setVisible

gistfile1.java

import java.awt.BorderLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class VisibleButton {
  public static void main(String[] args) {
    final JFrame f = new JFrame();
    f.setSize(800, 600);
    final JPanel p = new JPanel(new BorderLayout());
    final JButton bottom = new JButton("BYE");
    final JButton top = new JButton("HI");
    top.addMouseListener(new MouseAdapter() {

      @Override
      public void mouseClicked(MouseEvent e) {
        bottom.setVisible(true);
      }
    });
    p.add(top, BorderLayout.NORTH);
    bottom.setVisible(false);
    p.add(bottom, BorderLayout.SOUTH);

    f.setContentPane(p);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
}