How to own the object's monitor

Question

I have some coding like this.

  public class WaitTest {

  public static void main(String[] args) {
    Object object = new Object();
    try {
      synchronized (object) {
        object.wait(5000);
      }
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}

Does using synchronized (object) means WaitTest class is owning the monitor of object?

Answer 1

Classes don't own monitors, threads do.

In your example, WaitTest doesn't own the monitor, the main thread does.

In particular, no other thread would be able to enter a synchronized block on the same object, including calling any of the object's synchronized methods, if it had any such methods.

Answer 2

The thread owns the monitor, and there are three ways to own the monitor, according to the official JDK doc here: Object.notify

A thread becomes the owner of the object's monitor in one of three ways:

• By executing a synchronized instance method of that object.
• By executing the body of a synchronized statement that synchronizes on the object.
• For objects of type Class, by executing a synchronized static method of that class.