About reference to object before object's constructor is finished

Question

Every one of you know about this feature of JMM, that sometimes reference to object could receive value before constructor of this object is finish

Answer 1

Construct exit plays an important role here; the JLS says "A freeze action on final field f of o takes place when c exits". Publishing the reference before/after constructor exit are very different.

Informally

1 constructor enter{

2   assign final field

3   publish this

4 }constructor exit

5 publish the newly constructed object

[2] cannot be reordered beyond constructor exit. so [2] cannot be reordered after [5].

but [2] can be reordered after [3].