Simple Recursion - Programmers Heaven

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!


Welcome to the new platform of Programmer's Heaven! We apologize for the inconvenience caused, if you visited us from a broken link of the previous version. The main reason to move to a new platform is to provide more effective and collaborative experience to you all. Please feel free to experience the new platform and use its exciting features. Contact us for any issue that you need to get clarified. We are more than happy to help you.

Simple Recursion

circuz_phreakcircuz_phreak Posts: 49Member
Newbie here, having a minor problem with some code. I need to use recursion to reverse a string, except when printed, only integers should be printed, all other non integer input should not. i.e. 7h3hk1k6 prints :6137. So I have a main method, a recursion method, and a method which tests if its an integer. I marked further down where i think the problem is, because it works fine if all input is either a single character or integer, a series of characters (string), or a series of integers. Not sure how to make mixed input work. Because i think once it finds a value thats not a character and returns false, thats it, doesn't look anymore. Thanks for any help.

public class Recursion {
public static void main (String args[]){
String strInput = "";
strInput =
JOptionPane.showInputDialog(null, "Please enter a string");
' + "End Processing...");


public static String reverseDigits(String strInput) {
String charOne,
message = "No digits were found";
char charTest;
// Base case
if (strInput.length() <= 1 && isCharAnInt(strInput.charAt(0)) == true){
return strInput;

//recursive call
charOne = strInput.substring(0,1);
charTest = charOne.charAt(0);

if(isCharAnInt(charTest) == true){ //here's the problem!!!

return reverseDigits(strInput.substring(1)) + charOne;


return message;

public static boolean isCharAnInt(char charTest){

boolean isCharAnInt = true;

if(charTest < '0' || charTest > '9'){

isCharAnInt = false;


return isCharAnInt;


Sign In or Register to comment.