8 |
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|
9 |
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/** |
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* 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 |
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* additional insertion, extraction, and inspection operations. |
13 |
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* |
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* <p>Queues typically, but do not necessarily, order elements in a |
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* which would be removed by a call to {@link #remove() } or {@link #poll()}. |
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* Every <tt>Queue</tt> implementation must specify its ordering guarantees. |
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* |
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 |
23 |
> |
* <p>The {@link #offer offer} method adds an element if possible, otherwise |
24 |
> |
* returning <tt>false</tt>. This differs from the |
25 |
> |
* {@link java.util.Collection#add Collection.add} |
26 |
> |
* method, which throws an unchecked exception upon |
27 |
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* failure. It is designed for use in collections in which failure to |
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* add is a normal, rather than exceptional occurrence, for example, |
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* in fixed-capacity (or "bounded") queues. |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
60 |
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* |
61 |
< |
* @see Collection |
61 |
> |
* @see java.util.Collection |
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* @see LinkedList |
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* @see PriorityQueue |
64 |
< |
* @see java.util.concurrent.LinkedQueue |
64 |
> |
* @see java.util.concurrent.LinkedBlockingQueue |
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* @see java.util.concurrent.BlockingQueue |
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* @see java.util.concurrent.ArrayBlockingQueue |
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* @see java.util.concurrent.LinkedBlockingQueue |
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public interface Queue<E> extends Collection<E> { |
73 |
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|
74 |
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/** |
75 |
< |
* Add the specified element to this queue, if possible. |
75 |
> |
* Adds the specified element to this queue, if possible. |
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* |
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* @param o the element to add. |
78 |
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* @return <tt>true</tt> if it was possible to add the element to |
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boolean offer(E o); |
82 |
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|
83 |
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/** |
84 |
< |
* Retrieve and remove the head of this queue, if it is available. |
84 |
> |
* Retrieves and removes the head of this queue, if it is available. |
85 |
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* |
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* @return the head of this queue, or <tt>null</tt> if this |
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* queue is empty. |
89 |
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E poll(); |
90 |
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|
91 |
|
/** |
92 |
< |
* Retrieve and remove the head of this queue. |
92 |
> |
* Retrieves and removes the head of this queue. |
93 |
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* This method differs |
94 |
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* from the <tt>poll</tt> method in that it throws an exception if this |
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* queue is empty. |
100 |
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E remove(); |
101 |
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|
102 |
|
/** |
103 |
< |
* Retrieve, but do not remove, the head of this queue. |
103 |
> |
* Retrieves, but does not remove, the head of this queue. |
104 |
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* This method differs from the <tt>poll</tt> |
105 |
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* method only in that this method does not remove the head element from |
106 |
|
* this queue. |
110 |
|
E peek(); |
111 |
|
|
112 |
|
/** |
113 |
< |
* Retrieve, but do not remove, the head of this queue. This method |
113 |
> |
* Retrieves, but does not remove, the head of this queue. This method |
114 |
|
* differs from the <tt>peek</tt> method only in that it throws an |
115 |
|
* exception if this queue is empty. |
116 |
|
* |