Palindromes

This is a highly miscellaneous Java snippet to find palindromes.

It will read stdin line-by-line and spit back the palindromes it finds.

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import java.io.*;

class Palindrome {
    /* Return palindromes from a given list of words read from stdin */

    public static void main(String[] args) {
        boolean okay;
        String line;
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        do {
            try {
                /* Read a line, and spit it back again it if is a palindrome */
                line = input.readLine();
                if(isPalindrome(line)) {
                    System.out.println(line);
                }
                okay = true;
            } catch (Exception e) {
                /* Exception will be raised after end-of-file */
                okay = false;
            }
        } while(okay);
    }

    static boolean isPalindrome(String test) {
        /* Return true if a string is palindromic, false otherwise */
        int len = test.length();
        if(len <= 1) {
            /* Disallow null / single-char palindromes */
            return false;
        }

        for(int i = 0; i < len; i++) {
            /* Compare first and last, second and second-last, etc) */
            if(test.charAt(i) != test.charAt(len - 1 - i)) {
                /* Found different letters, stopping. */
                return false;
            }
        }
        return true;
    }
}

On a UNIX-like system, you could feed it a dictionary to list all of the palindromes like so:

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java Palindrome < /etc/dictionaries-common/words

On my computer that returns 57 palindromes made from ordinary words:

In alphabetical order, those are: aha bib bob boob civic dad deed deified did dud eke ere eve ewe eye gag gig hah huh kayak kook level ma’am madam MGM minim mom mum non noon nun oho pap peep pep pip poop pop pup radar redder refer rotor sagas sees seres sexes shahs sis solos stats tat tenet tit toot tot wow.

There are certainly more if we allow 1-letter words or case-insensitive matching (allowing all sorts of proper nouns), but I really don’t think they count.