public String[] keys() {
		Set<?> keyvalues = st.entrySet();
		String[] keys = new String[st.size()];
		Iterator<?> it = keyvalues.iterator();
		for (int i = 0; i < st.size(); i++) {
			@SuppressWarnings("rawtypes")
			Map.Entry entry = (Map.Entry) it.next();
			keys[i] = (String) entry.getKey();
		}
		return keys;
	}