public String strStr(String haystack, String needle) {
		if (needle == null || needle.length() == 0) {
			return haystack;
		}

		char[] xs = haystack.toCharArray();
		char[] ys = needle.toCharArray();

		for (int i = 0; i < xs.length - ys.length + 1; i++) {
			boolean found = true;
			for (int j = 0; j < ys.length; j++) {
				if (xs[i + j] != ys[j]) {
					found = false;
					break;
				}
			}
			if (found) {
				return new String(Arrays.copyOfRange(xs, i, xs.length));
			}
		}
		return null;
	}