| 8 |
|
|
| 9 |
|
/** |
| 10 |
|
* A collection designed for holding elements prior to processing. |
| 11 |
< |
* Besides basic {@link java.util.Collection Collection} operations, queues provide |
| 12 |
< |
* additional insertion, extraction, and inspection operations. |
| 11 |
> |
* Besides basic {@link java.util.Collection Collection} operations, |
| 12 |
> |
* queues provide additional insertion, extraction, and inspection |
| 13 |
> |
* operations. Each of these methods exists in two forms: one throws |
| 14 |
> |
* an exception if the operation fails, the other returns a special |
| 15 |
> |
* value (either <tt>null</tt> or <tt>false</tt>, depending on the |
| 16 |
> |
* operation). The latter form of the insert operation is designed |
| 17 |
> |
* specifically for use with capacity-restricted <tt>Queue</tt> |
| 18 |
> |
* implementations; in most implementations, insert operations cannot |
| 19 |
> |
* fail. |
| 20 |
> |
* |
| 21 |
> |
* <p><table BORDER CELLPADDING=3 CELLSPACING=1> |
| 22 |
> |
* <tr> |
| 23 |
> |
* <td></td> |
| 24 |
> |
* <td ALIGN=CENTER><em>Throws exception</em></td> |
| 25 |
> |
* <td ALIGN=CENTER><em>Returns special value</em></td> |
| 26 |
> |
* </tr> |
| 27 |
> |
* <tr> |
| 28 |
> |
* <td><b>Insert</b></td> |
| 29 |
> |
* <td>{@link #add add(e)}</td> |
| 30 |
> |
* <td>{@link #offer offer(e)}</td> |
| 31 |
> |
* </tr> |
| 32 |
> |
* <tr> |
| 33 |
> |
* <td><b>Remove</b></td> |
| 34 |
> |
* <td>{@link #remove remove()}</td> |
| 35 |
> |
* <td>{@link #poll poll()}</td> |
| 36 |
> |
* </tr> |
| 37 |
> |
* <tr> |
| 38 |
> |
* <td><b>Examine</b></td> |
| 39 |
> |
* <td>{@link #element element()}</td> |
| 40 |
> |
* <td>{@link #peek peek()}</td> |
| 41 |
> |
* </tr> |
| 42 |
> |
* </table> |
| 43 |
|
* |
| 44 |
|
* <p>Queues typically, but do not necessarily, order elements in a |
| 45 |
|
* FIFO (first-in-first-out) manner. Among the exceptions are |
| 120 |
|
* preferable to method {@link Collection#add}, which can fail to |
| 121 |
|
* insert an element only by throwing an exception. |
| 122 |
|
* |
| 123 |
< |
* @param o the element to insert. |
| 123 |
> |
* @param e the element to insert. |
| 124 |
|
* @return <tt>true</tt> if it was possible to add the element to |
| 125 |
|
* this queue, else <tt>false</tt> |
| 126 |
|
*/ |
| 127 |
< |
boolean offer(E o); |
| 127 |
> |
boolean offer(E e); |
| 128 |
|
|
| 129 |
|
/** |
| 130 |
|
* Retrieves and removes the head of this queue, or <tt>null</tt> |
| 137 |
|
|
| 138 |
|
/** |
| 139 |
|
* Retrieves and removes the head of this queue. This method |
| 140 |
< |
* differs from the <tt>poll</tt> method in that it throws an |
| 140 |
> |
* differs from the {@link #poll} method only in that it throws an |
| 141 |
|
* exception if this queue is empty. |
| 142 |
|
* |
| 143 |
|
* @return the head of this queue. |
| 156 |
|
|
| 157 |
|
/** |
| 158 |
|
* Retrieves, but does not remove, the head of this queue. This method |
| 159 |
< |
* differs from the <tt>peek</tt> method only in that it throws an |
| 159 |
> |
* differs from the {@link #peek} method only in that it throws an |
| 160 |
|
* exception if this queue is empty. |
| 161 |
|
* |
| 162 |
|
* @return the head of this queue. |
