随机生成六位数验证码(java随机生成数字代码)

package com.hzrc.commonserver.utils;

import java.util.Random;

public class GenerateRandomNumber {


    public static String generate(int n) {

        //定义取值范围
        String str = "0123456789";
        //容量为4
        StringBuilder sb = new StringBuilder(n);
        for (int i = 0; i < n; i++) {
            //遍历4次，拿到某个字符并且拼接
            char ch = str.charAt(new Random().nextInt(str.length()));
            sb.append(ch);
        }

        return sb.toString();
    }

    public static String generateFour() {

        return generate(4);

    }

    public static void main(String[] args) {

        System.out.println(generate(10));
        System.out.println(generateFour());

    }


}

知是行之始，行是知之成