| 23 |
|
* <tr> |
| 24 |
|
* <td></td> |
| 25 |
|
* <td ALIGN=CENTER><em>Throws exception</em></td> |
| 26 |
< |
* <td ALIGN=CENTER><em>Returns special value</em></td> |
| 26 |
> |
* <td ALIGN=CENTER><em>Special value</em></td> |
| 27 |
|
* </tr> |
| 28 |
|
* <tr> |
| 29 |
|
* <td><b>Insert</b></td> |
| 113 |
|
* @param <E> the type of elements held in this collection |
| 114 |
|
*/ |
| 115 |
|
public interface Queue<E> extends Collection<E> { |
| 116 |
– |
|
| 116 |
|
/** |
| 117 |
< |
* Inserts the specified element into this queue, if possible. When |
| 118 |
< |
* using queues that may impose insertion restrictions (for |
| 119 |
< |
* example capacity bounds), method <tt>offer</tt> is generally |
| 120 |
< |
* preferable to method {@link Collection#add}, which can fail to |
| 121 |
< |
* insert an element only by throwing an exception. |
| 122 |
< |
* |
| 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> |
| 117 |
> |
* Inserts the specified element into this queue if it is possible to do so |
| 118 |
> |
* immediately without violating capacity restrictions, returning |
| 119 |
> |
* <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt> |
| 120 |
> |
* if no space is currently available. |
| 121 |
> |
* |
| 122 |
> |
* @param e the element to add |
| 123 |
> |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
| 124 |
> |
* @throws IllegalStateException if the element cannot be added at this |
| 125 |
> |
* time due to capacity restrictions |
| 126 |
> |
* @throws NullPointerException if the specified element is null and |
| 127 |
> |
* this queue not permit null elements |
| 128 |
> |
* @throws ClassCastException if the class of the specified element |
| 129 |
> |
* prevents it from being added to this queue |
| 130 |
> |
* @throws IllegalArgumentException if some property of this element |
| 131 |
> |
* prevents it from being added to this queue |
| 132 |
|
*/ |
| 133 |
< |
boolean offer(E e); |
| 133 |
> |
boolean add(E e); |
| 134 |
|
|
| 135 |
|
/** |
| 136 |
< |
* Retrieves and removes the head of this queue, or <tt>null</tt> |
| 137 |
< |
* if this queue is empty. |
| 136 |
> |
* Inserts the specified element into this queue if it is possible to do |
| 137 |
> |
* so immediately without violating capacity restrictions. |
| 138 |
> |
* When using a capacity-restricted deque, this method is generally |
| 139 |
> |
* preferable to {@link #add}, which can fail to insert an element only |
| 140 |
> |
* by throwing an exception. |
| 141 |
|
* |
| 142 |
< |
* @return the head of this queue, or <tt>null</tt> if this |
| 143 |
< |
* queue is empty. |
| 142 |
> |
* @param e the element to add |
| 143 |
> |
* @return <tt>true</tt> if the element was added to this queue, else |
| 144 |
> |
* <tt>false</tt> |
| 145 |
> |
* @throws NullPointerException if the specified element is null and |
| 146 |
> |
* this queue does not permit null elements |
| 147 |
> |
* @throws ClassCastException if the class of the specified element |
| 148 |
> |
* prevents it from being added to this queue |
| 149 |
> |
* @throws IllegalArgumentException if some property of this element |
| 150 |
> |
* prevents it from being added to this queue |
| 151 |
|
*/ |
| 152 |
< |
E poll(); |
| 152 |
> |
boolean offer(E e); |
| 153 |
|
|
| 154 |
|
/** |
| 155 |
< |
* Retrieves and removes the head of this queue. This method |
| 156 |
< |
* differs from the {@link #poll} method only in that it throws an |
| 157 |
< |
* exception if this queue is empty. |
| 155 |
> |
* Retrieves and removes the head of this queue. This method differs |
| 156 |
> |
* from {@link #poll} only in that it throws an exception if this queue |
| 157 |
> |
* is empty. |
| 158 |
|
* |
| 159 |
< |
* @return the head of this queue. |
| 160 |
< |
* @throws NoSuchElementException if this queue is empty. |
| 159 |
> |
* @return the head of this queue |
| 160 |
> |
* @throws NoSuchElementException if this queue is empty |
| 161 |
|
*/ |
| 162 |
|
E remove(); |
| 163 |
|
|
| 164 |
|
/** |
| 165 |
< |
* Retrieves, but does not remove, the head of this queue, |
| 166 |
< |
* returning <tt>null</tt> if this queue is empty. |
| 165 |
> |
* Retrieves and removes the head of this queue, |
| 166 |
> |
* or returns <tt>null</tt> if this queue is empty. |
| 167 |
|
* |
| 168 |
< |
* @return the head of this queue, or <tt>null</tt> if this queue |
| 154 |
< |
* is empty. |
| 168 |
> |
* @return the head of this queue, or <tt>null</tt> if this queue is empty |
| 169 |
|
*/ |
| 170 |
< |
E peek(); |
| 170 |
> |
E poll(); |
| 171 |
|
|
| 172 |
|
/** |
| 173 |
|
* Retrieves, but does not remove, the head of this queue. This method |
| 174 |
< |
* differs from the {@link #peek} method only in that it throws an |
| 175 |
< |
* exception if this queue is empty. |
| 174 |
> |
* differs from {@link #peek} only in that it throws an exception if |
| 175 |
> |
* this queue is empty. |
| 176 |
|
* |
| 177 |
< |
* @return the head of this queue. |
| 178 |
< |
* @throws NoSuchElementException if this queue is empty. |
| 177 |
> |
* @return the head of this queue |
| 178 |
> |
* @throws NoSuchElementException if this queue is empty |
| 179 |
|
*/ |
| 180 |
|
E element(); |
| 181 |
+ |
|
| 182 |
+ |
/** |
| 183 |
+ |
* Retrieves, but does not remove, the head of this queue, |
| 184 |
+ |
* or returns <tt>null</tt> if this queue is empty. |
| 185 |
+ |
* |
| 186 |
+ |
* @return the head of this queue, or <tt>null</tt> if this queue is empty |
| 187 |
+ |
*/ |
| 188 |
+ |
E peek(); |
| 189 |
|
} |
