Regular Expression Matching

public class Solution {
public boolean isMatch(String s, String p) {
if (p.length() == 0) {
return s.length() == 0;
} else if (p.length() == 1 || p.charAt(1) != '*') {
if (s.length() < 1) {
return false;
} else if (s.charAt(0) != p.charAt(0) && p.charAt(0) != '.') {
return false;
} else {
return isMatch(s.substring(1), p.substring(1));
}
} else {
if (isMatch(s, p.substring(2))) {
return true;
}
int i = 0;
while (i < s.length() && (s.charAt(i) == p.charAt(0) || p.charAt(0) == '.')) {
if (isMatch(s.substring(i + 1), p.substring(2))) {
return true;
}
i++;
}
return false;
}
}
}