How can I change JLabel text during work of JButton?

Question

I would like my button 'licz' to: change text value of info to ''loading'', do something and change 'info' to "done". ('licz' is here a JButton, 'info' JLabel)

        licz.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            info.setText("Loading..."); // Here
            if(go())
            {   
                brute(0);
                info.setText("Done!"); //here
                if(odwrot)
                    JOptionPane.showMessageDialog(frame, "good");
                else
                    JOptionPane.showMessageDialog(frame, "bad");
            }
            else
            {
                JOptionPane.showMessageDialog(frame, "bad");
                info.setText("Done"); // And here
            }

        }
    });

But the program makes "something" first, changes 'info' label to "loading" and immediately to "done", how to keep these in case?

Answer 1

The event of actionPerformed is handled on the event handling thread, and should terminate fast to have a responsive GUI. Hence call invokeLater.

licz.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        info.setText("Loading...");
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                boolean good = false;
                if (go())
                {   
                    brute(0);
                    good = odwrot;
                }
                JOptionPane.showMessageDialog(frame, good ? "good" : "bad");
                info.setText("Done");
            }
        });
    }
});

Or in java 8:

licz.addActionListener((e) -> {
    info.setText("Loading...");
    EventQueue.invokeLater(() -> {
        boolean good = false;
        if (go())
        {   
            brute(0);
            good = odwrot;
        }
        JOptionPane.showMessageDialog(frame, good ? "good" : "bad");
        info.setText("Done");
    });
});