import java.awt.*;
import java.applet.*;
import java.awt.event.*;
public class add extends Applet implements ActionListener
{  
   TextField b1,b2,b3;
   Button a1,a2,a3,a4;
   public void init()
{
    b1=new TextField(4);
    b2=new TextField(4);
    b3=new TextField(5);
    a1=new Button("加");
    a2=new Button("減");
    a3=new Button("乘");
    a4=new Button("除");
    add(b1);add(b2);add(b3);add(a1);add(a2);add(a3);add(a4);
    a1.addActionListener(this);
    a2.addActionListener(this);
    a3.addActionListener(this);
    a4.addActionListener(this);
}
   public void actionPerformed(ActionEvent e)
{
    double n1,n2,n3;
    n1=Double.valueOf(b1.getText()).doubleValue();
    n2=Double.valueOf(b2.getText()).doubleValue();
    if(e.getSource()==a1){n3=n1+n2;b3.setText(""+n3);}
  else if(e.getSource()==a2){n3=n1-n2;b3.setText(""+n3);}
    else if(e.getSource()==a3){n3=n1*n2;b3.setText(""+n3);}
     else {n3=n1/n2;b3.setText(""+n3);}
}

}