public boolean isPermutation2(String s1, String s2) {
		if (s1.length() != s2.length()) {
			return false;
		}

		HashMap<Character, Integer> m = new HashMap<Character, Integer>();
		for (int i = 0; i < s1.length(); i++) {
			if (m.containsKey(s1.charAt(i))) {
				m.put(s1.charAt(i), m.get(s1.charAt(i)) + 1);
			} else {
				m.put(s1.charAt(i), 1);
			}

		}
		for (int j = 0; j < s2.length(); j++) {
			if (m.containsKey(s2.charAt(j))) {
				if (m.get(s2.charAt(j)) - 1 < 0) {
					return false;
				}
				m.put(s2.charAt(j), m.get(s2.charAt(j)) - 1);
			} else {
				return false;
			}
		}
		return true;
	}