递归方法将字符串中的每个字母向后打印3次

Question

I'm working on a recursive method that will return and print in my main method, each letter of a string three backwards. The string being (args[1]). So for instance, if the string is "stack". It should output to:

kkkcccaaatttsss

So far I managed to print the string backwards. How should I go about printing each string three times?

My code so far:

public static void main(String[] args){
    int number = Integer.parseInt(args[0]);
    String word = new String("");
    word = args[1];

    String methodddd = recursive1.method4(word, number);
    System.out.println(methodddd);
}

public static String method4(String word){
    int length = word.length();
    if (length == length*3){
     return "";
    }
    return word.substring(length-1, length) +  method4(word.substring(0, length-1));
}

Answer 1

You are very close: modify the return line to pre-pend substring three times, instead of pre-pending it once:

public static String method4(String word){
    int length = word.length();
    if (length == 0){
         return "";
    }
    String last = word.substring(length-1, length);
    return  last + last + last +  method4(word.substring(0, length-1));
}

Note the ending condition: length == length*3 is true if (and only if) length is zero.

Demo.

Answer 2

Here's the basic answer, in pseudocode:

recursive_stutter(s:string){
   if length of s is 0
      return
   letter = s[0]    // save the first character
   recursive_stutter(s from 1 to length)
   printf "%c%c%c",letter, letter,  letter
}