Coding Interview : How to find a missing number in a sorted array?

Here we need to get the following results

Sample Input : 1 3 4 5 6 7 8 9
Output : Missing number is 2

Sample Input : 1 2 3 4 5 7 8 9 10
Output : Missing number is 6

Program:

/**
 * @author Gaurav
 *
 */
public class MissingNumberPuzzle {

 /* main method */
 public static void main(String args[]) {
  int array[] = { 1, 2,3, 4, 5, 6 };
  System.out.println("Missing number is " + getMissingNumber(array));
 }

 // Business logic to find missing number
 static int getMissingNumber(int a[]) {
  int temp = a.length;
  for (int index = 0; index < temp; index++)
   if (a[index] != (index + 1))
    return (index + 1);

  // If all numbers from 1 to n
  // are present
  return temp + 1;
 }
}