Question

JButton btnNewButton = new JButton("Register Student");
btnNewButton.addMouseListener(new MouseAdapter() {
    @Override
    public void mouseClicked(MouseEvent arg0) {
        RegisterStudent panel_1 = new RegisterStudent();
        panel_1.setVisible(true);
    }
});
btnNewButton.setBounds(0, 162, 167, 37);
panel.add(btnNewButton);

Is there a way, that IF one specific window is open already, it cant be opened once again?
Because, i don’t want the user to click on a button several times, causing several windows to be opened with the same content?

Answer 1

Create the panel_1 variable outside of the mouse listener block and initialize it to null. When the mouse is clicked, check if panel_1 is null, and if it is, create it.

final RegisterStudent panel_1 = new RegisterStudent();
JButton btnNewButton = new JButton("Register Student");
btnNewButton.addMouseListener(new MouseAdapter() {
    @Override
    public void mouseClicked(MouseEvent arg0) {
        panel_1.setVisible(true);
    }
});
btnNewButton.setBounds(0, 162, 167, 37);
panel.add(btnNewButton);