@Override
	public void save() throws Exception {
		PrintWriter out = new PrintWriter("Calculator.out");
		for (int i=history.size()-1 ; i>=0 && i>=history.size()-5 ; i--) {
			out.println(history.get(i));
		}
		out.close();
	}

	@Override
	public void load() throws Exception {
		history.clear();
		BufferedReader in = new BufferedReader(new FileReader("Calculator.out"));
		String line;
		while ( (line = in.readLine()) != null) {
			history.add(line);
		}
		curIndex = history.size()-1;
		in.close();
	}