Question

Java Program Write a recursive method that takes a string and return a string where every character appears twice.

Output must match exactly as below: only two LL's since there is already two of the character

For example, if the string is “HELLO”, it will return “HHEELLOO”.

Write a program to test it. must be recursive!!!

Answer 1

import java.util.Scanner;

public class Twice {

    public static String twice(String s) {
        if(s.isEmpty()) {
            return "";
        } else {
            if(s.length() > 1 && s.charAt(0) == s.charAt(1)) {
                return s.substring(0, 2) + twice(s.substring(2));
            }
            return "" + s.charAt(0) + s.charAt(0) + twice(s.substring(1));
        }
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a string: ");
        System.out.println(twice(in.nextLine()));
    }

}