Is this a safe publication of object?

Question

I have a class Item

class Item {
  public int count;
  public Item(int count) {
    this.count = count;
  }
}

Then, I will put a reference

Answer 1

Yes, there is a visibility problem, as Holder.item is not final. So there is no guarantee that another thread will see its initialized value after the construction of Holder is finished.

And as @Gray pointed out, the JVM is free to reorder instructions in the absence of memory barriers (which can be created by a lock (synchronization), a final or volatile qualifier). Depending on the context, you must use one of these here to ensure safe publication.