java 获取不重复随机数

获取不重复随机数，自定义取值范围

import java.util.HashSet;
import java.util.Set;
 
/**
 * <p>
 *    获取不重复随机数
 * </p>
 *
 * @author passer
 * @since 2021-03-09
 */
public class RandomUtil {
 
    private static final Set set = new HashSet();
 
    private static Integer min;//随机数最小值
 
    private static Integer max;//随机数最大值
 
    /**
     *
     * @param min 随机数最小值
     * @param max 随机数最大值（不包含）
     */
    public RandomUtil(Integer min, Integer max){
 
        this.min = min;
 
        this.max = max;
    }
 
    /**
     *
     * @return 随机数
     */
    public String getRandom(){
 
        Integer num = new java.util.Random().nextInt(max - min) + min;
 
        boolean b = true;
 
        while (b){
 
            if(set.contains(num)){
 
                num = new java.util.Random().nextInt(max - min) + min;
 
            }else {
 
                set.add(num);
 
                return "" + num;
            }
            if(set.size() == max-min){
 
                b = false;
 
                num = null;
 
                return "" + num;
            }
        }
        return "" + num;
    }
    public void clearSet(){
 
        set.clear();
    }
 
    public static void main(String[] args) {
 
        RandomUtil randomUtil = new RandomUtil(100,1000);//声明一次
 
        for(int i = 0; i < 1000; i++){
 
            System.out.println(randomUtil.getRandom());
 
            if(i>900){
 
                randomUtil.clearSet();
            }
        }
    }
}