java二分查找方法

import java.util.Arrays;

public class Erfen

{

public static void main(String[] args)

{

int[] arr={12,18,15,23,11,64,22};

System.out.println("排序前:"+Arrays.toString(arr));

Arrays.sort(arr);

System.out.println("排序后:"+Arrays.toString(arr));

int start=0;

int end=arr.length-1;

int middle=0;

int key=10;

while(true)

{

middle=(start+end)/2;

if(arr[middle]==key)

{

System.out.println("查询的数字存在于"+middle+"下标");

break;

}

else if(arr[middle]>key)

{

end=middle-1;

}

else if(arr[middle]<key)

{

start=middle+1;

}

if(start>end)

{

System.out.println("该数字不存在!");

break;

}

}

}

}