import java.util.HashMap;
import java.util.Iterator;
import java.util.Random;

public class HashMapBench {

    public static void shuffle(String []seq) {
        Random g = new Random();
        int i, c;
        String t;

        for (i = 0; i < seq.length; i++) {
            c = g.nextInt(seq.length - i);
            t = seq[i];
            seq[i] = seq[i + c];
            seq[i + c] = t;
        }
    }

    public static void randomGetHashMapBench(int N) {
        HashMap<String, Integer> a = new HashMap<String, Integer>();
        String []seq = new String[N];
        int sum = 0;
        long start = 0;
        long duration = 0;
        Random g = new Random();

        for (int i = 0; i < N; i++) {
            String key = String.format("%09d", i);
            a.put(key, new Integer(i));
            seq[i] = key;
        }

        shuffle(seq);

        start = System.nanoTime();
        for (int i = 0; i < N; i++) {
            int k = g.nextInt(N);
            sum += a.get(seq[k]).intValue();
        }
        duration = System.nanoTime() - start;
        System.out.println(String.format("HashMap Random Access. N = %d: %f us/op. checksum: %d",
                    N, (double)duration/(double)(N * 1e3), sum));
    }
    public static void main(String args[]) {
        int nr_elems = 10;

        if (args.length > 0) {
            nr_elems = Integer.parseInt(args[0]);
        }
        randomGetHashMapBench(nr_elems);
    }
}