Download Java Programming/Print version - Computer Science & Engineering

Set or List or Queue
| Last |----------------------------------------------------------------|_elem_|
29.4.3 Queue
The Queue interface adds the following operations to the Collection interface:
E element()
boolean offer(E o)
E peek()
E poll()
E remove()
Retrieves, but does not remove, the head
of this queue. This method differs from
the peek method only in that it throws an
exception if this queue is empty
Inserts the specified element into this
queue, if possible.
Retrieves, but does not remove, the head
of this queue, returning null if this queue is
empty
Retrieves and removes the head of this
queue, or null if this queue is empty
Retrieves and removes the head of this
queue. This method differs from the poll
method in that it throws an exception if
this queue is empty.
• java.util.PriorityQueue<E>
orders elements according to an
order/priority specified at construc•
tion time, null element is not allowed.
Figure 21
java.util.concurrent.ArrayBlockingQueue<E>
: orders elements FIFO;
syncronized, thread safe.
java.util.concurrent.SynchronousQueue<E>
: each put must wait for a take, and vice
versa, does not have any internal
capacity, not even a capacity of one, an
element is only present when you try
to take it; you cannot add an element
(using any method) unless another
thread is trying to remove it
157