Print out the palindromes for a list of new line separated words read in from standard input. Usage: java Palindromes < /usr/share/dict/words

Palindromes.java

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Palindromes {
    public static void main(String[] args) {
        Set<String> words = new HashSet<String>();
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String word = scanner.next().toLowerCase();
            if (word.length() == 1) continue;
            words.add(word);
        }
        for (final String s : words) {
            StringBuilder sb = new StringBuilder(s.length());
            char[] letters = s.toCharArray();
            for (int i = letters.length-1; i >= 0; i--) {
                sb.append(letters[i]);
            }
            final String reversed = sb.toString();
            if (s.equals(reversed))
                System.out.println(s);
        }
    }
}