//二分查找算法的实现

    public static int binarySearch(int[] arr,int search) {

        int low=0;

        int high=arr.length-1;

        //找到中间的索引

        int middleIndex=0;

        while (low<high) {

             middleIndex=(low+high+1)/2;

            if (arr[middleIndex]==search) {

                return middleIndex;

            }

            else if(arr[middleIndex]>search) {

                high=middleIndex-1;

            }

            else {

                low=middleIndex+1;

            }

        }

        return middleIndex;

    }