Java:从同步块启动新线程时会发生什么? [英] Java: what happens when a new Thread is started from a synchronized block?

问题描述

这里的第一个问题:这是我不知道的Java中非常短却很基本的东西...

First question here: it is a very short yet fundamental thing in Java that I don't know...

在以下情况下，run()方法是否以某种方式执行了somemethod()确实获得的锁定?

In the following case, is the run() method somehow executed with the lock that somemethod() did acquire?

public synchronized void somemethod() {
    Thread t = new Thread( new Runnable() {
       void run() {
           ...          <-- is a lock held here ?
       }
    }
    t.start();
    ... 
    (lengthy stuff performed here, keeping the lock held)
    ...
}

推荐答案

否. run()在其自己的上下文中开始，即同步方式.它没有任何锁.如果这样的话，您可能会陷入死锁，或者会违反规范的规定，即在任何给定时间只有一个线程可以在对象上保持锁.

No. run() starts in its own context, synchronization-wise. It doesn't hold any locks. If it did, you would either have a deadlock or it would violate the specs that state that only one thread may hold the lock on an object at any given time.

如果run()要在同一对象上再次调用somemethod()，则必须等待创建它的somemethod()调用首先完成.

If run() was to call somemethod() again on the same object, it would have to wait for the somemethod() call that created it to complete first.

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