Writing a program to crack a PIN number using nested for-loops

[rcastillo106]

Hey I need help forming this program in my intro java programming class. Here;s what I have to do:

Write a program called CrackPIN (use nested for-loops) that guesses the PIN in the file.

I already created a .txt file in notepad with the pin. I actually even formed the .txt file through a program because that was the previous task before this one. I can't seem to figure this one out. Any help would be grateful. Thanks in advance.

[sonny]

where have you got to. what exactly do you need help with. a Brute force algorithm??
see these links...

How To Ask Questions The Smart Way

Java Forums - BB Code List

Starting Writing a Program

EDIT:
sorry i'm not being rude,, just trying to help you to get help

kind regards
Sonny

[rcastillo106]

Well, I wrote this program:

import java.lang.*;
import java.util.*;
import java.io.*;
import javax.swing.*;
public class FileLab3pt1 {
  public static void main (String[] args) {
    String pin = JOptionPane.showInputDialog("Please create a 4-digit PIN number");
    String confirm = JOptionPane.showInputDialog("Please re-enter your 4-digit PIN number.");
    FileOutputStream outPin;
    PrintStream writePin;
    
    try {
      outPin = new FileOutputStream("C:\\Temp\\pin.txt");
      writePin = new PrintStream(outPin);
     
      if (pin.equalsIgnoreCase(confirm))
      {
        writePin.println(pin);
        System.out.println("The pin matches");
        System.out.println ("Pin has been written and saved successfully.");
      }
      else{
        System.out.println("The pin does not match, please run program again to store pin.");
        System.exit(0);
      }
      writePin.close();
    }
    catch (Exception e){
      System.err.println ("There has been an error in writing the file, please run program again");
    }
  }
}

Now I have to read from my pin.txt file and form a code to crack the pin I created. The pin was just 0000. I'm not sure how to go about doing it because if I make a for loop starting from 0-10000, I still wont get it because the pin has 4 zeros. Is this more information?

[Eranga]

Please use code tags also, next time you are posting the code segments here.

[rcastillo106]

Sorry, kind of new to this. Thanks for the heads up

[Eranga]

I think it's better if you can read more about I/O streams in Java, it's really helpful to you. Seems to me you stuck on with how to read the file. Isn't it?

Lesson: Basic I/O (The Java™ Tutorials > Essential Classes)