How to print out a recursion method?

Question

public class RecursionPracticeProgram {
    KeyboardReader reader = new KeyboardReader();

public String backString(String s){
    s = reader.readLine("String: ");
    if(s.length()==0)
        return s;

    System.out.println(backString(s.substring(1)) + s.charAt(0));   

    return backString(s.substring(1)) + s.charAt(0);


} 

public void run(){
    backString("Fox");
}

I am doing some recursion work but am having trouble printing it out. I think I have the code correct for reversing a string but when I go to run the program it just builds and doesn't actually print anything out. How do I print it out properly?

Answer 1

You need to make sure to only read once and you call your method at all. Just do it like this:

public class RecursionPracticeProgram {
  public void run() {
    String input = reader.readLine("String: ");
    KeyboardReader reader = new KeyboardReader();
    System.out.println(reader.backstring(input));
  }

  public String backString(String s){
    if(s.length()==0)
        return s;
    System.out.println(backString(s.substring(1)) + s.charAt(0));   
    return backString(s.substring(1)) + s.charAt(0);
  }
}