oracle.adfnmc.java.util
Interface Queue

All Superinterfaces:

Collection, Iterable

All Known Implementing Classes:

LinkedList

public interface Queue
extends Collection

A kind of collection provides advanced operations than other basic collections, such as insertion, extraction, and inspection. Generally, a queue orders its elements by means of first-in-first-out. While priority queue orders its elements according to a comparator specified or the elements' natural order. Furthermore, a stack orders its elements last-in-first out. A typical queue does not allow null to be inserted as its element, while some implementations such as LinkedList allow it. But null should not be inserted even in these implementations, since method poll return null to indicate that there is no element left in the queue. Queue does not provide blocking queue methods, which will block until the operation of the method is allowed. BlockingQueue interface defines such methods.

Method Summary

java.lang.Object	element() Gets but not removes the element in the head of the queue.
boolean	offer(java.lang.Object o) Inserts the specified element into the queue provided that the condition allows such an operation.
java.lang.Object	peek() Gets but not removes the element in the head of the queue, or throws exception if there is no element in the queue.
java.lang.Object	poll() Gets and removes the element in the head of the queue, or returns null if there is no element in the queue.
java.lang.Object	remove() Gets and removes the element in the head of the queue.

Methods inherited from interface oracle.adfnmc.java.util.Collection

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

Method Detail

offer

boolean offer(java.lang.Object o)

Inserts the specified element into the queue provided that the condition allows such an operation. The method is generally preferable to the collection.add(E), since the latter might throw an exception if the operation fails.

Parameters:

o - the specified element to insert into the queue.

Returns:

true if the operation succeeds and false if it fails.

poll

java.lang.Object poll()

Gets and removes the element in the head of the queue, or returns null if there is no element in the queue.

Returns:

the element in the head of the queue or null if there is no element in the queue.

remove

java.lang.Object remove()

Gets and removes the element in the head of the queue. Throws a NoSuchElementException if there is no element in the queue.

Returns:

the element in the head of the queue.

Throws:

NoSuchElementException - if there is no element in the queue.

peek

java.lang.Object peek()

Gets but not removes the element in the head of the queue, or throws exception if there is no element in the queue.

Returns:

the element in the head of the queue or null if there is no element in the queue.

element

java.lang.Object element()

Gets but not removes the element in the head of the queue. Throws a NoSuchElementException if there is no element in the queue.

Returns:

the element in the head of the queue.

Throws:

NoSuchElementException - if there is no element in the queue.