Thread: Combination lock

For starters, I have no clue how to use the counter IV. I'm trying to create a combo lock with a 3 letter combo. in my test class I try to use the setPosition() method to try out a random or the original combo, but it cuts off after I type in the 2nd character and gives me this message "Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.String.charAt(String.java:658)
at CombinationLockTester.main(CombinationLockTester.j ava:27)
Java Result: 1"

Here's my code:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
import javax.swing.JOptionPane ;
/**
 *
 * @author John
 */
public class ComboLockTester
{
 public static void main (String args[])
 {
 
    ComboLock MasterLock = new ComboLock("J","A","P");
   System.out.println("The combination to MasterLock is " + MasterLock.getfirst() + MasterLock.getsecond()
           + MasterLock.getthird());
 
   String input = JOptionPane.showInputDialog("Enter first character");
   MasterLock.setPosition(input);
 
 
   String input2 = JOptionPane.showInputDialog("Enter second character");
   MasterLock.setPosition(input2);
 
   String input3 = JOptionPane.showInputDialog("Enter third character");
   MasterLock.setPosition(input3);
 
   System.out.println("The user entered combo is " + input + input2 + input3);
 
   MasterLock.tryToOpen();
 
   System.out.println(MasterLock.isOpen());
 
   MasterLock.lock();
 }
}

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
/**
 *
 * @author John
 */
public class ComboLock
{
    /**
     	Creates a lock with a given combination consisting of three
upper-case characters.
     	@param first the first letter of the combination
	@param second the second letter of the combination
@param third the third letter of the combination
   */
   private String first;
   private String second;
   private String third;
   private boolean open;
   private String Pos1;
   private String Pos2;
   private String Pos3;
   private int count;
 
 
 
   public ComboLock(String first, String second, String third)
   {
      open = false;
      this.first = first;
      this.second = second;
      this.third = third;
      count = 0;
   }
 
   public String getfirst()
   {
       return first;
   }
   public String getsecond()
   {
       return second;
   }
   public String getthird()
   {
       return third;
   }
 
   /**
      Set the dial to a position.
      @param aPosition a String consisting of a single uppercase
       letter (A..Z)
   */
   public void setPosition(String aPosition)
   {
       count++;
 
   if(count==0)
   {
       Pos1 = aPosition ;
   }
   else if(count == 1)
       {
           Pos2 = aPosition;
       }
   else if(count == 2)
   {
       Pos3 = aPosition;
   }
  }
 
   /**
      Try opening the lock.
   */
   public void tryToOpen()
   {
      if(Pos1.equals(first) && Pos2.equals(second) && Pos3.equals(third))
      {
          open = true;
          System.out.println("Combo correct! Lock is open.");
      }
      else
      {
          open = false;
          System.out.println("Wrong combo. Try again.");
      }
   }
 
   /**
   	 Check whether the lock is open.
   	 @return true or false indicating whether the lock is open.
   */
   public boolean isOpen()
   {
      return open;
   }
 
   /**
      Close the lock and print a message indicating that the lock is now closed
   */
   public void lock()
   {
      count = 0;
      open = false;
      System.out.println("The MasterLock is now locked");
   }
}

I think all i need to fix it is to find a way to let the test class know that when I call the setPosition method to link the respective characters, but like I said, I have no clue how to use counters. line 27 from that message is the following:
[code = java]
char Pos2 = input2.charAt(1);
[/code]
Thanks for any help!

So the string "input2" is longer than 1 character?

I cannot do that since I have to declare input2 before I print it, and since it is declared in the input it does not get the chance to print the length. As soon as type the second character and press enter, the program stops and only w.e is above line 27 gets executed.

I actually fixed the printing problem. Now the prototype program runs fully but I still can't get the arguments in the setPosition method to match the ones in the lock class. I know the counter is suppose to keep track of which user input is associated with its respective combo character so that it can tell me whether or not the original combo and the user input are the same, that is now the current problem. Thanks for the help btw. And sorry if I'm not being clear enough on the problem.

Okay, now regardless of the input, right or wrong it gives me this message in the out put right after it prints the user input:
"The combination to MasterLock is JAP
The user entered combo is JAP
Exception in thread "main" java.lang.NullPointerException
at ComboLock.tryToOpen(ComboLock.java:80)
at ComboLockTester.main(ComboLockTester.java:31)
Java Result: 1
BUILD SUCCESSFUL (total time: 7 seconds)"

--- Update ---

I also updated my codes on this thread.

Its because the test class does not know which input goes to which position. I'm sure I have to implement the counter into the test class. I don't know how though, like in the first input, the test class does not know that tat input is associated with the first parameter of the object, in this case "J" so if i input "N" the test class cannot compare them.