随机验证码生成

package com.Stringuse;

import java.util.Random;
 //使用StringBuilder的方发创建验证码
/*public class SuiJiMA {
    
    public static void main(String[] args) {
        
        StringBuilder   stringBuilder =  new StringBuilder();
        Random  random = new Random();
        for(int i=0; i<4;i++){
            
             int x = random.nextInt(10);
            stringBuilder.append(x);    
        }
        System.out.print("验证码："+stringBuilder);
    }
}*/

//   使用空字符串
public class SuiJiMA {
    public static void main(String[] args) {
        String st = " ";
        Random random = new Random();
        for(int i=0;i<4;i++){
            int x = random.nextInt(10);
            st = st + x;
        }
        System.out.println("验证码："+st);
    }
}

//生成随机字母验证码
public class SuiJiMA {
    public static void main(String[] args) {
      StringBuilder stringBuilder = new StringBuilder();
      Random random = new Random();
      for(int i=0;i<4;i++){
          int t = random.nextInt(2);
          char ch = t ==0? (char)(random.nextInt(26)+'a'):(char)(random.nextInt(26)+'A');
          stringBuilder.append(ch);
      }
      System.out.println(stringBuilder);
    }
}