| 19 |
|
* <p> A <tt>Queue</tt> implementation that extends this class must |
| 20 |
|
* minimally define a method {@link Queue#offer} which does not permit |
| 21 |
|
* insertion of <tt>null</tt> elements, along with methods {@link |
| 22 |
< |
* Queue#peek}, {@link Queue#poll}, {@link Collection#size}, {@link |
| 23 |
< |
* Collection#remove}, and a {@link Collection#iterator} supporting |
| 24 |
< |
* {@link Iterator#remove}. If these requirements cannot be met, |
| 25 |
< |
* consider instead subclassing {@link AbstractCollection}. |
| 22 |
> |
* Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and a |
| 23 |
> |
* {@link Collection#iterator} supporting {@link |
| 24 |
> |
* Iterator#remove}. Typically, additional methods will be overridden |
| 25 |
> |
* as well. If these requirements cannot be met, consider instead |
| 26 |
> |
* subclassing {@link AbstractCollection}. |
| 27 |
|
* |
| 28 |
|
* @since 1.5 |
| 29 |
|
* @author Doug Lea |
| 30 |
+ |
* @param <E> the type of elements held in this collection |
| 31 |
|
*/ |
| 32 |
|
public abstract class AbstractQueue<E> |
| 33 |
|
extends AbstractCollection<E> |
| 39 |
|
protected AbstractQueue() { |
| 40 |
|
} |
| 41 |
|
|
| 40 |
– |
/** |
| 41 |
– |
* Inserts the specified element to this queue, if possible. |
| 42 |
– |
* |
| 43 |
– |
* @param o the element to add. |
| 44 |
– |
* @return <tt>true</tt> if it was possible to add the element to |
| 45 |
– |
* this queue, else <tt>false</tt> |
| 46 |
– |
* @throws NullPointerException if the specified element is <tt>null</tt> |
| 47 |
– |
*/ |
| 48 |
– |
public boolean offer(E o) { return false; } |
| 49 |
– |
// FIXME: Replace above no-op with following abstract version |
| 50 |
– |
// when javac allows it. |
| 51 |
– |
// public abstract boolean offer(E o); |
| 42 |
|
|
| 43 |
|
/** |
| 44 |
|
* Adds the specified element to this queue. This implementation |
| 45 |
|
* returns <tt>true</tt> if <tt>offer</tt> succeeds, else |
| 46 |
|
* throws an IllegalStateException. |
| 47 |
< |
* th |
| 47 |
> |
* |
| 48 |
|
* @param o the element |
| 49 |
|
* @return <tt>true</tt> (as per the general contract of |
| 50 |
|
* <tt>Collection.add</tt>). |
| 103 |
|
; |
| 104 |
|
} |
| 105 |
|
|
| 116 |
– |
// Declarations that mostly just remove optionality clauses. |
| 117 |
– |
|
| 118 |
– |
/** |
| 119 |
– |
* Removes a single instance of the specified element from this |
| 120 |
– |
* queue, if one is present. More formally, removes an element |
| 121 |
– |
* <tt>e</tt> such that <tt>(o==null ? e==null : |
| 122 |
– |
* o.equals(e))</tt>, if the queue contains such an element. |
| 123 |
– |
* Returns <tt>true</tt> if the queue contained the specified |
| 124 |
– |
* element (or equivalently, if the queue changed as a result of |
| 125 |
– |
* the call). |
| 126 |
– |
* |
| 127 |
– |
* @param o the element to remove |
| 128 |
– |
* @return true if the element was removed |
| 129 |
– |
*/ |
| 130 |
– |
public abstract boolean remove(Object o); |
| 131 |
– |
|
| 132 |
– |
/** |
| 133 |
– |
* Removes from this queue all of its elements that are contained in |
| 134 |
– |
* the specified collection. <p> |
| 135 |
– |
* |
| 136 |
– |
* This implementation iterates over this queue, checking each |
| 137 |
– |
* element returned by the iterator in turn to see if it's contained |
| 138 |
– |
* in the specified collection. If it's so contained, it's removed from |
| 139 |
– |
* this queue with the iterator's <tt>remove</tt> method.<p> |
| 140 |
– |
* |
| 141 |
– |
* @param c elements to be removed from this collection. |
| 142 |
– |
* @return <tt>true</tt> if this queue changed as a result of the |
| 143 |
– |
* call. |
| 144 |
– |
* @throws NullPointerException if the specified collection is null. |
| 145 |
– |
*/ |
| 146 |
– |
public boolean removeAll(Collection<?> c) { |
| 147 |
– |
return super.removeAll(c); |
| 148 |
– |
} |
| 149 |
– |
|
| 150 |
– |
/** |
| 151 |
– |
* Retains only the elements in this queue that are contained in the |
| 152 |
– |
* specified collection. In other words, removes |
| 153 |
– |
* from this queue all of its elements that are not contained in the |
| 154 |
– |
* specified collection. <p> |
| 155 |
– |
* |
| 156 |
– |
* This implementation iterates over this queue, checking each |
| 157 |
– |
* element returned by the iterator in turn to see if it's contained |
| 158 |
– |
* in the specified collection. If it's not so contained, it's removed |
| 159 |
– |
* from this queue with the iterator's <tt>remove</tt> method.<p> |
| 160 |
– |
* |
| 161 |
– |
* @param c elements to be retained in this collection. |
| 162 |
– |
* @return <tt>true</tt> if this queue changed as a result of the |
| 163 |
– |
* call. |
| 164 |
– |
* @throws NullPointerException if the specified collection is null. |
| 165 |
– |
* |
| 166 |
– |
*/ |
| 167 |
– |
public boolean retainAll(Collection<?> c) { |
| 168 |
– |
return super.retainAll(c); |
| 169 |
– |
} |
| 170 |
– |
|
| 106 |
|
/** |
| 107 |
|
* Adds all of the elements in the specified collection to this |
| 108 |
< |
* queue. The behavior of this operation is undefined if the |
| 109 |
< |
* specified collection is modified while the operation is in |
| 110 |
< |
* progress. (This implies that the behavior of this call is |
| 111 |
< |
* undefined if the specified collection is this queue, and this |
| 112 |
< |
* queue is nonempty.) |
| 113 |
< |
* |
| 114 |
< |
* <p> This implementation iterates over the specified collection, |
| 115 |
< |
* and uses the <tt>add</tt> method to insert each object returned by |
| 116 |
< |
* the iterator to this queue, in turn. |
| 108 |
> |
* queue. Attempts to addAll of a queue to itself result in |
| 109 |
> |
* <tt>IllegalArgumentException</tt>. Further, the behavior of |
| 110 |
> |
* this operation is undefined if the specified collection is |
| 111 |
> |
* modified while the operation is in progress. |
| 112 |
> |
* |
| 113 |
> |
* <p>This implementation iterates over the specified collection, |
| 114 |
> |
* and adds each element returned by the iterator to this |
| 115 |
> |
* collection, in turn. A runtime exception encountered while |
| 116 |
> |
* trying to add an element (including, in particular, a |
| 117 |
> |
* <tt>null</tt> element) may result in only some of the elements |
| 118 |
> |
* having been successfully added when the associated exception is |
| 119 |
> |
* thrown. |
| 120 |
|
* |
| 121 |
< |
* @param c collection whose elements are to be added to this queue |
| 122 |
< |
* @return <tt>true</tt> if this queue changed as a result of the |
| 121 |
> |
* @param c collection whose elements are to be added to this collection. |
| 122 |
> |
* @return <tt>true</tt> if this collection changed as a result of the |
| 123 |
|
* call. |
| 124 |
< |
* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt> |
| 125 |
< |
* is <tt>null</tt> |
| 126 |
< |
* @throws IllegalStateException if any element cannot be added. |
| 124 |
> |
* @throws NullPointerException if the specified collection, or |
| 125 |
> |
* any of its elements are null. |
| 126 |
> |
* @throws IllegalArgumentException if c is this queue. |
| 127 |
|
* |
| 128 |
+ |
* @see #add(Object) |
| 129 |
|
*/ |
| 130 |
|
public boolean addAll(Collection<? extends E> c) { |
| 131 |
< |
return super.addAll(c); |
| 131 |
> |
if (c == null) |
| 132 |
> |
throw new NullPointerException(); |
| 133 |
> |
if (c == this) |
| 134 |
> |
throw new IllegalArgumentException(); |
| 135 |
> |
boolean modified = false; |
| 136 |
> |
Iterator<? extends E> e = c.iterator(); |
| 137 |
> |
while (e.hasNext()) { |
| 138 |
> |
if (add(e.next())) |
| 139 |
> |
modified = true; |
| 140 |
> |
} |
| 141 |
> |
return modified; |
| 142 |
|
} |
| 143 |
|
|
| 144 |
|
} |
