Can two instances be created at the same time?

Question

Kind of a follow up question to Why can't Java constructors be synchronized?: if an object's constructor can't be synchronized, does that mean it's impossible to create two instances at literally the same time? For instance:

public class OutgoingMessage {
    public OutgoingMessage() {
        this.creationTime = new Date();
    }
    Date creationTime;
}

Would creationDate.getTime() always return a different value? I'm aware of the basics of multitasking/multithreading but what about multiple CPU cores? In that case the operating system doesn't have to switch contexts or am I wrong here?

Answer 1

if an object's constructor can't be synchronized, does that mean it's impossible to create two instances at literally the same time?

No. As the answers in the other question state, a constructor can't be synchronized simply because nothing exists to synchronize on before the constructor is called. You could do something like this:

public OutgoingMessage(){
   synchronized(this){
      //synchronized constructor
   }
}

But then the question becomes: how on earth would two threads access the same constructor of the same instance at the same time? They couldn't, by the very definition of how constructors work. That's why you can't synchronize on a constructor- because it doesn't make any sense.

That is not saying that two instances of a class can't be constructed at the same time.