二分查找法

public class DichotomySearch {   public static void main(String[] args) {       int[] arr = new int[] { 12, 23, 34, 45, 56, 67, 77, 89, 90 };       System.out.println(search(arr, 12));   }   public static int search(int[] arr, int key) {       int start = 0;       int end = arr.length - 1;       while (start <= end) {           int middle = (start + end) / 2;           if (key < arr[middle]) {               end = middle - 1;           } else if (key > arr[middle]) {               start = middle + 1;           } else {               return middle;           }       }       return -1;   }}