Java中的线程和同步

Question

如果类中有synchronized方法并且1个线程进入它，则另一个线程可以在不同的对象上调用相同的方法。

Answer 1

Yes, if the method is not static .

A synchronized non-static method synchronizes on this . So this method:

public synchronized void foo() {
  // do stuff
}

is effectively equivalent to this one:

public void foo() {
  synchronized(this) {
    // do stuff
  }
}

A static synchronized method synchronizes on the current class. So a method like this:

public static synchronized void bar() {
  // do stuff
}

is effectively equivalent to this one:

public static void bar() {
  synchronized(ThisClass.class) {
    // do stuff
  }
}

Answer 2

If the method is marked as synchronized , then the lock is held on the object. This means that a call to the same method on a different object will not be locked.
However, if the method is a static one, then it is held by the entire class and it will not be possible for a second call to run it at the same time [and will be blocked]

Answer 3

是的，另一个线程可以从此类的实例调用此方法