See if a word is a palindrome

Palindrome.java

// compile with:
//   javac Palindrome.java
// run it with:
//   java Palindrome word
// where word is a word of your choosing

public class Palindrome {
    public static boolean is_palindrome(String s) {
        // if s is an empty string or s is a single character, return true
        if(s == "" || s.length() == 1) return true;

        // else if the first character is the same as the last character
        else if(s.charAt(0) == s.charAt(s.length()-1))

            // return whether the letters in between the first and last letter are also a palindrome
            return is_palindrome(s.substring(1, s.length() - 1));

        // if the first and last characters are not the same, then this is not a palindrome
        else return false;
    }

    public static void main(String[] args) {
        // if the first argument to java Palindrome is a palindrome, print 'true'
        if(is_palindrome(args[0])) 
            System.out.println("true");
    }
}