Regular Expression Matching

public class Solution {
    public boolean isMatch(String s, String p) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if(p == null||p.length() == 0) return s == null||s.length()==0;
        if(p.length() < 2 || p.charAt(1) != '*')
        {
            if((s.length() > 0 && p.length() > 0 && p.charAt(0) == s.charAt(0)) || (p.charAt(0) == '.' && s.length() != 0))
            {
                return isMatch(s.substring(1), p.substring(1));
            }
            return false;
        }
        else
        {
            while((s.length() > 0 && p.length() > 0 && p.charAt(0) == s.charAt(0)) || (p.charAt(0) == '.' && s.length() != 0))
            {
                if(isMatch(s, p.substring(2)))
                {
                    return true;
                }
                s = s.substring(1);
            }
            return isMatch(s, p.substring(2));

        }
    }
}