java多线程怎么按顺序打印
在Java中,可以使用多种方法按顺序打印多个线程。
- 使用join()方法:在每个线程的末尾调用前一个线程的join()方法,确保前一个线程执行完毕后再执行下一个线程。例如:
Thread t1 = new Thread(() -> {
System.out.println("线程1");
});
Thread t2 = new Thread(() -> {
try {
t1.join();
System.out.println("线程2");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
Thread t3 = new Thread(() -> {
try {
t2.join();
System.out.println("线程3");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
t1.start();
t2.start();
t3.start();
- 使用CountDownLatch:CountDownLatch是一个计数器,可以在一个或多个线程等待一组操作完成后再执行。例如:
CountDownLatch latch1 = new CountDownLatch(1);
CountDownLatch latch2 = new CountDownLatch(1);
Thread t1 = new Thread(() -> {
try {
latch1.await();
System.out.println("线程1");
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
latch2.countDown();
}
});
Thread t2 = new Thread(() -> {
try {
latch2.await();
System.out.println("线程2");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
Thread t3 = new Thread(() -> {
try {
latch2.await();
System.out.println("线程3");
} catch (InterruptedException e) {
e.printStackTrace();
}
});
t1.start();
t2.start();
t3.start();
latch1.countDown();
这样线程t2和t3会等待线程t1执行完毕后再执行。
- 使用Lock和Condition:使用Lock和Condition可以实现类似于CountDownLatch的功能。例如:
Lock lock = new ReentrantLock();
Condition condition1 = lock.newCondition();
Condition condition2 = lock.newCondition();
Thread t1 = new Thread(() -> {
try {
lock.lock();
System.out.println("线程1");
condition2.signal();
} finally {
lock.unlock();
}
});
Thread t2 = new Thread(() -> {
try {
lock.lock();
condition2.await();
System.out.println("线程2");
condition1.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
});
Thread t3 = new Thread(() -> {
try {
lock.lock();
condition1.await();
System.out.println("线程3");
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
});
t1.start();
t2.start();
t3.start();
这样线程t2和t3会等待线程t1执行完毕后再执行。
这些方法都可以按照指定的顺序打印多个线程,具体使用哪种方法取决于实际情况和需求。
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