20 |
|
* which would be removed by a call to {@link #remove() } or {@link #poll()}. |
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 java.util.Collection#add Collection.add(E)} |
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 |
|
* failure. It is designed for use in collections in which failure to |
28 |
|
* add is a normal, rather than exceptional occurrence, for example, |
72 |
|
public interface Queue<E> extends Collection<E> { |
73 |
|
|
74 |
|
/** |
75 |
< |
* Add the specified element to this queue, if possible. |
75 |
> |
* Adds the specified element to this queue, if possible. |
76 |
|
* |
77 |
|
* @param o the element to add. |
78 |
|
* @return <tt>true</tt> if it was possible to add the element to |
81 |
|
boolean offer(E o); |
82 |
|
|
83 |
|
/** |
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 |
|
* |
86 |
|
* @return the head of this queue, or <tt>null</tt> if this |
87 |
|
* queue is empty. |
89 |
|
E poll(); |
90 |
|
|
91 |
|
/** |
92 |
< |
* Retrieve and remove the head of this queue. |
92 |
> |
* Retrieves and removes the head of this queue. |
93 |
|
* This method differs |
94 |
|
* from the <tt>poll</tt> method in that it throws an exception if this |
95 |
|
* queue is empty. |
100 |
|
E remove(); |
101 |
|
|
102 |
|
/** |
103 |
< |
* Retrieve, but do not remove, the head of this queue. |
103 |
> |
* Retrieves, but does not remove, the head of this queue. |
104 |
|
* This method differs from the <tt>poll</tt> |
105 |
|
* 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 |
|
* |