Super-simple, super easy to understand pure random letter generator, the incoming digits can be generated by a random number (uppercase and lowercase letters mixed)

Code:

import java.util.Random;

public class RandomLetterUtil {

    public static String getRandomCode(int size) {  // 传入要生成的随机数的位数
        Random random = new Random();
        String str = "";
        for (int i = 0; i < size; i++) {
            int key = random.nextInt(2);
            switch (key) {
                case 0:
                    char code1 = (char) (random.nextInt(26) + 65);
                    str += code1;
                    break;
                case 1:
                    char code2 = (char) (random.nextInt(26) + 97);
                    str += code2;
                    break;
            }
        }
        return str;
    }

    // 主函数测试
    public static void main(String[] args) {
       	int size = 100;
        String randomCode = getRandomCode(size);  // 传入要生成的随机数的位数
        System.out.println("随机生成的"+size+"位数为："+randomCode);
    }
}

Renderings:

4:

6:

8:

12:

20:

100:
We first determine the number of bits before returning to look for generating random numbers is not meet the requirements, return str in the method; before adding an output str. length ();

System.out.println("随机生成的位数为："+str.length());