Java JOptionPane.PLAIN_MESSAGE

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;

public class Main extends JFrame implements ActionListener {
   private final JButton btn1 = new JButton("Click Me!");
   private final JButton btn2 = new JButton("No, click me!");
   //from  w ww  . j  a  va 2  s  . co m
   public Main() {
      super();
      this.setLayout(new FlowLayout());
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      btn1.addActionListener(this);
      btn2.addActionListener(this);
      getContentPane().add(btn1);
      getContentPane().add(btn2);
      pack();
      setVisible(true);
   }
   
   @Override
   public void actionPerformed(ActionEvent ev) {
      String message = "";
      if (ev.getSource() == btn1)
         message = "First button was clicked";
      else if (ev.getSource() == btn2)
         message = "Second button was clicked";

      JOptionPane.showMessageDialog(null, 
            message, "Aw yeah!",
            JOptionPane.PLAIN_MESSAGE);
   }
   
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            new Main();
      }
      });
   }
}