My first java application - simple calculator

yup!!! this is my first application in JAVA. its a calculator, yeh yeh it has bugs and 'm trying to take them off. but still eager to post this in my blog ;).

Anyways bug is the part of software cycle u see so its a bugfull calculator n soon a bugfree will be launched when i will learn jar creation. Kepp smiling and yes the mantra Happiness Always. dont forget it. cheers.

Please find the code below;

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;

public class CalC implements ActionListener {
private JFrame f;
private JButton b1, b2, b3, b4, b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16,b17,b18;
private JLabel l1;
public int sum = 0,res=0,n1=0,n2=0,sum1=1,d,n3=1;
public char a;

public CalC() {
f = new JFrame("Tabu's calculator");
b1 = new JButton("1");
b1.addActionListener(this);
b2 = new JButton("2");
b2.addActionListener(this);
b3 = new JButton("3");
b3.addActionListener(this);
b4 = new JButton("4");
b4.addActionListener(this);
b5 = new JButton("5");
b5.addActionListener(this);
b6 = new JButton("6");
b6.addActionListener(this);
b7 = new JButton("7");
b7.addActionListener(this);
b8 = new JButton("8");
b8.addActionListener(this);
b9 = new JButton("9");
b9.addActionListener(this);
b16 = new JButton("0");
b16.addActionListener(this);
b17 = new JButton("Reset");
b17.addActionListener(this);
b10 = new JButton("+");
b10.addActionListener(this);
b11 = new JButton("-");
b11.addActionListener(this);
b12 = new JButton("*");
b12.addActionListener(this);
b13 = new JButton("/");
b13.addActionListener(this);
b14 = new JButton("%");
b14.addActionListener(this);
b15 = new JButton("=");
b15.addActionListener(this);
b18 = new JButton("Exit");
b18.addActionListener(this);
l1 = new JLabel(" ");
}



public void launchFrame() {
f.setLayout (new GridLayout(7,3));
f.add(b1);
f.add(b2);
f.add(b3);
f.add(b4);
f.add(b5);
f.add(b6);
f.add(b7);
f.add(b8);
f.add(b9);
f.add(b16);
f.add(b10);
f.add(b11);
f.add(b12);
f.add(b13);
f.add(b14);
f.add(b15);
f.add(b17);
f.add(b18);
f.add(l1);
f.pack();
f.setSize(300,300);
f.setLocation(200,200);
f.setVisible(true);
}

public void actionPerformed (ActionEvent ev)
{
try
{
if(ev.getSource()==b1)
{
n1=n1*10+1;
l1.setText(" " +n1);

}

if(ev.getSource()==b2)
{
n1=n1*10+2;
l1.setText(" " +n1);
}

if(ev.getSource()==b3)
{
n1=n1*10+3;
l1.setText(" " +n1);
}

if(ev.getSource()==b4)
{
n1=n1*10+4;
l1.setText(" " +n1);
}

if(ev.getSource()==b5)
{
n1=n1*10+5;
l1.setText(" " +n1);

}

if(ev.getSource()==b6){
n1=n1*10+6;
l1.setText(" " +n1);
}

if(ev.getSource()==b7)
{
n1=n1*10+7;
l1.setText(" " +n1);
}

if(ev.getSource()==b8)
{
n1=n1*10+8;
l1.setText(" " +n1);
}

if(ev.getSource()==b9)
{
n1=n1*10+9;
l1.setText(" " +n1);
}

if(ev.getSource()==b16)
{
n1=n1*10+0;
l1.setText(" " +n1);
}

if(ev.getSource()==b10)
{
n2=n1;
n1=0;
sum= sum+n2;
l1.setText(" " +sum);
a='+';
}

if(ev.getSource()==b11)
{

if (n3==1)
{
n2=n1;
sum = n2;
l1.setText(" " +n2);
n3=0;
n1=0;
a='-';
}

else

{
n2=n1;
n1=0;
sum=sum-n2;
l1.setText(" " +sum);
n3=0;
a='-';
}
}

if(ev.getSource()==b12)
{
n2=n1;
n1=0;
sum1=sum1*n2;
l1.setText(" " +sum1);
a='*';
}


if(ev.getSource()==b13)
{
n2=n1;
n1=0;
l1.setText("singlw div only");
a='/';
}

if(ev.getSource()==b14)
{
n2=n1;
n1=0;
l1.setText(" " +n2);
a='%';
}


if(ev.getSource()==b17)
{
n1=0;
n2=0;
sum=0;
res=0;
l1.setText("00");
sum1=0;
n3=1;
}

if(ev.getSource()==b18)
{
f.setVisible(false);
}


if(ev.getSource()==b15)
{
switch (a)
{
case '+':
res =sum+ n1;
l1.setText(" " +res);
sum=res;
break;

case '-':
res = sum-n1;
l1.setText(" " +res);
sum=res;
break;


case '*':
res = n1*sum1;
l1.setText(" " +res);
sum1=res;
break;

case '/':


if(n2==0)
1.setText("/by0");
else

{
res = n2/n1;
l1.setText(" " +res);
}

break;


case '%':
res = n2%n1;
l1.setText(" " +res);
n1=0;
n2=0;
sum=0;
break;


}
a=' ';

}

}

catch(Exception e)
{
System.out.println("Error: " +e.getMessage());
}
}



public static void main(String args[]) {
CalC grid = new CalC();
grid.launchFrame();
}
}