MultiThreadHashMap

MultiThreadHashMap.java

public class MultiThreadHashMap {
    private static final Object PRESENT = new Object();
    public static void main(String[] args) throws InterruptedException, BrokenBarrierException {
        final Map<String,Object> map = new HashMap<>(); //let map do resize multiple times
        int N = 1000;
        final CyclicBarrier cyclicBarrier = new CyclicBarrier(N+1);
        for (int i = 0; i < N; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        cyclicBarrier.await();
                    } catch (InterruptedException e) {
                        //e.printStackTrace();
                    } catch (BrokenBarrierException e) {
                        //e.printStackTrace();
                    }
                    System.out.println("about to put value");
                    map.put(UUID.randomUUID().toString().replace("-",""), PRESENT);
                }
            }).start();
        }
        cyclicBarrier.await();
        System.out.println("about to finish");
        Thread.sleep(2000L);
    }
}