| 1 |
|
/* |
| 2 |
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
| 3 |
< |
* Expert Group and released to the public domain. Use, modify, and |
| 4 |
< |
* redistribute this code in any way without acknowledgement. |
| 3 |
> |
* Expert Group and released to the public domain, as explained at |
| 4 |
> |
* http://creativecommons.org/licenses/publicdomain |
| 5 |
|
*/ |
| 6 |
|
|
| 7 |
|
package java.util; |
| 8 |
|
|
| 9 |
|
/** |
| 10 |
< |
* <tt>AbstractQueue</tt> provides default implementations of |
| 11 |
< |
* {@link #add add}, {@link #remove remove}, and {@link #element element} |
| 12 |
< |
* based on |
| 13 |
< |
* {@link #offer offer}, {@link #poll poll}, and {@link #peek peek}, |
| 14 |
< |
* respectively but that |
| 15 |
< |
* throw exceptions instead of indicating failure via <tt>false</tt> or |
| 10 |
> |
* This class provides skeletal implementations of some {@link Queue} |
| 11 |
> |
* operations. The implementations in this class are appropriate when |
| 12 |
> |
* the base implementation does <em>not</em> allow <tt>null</tt> |
| 13 |
> |
* elements. Methods {@link #add add}, {@link #remove remove}, and |
| 14 |
> |
* {@link #element element} are based on {@link #offer offer}, {@link |
| 15 |
> |
* #poll poll}, and {@link #peek peek}, respectively but throw |
| 16 |
> |
* exceptions instead of indicating failure via <tt>false</tt> or |
| 17 |
|
* <tt>null</tt> returns. |
| 18 |
< |
* <p>The provided implementations all assume that the base implementation |
| 19 |
< |
* does <em>not</em> allow <tt>null</tt> elements. |
| 18 |
> |
* |
| 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}, 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 |
> |
* <p>This class is a member of the |
| 29 |
> |
* <a href="{@docRoot}/../guide/collections/index.html"> |
| 30 |
> |
* Java Collections Framework</a>. |
| 31 |
> |
* |
| 32 |
|
* @since 1.5 |
| 33 |
|
* @author Doug Lea |
| 34 |
+ |
* @param <E> the type of elements held in this collection |
| 35 |
|
*/ |
| 36 |
< |
public abstract class AbstractQueue<E> |
| 37 |
< |
extends AbstractCollection<E> |
| 36 |
> |
public abstract class AbstractQueue<E> |
| 37 |
> |
extends AbstractCollection<E> |
| 38 |
|
implements Queue<E> { |
| 39 |
|
|
| 40 |
< |
// note that optional methods are not optional here or in our subclasses, |
| 41 |
< |
// so we redefine each optional method to document that it is not optional |
| 42 |
< |
// We also inherit, or define, all necessary @throws comments |
| 40 |
> |
/** |
| 41 |
> |
* Constructor for use by subclasses. |
| 42 |
> |
*/ |
| 43 |
> |
protected AbstractQueue() { |
| 44 |
> |
} |
| 45 |
|
|
| 46 |
|
/** |
| 47 |
< |
* Adds the specified element to this queue. |
| 48 |
< |
* @return <tt>true</tt> (as per the general contract of |
| 49 |
< |
* <tt>Collection.add</tt>). |
| 47 |
> |
* Inserts the specified element into this queue if it is possible to do so |
| 48 |
> |
* immediately without violating capacity restrictions, returning |
| 49 |
> |
* <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt> |
| 50 |
> |
* if no space is currently available. |
| 51 |
> |
* |
| 52 |
> |
* <p>This implementation returns <tt>true</tt> if <tt>offer</tt> succeeds, |
| 53 |
> |
* else throws an <tt>IllegalStateException</tt>. |
| 54 |
|
* |
| 55 |
< |
* @throws NullPointerException if the element is null |
| 55 |
> |
* @param e the element to add |
| 56 |
> |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
| 57 |
> |
* @throws IllegalStateException if the element cannot be added at this |
| 58 |
> |
* time due to capacity restrictions |
| 59 |
> |
* @throws ClassCastException if the class of the specified element |
| 60 |
> |
* prevents it from being added to this queue |
| 61 |
> |
* @throws NullPointerException if the specified element is null and |
| 62 |
> |
* this queue not permit null elements |
| 63 |
> |
* @throws IllegalArgumentException if some property of this element |
| 64 |
> |
* prevents it from being added to this queue |
| 65 |
|
*/ |
| 66 |
< |
public boolean add(E o) { |
| 67 |
< |
if (offer(o)) |
| 66 |
> |
public boolean add(E e) { |
| 67 |
> |
if (offer(e)) |
| 68 |
|
return true; |
| 69 |
|
else |
| 70 |
|
throw new IllegalStateException("Queue full"); |
| 71 |
|
} |
| 72 |
|
|
| 73 |
|
/** |
| 74 |
< |
* Adds all of the elements in the specified collection to this queue. |
| 75 |
< |
* The behavior of this operation is undefined if |
| 76 |
< |
* the specified collection is modified while the operation is in |
| 48 |
< |
* progress. (This implies that the behavior of this call is undefined if |
| 49 |
< |
* the specified collection is this queue, and this queue is nonempty.) |
| 50 |
< |
* <p> |
| 51 |
< |
* This implementation iterates over the specified collection, and adds |
| 52 |
< |
* each object returned by the iterator to this collection, in turn. |
| 74 |
> |
* Retrieves and removes the head of this queue. This method differs |
| 75 |
> |
* from {@link #poll} only in that it throws an exception if this queue |
| 76 |
> |
* is empty. |
| 77 |
|
* |
| 78 |
< |
* @param c collection whose elements are to be added to this queue |
| 79 |
< |
* @return <tt>true</tt> if this collection changed as a result of the |
| 80 |
< |
* call. |
| 81 |
< |
* @throws NullPointerException if <tt>c</tt> is <tt>null</tt> |
| 82 |
< |
* |
| 78 |
> |
* <p>This implementation returns the result of <tt>poll</tt> |
| 79 |
> |
* unless the queue is empty. |
| 80 |
> |
* |
| 81 |
> |
* @return the head of this queue |
| 82 |
> |
* @throws NoSuchElementException if this queue is empty |
| 83 |
|
*/ |
| 60 |
– |
boolean addAll(Collection<? extends E> c) { |
| 61 |
– |
return super.addAll(c); |
| 62 |
– |
} |
| 63 |
– |
|
| 64 |
– |
/** @throws NoSuchElementException {@inheritDoc} */ |
| 84 |
|
public E remove() { |
| 85 |
|
E x = poll(); |
| 86 |
|
if (x != null) |
| 89 |
|
throw new NoSuchElementException(); |
| 90 |
|
} |
| 91 |
|
|
| 92 |
< |
/** @throws NoSuchElementException {@inheritDoc} */ |
| 92 |
> |
/** |
| 93 |
> |
* Retrieves, but does not remove, the head of this queue. This method |
| 94 |
> |
* differs from {@link #peek} only in that it throws an exception if |
| 95 |
> |
* this queue is empty. |
| 96 |
> |
* |
| 97 |
> |
* <p>This implementation returns the result of <tt>peek</tt> |
| 98 |
> |
* unless the queue is empty. |
| 99 |
> |
* |
| 100 |
> |
* @return the head of this queue |
| 101 |
> |
* @throws NoSuchElementException if this queue is empty |
| 102 |
> |
*/ |
| 103 |
|
public E element() { |
| 104 |
|
E x = peek(); |
| 105 |
|
if (x != null) |
| 109 |
|
} |
| 110 |
|
|
| 111 |
|
/** |
| 112 |
< |
* Removes all of the elements from this collection. |
| 113 |
< |
* The collection will be empty after this call returns. |
| 112 |
> |
* Removes all of the elements from this queue. |
| 113 |
> |
* The queue will be empty after this call returns. |
| 114 |
> |
* |
| 115 |
|
* <p>This implementation repeatedly invokes {@link #poll poll} until it |
| 116 |
|
* returns <tt>null</tt>. |
| 117 |
|
*/ |
| 120 |
|
; |
| 121 |
|
} |
| 122 |
|
|
| 123 |
< |
// XXX Remove this redundant declaration, pending response from Neal Gafter. |
| 124 |
< |
public abstract Iterator<E> iterator(); |
| 125 |
< |
} |
| 126 |
< |
|
| 127 |
< |
|
| 128 |
< |
|
| 129 |
< |
|
| 123 |
> |
/** |
| 124 |
> |
* Adds all of the elements in the specified collection to this |
| 125 |
> |
* queue. Attempts to addAll of a queue to itself result in |
| 126 |
> |
* <tt>IllegalArgumentException</tt>. Further, the behavior of |
| 127 |
> |
* this operation is undefined if the specified collection is |
| 128 |
> |
* modified while the operation is in progress. |
| 129 |
> |
* |
| 130 |
> |
* <p>This implementation iterates over the specified collection, |
| 131 |
> |
* and adds each element returned by the iterator to this |
| 132 |
> |
* queue, in turn. A runtime exception encountered while |
| 133 |
> |
* trying to add an element (including, in particular, a |
| 134 |
> |
* <tt>null</tt> element) may result in only some of the elements |
| 135 |
> |
* having been successfully added when the associated exception is |
| 136 |
> |
* thrown. |
| 137 |
> |
* |
| 138 |
> |
* @param c collection whose elements are to be added to this queue |
| 139 |
> |
* @return <tt>true</tt> if this queue changed as a result of the call |
| 140 |
> |
* @throws ClassCastException if the class of an element of the specified |
| 141 |
> |
* collection prevents it from being added to this queue |
| 142 |
> |
* @throws NullPointerException if the specified collection contains a |
| 143 |
> |
* null element and this queue does not permit null elements, |
| 144 |
> |
* or if the specified collection is null |
| 145 |
> |
* @throws IllegalArgumentException if some property of an element of the |
| 146 |
> |
* specified collection prevents it from being added to this |
| 147 |
> |
* queue, or if the specified collection is this queue |
| 148 |
> |
* @throws IllegalStateException if not all the elements can be added at |
| 149 |
> |
* this time due to insertion restrictions |
| 150 |
> |
* @see #add(Object) |
| 151 |
> |
*/ |
| 152 |
> |
public boolean addAll(Collection<? extends E> c) { |
| 153 |
> |
if (c == null) |
| 154 |
> |
throw new NullPointerException(); |
| 155 |
> |
if (c == this) |
| 156 |
> |
throw new IllegalArgumentException(); |
| 157 |
> |
boolean modified = false; |
| 158 |
> |
Iterator<? extends E> e = c.iterator(); |
| 159 |
> |
while (e.hasNext()) { |
| 160 |
> |
if (add(e.next())) |
| 161 |
> |
modified = true; |
| 162 |
> |
} |
| 163 |
> |
return modified; |
| 164 |
> |
} |
| 165 |
|
|
| 166 |
+ |
} |
