Binary Search: Searching last & first Element

Hi,

I have coded Binary Search in java but its returning -1 when i am trying to search last or first element. If first works then last doesnt work & if last works first doesnt work. My code is given below:

import javax.swing.*;

public class BinarySearch{

   int[ ] Array = new int[10];

   BinarySearch(int[ ] a ) {

      Array = a;

   }

   int BinarySearchAlg(int num, int first, int last ) {

      int index=-1;

      if(first < last) {

          int mid = first + ((last - first) / 2);

          //int mid = (first + last)/2;

  JOptionPane.showMessageDialog(null, "mid= " + mid);

          if(num == Array[mid])

             index = mid;

          else if(num < Array[mid])

             index = BinarySearchAlg(num, first, mid-1);

          else

        index = BinarySearchAlg(num, mid+1, last);

       }

       return index;

   }

   public static void main(String[ ] args) {

      int[ ] a = {1, 12, 19, 56, 100, 134, 145, 178, 199, 201};

      BinarySearch obj = new BinarySearch(a);

      int index=obj.BinarySearchAlg(1, 1, 10);

      //int index=obj.BinarySearchAlg(201, 0, 9);

      JOptionPane.showMessageDialog(null, "index= " + index);

   }

}

When i tried the following statement:

int index=obj.BinarySearchAlg(1, 1, 10);

it returns -1 (i.e it cant search 1 in the array

& when i tried:

int index=obj.BinarySearchAlg(201, 0, 9);

it returns -1(i.e. it cant search 201 in the array.

Somebody please guide me.

Zulfi.