// Coded calculation of Fibonacci sequence with memoization using a HashMap as data structure

import java.sql.Timestamp;
import java.util.HashMap;

public class FibMemoization {
    private static HashMap<Integer, Integer> results;

    private static void log(String message) {
        System.out.println(new Timestamp(System.currentTimeMillis()) + ": " + message);
    }

    private static int fib(int n) {
        if (n == 0) return 0;
        if (n == 1) return 1;

        // Lookup HashMap
        if (results.containsKey(n)) {
            return results.get(n);
        }

        // Calculate value
        log("Calculating fib(" + n + ")");
        int ans = fib(n - 1) + fib(n - 2);
        log("Calculated fib(" + n + ")");

        // Store in HashMap
        results.put(n, ans);

        return ans;
    }

    public static void main(String[] args) throws Exception {
        if (args.length == 0) {
            log("Please enter an integer argument");
            throw new Exception("Please enter an integer argument");
        }

        log("Will calculate fib(" + args[0] + ")");
        results = new HashMap<Integer, Integer>();
        log("Answer is: " + fib(Integer.parseInt(args[0])));
    }
}