当然前提是：有序数列，这里以升序为例！

public class binarySearch {    public static void main(String[] args) {            int arr[]={1,2,3,4,5,6,7,8,9};        int key=9;        //int result=binarySearchMethod_noDiGui(arr,key);//非递归实现        int result=binarySearchMethod_DiGui(arr,0,arr.length-1,key);//递归实现        System.out.println("结果："+result);    }       public static int  binarySearchMethod_noDiGui(int arr[],int key){              int left =0;       int right=arr.length-1;       int mid=(left+right)>>1;              while(left<=right){          if(arr[mid]==key){              return mid;          }else if(arr[mid]>key){              right=mid-1;          }else{              left=mid+1;          }          mid=(left+right)>>1;       }        return -1;    }      public static int binarySearchMethod_DiGui(int arr[],int left,int right,int key){              int mid=(left+right)>>1;              if(left>right){           return -1;       }              if(arr[mid]==key){           return mid;       }else if(arr[mid]>key){           right=mid-1;           return binarySearchMethod_DiGui(arr,left,right,key);       }else{           left=mid+1;           return binarySearchMethod_DiGui(arr,left,right,key);       }   }}