public static void main(String[] args) {
    
        char[] chs = new char[52];
        for (int i = 0; i < chs.length; i++) {
            //ASCII码表
            if(i <= 25){
              
                chs[i] = (char)(97 + i);
            }else{//27
          
                chs[i] = (char)(65 + i - 26);
            }
        }

   
        String code = "";

    
        Random r = new Random();
        for (int i = 0; i < 4; i++) {
            int randomIndex = r.nextInt(chs.length);
      
            //System.out.println(chs[randomIndex]);
            code = code + chs[randomIndex];
        }
        //System.out.println(result);
  
        int number = r.nextInt(10);
  
        code = code + number;


    
        char[] arr = code.toCharArray();
        for (int i = 0; i < arr.length; i++) {
            int index = r.nextInt(arr.length);
            char temp = arr[i];
            arr[i] = arr[index];
            arr[index] = temp;
        }

 
        String result = new String(arr);

        //输出打印
        System.out.println(result);

    }