来源于数据结构与算法分析中的折半查找

/**
 *Performs the standard binary search.
 *@return index where item is found,or -1 if not found. 
 *
 */
 public static <AnyType extends Comparable<? super AnyType>>int binarySearch(AnyType [] a, AnyType x){


int low = 0,high = a.length - 1;
while(low <= high){
  int mid = (low + high) / 2;
 if(a[mid].compareTo(x) < 0)
low = mid + 1;
   else if(a [mid].compareTo(x) > 0)
high = mid - 1;
else
  return mid;//Found


 }


return NOT_FOUND;  //NOT_FOUND is defined as -1

}

//Do not know is right, please understand!!!