JAVA codes for Image Comparison

You mean to compare two images whether they are equal?

Yup.. Irrespective of size of the image, I need to write a JAVA code, where it'l compare the image given as an input with another image already contained in my database and return true if comparison matches. For Eg., if I give an image of computer, my code should be able to compare with images of computer in my database and return the o/p.. Database codin part, leave it upto me. I just need help in, how Java compares two images..

Sorry for late reply actually i am busy in exams.
Well i have an idea how to compare two images check this code.
Use it to compare two images hope it works.But it's just an idea you can edit it on your own way.

import javax.swing.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
/*<Applet code="comp" height=400 width=400></applet>*/
public class comp extends JApplet implements ActionListener
{
Button b;
String str,str1;
public void init()
{
b=new Button("submit");
add(b);
setLayout(new FlowLayout());
b.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
repaint();
byte b1[]=new byte[60000];
byte b2[]=new byte[60000];
try
{
int i=0;
FileInputStream f1=new FileInputStream("kk.jpg");
f1.read(b1);
FileInputStream f2=new FileInputStream("kk1.jpg");
f2.read(b2);
while(b1!=3 || b2!=3)
{
if(b1==b2)
i++;
else
{
str="not matched";
break;
}
}
if(b1[i-1]==b2[i-1])
{
str="matched";
str1=Integer.toString(i);
}
}
catch(Exception ee)
{
System.out.println("Exception caught");
}
}
public void paint(Graphics g)
{
g.drawString(str,100,100);
g.drawString(str1,200,200);
}
}