Java实现一个二分查找

import java.util.*;public class BinarySearch {    public int getPos(int[] A, int n, int val) {        int position=-1; //返回的数组的位置        int low=0,high=n-1,mid=n/2;         if(n<=0||A==null){// 数组为空或者为null             position=-1;        }else{// 数组有元素        while(low<=high){            if(val>A[mid]){                low=mid+1;                mid=(low+high)/2;            }else if(val<A[mid]){                high=mid-1;                mid=(low+high)/2;            }else{                position=mid;                break ; //跳出循环            }        }        }          // 判断position         if(position==-1)             return position;        else{            while(position>=0&&A[position]==val){                position--;            }            return position+1;        }    }}