palindromes.java

import java.text.*;
import javax.swing.*;
import java.util.*;
import java.util.Scanner;
import java.util.Stack;

public class palindromes {
    public static void main(String[] args) {
        Scanner infile = new Scanner (System.in);
        String s = "";
        int StrLength;
        while (!s.equals("Q"))
        {
//          Explains what a palindrome is and asks user to enter test phrase.
                System.out.println("This program will test strings to see if they are palindromes.");
            System.out.println("A palindrome is a word or phrase that is spelled the same way frontwards and backwards.");
            System.out.println("Please enter a string to be tested (Enter 'Q' to quit):  ");

//          User enters test phrase.  If phrase == 'Q', program ends.
                s = infile.next();

//          Converts all letters to caps, removes all white-space and punctuation,
//                           initializes and stores the value of the length of String 2, initializes the stack.
                                 s.toUpperCase();
            s.replaceAll("\\W", "");
            s.replaceAll("\\s", "");
            StrLength = s.length() - 1;
            Stk s2 = new Stk(s.length());

            int i;

//          Pushes every letter in the string into the stack.
                for (i = 0; i <= StrLength; i++) {
                    s2.push(s.charAt(i));
                };
            char c;
            i = 0;

//          While S3 is not empty, compare popped character with character in same position in string.
//              If both are equal, continue until s3 is empty.  If there is any difference, end the loop.
                while (!s2.isEmpty()) {
                    c = s2.pop();
                    if (c == s.charAt(i)) {
                        i++;
                        if (i > StrLength) {
                            System.out.println("This string is a palindrome.  Please enter another string to test (Enter Q to quit).");
                            s = infile.next();
                            StrLength = 0;
                        };
                    }
                    else
                    {
                        System.out.println("This string is not a palindrome.  Please enter another string to test (Enter Q to quit).");
                        s = infile.next();
                        StrLength = 0;
                    };

                };
        };

    }

}