See if 2 words are anagrams

Anagram.java

// compile it with:
//   javac Anagram.java
// run it with:
//   java Anagram word1 word2
// where word1 and word2 are words of your choosing

public class Anagram {
    public static boolean is_anagram(String a, String b) {
        System.out.println("a: " + a + ", b: " + b );
        //if a == b or if their lengths are 0 then we are done and can return true
        if(a == b || a.length() == 0 && a.length() == 0)
            return true;

        //k is the last index of the first character of a
        int k = b.lastIndexOf(a.charAt(0));

        //#lastIndexOf returns -1 if there is no index for the letter we want to find
        //if k != -1 then we make #is_anagram check all the letters after the first (substring(1))
        //  and the 2nd word minus the k-th letter (the letter that matches the first letter of a).
        //  to do that we take all the letters before k (substring(0,k)) and add it to the letters
        //  after k to the end of the string (substring(k+1))
        if(k != -1)
            return is_anagram(a.substring(1), b.substring(0,k) + b.substring(k+1));

        // if k is in fact -1 then these words are not anagrams and we send back false
        else
            return false;
    }

    public static void main(String[] args) {
        if(is_anagram(args[0], args[1]))
            System.out.println("true");
    }
}