Problem with keyEvent

Question

i wrote this code
button.setMnemonic(KeyEvent.VK_ENTER);     and when i pressed the enter key ,the button did not respond
why?
but when i changed the code into
button.setMnemonic(KeyEvent.VK_D);when i pressed Alt+D The button was activated!
was there something missing in the first code?

Answer 1

"How can I make a JButton the default button of the root pane, so that pressing enter presses that button?"
Here, I make the final button the default button.
import java.awt.event.*;
import javax.swing.*;
public class DefaultButtonExample implements Runnable, ActionListener {
    public void run() {
        JPanel p = new JPanel();
        JButton btn = null;
        for(int i=0; i<5; ++i) {
            btn = new JButton("button #" + i);
            btn.addActionListener(this);
            p.add(btn);
        JFrame f = new JFrame("DefaultButtonExample");
        f.getRootPane().setDefaultButton(btn); //<<---
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(p);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    public void actionPerformed(ActionEvent evt) {
        System.out.println(evt.getActionCommand());
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new DefaultButtonExample());
}