BinarySearch（Java）

     private int binarySearch(int[] input, int target) {
         if (input == null) {
             return -1;
         }

         int index1 = 0;
         int index2 = input.length-1;
         while (index1 <= index2) {
             int mid = (index1+index2)/2;
             if (target == input[mid]) {
                 return mid;
             } else if(input[mid] < target) {
                 index1 = mid+1;
             } else {
                 index2 = mid-1;
             }
         }

         return -1;
     }