JPasswordField

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPasswordField;

public class Test
{
    public static void main(String[] args)
    {
        final JPasswordField pwd = new JPasswordField();
        
        final JCheckBox check = new JCheckBox("Afficher");
        check.addActionListener(new ActionListener()
        {
            private final char defaultChar = pwd.getEchoChar();
            
            @Override
            public void actionPerformed(ActionEvent e) 
            {
                if (check.isSelected())
                    pwd.setEchoChar('\0');
                else
                    pwd.setEchoChar(defaultChar);
            }
        });
        
        final JFrame frame = new JFrame();
        frame.setLayout(new GridLayout(2,1));
        frame.setLocationRelativeTo(null);
        frame.add(pwd);
        frame.add(check);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        
    }
}