8 |
|
|
9 |
|
/** |
10 |
|
* A collection designed for holding elements prior to processing. |
11 |
< |
* Besides basic {@link Collection} operations, queues provide |
11 |
> |
* Besides basic {@link java.util.Collection Collection} operations, queues provide |
12 |
|
* additional insertion, extraction, and inspection operations. |
13 |
|
* |
14 |
|
* <p>Queues typically, but do not necessarily, order elements in a |
18 |
|
* stacks) which order the elements LIFO (last-in-first-out). |
19 |
|
* Whatever the ordering used, the <em>head</em> of the queue is that element |
20 |
|
* which would be removed by a call to {@link #remove() } or {@link #poll()}. |
21 |
< |
* Every Queue implementation must specify its ordering guarantees. |
21 |
> |
* Every <tt>Queue</tt> implementation must specify its ordering guarantees. |
22 |
|
* |
23 |
|
* <p>The {@link #offer(E)} method adds an element if possible, otherwise |
24 |
< |
* returning <tt>false</tt>. This differs from the {@link |
25 |
< |
* Collections#add(Object)} method, which throws an unchecked exception upon |
24 |
> |
* returning <tt>false</tt>. This differs from the {@link java.util.Collection#add Collection.add(E)} |
25 |
> |
* method, which throws an unchecked exception upon |
26 |
|
* failure. It is designed for use in collections in which failure to |
27 |
|
* add is a normal, rather than exceptional occurrence, for example, |
28 |
|
* in fixed-capacity (or "bounded") queues. |
29 |
< |
* |
29 |
> |
* |
30 |
|
* <p>The {@link #remove()} and {@link #poll()} methods remove and |
31 |
|
* return the head of the queue. |
32 |
|
* Exactly which element is removed from the queue is a |
37 |
|
* while the <tt>poll()</tt> method returns <tt>null</tt>. |
38 |
|
* |
39 |
|
* <p>The {@link #element()} and {@link #peek()} methods return, but do |
40 |
< |
* not delete, the head of the queue. |
40 |
> |
* not remove, the head of the queue. |
41 |
|
* |
42 |
|
* <p>The <tt>Queue</tt> interface does not define the <i>blocking queue |
43 |
|
* methods</i>, which are common in concurrent programming. These methods, |
57 |
|
* <a href="{@docRoot}/../guide/collections/index.html"> |
58 |
|
* Java Collections Framework</a>. |
59 |
|
* |
60 |
< |
* @see Collection |
60 |
> |
* @see java.util.Collection |
61 |
|
* @see LinkedList |
62 |
|
* @see PriorityQueue |
63 |
|
* @see java.util.concurrent.LinkedQueue |
73 |
|
/** |
74 |
|
* Add the specified element to this queue, if possible. |
75 |
|
* |
76 |
< |
* @param element the element to add. |
77 |
< |
* @return <tt>true</tt> if it was possible to add the element to |
78 |
< |
* this queue. |
76 |
> |
* @param o the element to add. |
77 |
> |
* @return <tt>true</tt> if it was possible to add the element to |
78 |
> |
* this queue, else <tt>false</tt> |
79 |
|
*/ |
80 |
< |
boolean offer(E element); |
80 |
> |
boolean offer(E o); |
81 |
|
|
82 |
|
/** |
83 |
|
* Retrieve and remove the head of this queue, if it is available. |
84 |
|
* |
85 |
|
* @return the head of this queue, or <tt>null</tt> if this |
86 |
< |
* queue is empty. |
86 |
> |
* queue is empty. |
87 |
|
*/ |
88 |
|
E poll(); |
89 |
|
|
90 |
|
/** |
91 |
< |
* Retrieve and remove the head of this queue. |
91 |
> |
* Retrieve and remove the head of this queue. |
92 |
|
* This method differs |
93 |
< |
* from the <tt>poll</tt> method in that it throws an exception if the |
94 |
< |
* queue is empty. |
93 |
> |
* from the <tt>poll</tt> method in that it throws an exception if this |
94 |
> |
* queue is empty. |
95 |
|
* |
96 |
|
* @return the head of this queue. |
97 |
|
* @throws NoSuchElementException if this queue is empty. |
98 |
|
*/ |
99 |
< |
E remove() throws NoSuchElementException; |
99 |
> |
E remove(); |
100 |
|
|
101 |
|
/** |
102 |
< |
* Retrieve, but do not remove, the head of this queue, or <tt>null</tt> |
103 |
< |
* if this queue is empty. This method differs from the <tt>poll</tt> |
104 |
< |
* method only in that this method does not remove the element from |
102 |
> |
* Retrieve, but do not remove, the head of this queue. |
103 |
> |
* This method differs from the <tt>poll</tt> |
104 |
> |
* method only in that this method does not remove the head element from |
105 |
|
* this queue. |
106 |
|
* |
107 |
|
* @return the head of this queue, or <tt>null</tt> if this queue is empty. |
110 |
|
|
111 |
|
/** |
112 |
|
* Retrieve, but do not remove, the head of this queue. This method |
113 |
< |
* differs from the <tt>peek</tt> method only in that it throws an |
113 |
> |
* differs from the <tt>peek</tt> method only in that it throws an |
114 |
|
* exception if this queue is empty. |
115 |
|
* |
116 |
|
* @return the head of this queue. |
117 |
|
* @throws NoSuchElementException if this queue is empty. |
118 |
|
*/ |
119 |
< |
E element() throws NoSuchElementException; |
119 |
> |
E element(); |
120 |
|
} |
121 |
|
|
122 |
|
|