The Big Programming Thread - Page 602

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Executor {
    static final int NUM_TESTS = 3;
    static final int NUM_THREAD = 4;
    static final int THREAD_ITERATIONS = 500000; //500k
    static final Map<String, Integer> map = new HashMap<>(1);

    public static void main(String[] args) throws InterruptedException {
        for (int test = 0; test < NUM_TESTS; test++) {
            System.out.println("Started at: " + System.currentTimeMillis());
            ExecutorService es = Executors.newFixedThreadPool(NUM_THREAD);
            final CountDownLatch latch = new CountDownLatch(NUM_THREAD);
            for (int i = 0; i < NUM_THREAD; i++) {
                es.execute(() -> {
                    for (int k = 0; k < THREAD_ITERATIONS; k++) {
                        Integer newInteger1 = (int) Math.ceil(Math.random() * 1000000);
                        Integer newInteger2 = (int) Math.ceil(Math.random() * 1000000);

                        // 1. Attempt to retrieve a random Integer element
                        Integer retrievedInteger = map.get(String.valueOf(newInteger1));

                        // 2. Attempt to insert a random Integer element
                        map.put(String.valueOf(newInteger2), newInteger2);
                    }
                    latch.countDown();
                });
            }
            es.shutdown();
            latch.await();
            System.out.println(map.size());
            System.out.println("Finished at: " + System.currentTimeMillis());
        }
    }
}