Collector benchmark

App.java

package collectbenchmark;

import java.util.Arrays;
import java.util.Map;
import java.util.stream.Collectors;

import static java.lang.Integer.parseInt;
import static java.lang.System.nanoTime;
import static java.util.function.Function.identity;
import static java.util.stream.Collectors.toMap;
import static java.util.stream.IntStream.range;

/**
 * Hello world!
 */
public class App {
  public static void main(String[] args) {
    int objects = parseInt(args[0]);
    int iterations = parseInt(args[1]);
    int[] foos = range(0, objects).toArray();

    System.gc();
    System.out.println("Starting benchmark proper " + objects + " objects; " + iterations + " iterations");

    time(iterations, () -> {
      collectTest(foos);
    });
  }

  public static void time(int iters, Runnable runnable) {
    long start = nanoTime();
    for (int i = 0; i < iters; i++) {
      runnable.run();
    }
    long elapsed = nanoTime() - start;
    System.out.println("Elapsed time: " + elapsed + "ns");
  }

  public static int makeBar(int x) {
    return x * 2;
  }

  public static Map<Integer, Integer> collectTest(int[] foos) {
    return (Map<Integer, Integer>) Arrays.stream(foos).boxed().collect(toMap(identity(), App::makeBar));
  }
}