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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/publicdomain/zero/1.0/ |
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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.Objects; |
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import java.util.Spliterator; |
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import java.util.Spliterators; |
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import java.util.concurrent.locks.Condition; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.util.function.Consumer; |
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import java.util.function.Predicate; |
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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 deque |
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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) { |
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item = x; |
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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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addAll(c); |
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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 node as first element, or returns false if full. |
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*/ |
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private boolean linkFirst(Node<E> node) { |
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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.next = f; |
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first = node; |
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if (last == null) |
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last = node; |
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else |
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f.prev = node; |
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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 node as last element, or returns false if full. |
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*/ |
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private boolean linkLast(Node<E> node) { |
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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.prev = l; |
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last = node; |
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if (first == null) |
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first = node; |
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else |
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l.next = node; |
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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; |
249 |
if (p == null) |
250 |
first = null; |
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else |
252 |
p.next = null; |
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--count; |
254 |
notFull.signal(); |
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return item; |
256 |
} |
257 |
|
258 |
/** |
259 |
* Unlinks x. |
260 |
*/ |
261 |
void unlink(Node<E> x) { |
262 |
// assert lock.isHeldByCurrentThread(); |
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// assert x.item != null; |
264 |
Node<E> p = x.prev; |
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Node<E> n = x.next; |
266 |
if (p == null) { |
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unlinkFirst(); |
268 |
} else if (n == null) { |
269 |
unlinkLast(); |
270 |
} else { |
271 |
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. |
276 |
--count; |
277 |
notFull.signal(); |
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} |
279 |
} |
280 |
|
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// BlockingDeque methods |
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|
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/** |
284 |
* @throws IllegalStateException if this deque is full |
285 |
* @throws NullPointerException {@inheritDoc} |
286 |
*/ |
287 |
public void addFirst(E e) { |
288 |
if (!offerFirst(e)) |
289 |
throw new IllegalStateException("Deque full"); |
290 |
} |
291 |
|
292 |
/** |
293 |
* @throws IllegalStateException if this deque is full |
294 |
* @throws NullPointerException {@inheritDoc} |
295 |
*/ |
296 |
public void addLast(E e) { |
297 |
if (!offerLast(e)) |
298 |
throw new IllegalStateException("Deque full"); |
299 |
} |
300 |
|
301 |
/** |
302 |
* @throws NullPointerException {@inheritDoc} |
303 |
*/ |
304 |
public boolean offerFirst(E e) { |
305 |
if (e == null) throw new NullPointerException(); |
306 |
Node<E> node = new Node<E>(e); |
307 |
final ReentrantLock lock = this.lock; |
308 |
lock.lock(); |
309 |
try { |
310 |
return linkFirst(node); |
311 |
} finally { |
312 |
// checkInvariants(); |
313 |
lock.unlock(); |
314 |
} |
315 |
} |
316 |
|
317 |
/** |
318 |
* @throws NullPointerException {@inheritDoc} |
319 |
*/ |
320 |
public boolean offerLast(E e) { |
321 |
if (e == null) throw new NullPointerException(); |
322 |
Node<E> node = new Node<E>(e); |
323 |
final ReentrantLock lock = this.lock; |
324 |
lock.lock(); |
325 |
try { |
326 |
return linkLast(node); |
327 |
} finally { |
328 |
// checkInvariants(); |
329 |
lock.unlock(); |
330 |
} |
331 |
} |
332 |
|
333 |
/** |
334 |
* @throws NullPointerException {@inheritDoc} |
335 |
* @throws InterruptedException {@inheritDoc} |
336 |
*/ |
337 |
public void putFirst(E e) throws InterruptedException { |
338 |
if (e == null) throw new NullPointerException(); |
339 |
Node<E> node = new Node<E>(e); |
340 |
final ReentrantLock lock = this.lock; |
341 |
lock.lock(); |
342 |
try { |
343 |
while (!linkFirst(node)) |
344 |
notFull.await(); |
345 |
} finally { |
346 |
// checkInvariants(); |
347 |
lock.unlock(); |
348 |
} |
349 |
} |
350 |
|
351 |
/** |
352 |
* @throws NullPointerException {@inheritDoc} |
353 |
* @throws InterruptedException {@inheritDoc} |
354 |
*/ |
355 |
public void putLast(E e) throws InterruptedException { |
356 |
if (e == null) throw new NullPointerException(); |
357 |
Node<E> node = new Node<E>(e); |
358 |
final ReentrantLock lock = this.lock; |
359 |
lock.lock(); |
360 |
try { |
361 |
while (!linkLast(node)) |
362 |
notFull.await(); |
363 |
} finally { |
364 |
// checkInvariants(); |
365 |
lock.unlock(); |
366 |
} |
367 |
} |
368 |
|
369 |
/** |
370 |
* @throws NullPointerException {@inheritDoc} |
371 |
* @throws InterruptedException {@inheritDoc} |
372 |
*/ |
373 |
public boolean offerFirst(E e, long timeout, TimeUnit unit) |
374 |
throws InterruptedException { |
375 |
if (e == null) throw new NullPointerException(); |
376 |
Node<E> node = new Node<E>(e); |
377 |
long nanos = unit.toNanos(timeout); |
378 |
final ReentrantLock lock = this.lock; |
379 |
lock.lockInterruptibly(); |
380 |
try { |
381 |
while (!linkFirst(node)) { |
382 |
if (nanos <= 0L) |
383 |
return false; |
384 |
nanos = notFull.awaitNanos(nanos); |
385 |
} |
386 |
return true; |
387 |
} finally { |
388 |
// checkInvariants(); |
389 |
lock.unlock(); |
390 |
} |
391 |
} |
392 |
|
393 |
/** |
394 |
* @throws NullPointerException {@inheritDoc} |
395 |
* @throws InterruptedException {@inheritDoc} |
396 |
*/ |
397 |
public boolean offerLast(E e, long timeout, TimeUnit unit) |
398 |
throws InterruptedException { |
399 |
if (e == null) throw new NullPointerException(); |
400 |
Node<E> node = new Node<E>(e); |
401 |
long nanos = unit.toNanos(timeout); |
402 |
final ReentrantLock lock = this.lock; |
403 |
lock.lockInterruptibly(); |
404 |
try { |
405 |
while (!linkLast(node)) { |
406 |
if (nanos <= 0L) |
407 |
return false; |
408 |
nanos = notFull.awaitNanos(nanos); |
409 |
} |
410 |
return true; |
411 |
} finally { |
412 |
// checkInvariants(); |
413 |
lock.unlock(); |
414 |
} |
415 |
} |
416 |
|
417 |
/** |
418 |
* @throws NoSuchElementException {@inheritDoc} |
419 |
*/ |
420 |
public E removeFirst() { |
421 |
E x = pollFirst(); |
422 |
if (x == null) throw new NoSuchElementException(); |
423 |
return x; |
424 |
} |
425 |
|
426 |
/** |
427 |
* @throws NoSuchElementException {@inheritDoc} |
428 |
*/ |
429 |
public E removeLast() { |
430 |
E x = pollLast(); |
431 |
if (x == null) throw new NoSuchElementException(); |
432 |
return x; |
433 |
} |
434 |
|
435 |
public E pollFirst() { |
436 |
final ReentrantLock lock = this.lock; |
437 |
lock.lock(); |
438 |
try { |
439 |
return unlinkFirst(); |
440 |
} finally { |
441 |
// checkInvariants(); |
442 |
lock.unlock(); |
443 |
} |
444 |
} |
445 |
|
446 |
public E pollLast() { |
447 |
final ReentrantLock lock = this.lock; |
448 |
lock.lock(); |
449 |
try { |
450 |
return unlinkLast(); |
451 |
} finally { |
452 |
// checkInvariants(); |
453 |
lock.unlock(); |
454 |
} |
455 |
} |
456 |
|
457 |
public E takeFirst() throws InterruptedException { |
458 |
final ReentrantLock lock = this.lock; |
459 |
lock.lock(); |
460 |
try { |
461 |
E x; |
462 |
while ( (x = unlinkFirst()) == null) |
463 |
notEmpty.await(); |
464 |
return x; |
465 |
} finally { |
466 |
// checkInvariants(); |
467 |
lock.unlock(); |
468 |
} |
469 |
} |
470 |
|
471 |
public E takeLast() throws InterruptedException { |
472 |
final ReentrantLock lock = this.lock; |
473 |
lock.lock(); |
474 |
try { |
475 |
E x; |
476 |
while ( (x = unlinkLast()) == null) |
477 |
notEmpty.await(); |
478 |
return x; |
479 |
} finally { |
480 |
// checkInvariants(); |
481 |
lock.unlock(); |
482 |
} |
483 |
} |
484 |
|
485 |
public E pollFirst(long timeout, TimeUnit unit) |
486 |
throws InterruptedException { |
487 |
long nanos = unit.toNanos(timeout); |
488 |
final ReentrantLock lock = this.lock; |
489 |
lock.lockInterruptibly(); |
490 |
try { |
491 |
E x; |
492 |
while ( (x = unlinkFirst()) == null) { |
493 |
if (nanos <= 0L) |
494 |
return null; |
495 |
nanos = notEmpty.awaitNanos(nanos); |
496 |
} |
497 |
return x; |
498 |
} finally { |
499 |
// checkInvariants(); |
500 |
lock.unlock(); |
501 |
} |
502 |
} |
503 |
|
504 |
public E pollLast(long timeout, TimeUnit unit) |
505 |
throws InterruptedException { |
506 |
long nanos = unit.toNanos(timeout); |
507 |
final ReentrantLock lock = this.lock; |
508 |
lock.lockInterruptibly(); |
509 |
try { |
510 |
E x; |
511 |
while ( (x = unlinkLast()) == null) { |
512 |
if (nanos <= 0L) |
513 |
return null; |
514 |
nanos = notEmpty.awaitNanos(nanos); |
515 |
} |
516 |
return x; |
517 |
} finally { |
518 |
// checkInvariants(); |
519 |
lock.unlock(); |
520 |
} |
521 |
} |
522 |
|
523 |
/** |
524 |
* @throws NoSuchElementException {@inheritDoc} |
525 |
*/ |
526 |
public E getFirst() { |
527 |
E x = peekFirst(); |
528 |
if (x == null) throw new NoSuchElementException(); |
529 |
return x; |
530 |
} |
531 |
|
532 |
/** |
533 |
* @throws NoSuchElementException {@inheritDoc} |
534 |
*/ |
535 |
public E getLast() { |
536 |
E x = peekLast(); |
537 |
if (x == null) throw new NoSuchElementException(); |
538 |
return x; |
539 |
} |
540 |
|
541 |
public E peekFirst() { |
542 |
final ReentrantLock lock = this.lock; |
543 |
lock.lock(); |
544 |
try { |
545 |
return (first == null) ? null : first.item; |
546 |
} finally { |
547 |
// checkInvariants(); |
548 |
lock.unlock(); |
549 |
} |
550 |
} |
551 |
|
552 |
public E peekLast() { |
553 |
final ReentrantLock lock = this.lock; |
554 |
lock.lock(); |
555 |
try { |
556 |
return (last == null) ? null : last.item; |
557 |
} finally { |
558 |
// checkInvariants(); |
559 |
lock.unlock(); |
560 |
} |
561 |
} |
562 |
|
563 |
public boolean removeFirstOccurrence(Object o) { |
564 |
if (o == null) return false; |
565 |
final ReentrantLock lock = this.lock; |
566 |
lock.lock(); |
567 |
try { |
568 |
for (Node<E> p = first; p != null; p = p.next) { |
569 |
if (o.equals(p.item)) { |
570 |
unlink(p); |
571 |
return true; |
572 |
} |
573 |
} |
574 |
return false; |
575 |
} finally { |
576 |
// checkInvariants(); |
577 |
lock.unlock(); |
578 |
} |
579 |
} |
580 |
|
581 |
public boolean removeLastOccurrence(Object o) { |
582 |
if (o == null) return false; |
583 |
final ReentrantLock lock = this.lock; |
584 |
lock.lock(); |
585 |
try { |
586 |
for (Node<E> p = last; p != null; p = p.prev) { |
587 |
if (o.equals(p.item)) { |
588 |
unlink(p); |
589 |
return true; |
590 |
} |
591 |
} |
592 |
return false; |
593 |
} finally { |
594 |
// checkInvariants(); |
595 |
lock.unlock(); |
596 |
} |
597 |
} |
598 |
|
599 |
// BlockingQueue methods |
600 |
|
601 |
/** |
602 |
* Inserts the specified element at the end of this deque unless it would |
603 |
* violate capacity restrictions. When using a capacity-restricted deque, |
604 |
* it is generally preferable to use method {@link #offer(Object) offer}. |
605 |
* |
606 |
* <p>This method is equivalent to {@link #addLast}. |
607 |
* |
608 |
* @throws IllegalStateException if this deque is full |
609 |
* @throws NullPointerException if the specified element is null |
610 |
*/ |
611 |
public boolean add(E e) { |
612 |
addLast(e); |
613 |
return true; |
614 |
} |
615 |
|
616 |
/** |
617 |
* @throws NullPointerException if the specified element is null |
618 |
*/ |
619 |
public boolean offer(E e) { |
620 |
return offerLast(e); |
621 |
} |
622 |
|
623 |
/** |
624 |
* @throws NullPointerException {@inheritDoc} |
625 |
* @throws InterruptedException {@inheritDoc} |
626 |
*/ |
627 |
public void put(E e) throws InterruptedException { |
628 |
putLast(e); |
629 |
} |
630 |
|
631 |
/** |
632 |
* @throws NullPointerException {@inheritDoc} |
633 |
* @throws InterruptedException {@inheritDoc} |
634 |
*/ |
635 |
public boolean offer(E e, long timeout, TimeUnit unit) |
636 |
throws InterruptedException { |
637 |
return offerLast(e, timeout, unit); |
638 |
} |
639 |
|
640 |
/** |
641 |
* Retrieves and removes the head of the queue represented by this deque. |
642 |
* This method differs from {@link #poll poll} only in that it throws an |
643 |
* exception if this deque is empty. |
644 |
* |
645 |
* <p>This method is equivalent to {@link #removeFirst() removeFirst}. |
646 |
* |
647 |
* @return the head of the queue represented by this deque |
648 |
* @throws NoSuchElementException if this deque is empty |
649 |
*/ |
650 |
public E remove() { |
651 |
return removeFirst(); |
652 |
} |
653 |
|
654 |
public E poll() { |
655 |
return pollFirst(); |
656 |
} |
657 |
|
658 |
public E take() throws InterruptedException { |
659 |
return takeFirst(); |
660 |
} |
661 |
|
662 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
663 |
return pollFirst(timeout, unit); |
664 |
} |
665 |
|
666 |
/** |
667 |
* Retrieves, but does not remove, the head of the queue represented by |
668 |
* this deque. This method differs from {@link #peek peek} only in that |
669 |
* it throws an exception if this deque is empty. |
670 |
* |
671 |
* <p>This method is equivalent to {@link #getFirst() getFirst}. |
672 |
* |
673 |
* @return the head of the queue represented by this deque |
674 |
* @throws NoSuchElementException if this deque is empty |
675 |
*/ |
676 |
public E element() { |
677 |
return getFirst(); |
678 |
} |
679 |
|
680 |
public E peek() { |
681 |
return peekFirst(); |
682 |
} |
683 |
|
684 |
/** |
685 |
* Returns the number of additional elements that this deque can ideally |
686 |
* (in the absence of memory or resource constraints) accept without |
687 |
* blocking. This is always equal to the initial capacity of this deque |
688 |
* less the current {@code size} of this deque. |
689 |
* |
690 |
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
691 |
* an element will succeed by inspecting {@code remainingCapacity} |
692 |
* because it may be the case that another thread is about to |
693 |
* insert or remove an element. |
694 |
*/ |
695 |
public int remainingCapacity() { |
696 |
final ReentrantLock lock = this.lock; |
697 |
lock.lock(); |
698 |
try { |
699 |
return capacity - count; |
700 |
} finally { |
701 |
// checkInvariants(); |
702 |
lock.unlock(); |
703 |
} |
704 |
} |
705 |
|
706 |
/** |
707 |
* @throws UnsupportedOperationException {@inheritDoc} |
708 |
* @throws ClassCastException {@inheritDoc} |
709 |
* @throws NullPointerException {@inheritDoc} |
710 |
* @throws IllegalArgumentException {@inheritDoc} |
711 |
*/ |
712 |
public int drainTo(Collection<? super E> c) { |
713 |
return drainTo(c, Integer.MAX_VALUE); |
714 |
} |
715 |
|
716 |
/** |
717 |
* @throws UnsupportedOperationException {@inheritDoc} |
718 |
* @throws ClassCastException {@inheritDoc} |
719 |
* @throws NullPointerException {@inheritDoc} |
720 |
* @throws IllegalArgumentException {@inheritDoc} |
721 |
*/ |
722 |
public int drainTo(Collection<? super E> c, int maxElements) { |
723 |
Objects.requireNonNull(c); |
724 |
if (c == this) |
725 |
throw new IllegalArgumentException(); |
726 |
if (maxElements <= 0) |
727 |
return 0; |
728 |
final ReentrantLock lock = this.lock; |
729 |
lock.lock(); |
730 |
try { |
731 |
int n = Math.min(maxElements, count); |
732 |
for (int i = 0; i < n; i++) { |
733 |
c.add(first.item); // In this order, in case add() throws. |
734 |
unlinkFirst(); |
735 |
} |
736 |
return n; |
737 |
} finally { |
738 |
// checkInvariants(); |
739 |
lock.unlock(); |
740 |
} |
741 |
} |
742 |
|
743 |
// Stack methods |
744 |
|
745 |
/** |
746 |
* @throws IllegalStateException if this deque is full |
747 |
* @throws NullPointerException {@inheritDoc} |
748 |
*/ |
749 |
public void push(E e) { |
750 |
addFirst(e); |
751 |
} |
752 |
|
753 |
/** |
754 |
* @throws NoSuchElementException {@inheritDoc} |
755 |
*/ |
756 |
public E pop() { |
757 |
return removeFirst(); |
758 |
} |
759 |
|
760 |
// Collection methods |
761 |
|
762 |
/** |
763 |
* Removes the first occurrence of the specified element from this deque. |
764 |
* If the deque does not contain the element, it is unchanged. |
765 |
* More formally, removes the first element {@code e} such that |
766 |
* {@code o.equals(e)} (if such an element exists). |
767 |
* Returns {@code true} if this deque contained the specified element |
768 |
* (or equivalently, if this deque changed as a result of the call). |
769 |
* |
770 |
* <p>This method is equivalent to |
771 |
* {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. |
772 |
* |
773 |
* @param o element to be removed from this deque, if present |
774 |
* @return {@code true} if this deque changed as a result of the call |
775 |
*/ |
776 |
public boolean remove(Object o) { |
777 |
return removeFirstOccurrence(o); |
778 |
} |
779 |
|
780 |
/** |
781 |
* Returns the number of elements in this deque. |
782 |
* |
783 |
* @return the number of elements in this deque |
784 |
*/ |
785 |
public int size() { |
786 |
final ReentrantLock lock = this.lock; |
787 |
lock.lock(); |
788 |
try { |
789 |
return count; |
790 |
} finally { |
791 |
// checkInvariants(); |
792 |
lock.unlock(); |
793 |
} |
794 |
} |
795 |
|
796 |
/** |
797 |
* Returns {@code true} if this deque contains the specified element. |
798 |
* More formally, returns {@code true} if and only if this deque contains |
799 |
* at least one element {@code e} such that {@code o.equals(e)}. |
800 |
* |
801 |
* @param o object to be checked for containment in this deque |
802 |
* @return {@code true} if this deque contains the specified element |
803 |
*/ |
804 |
public boolean contains(Object o) { |
805 |
if (o == null) return false; |
806 |
final ReentrantLock lock = this.lock; |
807 |
lock.lock(); |
808 |
try { |
809 |
for (Node<E> p = first; p != null; p = p.next) |
810 |
if (o.equals(p.item)) |
811 |
return true; |
812 |
return false; |
813 |
} finally { |
814 |
// checkInvariants(); |
815 |
lock.unlock(); |
816 |
} |
817 |
} |
818 |
|
819 |
/** |
820 |
* Appends all of the elements in the specified collection to the end of |
821 |
* this deque, in the order that they are returned by the specified |
822 |
* collection's iterator. Attempts to {@code addAll} of a deque to |
823 |
* itself result in {@code IllegalArgumentException}. |
824 |
* |
825 |
* @param c the elements to be inserted into this deque |
826 |
* @return {@code true} if this deque changed as a result of the call |
827 |
* @throws NullPointerException if the specified collection or any |
828 |
* of its elements are null |
829 |
* @throws IllegalArgumentException if the collection is this deque |
830 |
* @throws IllegalStateException if this deque is full |
831 |
* @see #add(Object) |
832 |
*/ |
833 |
public boolean addAll(Collection<? extends E> c) { |
834 |
if (c == this) |
835 |
// As historically specified in AbstractQueue#addAll |
836 |
throw new IllegalArgumentException(); |
837 |
|
838 |
// Copy c into a private chain of Nodes |
839 |
Node<E> beg = null, end = null; |
840 |
int n = 0; |
841 |
for (E e : c) { |
842 |
Objects.requireNonNull(e); |
843 |
n++; |
844 |
Node<E> newNode = new Node<E>(e); |
845 |
if (beg == null) |
846 |
beg = end = newNode; |
847 |
else { |
848 |
end.next = newNode; |
849 |
newNode.prev = end; |
850 |
end = newNode; |
851 |
} |
852 |
} |
853 |
if (beg == null) |
854 |
return false; |
855 |
|
856 |
// Atomically append the chain at the end |
857 |
final ReentrantLock lock = this.lock; |
858 |
lock.lock(); |
859 |
try { |
860 |
if (count + n <= capacity) { |
861 |
beg.prev = last; |
862 |
if (first == null) |
863 |
first = beg; |
864 |
else |
865 |
last.next = beg; |
866 |
last = end; |
867 |
count += n; |
868 |
notEmpty.signalAll(); |
869 |
return true; |
870 |
} |
871 |
} finally { |
872 |
// checkInvariants(); |
873 |
lock.unlock(); |
874 |
} |
875 |
// Fall back to historic non-atomic implementation, failing |
876 |
// with IllegalStateException when the capacity is exceeded. |
877 |
return super.addAll(c); |
878 |
} |
879 |
|
880 |
/** |
881 |
* Returns an array containing all of the elements in this deque, in |
882 |
* proper sequence (from first to last element). |
883 |
* |
884 |
* <p>The returned array will be "safe" in that no references to it are |
885 |
* maintained by this deque. (In other words, this method must allocate |
886 |
* a new array). The caller is thus free to modify the returned array. |
887 |
* |
888 |
* <p>This method acts as bridge between array-based and collection-based |
889 |
* APIs. |
890 |
* |
891 |
* @return an array containing all of the elements in this deque |
892 |
*/ |
893 |
@SuppressWarnings("unchecked") |
894 |
public Object[] toArray() { |
895 |
final ReentrantLock lock = this.lock; |
896 |
lock.lock(); |
897 |
try { |
898 |
Object[] a = new Object[count]; |
899 |
int k = 0; |
900 |
for (Node<E> p = first; p != null; p = p.next) |
901 |
a[k++] = p.item; |
902 |
return a; |
903 |
} finally { |
904 |
// checkInvariants(); |
905 |
lock.unlock(); |
906 |
} |
907 |
} |
908 |
|
909 |
/** |
910 |
* Returns an array containing all of the elements in this deque, in |
911 |
* proper sequence; the runtime type of the returned array is that of |
912 |
* the specified array. If the deque fits in the specified array, it |
913 |
* is returned therein. Otherwise, a new array is allocated with the |
914 |
* runtime type of the specified array and the size of this deque. |
915 |
* |
916 |
* <p>If this deque fits in the specified array with room to spare |
917 |
* (i.e., the array has more elements than this deque), the element in |
918 |
* the array immediately following the end of the deque is set to |
919 |
* {@code null}. |
920 |
* |
921 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
922 |
* array-based and collection-based APIs. Further, this method allows |
923 |
* precise control over the runtime type of the output array, and may, |
924 |
* under certain circumstances, be used to save allocation costs. |
925 |
* |
926 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
927 |
* The following code can be used to dump the deque into a newly |
928 |
* allocated array of {@code String}: |
929 |
* |
930 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
931 |
* |
932 |
* Note that {@code toArray(new Object[0])} is identical in function to |
933 |
* {@code toArray()}. |
934 |
* |
935 |
* @param a the array into which the elements of the deque are to |
936 |
* be stored, if it is big enough; otherwise, a new array of the |
937 |
* same runtime type is allocated for this purpose |
938 |
* @return an array containing all of the elements in this deque |
939 |
* @throws ArrayStoreException if the runtime type of the specified array |
940 |
* is not a supertype of the runtime type of every element in |
941 |
* this deque |
942 |
* @throws NullPointerException if the specified array is null |
943 |
*/ |
944 |
@SuppressWarnings("unchecked") |
945 |
public <T> T[] toArray(T[] a) { |
946 |
final ReentrantLock lock = this.lock; |
947 |
lock.lock(); |
948 |
try { |
949 |
if (a.length < count) |
950 |
a = (T[])java.lang.reflect.Array.newInstance |
951 |
(a.getClass().getComponentType(), count); |
952 |
|
953 |
int k = 0; |
954 |
for (Node<E> p = first; p != null; p = p.next) |
955 |
a[k++] = (T)p.item; |
956 |
if (a.length > k) |
957 |
a[k] = null; |
958 |
return a; |
959 |
} finally { |
960 |
// checkInvariants(); |
961 |
lock.unlock(); |
962 |
} |
963 |
} |
964 |
|
965 |
public String toString() { |
966 |
return Helpers.collectionToString(this); |
967 |
} |
968 |
|
969 |
/** |
970 |
* Atomically removes all of the elements from this deque. |
971 |
* The deque will be empty after this call returns. |
972 |
*/ |
973 |
public void clear() { |
974 |
final ReentrantLock lock = this.lock; |
975 |
lock.lock(); |
976 |
try { |
977 |
for (Node<E> f = first; f != null; ) { |
978 |
f.item = null; |
979 |
Node<E> n = f.next; |
980 |
f.prev = null; |
981 |
f.next = null; |
982 |
f = n; |
983 |
} |
984 |
first = last = null; |
985 |
count = 0; |
986 |
notFull.signalAll(); |
987 |
} finally { |
988 |
// checkInvariants(); |
989 |
lock.unlock(); |
990 |
} |
991 |
} |
992 |
|
993 |
/** |
994 |
* Used for any element traversal that is not entirely under lock. |
995 |
* Such traversals must handle both: |
996 |
* - dequeued nodes (p.next == p) |
997 |
* - (possibly multiple) interior removed nodes (p.item == null) |
998 |
*/ |
999 |
Node<E> succ(Node<E> p) { |
1000 |
if (p == (p = p.next)) |
1001 |
p = first; |
1002 |
return p; |
1003 |
} |
1004 |
|
1005 |
/** |
1006 |
* Returns an iterator over the elements in this deque in proper sequence. |
1007 |
* The elements will be returned in order from first (head) to last (tail). |
1008 |
* |
1009 |
* <p>The returned iterator is |
1010 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1011 |
* |
1012 |
* @return an iterator over the elements in this deque in proper sequence |
1013 |
*/ |
1014 |
public Iterator<E> iterator() { |
1015 |
return new Itr(); |
1016 |
} |
1017 |
|
1018 |
/** |
1019 |
* Returns an iterator over the elements in this deque in reverse |
1020 |
* sequential order. The elements will be returned in order from |
1021 |
* last (tail) to first (head). |
1022 |
* |
1023 |
* <p>The returned iterator is |
1024 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1025 |
* |
1026 |
* @return an iterator over the elements in this deque in reverse order |
1027 |
*/ |
1028 |
public Iterator<E> descendingIterator() { |
1029 |
return new DescendingItr(); |
1030 |
} |
1031 |
|
1032 |
/** |
1033 |
* Base class for LinkedBlockingDeque iterators. |
1034 |
*/ |
1035 |
private abstract class AbstractItr implements Iterator<E> { |
1036 |
/** |
1037 |
* The next node to return in next(). |
1038 |
*/ |
1039 |
Node<E> next; |
1040 |
|
1041 |
/** |
1042 |
* nextItem holds on to item fields because once we claim that |
1043 |
* an element exists in hasNext(), we must return item read |
1044 |
* under lock even if it was in the process of being removed |
1045 |
* when hasNext() was called. |
1046 |
*/ |
1047 |
E nextItem; |
1048 |
|
1049 |
/** |
1050 |
* Node returned by most recent call to next. Needed by remove. |
1051 |
* Reset to null if this element is deleted by a call to remove. |
1052 |
*/ |
1053 |
private Node<E> lastRet; |
1054 |
|
1055 |
abstract Node<E> firstNode(); |
1056 |
abstract Node<E> nextNode(Node<E> n); |
1057 |
|
1058 |
private Node<E> succ(Node<E> p) { |
1059 |
if (p == (p = nextNode(p))) |
1060 |
p = firstNode(); |
1061 |
return p; |
1062 |
} |
1063 |
|
1064 |
AbstractItr() { |
1065 |
// set to initial position |
1066 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1067 |
lock.lock(); |
1068 |
try { |
1069 |
if ((next = firstNode()) != null) |
1070 |
nextItem = next.item; |
1071 |
} finally { |
1072 |
// checkInvariants(); |
1073 |
lock.unlock(); |
1074 |
} |
1075 |
} |
1076 |
|
1077 |
public boolean hasNext() { |
1078 |
return next != null; |
1079 |
} |
1080 |
|
1081 |
public E next() { |
1082 |
Node<E> p; |
1083 |
if ((p = next) == null) |
1084 |
throw new NoSuchElementException(); |
1085 |
lastRet = p; |
1086 |
E x = nextItem; |
1087 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1088 |
lock.lock(); |
1089 |
try { |
1090 |
E e = null; |
1091 |
for (p = nextNode(p); p != null && (e = p.item) == null; ) |
1092 |
p = succ(p); |
1093 |
next = p; |
1094 |
nextItem = e; |
1095 |
} finally { |
1096 |
// checkInvariants(); |
1097 |
lock.unlock(); |
1098 |
} |
1099 |
return x; |
1100 |
} |
1101 |
|
1102 |
public void forEachRemaining(Consumer<? super E> action) { |
1103 |
// A variant of forEachFrom |
1104 |
Objects.requireNonNull(action); |
1105 |
Node<E> p; |
1106 |
if ((p = next) == null) return; |
1107 |
lastRet = p; |
1108 |
next = null; |
1109 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1110 |
final int batchSize = 32; |
1111 |
Object[] es = null; |
1112 |
int n, len = 1; |
1113 |
do { |
1114 |
lock.lock(); |
1115 |
try { |
1116 |
if (es == null) { |
1117 |
p = nextNode(p); |
1118 |
for (Node<E> q = p; q != null; q = succ(q)) |
1119 |
if (q.item != null && ++len == batchSize) |
1120 |
break; |
1121 |
es = new Object[len]; |
1122 |
es[0] = nextItem; |
1123 |
nextItem = null; |
1124 |
n = 1; |
1125 |
} else |
1126 |
n = 0; |
1127 |
for (; p != null && n < len; p = succ(p)) |
1128 |
if ((es[n] = p.item) != null) { |
1129 |
lastRet = p; |
1130 |
n++; |
1131 |
} |
1132 |
} finally { |
1133 |
// checkInvariants(); |
1134 |
lock.unlock(); |
1135 |
} |
1136 |
for (int i = 0; i < n; i++) { |
1137 |
@SuppressWarnings("unchecked") E e = (E) es[i]; |
1138 |
action.accept(e); |
1139 |
} |
1140 |
} while (n > 0 && p != null); |
1141 |
} |
1142 |
|
1143 |
public void remove() { |
1144 |
Node<E> n = lastRet; |
1145 |
if (n == null) |
1146 |
throw new IllegalStateException(); |
1147 |
lastRet = null; |
1148 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1149 |
lock.lock(); |
1150 |
try { |
1151 |
if (n.item != null) |
1152 |
unlink(n); |
1153 |
} finally { |
1154 |
// checkInvariants(); |
1155 |
lock.unlock(); |
1156 |
} |
1157 |
} |
1158 |
} |
1159 |
|
1160 |
/** Forward iterator */ |
1161 |
private class Itr extends AbstractItr { |
1162 |
Itr() {} // prevent access constructor creation |
1163 |
Node<E> firstNode() { return first; } |
1164 |
Node<E> nextNode(Node<E> n) { return n.next; } |
1165 |
} |
1166 |
|
1167 |
/** Descending iterator */ |
1168 |
private class DescendingItr extends AbstractItr { |
1169 |
DescendingItr() {} // prevent access constructor creation |
1170 |
Node<E> firstNode() { return last; } |
1171 |
Node<E> nextNode(Node<E> n) { return n.prev; } |
1172 |
} |
1173 |
|
1174 |
/** |
1175 |
* A customized variant of Spliterators.IteratorSpliterator. |
1176 |
* Keep this class in sync with (very similar) LBQSpliterator. |
1177 |
*/ |
1178 |
private final class LBDSpliterator implements Spliterator<E> { |
1179 |
static final int MAX_BATCH = 1 << 25; // max batch array size; |
1180 |
Node<E> current; // current node; null until initialized |
1181 |
int batch; // batch size for splits |
1182 |
boolean exhausted; // true when no more nodes |
1183 |
long est = size(); // size estimate |
1184 |
|
1185 |
LBDSpliterator() {} |
1186 |
|
1187 |
public long estimateSize() { return est; } |
1188 |
|
1189 |
public Spliterator<E> trySplit() { |
1190 |
Node<E> h; |
1191 |
if (!exhausted && |
1192 |
((h = current) != null || (h = first) != null) |
1193 |
&& h.next != null) { |
1194 |
int n = batch = Math.min(batch + 1, MAX_BATCH); |
1195 |
Object[] a = new Object[n]; |
1196 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1197 |
int i = 0; |
1198 |
Node<E> p = current; |
1199 |
lock.lock(); |
1200 |
try { |
1201 |
if (p != null || (p = first) != null) |
1202 |
for (; p != null && i < n; p = succ(p)) |
1203 |
if ((a[i] = p.item) != null) |
1204 |
i++; |
1205 |
} finally { |
1206 |
// checkInvariants(); |
1207 |
lock.unlock(); |
1208 |
} |
1209 |
if ((current = p) == null) { |
1210 |
est = 0L; |
1211 |
exhausted = true; |
1212 |
} |
1213 |
else if ((est -= i) < 0L) |
1214 |
est = 0L; |
1215 |
if (i > 0) |
1216 |
return Spliterators.spliterator |
1217 |
(a, 0, i, (Spliterator.ORDERED | |
1218 |
Spliterator.NONNULL | |
1219 |
Spliterator.CONCURRENT)); |
1220 |
} |
1221 |
return null; |
1222 |
} |
1223 |
|
1224 |
public boolean tryAdvance(Consumer<? super E> action) { |
1225 |
Objects.requireNonNull(action); |
1226 |
if (!exhausted) { |
1227 |
E e = null; |
1228 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1229 |
lock.lock(); |
1230 |
try { |
1231 |
Node<E> p; |
1232 |
if ((p = current) != null || (p = first) != null) |
1233 |
do { |
1234 |
e = p.item; |
1235 |
p = succ(p); |
1236 |
} while (e == null && p != null); |
1237 |
if ((current = p) == null) |
1238 |
exhausted = true; |
1239 |
} finally { |
1240 |
// checkInvariants(); |
1241 |
lock.unlock(); |
1242 |
} |
1243 |
if (e != null) { |
1244 |
action.accept(e); |
1245 |
return true; |
1246 |
} |
1247 |
} |
1248 |
return false; |
1249 |
} |
1250 |
|
1251 |
public void forEachRemaining(Consumer<? super E> action) { |
1252 |
Objects.requireNonNull(action); |
1253 |
if (!exhausted) { |
1254 |
exhausted = true; |
1255 |
Node<E> p = current; |
1256 |
current = null; |
1257 |
forEachFrom(action, p); |
1258 |
} |
1259 |
} |
1260 |
|
1261 |
public int characteristics() { |
1262 |
return (Spliterator.ORDERED | |
1263 |
Spliterator.NONNULL | |
1264 |
Spliterator.CONCURRENT); |
1265 |
} |
1266 |
} |
1267 |
|
1268 |
/** |
1269 |
* Returns a {@link Spliterator} over the elements in this deque. |
1270 |
* |
1271 |
* <p>The returned spliterator is |
1272 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1273 |
* |
1274 |
* <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT}, |
1275 |
* {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}. |
1276 |
* |
1277 |
* @implNote |
1278 |
* The {@code Spliterator} implements {@code trySplit} to permit limited |
1279 |
* parallelism. |
1280 |
* |
1281 |
* @return a {@code Spliterator} over the elements in this deque |
1282 |
* @since 1.8 |
1283 |
*/ |
1284 |
public Spliterator<E> spliterator() { |
1285 |
return new LBDSpliterator(); |
1286 |
} |
1287 |
|
1288 |
/** |
1289 |
* @throws NullPointerException {@inheritDoc} |
1290 |
*/ |
1291 |
public void forEach(Consumer<? super E> action) { |
1292 |
Objects.requireNonNull(action); |
1293 |
forEachFrom(action, null); |
1294 |
} |
1295 |
|
1296 |
/** |
1297 |
* Runs action on each element found during a traversal starting at p. |
1298 |
* If p is null, traversal starts at head. |
1299 |
*/ |
1300 |
void forEachFrom(Consumer<? super E> action, Node<E> p) { |
1301 |
// Extract batches of elements while holding the lock; then |
1302 |
// run the action on the elements while not |
1303 |
final ReentrantLock lock = this.lock; |
1304 |
final int batchSize = 32; // max number of elements per batch |
1305 |
Object[] es = null; // container for batch of elements |
1306 |
int n, len = 0; |
1307 |
do { |
1308 |
lock.lock(); |
1309 |
try { |
1310 |
if (es == null) { |
1311 |
if (p == null) p = first; |
1312 |
for (Node<E> q = p; q != null; q = succ(q)) |
1313 |
if (q.item != null && ++len == batchSize) |
1314 |
break; |
1315 |
es = new Object[len]; |
1316 |
} |
1317 |
for (n = 0; p != null && n < len; p = succ(p)) |
1318 |
if ((es[n] = p.item) != null) |
1319 |
n++; |
1320 |
} finally { |
1321 |
// checkInvariants(); |
1322 |
lock.unlock(); |
1323 |
} |
1324 |
for (int i = 0; i < n; i++) { |
1325 |
@SuppressWarnings("unchecked") E e = (E) es[i]; |
1326 |
action.accept(e); |
1327 |
} |
1328 |
} while (n > 0 && p != null); |
1329 |
} |
1330 |
|
1331 |
/** |
1332 |
* @throws NullPointerException {@inheritDoc} |
1333 |
*/ |
1334 |
public boolean removeIf(Predicate<? super E> filter) { |
1335 |
Objects.requireNonNull(filter); |
1336 |
return bulkRemove(filter); |
1337 |
} |
1338 |
|
1339 |
/** |
1340 |
* @throws NullPointerException {@inheritDoc} |
1341 |
*/ |
1342 |
public boolean removeAll(Collection<?> c) { |
1343 |
Objects.requireNonNull(c); |
1344 |
return bulkRemove(e -> c.contains(e)); |
1345 |
} |
1346 |
|
1347 |
/** |
1348 |
* @throws NullPointerException {@inheritDoc} |
1349 |
*/ |
1350 |
public boolean retainAll(Collection<?> c) { |
1351 |
Objects.requireNonNull(c); |
1352 |
return bulkRemove(e -> !c.contains(e)); |
1353 |
} |
1354 |
|
1355 |
/** Implementation of bulk remove methods. */ |
1356 |
@SuppressWarnings("unchecked") |
1357 |
private boolean bulkRemove(Predicate<? super E> filter) { |
1358 |
boolean removed = false; |
1359 |
Node<E> p = null; |
1360 |
final ReentrantLock lock = this.lock; |
1361 |
Node<E>[] nodes = null; |
1362 |
int n, len = 0; |
1363 |
do { |
1364 |
// 1. Extract batch of up to 64 elements while holding the lock. |
1365 |
long deathRow = 0; // "bitset" of size 64 |
1366 |
lock.lock(); |
1367 |
try { |
1368 |
if (nodes == null) { |
1369 |
if (p == null) p = first; |
1370 |
for (Node<E> q = p; q != null; q = succ(q)) |
1371 |
if (q.item != null && ++len == 64) |
1372 |
break; |
1373 |
nodes = (Node<E>[]) new Node<?>[len]; |
1374 |
} |
1375 |
for (n = 0; p != null && n < len; p = succ(p)) |
1376 |
nodes[n++] = p; |
1377 |
} finally { |
1378 |
// checkInvariants(); |
1379 |
lock.unlock(); |
1380 |
} |
1381 |
|
1382 |
// 2. Run the filter on the elements while lock is free. |
1383 |
for (int i = 0; i < n; i++) { |
1384 |
final E e; |
1385 |
if ((e = nodes[i].item) != null && filter.test(e)) |
1386 |
deathRow |= 1L << i; |
1387 |
} |
1388 |
|
1389 |
// 3. Remove any filtered elements while holding the lock. |
1390 |
if (deathRow != 0) { |
1391 |
lock.lock(); |
1392 |
try { |
1393 |
for (int i = 0; i < n; i++) { |
1394 |
final Node<E> q; |
1395 |
if ((deathRow & (1L << i)) != 0L |
1396 |
&& (q = nodes[i]).item != null) { |
1397 |
unlink(q); |
1398 |
removed = true; |
1399 |
} |
1400 |
} |
1401 |
} finally { |
1402 |
// checkInvariants(); |
1403 |
lock.unlock(); |
1404 |
} |
1405 |
} |
1406 |
} while (n > 0 && p != null); |
1407 |
return removed; |
1408 |
} |
1409 |
|
1410 |
/** |
1411 |
* Saves this deque to a stream (that is, serializes it). |
1412 |
* |
1413 |
* @param s the stream |
1414 |
* @throws java.io.IOException if an I/O error occurs |
1415 |
* @serialData The capacity (int), followed by elements (each an |
1416 |
* {@code Object}) in the proper order, followed by a null |
1417 |
*/ |
1418 |
private void writeObject(java.io.ObjectOutputStream s) |
1419 |
throws java.io.IOException { |
1420 |
final ReentrantLock lock = this.lock; |
1421 |
lock.lock(); |
1422 |
try { |
1423 |
// Write out capacity and any hidden stuff |
1424 |
s.defaultWriteObject(); |
1425 |
// Write out all elements in the proper order. |
1426 |
for (Node<E> p = first; p != null; p = p.next) |
1427 |
s.writeObject(p.item); |
1428 |
// Use trailing null as sentinel |
1429 |
s.writeObject(null); |
1430 |
} finally { |
1431 |
// checkInvariants(); |
1432 |
lock.unlock(); |
1433 |
} |
1434 |
} |
1435 |
|
1436 |
/** |
1437 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1438 |
* @param s the stream |
1439 |
* @throws ClassNotFoundException if the class of a serialized object |
1440 |
* could not be found |
1441 |
* @throws java.io.IOException if an I/O error occurs |
1442 |
*/ |
1443 |
private void readObject(java.io.ObjectInputStream s) |
1444 |
throws java.io.IOException, ClassNotFoundException { |
1445 |
s.defaultReadObject(); |
1446 |
count = 0; |
1447 |
first = null; |
1448 |
last = null; |
1449 |
// Read in all elements and place in queue |
1450 |
for (;;) { |
1451 |
@SuppressWarnings("unchecked") E item = (E)s.readObject(); |
1452 |
if (item == null) |
1453 |
break; |
1454 |
add(item); |
1455 |
} |
1456 |
} |
1457 |
|
1458 |
void checkInvariants() { |
1459 |
// assert lock.isHeldByCurrentThread(); |
1460 |
// Nodes may get self-linked or lose their item, but only |
1461 |
// after being unlinked and becoming unreachable from first. |
1462 |
for (Node<E> p = first; p != null; p = p.next) { |
1463 |
// assert p.next != p; |
1464 |
// assert p.item != null; |
1465 |
} |
1466 |
} |
1467 |
|
1468 |
} |