主线程等待子线程结束

public class Test {
    public static void main(String[] args) {
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
        });
        t.start();
        // 调用了start方法且线程没死亡返回true
        while (t.isAlive()) {
        }
        System.out.println("main");
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
        });
        t.start();
        t.join();
        System.out.println("main");
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(1);
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
            countDownLatch.countDown();
        });
        t.start();
        countDownLatch.await();
        System.out.println("main");
    }
}

public class Test {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        Callable<Integer> myCallable = new MyCallable();
        FutureTask<Integer> futureTask = new FutureTask<>(myCallable);
        Thread thread = new Thread(futureTask);
        thread.start();
        futureTask.get();
        System.out.println("main");
    }
}
class MyCallable implements Callable<Integer> {
    @Override
    public Integer call() throws InterruptedException {
        Thread.sleep(5000);
        System.out.println("-----------");
        return 1;
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        BlockingQueue queue = new ArrayBlockingQueue(1);
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
            try {
                queue.put("1");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t.start();
        queue.take();
        System.out.println("main");
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException, BrokenBarrierException {
        CyclicBarrier barrier = new CyclicBarrier(2);
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
            try {
                barrier.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (BrokenBarrierException e) {
                e.printStackTrace();
            }
        });
        t.start();
        barrier.await();
        System.out.println("main");
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException, BrokenBarrierException {
        Thread mainThread = Thread.currentThread();
        Thread t = new Thread(() -> {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("-------");
            LockSupport.unpark(mainThread);
        });
        t.start();
        LockSupport.park();
        System.out.println("main");
    }
}