Thread Confinement

Question

I am reading Java Concurrency in Practice and kind of confused with the thread confinement concept. The book says that

When an object is confined to a

Answer 1

So when an object is confined to a thread, no other thread can have access to it?

That's what thread confinement means - the object can only EVER be accessed by one thread.

Is that what it means to be confined to a thread?

See above.

How does one keep an object confined to a thread?

The general principle is to not put the reference somewhere that would allow another thread to see it. It is a little bit complicated to enumerate a set of rules that will ensure this, but (for instance) if

• you create a new object, and
• you never assign the object's reference to an instance or class variable, and
• you never call a method that does this for the reference,
• then the object will be thread confined.