JAVA-生成随机数和验证码

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

public class RandomAndThreadLocalRandomAndUUIDDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Random random = new Random();
		System.out.println(random.nextInt(50));
		
		ThreadLocalRandom tlRandom = ThreadLocalRandom.current();
		System.out.println(tlRandom.nextInt(20, 30));
		
		//UUID一般用来表示一个随机的唯一的一个字符串
		String uuid = UUID.randomUUID().toString();
		System.out.println(uuid);
		
		//生成一个五位数的随机字符串
		//1、用UUID截取前五位实现
		String code = UUID.randomUUID().toString().substring(0,5);
		System.out.println(code);
		System.out.println("-------------------------------");
		//2、随机取出字符串中五位数实现
		String str = "ABCDEFGHIJKLMNOOPQRSTUVWXYZ";
		str += str.toLowerCase();
		str += "0123456789";
		StringBuilder sb = new StringBuilder(5);
		for(int i = 0;i<5;i++)
		{
			char ch = str.charAt(new Random().nextInt(str.length()));
			sb.append(ch);
		}
		System.out.println(sb);
	}

}

15
26
f6b151ae-2961-446d-a949-6815013a6192
d46e8
-------------------------------
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