I am fairly new to the concept of a binary search, and am trying to write a program that does this in Java for personal practice. I understand the concept of this well, but my code is not working.

There is a run-time exception happening in my code that just caused Eclipse, and then my computer, to crash... there are no compile-time errors here though.

public class BinarySearch
{
    // instance variables
    int[] arr;
    int iterations;

    // constructor
    public BinarySearch(int[] arr)
    {
        this.arr = arr;
        iterations = 0;
    }

    // instance method
    public int findTarget(int targ, int[] sorted)
    {
        int firstIndex = 1;
        int lastIndex = sorted.length;
        int middleIndex = (firstIndex + lastIndex) / 2;
        int result = sorted[middleIndex - 1];

        while(result != targ)
        {
            if(result > targ)
            {
                firstIndex = middleIndex + 1;
                middleIndex = (firstIndex + lastIndex) / 2;
                result = sorted[middleIndex - 1];

                iterations++;
            }
            else
            {
                lastIndex = middleIndex + 1;
                middleIndex = (firstIndex + lastIndex) / 2;
                result = sorted[middleIndex - 1];

                iterations++;
            }
        }
        return result;
    }


    // main method
    public static void main(String[] args)
    {
        int[] sortedArr = new int[]
        {
            1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29
        };
        BinarySearch obj = new BinarySearch(sortedArr);

        int target = sortedArr[8];
        int result = obj.findTarget(target, sortedArr);

        System.out.println("The original target was -- " + target + ".\n" +
                            "The result found was -- " + result + ".\n" +
                            "This took " + obj.iterations + " iterations to find.");        
    } // end of main method
} // end of class BinarySearch