Regular expression implementation in java

LeetCodeSix

package com.westudio.java;

public class LeetCodeSix {

    private static boolean isMatch(String s, String p) {

        if (p.length() == 0) {
            return s.length() == 0;
        }

        if (p.length() == 1 || p.charAt(1) != '*') {
            if (s.length() < 1 || (p.charAt(0) != s.charAt(0) && p.charAt(0) != '.')) {
                return false;
            }

            return isMatch(s.substring(1), p.substring(1));
        } else {
            int len = s.length();

            int i = -1;
            while (i < len && (i < 0 || p.charAt(0) == '.' || s.charAt(i) == p.charAt(0))) {
                if (isMatch(s.substring(i + 1), p.substring(2))) {
                    return true;
                }
                i ++;
            }

            return false;
        }
    }

    public static void main(String[] args) {
        String s = "aab";
        String p = "c*a*b";

        System.out.println(isMatch(s, p));
    }
}