Palindromes.java.html

  1  public class Palindromes
  2  {
  3     public static void main(String[] args)
  4     {
  5        String sentence1 = "Madam, I'm Adam!";      
  6        System.out.println(sentence1);
  7        System.out.println("Palindrome: " + isPalindrome(sentence1));
  8        String sentence2 = "Sir, I'm Eve!";      
  9        System.out.println(sentence2);
 10        System.out.println("Palindrome: " + isPalindrome(sentence2));
 11     }
 12  
 13     /**
 14        Tests whether a text is a palindrome.
 15        @param text a string that is being checked
 16        @return true if text is a palindrome, false otherwise
 17     */
 18     public static boolean isPalindrome(String text)
 19     {
 20        int length = text.length();
 21  
 22        // Separate case for shortest strings. 
 23        if (length <= 1) { return true; }
 24        else
 25        {
 26           // Get first and last characters, converted to lowercase. 
 27           char first = Character.toLowerCase(text.charAt(0));
 28           char last = Character.toLowerCase(text.charAt(length - 1));
 29  
 30           if (Character.isLetter(first) && Character.isLetter(last))
 31           {
 32              // Both are letters. 
 33              if (first == last)
 34              {
 35                 // Remove both first and last character. 
 36                 String shorter = text.substring(1, length - 1);
 37                 return isPalindrome(shorter);
 38              }
 39              else
 40              {
 41                 return false;
 42              }
 43           }
 44           else if (!Character.isLetter(last))
 45           {
 46              // Remove last character. 
 47              String shorter = text.substring(0, length - 1); 
 48              return isPalindrome(shorter);
 49           }
 50           else
 51           {
 52              // Remove first character. 
 53              String shorter = text.substring(1); 
 54              return isPalindrome(shorter);
 55           }
 56        }
 57     }   
 58  }