Question

the method java.util.concurrent.BlockingQueue.add(E e)’s JavaDoc reads:

boolean add(E e)

Inserts the specified element into
this queue if it is possible to do so
immediately without violating capacity
restrictions, returning true upon
success and throwing an
IllegalStateException if no space is
currently available. When using a
capacity-restricted queue, it is
generally preferable to use offer.

My question is: will it ever return false? if not, why does this method return a boolean?
It seems weird to me. What is the design decision behind this?

Thanks for your knowledge!
Manuel

Answer 1

It follows the contract of Collection.add(E e) (since BlockingQueue is a subtype of Collection):

If a collection refuses to add a
particular element for any reason
other than that it already contains
the element, it must throw an
exception (rather than returning
false). This preserves the invariant
that a collection always contains the
specified element after this call
returns.