Java的随机数

三种随机数

测试1

测试2

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

/**
 * 随机数测试
 * @author HailongYao
 */
public class ThreadLocalRandomDemo {

    public static void main(String[] args) {
        ThreadLocalRandom random = ThreadLocalRandom.current();
        System.out.println(random.nextInt(50,100));//随即生成一个[50，100）的随机整数

        System.out.println(UUID.randomUUID().toString());//随机生成字符串

        //生成4位验证码，包含大小写和数字
        String str = "QWERTYUIOPLKJHGFDSAZXCVBNM";
        str += str.toLowerCase();
        str += "0123456789";
        StringBuilder sb = new StringBuilder(4);
        for (int i = 0; i < 4; i++) {
            char c = str.charAt(new Random().nextInt(str.length()));
            sb.append(c);
        }
        System.out.println(sb.toString());
    }

}

结果：