二分查找算法

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;

public class BinarySearch {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ArrayList<Integer> arrayList = new ArrayList<>();
        System.out.println("输入添加数字的个数：");
        int n = sc.nextInt();

        for (int i = 0; i < n; i++) {
            arrayList.add(sc.nextInt());
        }
        System.out.println("当前列表："+arrayList);
       /* for (int i = 0; i < arrayList.size(); i++) {
            Collections.sort(arrayList);
        }
        System.out.println("排序后："+arrayList);*/
        System.out.println("输入要查找的数字：");
        int num=sc.nextInt();


        found(arrayList, num);

    }
    public static void found(ArrayList<Integer> str, int item){
        int low = 0;
        int high = str.size()-1;
        int guss=0;
        while (low <= high) {
            int mid = (low + high) / 2;
            guss = str.get(mid);
            if (guss == item) {
                System.out.println("找到了所找数字： "+guss+" 且在第"+(mid+1)+"个位置");
                break;
            }
            if (guss > item) {
                high = mid - 1;
            }else {
                low = mid + 1;
            }
        }
        if (guss!=item) {
            System.out.println("None");
        }

    }
}