代码执行完毕后，为何未能正常关闭退出？

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一个多线程实例代码，控制台可以正常输出结果，但没有输出Process finished with exit code 0，说明程序没有退出，这是什么原因？

javapublic class CyclicBarrierTest implements Runnable { private static final CyclicBarrier barrier=new CyclicBarrier(2);

@Override public void run() { try { barrier.await(); } catch (InterruptedException | BrokenBarrierException e) { e.printStackTrace(); } }

public static void main(String[] args) { Thread t1=new Thread(new CyclicBarrierTest()); Thread t2=new Thread(new CyclicBarrierTest());

t1.start(); t2.start(); }}

一个多线程的实例代码，控制台可以正常输出结果4，但是没有输出“Process finished with exit code 0”，表明程序没有退出，这是什么原因？

public class CyclicBarrierTest implements Runnable { private CyclicBarrier cyclicBarrier = new CyclicBarrier(4, this); private Executor executor = Executors.newFixedThreadPool(4); private ConcurrentMap concurrentMap = new ConcurrentHashMap<>(); private void calculate() { for (int i = 0; i < 4; i++) { executor.execute(new Runnable() { @Override public void run() { concurrentMap.put(Thread.currentThread().getName(), 1); try { cyclicBarrier.await(); } catch (InterruptedException e) { e.printStackTrace(); } catch (BrokenBarrierException e) { e.printStackTrace(); } } }); } } public static void main(String[] args) throws InterruptedException { CyclicBarrierTest cyclicBarrierTest = new CyclicBarrierTest(); cyclicBarrierTest.calculate(); Thread.sleep(1000); System.out.println(cyclicBarrierTest.concurrentMap.get("result")); } @Override public void run() { Integer result = 0; for (Map.Entry entry : concurrentMap.entrySet()) { result += entry.getValue(); } concurrentMap.put("result", result); } }