. The sleep gives the JVM enough time to create the other thread, which then allows the JVM to keep running.

Upvotes: 3

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