random number

package com.Annual.util;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Random;
import java.util.Set;

public class AnnualUtil {

/**
* Generate random numbers from 0 to max
* @param max
* @return
*/
public static int random(int max) {
Random random = new Random();
return random.nextInt(max);
}

/**
* The random number min generated from min to max cannot be 0
* @param min
* @param max
* @return
*/
public static int random(int min, int max) {
Random random = new Random();
return random.nextInt(max) % (max - min + 1) + min ;
}


/**
     * Generate drawPeople different random numbers, and the random number interval is [0,numPeople)
     * @param n
     * @return
     */
    public static Set<Integer> getDiffSetNO(int drawPeople , int numPeople){
     
    Set<Integer > randomSet = new HashSet<>();
    //Randomly generate drawPeople random numbers
//Use set to add an infinite loop to ensure that {drawPeople} non-repeating random numbers are generated
while (true) {
randomSet.add(new Random(). nextInt(numPeople));
if(randomSet.size() >= drawPeople){
break;
}
}
        return randomSet;
    }

/**
     * Generate n different random numbers, and the random number interval is [0,10)
     * @ param n
     * @return
     */
    public static ArrayList getDiffNO(int n){
        // Generate [0-n) non-repeating random numbers
        // list is used to store these random numbers
        ArrayList list = new ArrayList();
        Random rand = new Random();
        boolean[ ] bool = new boolean[n];
        int num = 0;
        for (int i = 0; i < n; i++) {
            do {
                // continue loop if the same number is generated
                num = rand.nextInt(n);
            } while (bool[num]);
            bool[num] = true;
            list.add(num);
        }
        return list;
    }
   

public static void main(String[] args){
System.out.println(AnnualUtil.random(4)) ;
System.out.println(AnnualUtil.random(3,4));

Random ran1 = new Random(11);
        System.out.println("Use a Random object with seed 10 to generate a random sequence of integers in [0,10): ");
        for (int i = 0; i < 10; i++) {
            System.out.print(ran1.nextInt(1000) + " ");
        }
       
        System.out.println();
        Random ran2 = new Random(11 );
        System.out.println("Generate a random sequence of integers in [0,10) using another Random object with a seed of 10: ");
        for (int i = 0; i < 10; i++) {
            System.out. print(ran2.nextInt(1000) + " ");
        }
       
        // In addition, using Random directly cannot avoid generating repeated numbers. If you need to generate a sequence of non-repeating random numbers, you need to use the array and collection class
        ArrayList list=AnnualUtil.getDiffNO (20);
        System.out.println();
        System.out.println("generate n different random numbers getDiffNO: "+list);
       
        Set<Integer> randomSet = AnnualUtil.getDiffSetNO(20, 100);
        System.out.println();
        System.out.println ("generated n different random numbers getDiffSetNO: "+randomSet);
}
}