public class MapConcurrencyTest { static final int ITERATION_COUNT = 10000000; static CountDownLatch latch; static Map map; static List times; private void init(Map m) { latch = new CountDownLatch(20); map = m; for (int i = 1; i <= 1000; i++) { map.put(i, i); } } @Test public void test() throws InterruptedException { for (Map m : new Map[]{ new HashMap(), new ConcurrentHashMap(), new Hashtable() }) { times = new ArrayList<>(); for (int t = 0; t < 10; t++) { init(m); long start = System.currentTimeMillis(); // Create 10 Writer Threads for (int counter = 0; counter < 10; counter++) { new Thread(() -> { for (int i = 1; i <= ITERATION_COUNT; i++) { int key = i % 1000 + 1; map.put(key, key); } latch.countDown(); }).start(); } // Create 10 Reader Threads for (int counter = 0; counter < 10; counter++) { new Thread(() -> { for (int i = 1; i <= ITERATION_COUNT; i++) { int key = i % 1000 + 1; map.get(key); } latch.countDown(); }).start(); } // Wait for all threads to complete latch.await(); long time = System.currentTimeMillis() - start; times.add(time); } System.out.println("Map: " + m.getClass().getSimpleName()); System.out.println("Execution Times: " + Arrays.toString(times.toArray())); System.out.println("Average execution Time: " + times.stream().mapToLong(Long::longValue).average().getAsDouble() + "ms"); System.out.println(); } } }

Hashtable vs ConcurrentHashMap