CAPTCHA using Java

             GENERATING & VALIDATING CAPTCHA

INTRODUCTION

CAPTCHA (an acronym for Completely Automated Public Turing test to tell Computers and Human Apart") is a type of challenge-response test used in computing to determine whether or not the user is human. 

For more information click here.

Its just a simple program to generate CAPTCHA using JAVA.

PROGRAM

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

/*

<applet code="Captcha.class"  width=300 height=400></applet>

*/

public class Captcha extends JApplet{
JLabel text,text1,captcha,result;
JTextField edit;
JButton submit,refresh;
String str = "ABCD123";
int n=str.length();
char ran;
char[] ran1=new char[7];
String ran2;
public Captcha(){
JFrame frame = new JFrame("CAPTCHA PAGE!!");
frame.setLayout(new FlowLayout());
frame.setSize(300, 300);
text = new JLabel("This is a Computer generated Login Page. You need to enter the text (shown below) to proceed. ");
text1 = new JLabel("CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) !!");
result = new JLabel();
captcha = new JLabel();
edit = new JTextField(7);
Random r = new Random();
for(int i=0;i<n;i++)
{
ran=str.charAt(r.nextInt(n));
ran1[i]=ran;
ran2=new String(ran1);
}
captcha.setText(ran2);
submit =new JButton("SUBMIT..");
submit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
if(edit.getText().compareTo(captcha.getText())==0)
{
result.setText("SUCCESSFULL !!!!");
}
else
{
result.setText("CAPTCHA ERROR !!!!");
}
}
});
refresh = new JButton("REFRESH");
refresh.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
Random r = new Random();
for(int i=0;i<n;i++)
{
ran=str.charAt(r.nextInt(n));
ran1[i]=ran;
ran2=new String(ran1);
}
captcha.setText(ran2);
}
});
frame.add(text);
frame.add(text1);
frame.add(captcha);
frame.add(edit);
frame.add(submit);
frame.add(refresh);
frame.add(result);
frame.setVisible(true);
}
}

INSTRUCTIONS

To run the program in Windows:

• Save above program to any file with extension 'java', eg-"Captcha.java" on any directory. 
• Open Command Prompt: Start->Run->cmd
• Go to the directory where you have stored the program.
• Type "javac your_file_name.java", in this case its "javac Captcha.java"
• Type "appletviewer your_file_name.java", in this case its "appletviewer Captcha.java"
• You would see your applet.

To run the program in Unix -based Operating System (Linux, Fedora)  you have to open Terminal and follow the above steps.