java随机数的生成

1.代码

package com.xtm.java.test;

import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

public class Test{
    public static void main(String args[]){
        Random random = new Random(System.currentTimeMillis());
        //生成0～19的随机数
        int val1 = random.nextInt(20);
        ThreadLocalRandom threadLocalRandom = ThreadLocalRandom.current();
        //生成4～20的随机数
        int val2 = threadLocalRandom.nextInt(4, 20);
        System.out.println(val1+"-----"+val2);


    }

}