Thread: Guessing Game Program Problem.. ArrayIndexOutOfBoundsException while printing?

I am having a strange problem with my Guessing Game program. The program takes an argument integer between 1 and 100 as a secret number, and the program will guess random numbers until it finds your number. Each incorrect guess is recorded in a vector and the guesses are printed after the secret number is found. It seems to work perfectly fine except that when printing out the guesses, I get an ArrayIndexOutOfBounds exception. Can anyone see the problem?? -Thanks

import java.util.Vector;
 
public class GuessingGame{
	int target;
	int counter = 0;
	Vector<Integer> guesses;
 
	public static void main(String []args){
		int secretNumber = Integer.parseInt(args[0]);
		GuessingGame g = new GuessingGame(secretNumber);
		g.startGuessing();
		g.printGuesses();
	}
 
	public GuessingGame(int i){
		target = i;
		guesses = new Vector<Integer>(100, 25);
	}
 
	public void startGuessing(){
		while(1 == 1){
			int guess = 1 + (int) (Math.random() * (100 - 1) + 1);
			if(guess == target){
				System.out.println("Target Found!  " + guess);
				break;
			}else{
				guesses.add(guess);
			}
			counter++;
		}
	}
 
	public void printGuesses(){
		for(int i = 0; i < guesses.capacity() - 1; i++){
			System.out.println("Guesses: " + guesses.elementAt(i));
		}
	}
}

I suspect that the capacity of an instance of Vector is not what you think it is. What it is is explained at the start of the Vector API docs.

Almost certainly you should be dealing with the collection's size not its capacity. There is a size() method for obtaining this. Also Vector has a no argument constructor and you should use that unless you have some reason not to. (And that reason will be based on an understanding of what capacity means...)

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Once you have the program doing what you want with Vector consider rewriting it to use one the more modern List implementations like ArrayList. This would be the most straight forward approach again, unless your program has some compelling reason to use Vector. The only such reason that I've some across involves Swing (a graphical user interface) and your program doesn't use Swing.

Thanks! That was exactly the problem, I thought there was a size() method for Vectors but I couldn't remember, and the only reason I am using vector for this is because the assignment calls you using a vector Thanks for your help pbrockway2

You're welcome.