二分查找

 1 package cn.zhang.Array;
 2 
 3 import java.util.Arrays;
 4 
 5 /**
 6   * 测试二分查找(折半检索)
 7  * @author 张涛
 8  *
 9  */
10 public class TestBinarySearch {
11     public static void main(String[] args){
12         int[] a = {10,9,8,7,6,5,4,3,2,1};
13         
14         Arrays.sort(a);//先排序
15         System.out.println(Arrays.toString(a));
16         
17         System.out.println(myBinarySearch(a,1));//调用方法
18         
19     }
20     
21     public static int myBinarySearch(int[] arr,int value){
22         
23         int low = 0;//最小索引值
24         int high = arr.length - 1;//最大索引值
25         
26         while(low<=high) {
27             int mid = (low + high) / 2;
28             
29             if(arr[mid] == value) {
30                 return mid;
31             }
32             else if(arr[mid]>value) {
33                 high = mid - 1;
34             }
35             else if(arr[mid]<value) {
36                 low = mid + 1;
37             }
38         }
39         return -1;
40     }
41 }