import java.applet.*;
import java.awt.*;
import java.awt.event.*;


public class Button2a extends Applet implements ActionListener{
      Button button1=new Button("ボタン1");
      Button button2=new Button("ボタン2");
      Button button3=new Button("ボタン3");
      Button button4=new Button("ボタン4");
      int a=0;


public void init (){
       add(button1);
       add(button2);
       add(button3);
       add(button4);
       button1.addActionListener(this);
       button2.addActionListener(this);
       button3.addActionListener(this);
       button4.addActionListener(this);
     }


public void actionPerformed(ActionEvent evt){
         if(evt.getSource()==button1) {a=1;}
         if(evt.getSource()==button2) {a=2;}
         if(evt.getSource()==button3) {a=3;}
         if(evt.getSource()==button4) {a=4;}
         repaint();
}

public void paint (Graphics g){
         g.drawString("a="+a,50,50);
         }
}