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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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package java.util.concurrent; |
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|
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import java.util.AbstractQueue; |
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import java.util.Collection; |
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import java.util.Iterator; |
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import java.util.NoSuchElementException; |
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import java.util.concurrent.locks.Condition; |
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import java.util.concurrent.locks.ReentrantLock; |
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|
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/** |
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* An optionally-bounded {@linkplain BlockingDeque blocking deque} based on |
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* linked nodes. |
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* |
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* <p> The optional capacity bound constructor argument serves as a |
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* way to prevent excessive expansion. The capacity, if unspecified, |
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
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* dynamically created upon each insertion unless this would bring the |
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* deque above capacity. |
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* |
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* <p>Most operations run in constant time (ignoring time spent |
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* blocking). Exceptions include {@link #remove(Object) remove}, |
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* {@link #removeFirstOccurrence removeFirstOccurrence}, {@link |
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* #removeLastOccurrence removeLastOccurrence}, {@link #contains |
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* contains}, {@link #iterator iterator.remove()}, and the bulk |
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* operations, all of which run in linear time. |
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* |
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* <p>This class and its iterator implement all of the |
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* <em>optional</em> methods of the {@link Collection} and {@link |
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* Iterator} interfaces. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.6 |
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* @author Doug Lea |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class LinkedBlockingDeque<E> |
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extends AbstractQueue<E> |
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implements BlockingDeque<E>, java.io.Serializable { |
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|
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/* |
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* Implemented as a simple doubly-linked list protected by a |
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* single lock and using conditions to manage blocking. |
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* |
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* To implement weakly consistent iterators, it appears we need to |
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* keep all Nodes GC-reachable from a predecessor dequeued Node. |
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* That would cause two problems: |
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* - allow a rogue Iterator to cause unbounded memory retention |
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* - cause cross-generational linking of old Nodes to new Nodes if |
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* a Node was tenured while live, which generational GCs have a |
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* hard time dealing with, causing repeated major collections. |
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* However, only non-deleted Nodes need to be reachable from |
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* dequeued Nodes, and reachability does not necessarily have to |
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* be of the kind understood by the GC. We use the trick of |
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* linking a Node that has just been dequeued to itself. Such a |
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* self-link implicitly means to jump to "first" (for next links) |
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* or "last" (for prev links). |
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*/ |
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|
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/* |
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* We have "diamond" multiple interface/abstract class inheritance |
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* here, and that introduces ambiguities. Often we want the |
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* BlockingDeque javadoc combined with the AbstractQueue |
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* implementation, so a lot of method specs are duplicated here. |
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*/ |
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|
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private static final long serialVersionUID = -387911632671998426L; |
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|
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/** Doubly-linked list node class */ |
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static final class Node<E> { |
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/** |
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* The item, or null if this node has been removed. |
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*/ |
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E item; |
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|
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/** |
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* One of: |
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* - the real predecessor Node |
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* - this Node, meaning the predecessor is tail |
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* - null, meaning there is no predecessor |
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*/ |
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Node<E> prev; |
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|
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/** |
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* One of: |
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* - the real successor Node |
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* - this Node, meaning the successor is head |
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* - null, meaning there is no successor |
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*/ |
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Node<E> next; |
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|
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Node(E x, Node<E> p, Node<E> n) { |
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item = x; |
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prev = p; |
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next = n; |
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} |
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} |
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|
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/** |
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* Pointer to first node. |
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* Invariant: (first == null && last == null) || |
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* (first.prev == null && first.item != null) |
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*/ |
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transient Node<E> first; |
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|
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/** |
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* Pointer to last node. |
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* Invariant: (first == null && last == null) || |
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* (last.next == null && last.item != null) |
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*/ |
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transient Node<E> last; |
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|
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/** Number of items in the deque */ |
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private transient int count; |
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|
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/** Maximum number of items in the deque */ |
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private final int capacity; |
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|
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/** Main lock guarding all access */ |
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final ReentrantLock lock = new ReentrantLock(); |
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|
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/** Condition for waiting takes */ |
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private final Condition notEmpty = lock.newCondition(); |
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|
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/** Condition for waiting puts */ |
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private final Condition notFull = lock.newCondition(); |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with a capacity of |
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* {@link Integer#MAX_VALUE}. |
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*/ |
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public LinkedBlockingDeque() { |
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this(Integer.MAX_VALUE); |
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} |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity. |
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* |
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* @param capacity the capacity of this deque |
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* @throws IllegalArgumentException if {@code capacity} is less than 1 |
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*/ |
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public LinkedBlockingDeque(int capacity) { |
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if (capacity <= 0) throw new IllegalArgumentException(); |
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this.capacity = capacity; |
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} |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with a capacity of |
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* {@link Integer#MAX_VALUE}, initially containing the elements of |
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* the given collection, added in traversal order of the |
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* collection's iterator. |
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* |
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* @param c the collection of elements to initially contain |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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public LinkedBlockingDeque(Collection<? extends E> c) { |
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this(Integer.MAX_VALUE); |
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final ReentrantLock lock = this.lock; |
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lock.lock(); // Never contended, but necessary for visibility |
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try { |
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for (E e : c) { |
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if (e == null) |
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throw new NullPointerException(); |
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if (!linkLast(e)) |
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throw new IllegalStateException("Deque full"); |
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} |
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} finally { |
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lock.unlock(); |
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} |
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} |
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|
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|
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// Basic linking and unlinking operations, called only while holding lock |
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|
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/** |
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* Links e as first element, or returns false if full. |
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*/ |
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private boolean linkFirst(E e) { |
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// assert lock.isHeldByCurrentThread(); |
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if (count >= capacity) |
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return false; |
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Node<E> f = first; |
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Node<E> x = new Node<E>(e, null, f); |
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first = x; |
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if (last == null) |
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last = x; |
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else |
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f.prev = x; |
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++count; |
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notEmpty.signal(); |
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return true; |
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} |
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|
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/** |
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* Links e as last element, or returns false if full. |
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*/ |
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private boolean linkLast(E e) { |
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// assert lock.isHeldByCurrentThread(); |
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if (count >= capacity) |
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return false; |
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Node<E> l = last; |
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Node<E> x = new Node<E>(e, l, null); |
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last = x; |
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if (first == null) |
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first = x; |
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else |
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l.next = x; |
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++count; |
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notEmpty.signal(); |
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return true; |
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} |
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|
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/** |
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* Removes and returns first element, or null if empty. |
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*/ |
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private E unlinkFirst() { |
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// assert lock.isHeldByCurrentThread(); |
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Node<E> f = first; |
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if (f == null) |
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return null; |
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Node<E> n = f.next; |
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E item = f.item; |
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f.item = null; |
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f.next = f; // help GC |
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first = n; |
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if (n == null) |
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last = null; |
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else |
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n.prev = null; |
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--count; |
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notFull.signal(); |
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return item; |
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} |
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|
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/** |
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* Removes and returns last element, or null if empty. |
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*/ |
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private E unlinkLast() { |
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// assert lock.isHeldByCurrentThread(); |
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Node<E> l = last; |
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if (l == null) |
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return null; |
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Node<E> p = l.prev; |
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E item = l.item; |
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l.item = null; |
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l.prev = l; // help GC |
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last = p; |
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if (p == null) |
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first = null; |
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else |
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p.next = null; |
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--count; |
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notFull.signal(); |
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return item; |
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} |
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|
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/** |
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* Unlinks x. |
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*/ |
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void unlink(Node<E> x) { |
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// assert lock.isHeldByCurrentThread(); |
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Node<E> p = x.prev; |
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Node<E> n = x.next; |
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if (p == null) { |
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unlinkFirst(); |
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} else if (n == null) { |
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unlinkLast(); |
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} else { |
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p.next = n; |
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n.prev = p; |
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x.item = null; |
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// Don't mess with x's links. They may still be in use by |
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// an iterator. |
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--count; |
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notFull.signal(); |
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} |
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} |
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|
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// BlockingDeque methods |
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|
290 |
/** |
291 |
* @throws IllegalStateException {@inheritDoc} |
292 |
* @throws NullPointerException {@inheritDoc} |
293 |
*/ |
294 |
public void addFirst(E e) { |
295 |
if (!offerFirst(e)) |
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throw new IllegalStateException("Deque full"); |
297 |
} |
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|
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/** |
300 |
* @throws IllegalStateException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
302 |
*/ |
303 |
public void addLast(E e) { |
304 |
if (!offerLast(e)) |
305 |
throw new IllegalStateException("Deque full"); |
306 |
} |
307 |
|
308 |
/** |
309 |
* @throws NullPointerException {@inheritDoc} |
310 |
*/ |
311 |
public boolean offerFirst(E e) { |
312 |
if (e == null) throw new NullPointerException(); |
313 |
final ReentrantLock lock = this.lock; |
314 |
lock.lock(); |
315 |
try { |
316 |
return linkFirst(e); |
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} finally { |
318 |
lock.unlock(); |
319 |
} |
320 |
} |
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|
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/** |
323 |
* @throws NullPointerException {@inheritDoc} |
324 |
*/ |
325 |
public boolean offerLast(E e) { |
326 |
if (e == null) throw new NullPointerException(); |
327 |
final ReentrantLock lock = this.lock; |
328 |
lock.lock(); |
329 |
try { |
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return linkLast(e); |
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} finally { |
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lock.unlock(); |
333 |
} |
334 |
} |
335 |
|
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/** |
337 |
* @throws NullPointerException {@inheritDoc} |
338 |
* @throws InterruptedException {@inheritDoc} |
339 |
*/ |
340 |
public void putFirst(E e) throws InterruptedException { |
341 |
if (e == null) throw new NullPointerException(); |
342 |
final ReentrantLock lock = this.lock; |
343 |
lock.lock(); |
344 |
try { |
345 |
while (!linkFirst(e)) |
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notFull.await(); |
347 |
} finally { |
348 |
lock.unlock(); |
349 |
} |
350 |
} |
351 |
|
352 |
/** |
353 |
* @throws NullPointerException {@inheritDoc} |
354 |
* @throws InterruptedException {@inheritDoc} |
355 |
*/ |
356 |
public void putLast(E e) throws InterruptedException { |
357 |
if (e == null) throw new NullPointerException(); |
358 |
final ReentrantLock lock = this.lock; |
359 |
lock.lock(); |
360 |
try { |
361 |
while (!linkLast(e)) |
362 |
notFull.await(); |
363 |
} finally { |
364 |
lock.unlock(); |
365 |
} |
366 |
} |
367 |
|
368 |
/** |
369 |
* @throws NullPointerException {@inheritDoc} |
370 |
* @throws InterruptedException {@inheritDoc} |
371 |
*/ |
372 |
public boolean offerFirst(E e, long timeout, TimeUnit unit) |
373 |
throws InterruptedException { |
374 |
if (e == null) throw new NullPointerException(); |
375 |
long nanos = unit.toNanos(timeout); |
376 |
final ReentrantLock lock = this.lock; |
377 |
lock.lockInterruptibly(); |
378 |
try { |
379 |
while (!linkFirst(e)) { |
380 |
if (nanos <= 0) |
381 |
return false; |
382 |
nanos = notFull.awaitNanos(nanos); |
383 |
} |
384 |
return true; |
385 |
} finally { |
386 |
lock.unlock(); |
387 |
} |
388 |
} |
389 |
|
390 |
/** |
391 |
* @throws NullPointerException {@inheritDoc} |
392 |
* @throws InterruptedException {@inheritDoc} |
393 |
*/ |
394 |
public boolean offerLast(E e, long timeout, TimeUnit unit) |
395 |
throws InterruptedException { |
396 |
if (e == null) throw new NullPointerException(); |
397 |
long nanos = unit.toNanos(timeout); |
398 |
final ReentrantLock lock = this.lock; |
399 |
lock.lockInterruptibly(); |
400 |
try { |
401 |
while (!linkLast(e)) { |
402 |
if (nanos <= 0) |
403 |
return false; |
404 |
nanos = notFull.awaitNanos(nanos); |
405 |
} |
406 |
return true; |
407 |
} finally { |
408 |
lock.unlock(); |
409 |
} |
410 |
} |
411 |
|
412 |
/** |
413 |
* @throws NoSuchElementException {@inheritDoc} |
414 |
*/ |
415 |
public E removeFirst() { |
416 |
E x = pollFirst(); |
417 |
if (x == null) throw new NoSuchElementException(); |
418 |
return x; |
419 |
} |
420 |
|
421 |
/** |
422 |
* @throws NoSuchElementException {@inheritDoc} |
423 |
*/ |
424 |
public E removeLast() { |
425 |
E x = pollLast(); |
426 |
if (x == null) throw new NoSuchElementException(); |
427 |
return x; |
428 |
} |
429 |
|
430 |
public E pollFirst() { |
431 |
final ReentrantLock lock = this.lock; |
432 |
lock.lock(); |
433 |
try { |
434 |
return unlinkFirst(); |
435 |
} finally { |
436 |
lock.unlock(); |
437 |
} |
438 |
} |
439 |
|
440 |
public E pollLast() { |
441 |
final ReentrantLock lock = this.lock; |
442 |
lock.lock(); |
443 |
try { |
444 |
return unlinkLast(); |
445 |
} finally { |
446 |
lock.unlock(); |
447 |
} |
448 |
} |
449 |
|
450 |
public E takeFirst() throws InterruptedException { |
451 |
final ReentrantLock lock = this.lock; |
452 |
lock.lock(); |
453 |
try { |
454 |
E x; |
455 |
while ( (x = unlinkFirst()) == null) |
456 |
notEmpty.await(); |
457 |
return x; |
458 |
} finally { |
459 |
lock.unlock(); |
460 |
} |
461 |
} |
462 |
|
463 |
public E takeLast() throws InterruptedException { |
464 |
final ReentrantLock lock = this.lock; |
465 |
lock.lock(); |
466 |
try { |
467 |
E x; |
468 |
while ( (x = unlinkLast()) == null) |
469 |
notEmpty.await(); |
470 |
return x; |
471 |
} finally { |
472 |
lock.unlock(); |
473 |
} |
474 |
} |
475 |
|
476 |
public E pollFirst(long timeout, TimeUnit unit) |
477 |
throws InterruptedException { |
478 |
long nanos = unit.toNanos(timeout); |
479 |
final ReentrantLock lock = this.lock; |
480 |
lock.lockInterruptibly(); |
481 |
try { |
482 |
E x; |
483 |
while ( (x = unlinkFirst()) == null) { |
484 |
if (nanos <= 0) |
485 |
return null; |
486 |
nanos = notEmpty.awaitNanos(nanos); |
487 |
} |
488 |
return x; |
489 |
} finally { |
490 |
lock.unlock(); |
491 |
} |
492 |
} |
493 |
|
494 |
public E pollLast(long timeout, TimeUnit unit) |
495 |
throws InterruptedException { |
496 |
long nanos = unit.toNanos(timeout); |
497 |
final ReentrantLock lock = this.lock; |
498 |
lock.lockInterruptibly(); |
499 |
try { |
500 |
E x; |
501 |
while ( (x = unlinkLast()) == null) { |
502 |
if (nanos <= 0) |
503 |
return null; |
504 |
nanos = notEmpty.awaitNanos(nanos); |
505 |
} |
506 |
return x; |
507 |
} finally { |
508 |
lock.unlock(); |
509 |
} |
510 |
} |
511 |
|
512 |
/** |
513 |
* @throws NoSuchElementException {@inheritDoc} |
514 |
*/ |
515 |
public E getFirst() { |
516 |
E x = peekFirst(); |
517 |
if (x == null) throw new NoSuchElementException(); |
518 |
return x; |
519 |
} |
520 |
|
521 |
/** |
522 |
* @throws NoSuchElementException {@inheritDoc} |
523 |
*/ |
524 |
public E getLast() { |
525 |
E x = peekLast(); |
526 |
if (x == null) throw new NoSuchElementException(); |
527 |
return x; |
528 |
} |
529 |
|
530 |
public E peekFirst() { |
531 |
final ReentrantLock lock = this.lock; |
532 |
lock.lock(); |
533 |
try { |
534 |
return (first == null) ? null : first.item; |
535 |
} finally { |
536 |
lock.unlock(); |
537 |
} |
538 |
} |
539 |
|
540 |
public E peekLast() { |
541 |
final ReentrantLock lock = this.lock; |
542 |
lock.lock(); |
543 |
try { |
544 |
return (last == null) ? null : last.item; |
545 |
} finally { |
546 |
lock.unlock(); |
547 |
} |
548 |
} |
549 |
|
550 |
public boolean removeFirstOccurrence(Object o) { |
551 |
if (o == null) return false; |
552 |
final ReentrantLock lock = this.lock; |
553 |
lock.lock(); |
554 |
try { |
555 |
for (Node<E> p = first; p != null; p = p.next) { |
556 |
if (o.equals(p.item)) { |
557 |
unlink(p); |
558 |
return true; |
559 |
} |
560 |
} |
561 |
return false; |
562 |
} finally { |
563 |
lock.unlock(); |
564 |
} |
565 |
} |
566 |
|
567 |
public boolean removeLastOccurrence(Object o) { |
568 |
if (o == null) return false; |
569 |
final ReentrantLock lock = this.lock; |
570 |
lock.lock(); |
571 |
try { |
572 |
for (Node<E> p = last; p != null; p = p.prev) { |
573 |
if (o.equals(p.item)) { |
574 |
unlink(p); |
575 |
return true; |
576 |
} |
577 |
} |
578 |
return false; |
579 |
} finally { |
580 |
lock.unlock(); |
581 |
} |
582 |
} |
583 |
|
584 |
// BlockingQueue methods |
585 |
|
586 |
/** |
587 |
* Inserts the specified element at the end of this deque unless it would |
588 |
* violate capacity restrictions. When using a capacity-restricted deque, |
589 |
* it is generally preferable to use method {@link #offer(Object) offer}. |
590 |
* |
591 |
* <p>This method is equivalent to {@link #addLast}. |
592 |
* |
593 |
* @throws IllegalStateException if the element cannot be added at this |
594 |
* time due to capacity restrictions |
595 |
* @throws NullPointerException if the specified element is null |
596 |
*/ |
597 |
public boolean add(E e) { |
598 |
addLast(e); |
599 |
return true; |
600 |
} |
601 |
|
602 |
/** |
603 |
* @throws NullPointerException if the specified element is null |
604 |
*/ |
605 |
public boolean offer(E e) { |
606 |
return offerLast(e); |
607 |
} |
608 |
|
609 |
/** |
610 |
* @throws NullPointerException {@inheritDoc} |
611 |
* @throws InterruptedException {@inheritDoc} |
612 |
*/ |
613 |
public void put(E e) throws InterruptedException { |
614 |
putLast(e); |
615 |
} |
616 |
|
617 |
/** |
618 |
* @throws NullPointerException {@inheritDoc} |
619 |
* @throws InterruptedException {@inheritDoc} |
620 |
*/ |
621 |
public boolean offer(E e, long timeout, TimeUnit unit) |
622 |
throws InterruptedException { |
623 |
return offerLast(e, timeout, unit); |
624 |
} |
625 |
|
626 |
/** |
627 |
* Retrieves and removes the head of the queue represented by this deque. |
628 |
* This method differs from {@link #poll poll} only in that it throws an |
629 |
* exception if this deque is empty. |
630 |
* |
631 |
* <p>This method is equivalent to {@link #removeFirst() removeFirst}. |
632 |
* |
633 |
* @return the head of the queue represented by this deque |
634 |
* @throws NoSuchElementException if this deque is empty |
635 |
*/ |
636 |
public E remove() { |
637 |
return removeFirst(); |
638 |
} |
639 |
|
640 |
public E poll() { |
641 |
return pollFirst(); |
642 |
} |
643 |
|
644 |
public E take() throws InterruptedException { |
645 |
return takeFirst(); |
646 |
} |
647 |
|
648 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
649 |
return pollFirst(timeout, unit); |
650 |
} |
651 |
|
652 |
/** |
653 |
* Retrieves, but does not remove, the head of the queue represented by |
654 |
* this deque. This method differs from {@link #peek peek} only in that |
655 |
* it throws an exception if this deque is empty. |
656 |
* |
657 |
* <p>This method is equivalent to {@link #getFirst() getFirst}. |
658 |
* |
659 |
* @return the head of the queue represented by this deque |
660 |
* @throws NoSuchElementException if this deque is empty |
661 |
*/ |
662 |
public E element() { |
663 |
return getFirst(); |
664 |
} |
665 |
|
666 |
public E peek() { |
667 |
return peekFirst(); |
668 |
} |
669 |
|
670 |
/** |
671 |
* Returns the number of additional elements that this deque can ideally |
672 |
* (in the absence of memory or resource constraints) accept without |
673 |
* blocking. This is always equal to the initial capacity of this deque |
674 |
* less the current {@code size} of this deque. |
675 |
* |
676 |
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
677 |
* an element will succeed by inspecting {@code remainingCapacity} |
678 |
* because it may be the case that another thread is about to |
679 |
* insert or remove an element. |
680 |
*/ |
681 |
public int remainingCapacity() { |
682 |
final ReentrantLock lock = this.lock; |
683 |
lock.lock(); |
684 |
try { |
685 |
return capacity - count; |
686 |
} finally { |
687 |
lock.unlock(); |
688 |
} |
689 |
} |
690 |
|
691 |
/** |
692 |
* @throws UnsupportedOperationException {@inheritDoc} |
693 |
* @throws ClassCastException {@inheritDoc} |
694 |
* @throws NullPointerException {@inheritDoc} |
695 |
* @throws IllegalArgumentException {@inheritDoc} |
696 |
*/ |
697 |
public int drainTo(Collection<? super E> c) { |
698 |
return drainTo(c, Integer.MAX_VALUE); |
699 |
} |
700 |
|
701 |
/** |
702 |
* @throws UnsupportedOperationException {@inheritDoc} |
703 |
* @throws ClassCastException {@inheritDoc} |
704 |
* @throws NullPointerException {@inheritDoc} |
705 |
* @throws IllegalArgumentException {@inheritDoc} |
706 |
*/ |
707 |
public int drainTo(Collection<? super E> c, int maxElements) { |
708 |
if (c == null) |
709 |
throw new NullPointerException(); |
710 |
if (c == this) |
711 |
throw new IllegalArgumentException(); |
712 |
final ReentrantLock lock = this.lock; |
713 |
lock.lock(); |
714 |
try { |
715 |
int n = Math.min(maxElements, count); |
716 |
for (int i = 0; i < n; i++) { |
717 |
c.add(first.item); // In this order, in case add() throws. |
718 |
unlinkFirst(); |
719 |
} |
720 |
return n; |
721 |
} finally { |
722 |
lock.unlock(); |
723 |
} |
724 |
} |
725 |
|
726 |
// Stack methods |
727 |
|
728 |
/** |
729 |
* @throws IllegalStateException {@inheritDoc} |
730 |
* @throws NullPointerException {@inheritDoc} |
731 |
*/ |
732 |
public void push(E e) { |
733 |
addFirst(e); |
734 |
} |
735 |
|
736 |
/** |
737 |
* @throws NoSuchElementException {@inheritDoc} |
738 |
*/ |
739 |
public E pop() { |
740 |
return removeFirst(); |
741 |
} |
742 |
|
743 |
// Collection methods |
744 |
|
745 |
/** |
746 |
* Removes the first occurrence of the specified element from this deque. |
747 |
* If the deque does not contain the element, it is unchanged. |
748 |
* More formally, removes the first element {@code e} such that |
749 |
* {@code o.equals(e)} (if such an element exists). |
750 |
* Returns {@code true} if this deque contained the specified element |
751 |
* (or equivalently, if this deque changed as a result of the call). |
752 |
* |
753 |
* <p>This method is equivalent to |
754 |
* {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. |
755 |
* |
756 |
* @param o element to be removed from this deque, if present |
757 |
* @return {@code true} if this deque changed as a result of the call |
758 |
*/ |
759 |
public boolean remove(Object o) { |
760 |
return removeFirstOccurrence(o); |
761 |
} |
762 |
|
763 |
/** |
764 |
* Returns the number of elements in this deque. |
765 |
* |
766 |
* @return the number of elements in this deque |
767 |
*/ |
768 |
public int size() { |
769 |
final ReentrantLock lock = this.lock; |
770 |
lock.lock(); |
771 |
try { |
772 |
return count; |
773 |
} finally { |
774 |
lock.unlock(); |
775 |
} |
776 |
} |
777 |
|
778 |
/** |
779 |
* Returns {@code true} if this deque contains the specified element. |
780 |
* More formally, returns {@code true} if and only if this deque contains |
781 |
* at least one element {@code e} such that {@code o.equals(e)}. |
782 |
* |
783 |
* @param o object to be checked for containment in this deque |
784 |
* @return {@code true} if this deque contains the specified element |
785 |
*/ |
786 |
public boolean contains(Object o) { |
787 |
if (o == null) return false; |
788 |
final ReentrantLock lock = this.lock; |
789 |
lock.lock(); |
790 |
try { |
791 |
for (Node<E> p = first; p != null; p = p.next) |
792 |
if (o.equals(p.item)) |
793 |
return true; |
794 |
return false; |
795 |
} finally { |
796 |
lock.unlock(); |
797 |
} |
798 |
} |
799 |
|
800 |
/* |
801 |
* TODO: Add support for more efficient bulk operations. |
802 |
* |
803 |
* We don't want to acquire the lock for every iteration, but we |
804 |
* also want other threads a chance to interact with the |
805 |
* collection, especially when count is close to capacity. |
806 |
*/ |
807 |
|
808 |
// /** |
809 |
// * Adds all of the elements in the specified collection to this |
810 |
// * queue. Attempts to addAll of a queue to itself result in |
811 |
// * {@code IllegalArgumentException}. Further, the behavior of |
812 |
// * this operation is undefined if the specified collection is |
813 |
// * modified while the operation is in progress. |
814 |
// * |
815 |
// * @param c collection containing elements to be added to this queue |
816 |
// * @return {@code true} if this queue changed as a result of the call |
817 |
// * @throws ClassCastException {@inheritDoc} |
818 |
// * @throws NullPointerException {@inheritDoc} |
819 |
// * @throws IllegalArgumentException {@inheritDoc} |
820 |
// * @throws IllegalStateException {@inheritDoc} |
821 |
// * @see #add(Object) |
822 |
// */ |
823 |
// public boolean addAll(Collection<? extends E> c) { |
824 |
// if (c == null) |
825 |
// throw new NullPointerException(); |
826 |
// if (c == this) |
827 |
// throw new IllegalArgumentException(); |
828 |
// final ReentrantLock lock = this.lock; |
829 |
// lock.lock(); |
830 |
// try { |
831 |
// boolean modified = false; |
832 |
// for (E e : c) |
833 |
// if (linkLast(e)) |
834 |
// modified = true; |
835 |
// return modified; |
836 |
// } finally { |
837 |
// lock.unlock(); |
838 |
// } |
839 |
// } |
840 |
|
841 |
/** |
842 |
* Returns an array containing all of the elements in this deque, in |
843 |
* proper sequence (from first to last element). |
844 |
* |
845 |
* <p>The returned array will be "safe" in that no references to it are |
846 |
* maintained by this deque. (In other words, this method must allocate |
847 |
* a new array). The caller is thus free to modify the returned array. |
848 |
* |
849 |
* <p>This method acts as bridge between array-based and collection-based |
850 |
* APIs. |
851 |
* |
852 |
* @return an array containing all of the elements in this deque |
853 |
*/ |
854 |
@SuppressWarnings("unchecked") |
855 |
public Object[] toArray() { |
856 |
final ReentrantLock lock = this.lock; |
857 |
lock.lock(); |
858 |
try { |
859 |
Object[] a = new Object[count]; |
860 |
int k = 0; |
861 |
for (Node<E> p = first; p != null; p = p.next) |
862 |
a[k++] = p.item; |
863 |
return a; |
864 |
} finally { |
865 |
lock.unlock(); |
866 |
} |
867 |
} |
868 |
|
869 |
/** |
870 |
* Returns an array containing all of the elements in this deque, in |
871 |
* proper sequence; the runtime type of the returned array is that of |
872 |
* the specified array. If the deque fits in the specified array, it |
873 |
* is returned therein. Otherwise, a new array is allocated with the |
874 |
* runtime type of the specified array and the size of this deque. |
875 |
* |
876 |
* <p>If this deque fits in the specified array with room to spare |
877 |
* (i.e., the array has more elements than this deque), the element in |
878 |
* the array immediately following the end of the deque is set to |
879 |
* {@code null}. |
880 |
* |
881 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
882 |
* array-based and collection-based APIs. Further, this method allows |
883 |
* precise control over the runtime type of the output array, and may, |
884 |
* under certain circumstances, be used to save allocation costs. |
885 |
* |
886 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
887 |
* The following code can be used to dump the deque into a newly |
888 |
* allocated array of {@code String}: |
889 |
* |
890 |
* <pre> |
891 |
* String[] y = x.toArray(new String[0]);</pre> |
892 |
* |
893 |
* Note that {@code toArray(new Object[0])} is identical in function to |
894 |
* {@code toArray()}. |
895 |
* |
896 |
* @param a the array into which the elements of the deque are to |
897 |
* be stored, if it is big enough; otherwise, a new array of the |
898 |
* same runtime type is allocated for this purpose |
899 |
* @return an array containing all of the elements in this deque |
900 |
* @throws ArrayStoreException if the runtime type of the specified array |
901 |
* is not a supertype of the runtime type of every element in |
902 |
* this deque |
903 |
* @throws NullPointerException if the specified array is null |
904 |
*/ |
905 |
@SuppressWarnings("unchecked") |
906 |
public <T> T[] toArray(T[] a) { |
907 |
final ReentrantLock lock = this.lock; |
908 |
lock.lock(); |
909 |
try { |
910 |
if (a.length < count) |
911 |
a = (T[])java.lang.reflect.Array.newInstance |
912 |
(a.getClass().getComponentType(), count); |
913 |
|
914 |
int k = 0; |
915 |
for (Node<E> p = first; p != null; p = p.next) |
916 |
a[k++] = (T)p.item; |
917 |
if (a.length > k) |
918 |
a[k] = null; |
919 |
return a; |
920 |
} finally { |
921 |
lock.unlock(); |
922 |
} |
923 |
} |
924 |
|
925 |
public String toString() { |
926 |
final ReentrantLock lock = this.lock; |
927 |
lock.lock(); |
928 |
try { |
929 |
return super.toString(); |
930 |
} finally { |
931 |
lock.unlock(); |
932 |
} |
933 |
} |
934 |
|
935 |
/** |
936 |
* Atomically removes all of the elements from this deque. |
937 |
* The deque will be empty after this call returns. |
938 |
*/ |
939 |
public void clear() { |
940 |
final ReentrantLock lock = this.lock; |
941 |
lock.lock(); |
942 |
try { |
943 |
for (Node<E> f = first; f != null; ) { |
944 |
f.item = null; |
945 |
Node<E> n = f.next; |
946 |
f.prev = null; |
947 |
f.next = null; |
948 |
f = n; |
949 |
} |
950 |
first = last = null; |
951 |
count = 0; |
952 |
notFull.signalAll(); |
953 |
} finally { |
954 |
lock.unlock(); |
955 |
} |
956 |
} |
957 |
|
958 |
/** |
959 |
* Returns an iterator over the elements in this deque in proper sequence. |
960 |
* The elements will be returned in order from first (head) to last (tail). |
961 |
* The returned {@code Iterator} is a "weakly consistent" iterator that |
962 |
* will never throw {@link java.util.ConcurrentModificationException |
963 |
* ConcurrentModificationException}, |
964 |
* and guarantees to traverse elements as they existed upon |
965 |
* construction of the iterator, and may (but is not guaranteed to) |
966 |
* reflect any modifications subsequent to construction. |
967 |
* |
968 |
* @return an iterator over the elements in this deque in proper sequence |
969 |
*/ |
970 |
public Iterator<E> iterator() { |
971 |
return new Itr(); |
972 |
} |
973 |
|
974 |
/** |
975 |
* Returns an iterator over the elements in this deque in reverse |
976 |
* sequential order. The elements will be returned in order from |
977 |
* last (tail) to first (head). |
978 |
* The returned {@code Iterator} is a "weakly consistent" iterator that |
979 |
* will never throw {@link java.util.ConcurrentModificationException |
980 |
* ConcurrentModificationException}, |
981 |
* and guarantees to traverse elements as they existed upon |
982 |
* construction of the iterator, and may (but is not guaranteed to) |
983 |
* reflect any modifications subsequent to construction. |
984 |
*/ |
985 |
public Iterator<E> descendingIterator() { |
986 |
return new DescendingItr(); |
987 |
} |
988 |
|
989 |
/** |
990 |
* Base class for Iterators for LinkedBlockingDeque |
991 |
*/ |
992 |
private abstract class AbstractItr implements Iterator<E> { |
993 |
/** |
994 |
* The next node to return in next() |
995 |
*/ |
996 |
Node<E> next; |
997 |
|
998 |
/** |
999 |
* nextItem holds on to item fields because once we claim that |
1000 |
* an element exists in hasNext(), we must return item read |
1001 |
* under lock (in advance()) even if it was in the process of |
1002 |
* being removed when hasNext() was called. |
1003 |
*/ |
1004 |
E nextItem; |
1005 |
|
1006 |
/** |
1007 |
* Node returned by most recent call to next. Needed by remove. |
1008 |
* Reset to null if this element is deleted by a call to remove. |
1009 |
*/ |
1010 |
private Node<E> lastRet; |
1011 |
|
1012 |
abstract Node<E> firstNode(); |
1013 |
abstract Node<E> nextNode(Node<E> n); |
1014 |
|
1015 |
AbstractItr() { |
1016 |
// set to initial position |
1017 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1018 |
lock.lock(); |
1019 |
try { |
1020 |
next = firstNode(); |
1021 |
nextItem = (next == null) ? null : next.item; |
1022 |
} finally { |
1023 |
lock.unlock(); |
1024 |
} |
1025 |
} |
1026 |
|
1027 |
/** |
1028 |
* Advances next. |
1029 |
*/ |
1030 |
void advance() { |
1031 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1032 |
lock.lock(); |
1033 |
try { |
1034 |
// assert next != null; |
1035 |
Node<E> s = nextNode(next); |
1036 |
if (s == next) { |
1037 |
next = firstNode(); |
1038 |
} else { |
1039 |
// Skip over removed nodes. |
1040 |
// May be necessary if multiple interior Nodes are removed. |
1041 |
while (s != null && s.item == null) |
1042 |
s = nextNode(s); |
1043 |
next = s; |
1044 |
} |
1045 |
nextItem = (next == null) ? null : next.item; |
1046 |
} finally { |
1047 |
lock.unlock(); |
1048 |
} |
1049 |
} |
1050 |
|
1051 |
public boolean hasNext() { |
1052 |
return next != null; |
1053 |
} |
1054 |
|
1055 |
public E next() { |
1056 |
if (next == null) |
1057 |
throw new NoSuchElementException(); |
1058 |
lastRet = next; |
1059 |
E x = nextItem; |
1060 |
advance(); |
1061 |
return x; |
1062 |
} |
1063 |
|
1064 |
public void remove() { |
1065 |
Node<E> n = lastRet; |
1066 |
if (n == null) |
1067 |
throw new IllegalStateException(); |
1068 |
lastRet = null; |
1069 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1070 |
lock.lock(); |
1071 |
try { |
1072 |
if (n.item != null) |
1073 |
unlink(n); |
1074 |
} finally { |
1075 |
lock.unlock(); |
1076 |
} |
1077 |
} |
1078 |
} |
1079 |
|
1080 |
/** Forward iterator */ |
1081 |
private class Itr extends AbstractItr { |
1082 |
Node<E> firstNode() { return first; } |
1083 |
Node<E> nextNode(Node<E> n) { return n.next; } |
1084 |
} |
1085 |
|
1086 |
/** Descending iterator */ |
1087 |
private class DescendingItr extends AbstractItr { |
1088 |
Node<E> firstNode() { return last; } |
1089 |
Node<E> nextNode(Node<E> n) { return n.prev; } |
1090 |
} |
1091 |
|
1092 |
/** |
1093 |
* Save the state of this deque to a stream (that is, serialize it). |
1094 |
* |
1095 |
* @serialData The capacity (int), followed by elements (each an |
1096 |
* {@code Object}) in the proper order, followed by a null |
1097 |
* @param s the stream |
1098 |
*/ |
1099 |
private void writeObject(java.io.ObjectOutputStream s) |
1100 |
throws java.io.IOException { |
1101 |
final ReentrantLock lock = this.lock; |
1102 |
lock.lock(); |
1103 |
try { |
1104 |
// Write out capacity and any hidden stuff |
1105 |
s.defaultWriteObject(); |
1106 |
// Write out all elements in the proper order. |
1107 |
for (Node<E> p = first; p != null; p = p.next) |
1108 |
s.writeObject(p.item); |
1109 |
// Use trailing null as sentinel |
1110 |
s.writeObject(null); |
1111 |
} finally { |
1112 |
lock.unlock(); |
1113 |
} |
1114 |
} |
1115 |
|
1116 |
/** |
1117 |
* Reconstitute this deque from a stream (that is, |
1118 |
* deserialize it). |
1119 |
* @param s the stream |
1120 |
*/ |
1121 |
private void readObject(java.io.ObjectInputStream s) |
1122 |
throws java.io.IOException, ClassNotFoundException { |
1123 |
s.defaultReadObject(); |
1124 |
count = 0; |
1125 |
first = null; |
1126 |
last = null; |
1127 |
// Read in all elements and place in queue |
1128 |
for (;;) { |
1129 |
@SuppressWarnings("unchecked") |
1130 |
E item = (E)s.readObject(); |
1131 |
if (item == null) |
1132 |
break; |
1133 |
add(item); |
1134 |
} |
1135 |
} |
1136 |
|
1137 |
} |