数组的二分查找

执行二分查找的前提：这个数组必须是有序的。
 1 package com.demo.sort;
 2 
 3 public class BinarySearch {
 4     /**
 5     * 二分查找算法
 6     *
 7     * @param srcArray 有序数组
 8     * @param des 查找元素
 9     * @return des的数组下标，没找到返回-1
10     */
11     
12     //循环
13     public static int binarySearch(int[] srcArray, int des) {
14         int left = 0;
15         int right = srcArray.length - 1;
16         while (left <= right) {
17             int middle = (left + right) / 2;
18             if (des == srcArray[middle]) {
19                 return middle;
20             } else if (des < srcArray[middle]) {
21                 right = middle - 1;
22             } else {
23                 left = middle + 1;
24             }
25         }
26         return -1;
27     }
28     
29     //递归
30      public static int binSearch(int srcArray[], int start, int end, int key) {   
31             int mid = (end - start) / 2 + start;   
32             if (srcArray[mid] == key) {   
33                 return mid;   
34             }   
35             if (start >= end) {   
36                 return -1;   
37             } else if (key > srcArray[mid]) {   
38                 return binSearch(srcArray, mid + 1, end, key);   
39             } else if (key < srcArray[mid]) {   
40                 return binSearch(srcArray, start, mid - 1, key);   
41             }   
42             return -1;   
43         } 
44     
45     public static void main(String[] args){
46         int[] src = new int[] { 1, 3, 5, 7, 8, 9 };
47         System.out.println(binarySearch(src, 9));
48     }
49 
50 }