折半查找

折半查找：

public static int binarySearch(int[] arr, int key) {    int low = 0;    int high = arr.length - 1;    while (low <= high) {        int mid = (low + high) / 2;        if (arr[mid] == key) {            return mid;        } else if (arr[mid] > key) {            high = mid - 1;        } else {            low = mid + 1;        }    }    return -1;}