异或法寻找1到1000中重复的数字（java日记）

import java.util.Random;
public class 寻找多余的数 {
    public static void main(String[] args) {
        int N=1001;
        int[] arr=new int[N];
        for (int i = 0; i < N-1; i++) {
            arr[i]=i+1;
        }
        Random randInt=new Random();
        arr[N-1]=randInt.nextInt(N-1)+1;//括号里面表示范围从[0-1000),后面+1表范围右移一位[1-1001)
        int index=randInt.nextInt(N);
        swap(arr,index,N-1);//随机下标交换
        int num=searchRedundantNumber(arr);
        System.out.println(arr[index]);
        System.out.println(num);
    }
    public static int searchRedundantNumber(int[] arr){
        int num=0;
        for (int i = 0; i < arr.length; i++) {
            num=arr[i]^num;
        }

        for (int i = 1; i < arr.length; i++) {
            num=num^i;
        }
        return num;
    }
    public static void swap(int[] arr, int i ,int j){
        arr[i]=arr[i]^arr[j];
        arr[j]=arr[i]^arr[j];
        arr[i]=arr[i]^arr[j];
    }
}