这里实际是考察线程间的通信，正常情况下，主线程里启动异步线程执行某个方法，理论上主线程和这个异步线程是并行执行，互不干扰，但是现在要求异步线程执行完毕方法之后，才能继续执行主线程，实际是如何阻塞主线程，到底有几种写法呢？废话少说，直接上代码！
首先先给出需要执行的方法（可以自定义）：
public class Compute {public static int fibo(int a) {if ( a < 2) {return 1;}return fibo(a-1) + fibo(a-2);}}
方式一：Thread.sleep()方法，让主线程休眠
代码：
public static void main(String[] args) throws InterruptedException {long start = System.currentTimeMillis();//异步执行new Thread(() -> {int result = Compute.fibo(7);System.out.println("异步线程执行结果："+result);}).start();Thread.sleep(10000);System.out.println("main线程结束。。。");}
执行结果：
方式二：用join方法阻塞主线程
代码：
public static void main(String[] args) throws InterruptedException {MyThread myThread = new MyThread();myThread.start();myThread.join();System.out.println("main线程结束。。。");}private static class MyThread extends Thread{@Overridepublic void run(){int result = Compute.fibo(7);System.out.println("异步线程执行结果："+result);}}
执行结果：
方式三：wait+synchronized阻塞主线程
代码：
public static void main(String[] args) throws InterruptedException {long start = System.currentTimeMillis();Object obj = new Object();MyThread myThread = new MyThread();myThread.start();synchronized (obj){obj.wait(1000);}System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static class MyThread extends Thread{@Overridepublic void run(){int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);}}
执行结果：
方式四：wait+notify+synchronized
public static void main(String[] args) throws InterruptedException {long start = System.currentTimeMillis();Object obj = new Object();MyThread myThread = new MyThread(obj);myThread.start();synchronized (obj){obj.wait();}System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static class MyThread extends Thread{Object obj;public MyThread(Object obj){this.obj = obj;}@Overridepublic void run(){int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);synchronized (obj) {obj.notify();}}}
执行结果：
方式五：ReentrantLock+Condition
private final static ReentrantLock reentrantLock = new ReentrantLock(true);private final static Condition condition = reentrantLock.newCondition();public static void main(String[] args) throws InterruptedException {long start = System.currentTimeMillis();Object obj = new Object();//异步执行new Thread(() -> {ThreadWork05.handler(obj);}).start();ThreadWork05.mainHandler(start);}private static void mainHandler(long start) throws InterruptedException {try {reentrantLock.lock();condition.await();System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}finally {reentrantLock.unlock();}}private static void handler(Object obj) {try {reentrantLock.lock();int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);condition.signal();}finally {reentrantLock.unlock();}}
执行结果：
方式六：CountDownLatch
public static void main(String[] args) throws InterruptedException {CountDownLatch latch = new CountDownLatch(1);long start = System.currentTimeMillis();//异步执行new Thread(() -> {handler();latch.countDown();}).start();latch.await();System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static void handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);}
执行结果：
方式七：LockSupport.park和unpark
public static void main(String[] args) {long start = System.currentTimeMillis();Thread mainThread = Thread.currentThread();//异步执行Thread t = new Thread(new Runnable() {@Overridepublic void run() {handler(mainThread);}});t.start();LockSupport.park(mainThread);System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static void handler(Thread mainThread) {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);LockSupport.unpark(mainThread);}
执行结果：
方式八：LockSupport.parkNanos 超时时间
public static void main(String[] args) {long start = System.currentTimeMillis();Thread mainThread = Thread.currentThread();//异步执行Thread t = new Thread(new Runnable() {@Overridepublic void run() {handler();}});t.start();LockSupport.parkNanos(mainThread, 100L);System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static void handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);}
执行结果：
方式九：LockSupport.parkUntil 截止到某时间点释放方式
public static void main(String[] args) {long start = System.currentTimeMillis();Thread mainThread = Thread.currentThread();//异步执行Thread t = new Thread(new Runnable() {@Overridepublic void run() {handler();}});t.start();LockSupport.parkUntil(mainThread, System.currentTimeMillis()+1000);System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static void handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);}
执行结果：
方式十：CountDownLatch.await(long t, TimeUtil t)
public static void main(String[] args) throws InterruptedException {CountDownLatch latch = new CountDownLatch(1);long start = System.currentTimeMillis();//异步执行new Thread(() -> {handler();}).start();latch.await(100, TimeUnit.MILLISECONDS);System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static void handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);}
执行结果：
方式十一：ExecutorService.submit+Future.get()阻塞 线程池
public static void main(String[] args) {long start = System.currentTimeMillis();ExecutorService executorService = new ThreadPoolExecutor(2,2,0L,TimeUnit.MILLISECONDS,new LinkedBlockingQueue<>());Future<Integer> future = executorService.submit(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {return handler();}});try {System.out.println("异步线程输出结果："+future.get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}executorService.shutdown();System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static int handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);return result;}
执行结果：
方式十二：线程池+synchronized 方式，下面要么同时锁住oo，要么同时锁住mainThread，效果一样
public static void main(String[] args) {Object oo = new Object();Thread mainThread = Thread.currentThread();long start = System.currentTimeMillis();ExecutorService executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE,60L, TimeUnit.SECONDS,new SynchronousQueue<Runnable>());executorService.execute(new Runnable() {@Overridepublic void run() {handler(oo, mainThread);}});executorService.shutdown();synchronized (mainThread){try {mainThread.wait();} catch (InterruptedException e) {e.printStackTrace();}}System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static int handler(Object oo, Thread mainThread) {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);synchronized (mainThread){mainThread.notify();}return result;}
执行结果：
方式十三：FutureTask+异步线程启动+future.get()阻塞
public static void main(String[] args) {long start = System.currentTimeMillis();FutureTask<Integer> futureTask = new FutureTask<>(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {return handler();}});//异步启动new Thread(futureTask).start();try {System.out.println("异步线程输出结果："+futureTask.get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static int handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);return result;}
执行结果：
方式十四：CompletableFuture.supplyAsync() ，分为指定线程池和默认线程池两种
public static void main(String[] args) throws ExecutionException, InterruptedException {long start = System.currentTimeMillis();//如果不指定线程池默认使用monPool()// CompletableFuture<Integer> integerCompletableFuture = CompletableFuture.supplyAsync(() -> {// return handler();// });//也可以指定线程池ExecutorService executorService = new ThreadPoolExecutor(2,2,0L,TimeUnit.MILLISECONDS,new LinkedBlockingQueue<>());CompletableFuture<Integer> integerCompletableFuture = CompletableFuture.supplyAsync(() -> {return handler();}, executorService);System.out.println("异步输出结果："+integerCompletableFuture.get());//如果指定了线程池得关闭executorService.shutdown();System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static int handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);return result;}
执行结果：
方式十五：CompletableFuture.runAsync() ，分为指定线程池和默认线程池两种
public static void main(String[] args) throws ExecutionException, InterruptedException {long start = System.currentTimeMillis();//如果不指定线程池默认使用monPool()CompletableFuture<Void> integerCompletableFuture = CompletableFuture.runAsync(() -> {handler();});//也可以指定线程池// ExecutorService executorService = new ThreadPoolExecutor(2,2,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue<>());// CompletableFuture<Void> integerCompletableFuture = CompletableFuture.runAsync(() -> {// handler();// }, executorService);//runAsync没有返回值，输出为nullSystem.out.println("异步输出结果："+integerCompletableFuture.get());//如果指定了线程池得关闭// executorService.shutdown();System.out.println("线程："+Thread.currentThread().getName()+" 使用时间："+(System.currentTimeMillis()-start)+"ms");}private static int handler() {int result = Compute.fibo(7);System.out.println("线程："+Thread.currentThread().getName()+" 异步计算结果："+result);return result;}
执行结果：
