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dl |
1.2 |
/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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dl |
1.24 |
* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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dl |
1.2 |
*/ |
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tim |
1.1 |
package java.util; |
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/** |
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dl |
1.14 |
* This class provides skeletal implementations of some {@link Queue} |
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* operations. The implementations in this class are appropriate when |
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* the base implementation does <em>not</em> allow <tt>null</tt> |
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* elements. Methods {@link #add add}, {@link #remove remove}, and |
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* {@link #element element} are based on {@link #offer offer}, {@link |
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* #poll poll}, and {@link #peek peek}, respectively but throw |
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* exceptions instead of indicating failure via <tt>false</tt> or |
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dholmes |
1.9 |
* <tt>null</tt> returns. |
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1.14 |
* |
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* <p> A <tt>Queue</tt> implementation that extends this class must |
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* minimally define a method {@link Queue#offer} which does not permit |
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* insertion of <tt>null</tt> elements, along with methods {@link |
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1.16 |
* Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and a |
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* {@link Collection#iterator} supporting {@link |
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1.18 |
* Iterator#remove}. Typically, additional methods will be overridden |
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1.16 |
* as well. If these requirements cannot be met, consider instead |
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* subclassing {@link AbstractCollection}. |
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1.14 |
* |
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1.25 |
* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
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jsr166 |
1.26 |
* |
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dl |
1.4 |
* @since 1.5 |
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* @author Doug Lea |
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1.21 |
* @param <E> the type of elements held in this collection |
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tim |
1.1 |
*/ |
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tim |
1.10 |
public abstract class AbstractQueue<E> |
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extends AbstractCollection<E> |
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dholmes |
1.9 |
implements Queue<E> { |
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tim |
1.5 |
|
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1.14 |
/** |
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* Constructor for use by subclasses. |
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*/ |
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protected AbstractQueue() { |
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} |
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tim |
1.1 |
|
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dholmes |
1.12 |
/** |
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jsr166 |
1.28 |
* Inserts the specified element into this queue if it is possible to do so |
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* immediately without violating capacity restrictions, returning |
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* <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt> |
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* if no space is currently available. |
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* |
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* <p>This implementation returns <tt>true</tt> if <tt>offer</tt> succeeds, |
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* else throws an <tt>IllegalStateException</tt>. |
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* |
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* @param e the element to add |
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jsr166 |
1.31 |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
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jsr166 |
1.28 |
* @throws IllegalStateException if the element cannot be added at this |
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* time due to capacity restrictions |
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jsr166 |
1.29 |
* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this queue |
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jsr166 |
1.28 |
* @throws NullPointerException if the specified element is null and |
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jsr166 |
1.33 |
* this queue does not permit null elements |
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jsr166 |
1.28 |
* @throws IllegalArgumentException if some property of this element |
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* prevents it from being added to this queue |
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dholmes |
1.9 |
*/ |
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jsr166 |
1.27 |
public boolean add(E e) { |
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if (offer(e)) |
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1.1 |
return true; |
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else |
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throw new IllegalStateException("Queue full"); |
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} |
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dholmes |
1.9 |
/** |
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jsr166 |
1.28 |
* Retrieves and removes the head of this queue. This method differs |
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jsr166 |
1.31 |
* from {@link #poll poll} only in that it throws an exception if this |
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* queue is empty. |
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jsr166 |
1.28 |
* |
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* <p>This implementation returns the result of <tt>poll</tt> |
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dl |
1.14 |
* unless the queue is empty. |
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dholmes |
1.9 |
* |
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jsr166 |
1.28 |
* @return the head of this queue |
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* @throws NoSuchElementException if this queue is empty |
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dholmes |
1.9 |
*/ |
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tim |
1.8 |
public E remove() { |
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tim |
1.1 |
E x = poll(); |
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if (x != null) |
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return x; |
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else |
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throw new NoSuchElementException(); |
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} |
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dl |
1.14 |
/** |
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jsr166 |
1.28 |
* Retrieves, but does not remove, the head of this queue. This method |
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jsr166 |
1.31 |
* differs from {@link #peek peek} only in that it throws an exception if |
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jsr166 |
1.28 |
* this queue is empty. |
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* |
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* <p>This implementation returns the result of <tt>peek</tt> |
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dl |
1.14 |
* unless the queue is empty. |
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* |
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jsr166 |
1.28 |
* @return the head of this queue |
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* @throws NoSuchElementException if this queue is empty |
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dl |
1.14 |
*/ |
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tim |
1.8 |
public E element() { |
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tim |
1.1 |
E x = peek(); |
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if (x != null) |
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return x; |
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else |
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throw new NoSuchElementException(); |
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} |
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dholmes |
1.9 |
/** |
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jsr166 |
1.26 |
* Removes all of the elements from this queue. |
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* The queue will be empty after this call returns. |
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jsr166 |
1.28 |
* |
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dholmes |
1.9 |
* <p>This implementation repeatedly invokes {@link #poll poll} until it |
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* returns <tt>null</tt>. |
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*/ |
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tim |
1.1 |
public void clear() { |
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while (poll() != null) |
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; |
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} |
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dl |
1.19 |
|
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/** |
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* Adds all of the elements in the specified collection to this |
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* queue. Attempts to addAll of a queue to itself result in |
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* <tt>IllegalArgumentException</tt>. Further, the behavior of |
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* this operation is undefined if the specified collection is |
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* modified while the operation is in progress. |
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* |
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* <p>This implementation iterates over the specified collection, |
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* and adds each element returned by the iterator to this |
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jsr166 |
1.26 |
* queue, in turn. A runtime exception encountered while |
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dl |
1.19 |
* trying to add an element (including, in particular, a |
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* <tt>null</tt> element) may result in only some of the elements |
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* having been successfully added when the associated exception is |
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* thrown. |
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* |
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jsr166 |
1.30 |
* @param c collection containing elements to be added to this queue |
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jsr166 |
1.28 |
* @return <tt>true</tt> if this queue changed as a result of the call |
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jsr166 |
1.29 |
* @throws ClassCastException if the class of an element of the specified |
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* collection prevents it from being added to this queue |
142 |
jsr166 |
1.28 |
* @throws NullPointerException if the specified collection contains a |
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* null element and this queue does not permit null elements, |
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* or if the specified collection is null |
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* @throws IllegalArgumentException if some property of an element of the |
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jsr166 |
1.29 |
* specified collection prevents it from being added to this |
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* queue, or if the specified collection is this queue |
148 |
jsr166 |
1.28 |
* @throws IllegalStateException if not all the elements can be added at |
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* this time due to insertion restrictions |
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dl |
1.19 |
* @see #add(Object) |
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*/ |
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public boolean addAll(Collection<? extends E> c) { |
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if (c == null) |
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throw new NullPointerException(); |
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if (c == this) |
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throw new IllegalArgumentException(); |
157 |
jozart |
1.23 |
boolean modified = false; |
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Iterator<? extends E> e = c.iterator(); |
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while (e.hasNext()) { |
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if (add(e.next())) |
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modified = true; |
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} |
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return modified; |
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dl |
1.19 |
} |
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166 |
dl |
1.14 |
} |