How do I close a socket or an I/O Stream in the windowClosing event of a Java window?

Question

I'm having trouble closing my socket when exiting my Java application. I thought that an easy way to make sure the socket gets closed is to hook it on windowClosing in a Swing JFrame like this:

    frame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            input.close();
            output.close();
            socket.close();

            frame.dispose();
            System.exit(0);
        }
    });

But then I have to handle the IOException that close() creates, and I can't throw it when overriding the event method like that.

How can I make sure that my streams and my socket get closed when the program does?

Thanks.

Answer 1

You don't need to throw it. Just catch it.

try {
  if(null != input) {
    input.close();
  }
} catch(IOException ex) {
  // Log or ignore the exception.
}

Also, you don't need to call the dispose() or System.exit(0); methods if your main application Frame is already closing.

Make sure that the following is set on your main Application JFrame.

 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Answer 2

Make sure that you don't block the event dispatch thread -- the close() methods might block in some cases.

Answer 3

Solved this problem by catching the IOException, as S73417H said, and making sure to close the streams in this order: output, input, socket. Thanks to everyone who answered.