Simple Calculator

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

/*
<applet code="Cal" width=300 height=300>
</applet>
*/

public class Cal extends Applet
implements ActionListener
{
String msg=" ";
int v1,v2,result;
TextField t1;
Button b[]=new Button[10];
Button add,sub,mul,div,clear,mod,EQ;
char OP;
public void init()
{
Color k=new Color(120,89,90);
setBackground(k);
t1=new TextField(10);
GridLayout gl=new GridLayout(4,5);
setLayout(gl);
for(int i=0;i<10;i++)
{
b[i]=new Button(""+i);
}
add=new Button("add");
sub=new Button("sub");
mul=new Button("mul");
div=new Button("div");
mod=new Button("mod");
clear=new Button("clear");
EQ=new Button("EQ");
t1.addActionListener(this);
add(t1);
for(int i=0;i<10;i++)
{
add(b[i]);
}
add(add);
add(sub);
add(mul);
add(div);
add(mod);
add(clear);
add(EQ);
for(int i=0;i<10;i++)
{
b[i].addActionListener(this);
}
add.addActionListener(this);
sub.addActionListener(this);
mul.addActionListener(this);
div.addActionListener(this);
mod.addActionListener(this);
clear.addActionListener(this);
EQ.addActionListener(this);
}

public void actionPerformed(ActionEvent ae)
{
String str=ae.getActionCommand();
char ch=str.charAt(0);
if ( Character.isDigit(ch))
t1.setText(t1.getText()+str);
else
if(str.equals("add"))
{
v1=Integer.parseInt(t1.getText());
OP='+';
t1.setText("");
}
else if(str.equals("sub"))
{
v1=Integer.parseInt(t1.getText());
OP='-';
t1.setText("");
}
else if(str.equals("mul"))
{
v1=Integer.parseInt(t1.getText());
OP='*';
t1.setText("");
}
else if(str.equals("div"))
{
v1=Integer.parseInt(t1.getText());
OP='/';
t1.setText("");
}
else if(str.equals("mod"))
{
v1=Integer.parseInt(t1.getText());
OP='%';
t1.setText("");
}
if(str.equals("EQ"))
{
v2=Integer.parseInt(t1.getText());
if(OP=='+')
result=v1+v2;
else if(OP=='-')
result=v1-v2;
else if(OP=='*')
result=v1*v2;
else if(OP=='/')
result=v1/v2;
else if(OP=='%')
result=v1%v2;
t1.setText(""+result);
}
if(str.equals("clear"))
{
t1.setText("");
}
}
}