public class Halffind{
    public static void main(String[] args){
        int[] arr={1,2,4,5,7,8,9};
        int Aim = 8;
        int low=0;
        int high=arr.length-1;
        while(low <=high){
            int mid = (low+high)/2;
            if(Aim == arr[mid]){
                System.out.println(mid+1
 
);
                break;
            }
            if(Aim<arr[mid]){
                high = mid-1;//這裡mid已經比較過了，由於要比較小的值，所以需要mid-1；
                //System.out.println(high);
            }
            if(Aim > arr[mid]){
                low = mid+1;
                //System.out.println(low);
            }

        }
    }