// package chapter7;

/**
 * Title:        Chapter 7, "Strings"
 * Description:  Examples for Chapter 7
 * Copyright:    Copyright (c) 2000
 * Company:      Armstrong Atlantic State University
 * @author Y. Daniel Liang
 * @version 1.0
 */

// import chapter2.MyInput;

public class PalindromeIgnoreNonAlphanumeric
{
  /** Main method */
  public static void main(String[] args)
  {
    System.out.print("Enter a string: ");
    String s = MyInput.readString();
    System.out.println("Ignoring non-alphanumeric characters, is "
      + s + " a palindrome? " + isPalindrome(s));
  }

  /** Return true if a string is a palindrome*/
  public static boolean isPalindrome(String s)
  {
    // Create a new string be eliminating non-alphanumeric chars
    String s1 = filter(s);

    // Create a new string that is the reversal of s1
    String s2 = reverse(s1);

    // Compare is the reversal is the same as the original string
    return s2.equals(s1);
  }

  /** Create a new string be eliminating non-alphanumeric chars*/
  public static String filter(String s)
  {
    // Create a string buffer
    StringBuffer strBuf = new StringBuffer();

    // Examine each char in the string to skip alphanumeric char
    for (int i=0; i<s.length(); i++)
    {
      if (isAlphanumeric(s.charAt(i)))
      {
        strBuf.append(s.charAt(i));
      }
    }

    // Return a new filtered string
    return strBuf.toString();
  }

  /** Return true if a string is alphanumeric*/
  public static boolean isAlphanumeric(char c)
  {
    return (('a' <= c) && (c <= 'z')) ||
           (('A' <= c) && (c <= 'Z')) ||
           (('0' <= c) && (c <= '9'));
  }

  /** Create a new string by reversing a specified string*/
  public static String reverse(String s)
  {
    StringBuffer s1 = new StringBuffer(s);
    s1.reverse(); // Use the reverse method for StringBuffer object
    return s1.toString();
  }
}