Menu driven palindrome tester getting stack Overflow error - menu

Question

I'm doing this for a class, and I'm really not terribly awesome at this as I'm over a decade out of practice. I'm trying to write a program that displays a menu so the user can choose between methods of determining if it's a palindrome.
It then needs to redisplay the menu once it has completed the test. I'm getting a stack overflow error in the isPalindrome method since I combined the 2 classes into one class, which I thought would fix another problem I was having with the output! Any thoughts or directions I can take?
import java.util.Scanner;
public class PalHelper
{
public String pal;
public void MenuList()
{
System.out.println("How would you like to check your phrase?");
System.out.println("1. Check the first letter like it's the last letter - Leave no phrase unturned!");
System.out.println("2. I Prefer my Palindromes have the gentle treatment");
System.out.println("3. We're done here");
System.out.print("Selection: ");
}
public PalHelper()
{
Scanner decision = new Scanner(System.in);
MenuList();
switch (decision.nextInt())
{
//to access the character by character method of determination
case 1:
System.out.print("Enter Phrase to Test, the Hard Way:");
Scanner keyboard1 = new Scanner(System.in); //declares scanner variable for user entry
String UserInput1 = keyboard1.next();//Phrase variable
Boolean test1 = isPalindrome(UserInput1);
if (test1 == true){
System.out.println(UserInput1+" is a palindrome. That doesn't make you smart.");
}
else {
System.out.println(UserInput1+" is a not palindrome. Why don't you think a little harder and try again.");
}
System.out.println("..\n..\n..\n");
keyboard1.close();
new MenuList();
break;
//to access the string buffer method of determination
case 2:
System.out.print("Thank you for choosing the gentle way, please enter your phrase:");
Scanner keyboard2 = new Scanner(System.in); //declares scanner variable for user entry
String UserInput2 = keyboard2.next();
Boolean test2 = isPalindrome2(UserInput2);
if (test2 == true){
System.out.println(UserInput2+" is a palindrome. Congratulations! You are so wonderful!");
}
else {
System.out.println(UserInput2+" is a not palindrome. It's ok, I'm sure you'll get it next time.");
}
System.out.println("..\n..\n..\n");
keyboard2.close();
new MenuList();
break;
//exit menu
case 3:
System.out.println ( "Too bad – I hid a boot!" );
break;
//response to input other than 1,2,3
default:
System.out.println ( "No sir! Away! A papaya war is on." );
System.out.println("..\n..\n..\n");
new MenuList();
break;
}// close switch
}//close pal helper
public void Palindrome(String UserInput) {
}
public boolean isPalindrome(String UserInput) {
pal = UserInput.toUpperCase();
if (pal.length() <= 1) {//one character, automatically a palindrome
return true;
}
char start = pal.charAt(0);
char end = pal.charAt(pal.length()-1);
if (Character.isLetter(start) &&
Character.isLetter(end)) {//check if first and last characters match
if (start != end) {
return false; //if the beginning & ending characters are not the same it's not a palindrome
}
else {
Palindrome subpal = new Palindrome(pal.substring(1,pal.length()-1));
return subpal.isPalindrome(); //check middle dropping start and end letters
}
}
else if (!Character.isLetter(start)) {
Palindrome subpal = new Palindrome(pal.substring(1));
return subpal.isPalindrome(pal); //check if first letter is a letter, drop if not
}
else {
Palindrome subpal = new Palindrome(pal.substring(0,pal.length()-1));
return subpal.isPalindrome(pal); //check if first letter is a letter, drop if not
}
}//close isPalindrome
public boolean isPalindrome2(String UserInput){
pal = UserInput.toUpperCase();
pal = pal.replaceAll("\\W", "");//gets rid of space and punctuation
StringBuffer check = new StringBuffer(pal);//reverses pal string and creates new stringbuffer for check
check.reverse();
if (check.toString().equals(pal)){//checks for equality between pal and it's reverse
return true;
}
else {
return false;
}
}//close isPalindrome2
public static void main (String[]args)
{
new PalHelper();
}//close main
}//close class

Answer 1

Aside from my comment above, there is a problem that I noticed: in some cases, you construct a new Palindrome instance with the substring, but pass the full string while recursing to the isPalindrome() method. This causes the recursion to never terminate (which also makes your code hard to follow).

Answer 2

Your example is missing something, the following line has missing closing brackets:
Palindrome subpal = new Palindrome(pal.substring(1,pal.length()-1);
Your comments dont seem to match the code:
return subpal.isPalindrome(pal); //check if first letter is a letter, drop if not
Try adding Output to the Method isPalindrome() or debug it. You are probably not calling it with the right Strings and end up looping over the same Strings over and over.
public boolean isPalindrome(String UserInput) {
System.out.println(UserInput);
...
Edit: If your code really is exaclty like you posted then vhallac is right, you call isPalindrome() with the full String.