What is the difference between the add and offer methods in a Queue in Java?

Question

Take the PriorityQueue for example http://java.sun.com/j2se/1.5.0/docs/api/java/util/PriorityQueue.html#offer(E)

Can anyone give me an example of a Queu

Answer 1

The Queue interface specifies that add() will throw an IllegalStateException if no space is currently available (and otherwise return true) while offer() will return false if the element couldn't be inserted due to capacity restrictions.

The reason they are the same in a PriorityQueue is that this queue is specified to be unbounded, i.e. there are no capacity restrictions. In the case of no capacity restrictions, the contracts of add() and offer() display the same behaviour.