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revision 1.28, Mon May 2 17:34:02 2005 UTC revision 1.29, Sat May 14 02:11:52 2005 UTC
# Line 23  Line 23 
23   *  <tr>   *  <tr>
24   *    <td></td>   *    <td></td>
25   *    <td ALIGN=CENTER><em>Throws exception</em></td>   *    <td ALIGN=CENTER><em>Throws exception</em></td>
26   *    <td ALIGN=CENTER><em>Returns special value</em></td>   *    <td ALIGN=CENTER><em>Special value</em></td>
27   *  </tr>   *  </tr>
28   *  <tr>   *  <tr>
29   *    <td><b>Insert</b></td>   *    <td><b>Insert</b></td>
# Line 113  Line 113 
113   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
114   */   */
115  public interface Queue<E> extends Collection<E> {  public interface Queue<E> extends Collection<E> {
   
116      /**      /**
117       * Inserts the specified element into this queue, if possible.  When       * Inserts the specified element into this queue if it is possible to do so
118       * using queues that may impose insertion restrictions (for       * immediately without violating capacity restrictions, returning
119       * example capacity bounds), method <tt>offer</tt> is generally       * <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt>
120       * preferable to method {@link Collection#add}, which can fail to       * if no space is currently available.
121       * insert an element only by throwing an exception.       *
122       *       * @param e the element to add
123       * @param e the element to insert.       * @return <tt>true</tt> (as per the spec for {@link Collection#add})
124       * @return <tt>true</tt> if it was possible to add the element to       * @throws IllegalStateException if the element cannot be added at this
125       * this queue, else <tt>false</tt>       *         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);      boolean add(E e);
134    
135      /**      /**
136       * Retrieves and removes the head of this queue, or <tt>null</tt>       * Inserts the specified element into this queue if it is possible to do
137       * if this queue is empty.       * so immediately without violating capacity restrictions.
138       *       * When using a capacity-restricted deque, this method is generally
139       * @return the head of this queue, or <tt>null</tt> if this       * preferable to {@link #add}, which can fail to insert an element only
140       *         queue is empty.       * by throwing an exception.
141         *
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();      boolean offer(E e);
153    
154      /**      /**
155       * Retrieves and removes the head of this queue.  This method       * Retrieves and removes the head of this queue.  This method differs
156       * differs from the {@link #poll} method only in that it throws an       * from {@link #poll} only in that it throws an exception if this queue
157       * exception if this queue is empty.       * is empty.
158       *       *
159       * @return the head of this queue.       * @return the head of this queue
160       * @throws NoSuchElementException if this queue is empty.       * @throws NoSuchElementException if this queue is empty
161       */       */
162      E remove();      E remove();
163    
164      /**      /**
165       * Retrieves, but does not remove, the head of this queue,       * Retrieves and removes the head of this queue,
166       * returning <tt>null</tt> if this queue is empty.       * 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       * @return the head of this queue, or <tt>null</tt> if this queue is empty
      * is empty.  
169       */       */
170      E peek();      E poll();
171    
172      /**      /**
173       * Retrieves, but does not remove, the head of this queue.  This method       * 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       * differs from {@link #peek} only in that it throws an exception if
175       * exception if this queue is empty.       * this queue is empty.
176       *       *
177       * @return the head of this queue.       * @return the head of this queue
178       * @throws NoSuchElementException if this queue is empty.       * @throws NoSuchElementException if this queue is empty
179       */       */
180      E element();      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  }  }

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