Calculator.java

import java.awt.*;
import java.awt.event.*;
class Calculator extends Frame implements ActionListener
{
TextField tf;
Panel p;
Button b;
int n1,n2,res;
char op;
Calculator( )
{
setSize(300,400);
setVisible(true);
setTitle("Calculator");
setLayout(new BorderLayout( ));
tf=new TextField(25);
add(tf,BorderLayout.NORTH);
p=new Panel(new GridLayout(4,4));
add(p,BorderLayout.CENTER);
String a[ ]={"7","8","9","/","4","5","6","-","1","2","3","*","0","C","=","+"};
for(String i:a)
{
   b=new Button(i);
   p.add(b);
   b.addActionListener(this);
}
addWindowListener(new WindowAdapter()
{ 
public void windowClosing(WindowEvent w)
{  System.exit(0);}
});
}
public void actionPerformed(ActionEvent ae)
{
 String s=ae.getActionCommand();
 if(s.matches("[0-9]"))
 {
  tf.setText(tf.getText()+s);
 }
 else if(s.equals("C"))
 {
  tf.setText("");
 }
 else if(s.equals("+")||s.equals("-")||s.equals("*")||s.equals("/"))
 {
  n1=Integer.parseInt(tf.getText());
  op=s.charAt(0);
  tf.setText("");
 }
 else if(s.equals("="))
 {
  n2=Integer.parseInt(tf.getText());
  switch(op)
  {
   case '+': 
    res=n1+n2;
    break;
   case '-':
    res=n1-n2;
    break;
   case '*':
    res=n1*n2;
    break;
   case '/':
    try
    {
     res=n1/n2;
    }
    catch(ArithmeticException i)
    {
     tf.setText("Cannot divide by Zero");
     return;
    }
    break;
  }
  tf.setText(String.valueOf(res));
  }
}
public static void main(String args[])
{
 new Calculator();
}
}