Simple java Calculator program

JAVA CALULATOR PROGRAM:

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
//<applet code="cal" width=500 height=500></applet>
public class cal  extends Applet implements ActionListener
{
int a,b,c;
TextField t1;
Button

b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;
String s,s1,s2,s3,s4;
public void init()
{
setLayout(null);
t1=new TextField(10);
t1.setBounds(80,200,260,40);
add(t1);
b1=new Button("0");
b2=new Button("1");
b3=new Button("2");
b4=new Button("3");
b5=new Button("4");
b6=new Button("5");
b7=new Button("6");
b8=new Button("7");
b9=new Button("8");
b10=new Button("9");
b11=new Button("+");
b12=new Button("-");
b13=new Button("*");
b14=new Button("/");
b15=new Button("=");
b16=new Button("CLR");
b1.setBounds(90,260,40,30);
add(b1);
b2.setBounds(140,260,40,30);
add(b2);
b3.setBounds(190,260,40,30);
add(b3);
b4.setBounds(240,260,40,30);
add(b4);
b5.setBounds(290,260,40,30);
add(b5);
b6.setBounds(90,300,40,30);
add(b6);
b7.setBounds(140,300,40,30);
add(b7);
b8.setBounds(190,300,40,30);
add(b8);
b9.setBounds(240,300,40,30);
add(b9);
b10.setBounds(290,300,40,30);
add(b10);
b11.setBounds(90,340,40,30);
add(b11);
b12.setBounds(140,340,40,30);
add(b12);
b13.setBounds(190,340,40,30);
add(b13);
b14.setBounds(240,340,40,30);
add(b14);
b15.setBounds(290,340,40,30);
add(b15);
b16.setBounds(90,380,70,20);
add(b16);
b1.addActionListener(this);
b2.addActionListener(this);
b3.addActionListener(this);
b4.addActionListener(this);
b5.addActionListener(this);
b6.addActionListener(this);
b7.addActionListener(this);
b8.addActionListener(this);
b9.addActionListener(this);
b10.addActionListener(this);
b11.addActionListener(this);
b12.addActionListener(this);
b13.addActionListener(this);
b14.addActionListener(this);
b15.addActionListener(this);
b16.addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
repaint();
s=ae.getActionCommand();
if(s.equals("0") || s.equals("1") || s.equals("2")||

s.equals("3") || s.equals("4") || s.equals("5")||s.equals

("6")||s.equals("7")||s.equals("8")||s.equals("9"))
{
s1=t1.getText()+s;
t1.setText(s1);
}

if(s.equals("+"))
{
s2=t1.getText();
t1.setText("");
s3="+";
}

if(s.equals("-"))
{
s2=t1.getText();
t1.setText("");
s3="-";
}

if(s.equals("*"))
{
s2=t1.getText();
t1.setText("");
s3="*";
}

if(s.equals("/"))
{
s2=t1.getText();
t1.setText("");
s3="/";
}

if(s.equals("="))
{
s4=t1.getText();
a=Integer.parseInt(s2);
b=Integer.parseInt(s4);
if(s3.equals("+"))
c=a+b;

if(s3.equals("-"))
c=a-b;

if(s3.equals("*"))
c=a*b;
if(s3.equals("/"))
c=a/b;
t1.setText(String.valueOf(c));
}

if(s.equals("CLR"))
{

t1.setText("");

}

}
public void paint(Graphics g)
{
setBackground(Color.green);
g.drawRect(80,200,260,200);
showStatus("ASHUSOFTECH");
g.drawString("CALCULATER",200,50);
}
}