1111 lines
38 KiB
Java
1111 lines
38 KiB
Java
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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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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package java.util.concurrent;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.VarHandle;
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import java.util.AbstractQueue;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Comparator;
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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.PriorityQueue;
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import java.util.Queue;
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import java.util.SortedSet;
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import java.util.Spliterator;
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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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import jdk.internal.access.SharedSecrets;
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import jdk.internal.util.ArraysSupport;
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/**
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* An unbounded {@linkplain BlockingQueue blocking queue} that uses
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* the same ordering rules as class {@link PriorityQueue} and supplies
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* blocking retrieval operations. While this queue is logically
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* unbounded, attempted additions may fail due to resource exhaustion
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* (causing {@code OutOfMemoryError}). This class does not permit
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* {@code null} elements. A priority queue relying on {@linkplain
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* Comparable natural ordering} also does not permit insertion of
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* non-comparable objects (doing so results in
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* {@code ClassCastException}).
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*
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* <p>This class and its iterator implement all of the <em>optional</em>
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* methods of the {@link Collection} and {@link Iterator} interfaces.
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* The Iterator provided in method {@link #iterator()} and the
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* Spliterator provided in method {@link #spliterator()} are <em>not</em>
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* guaranteed to traverse the elements of the PriorityBlockingQueue in
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* any particular order. If you need ordered traversal, consider using
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* {@code Arrays.sort(pq.toArray())}. Also, method {@code drainTo} can
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* be used to <em>remove</em> some or all elements in priority order and
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* place them in another collection.
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*
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* <p>Operations on this class make no guarantees about the ordering
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* of elements with equal priority. If you need to enforce an
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* ordering, you can define custom classes or comparators that use a
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* secondary key to break ties in primary priority values. For
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* example, here is a class that applies first-in-first-out
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* tie-breaking to comparable elements. To use it, you would insert a
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* {@code new FIFOEntry(anEntry)} instead of a plain entry object.
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*
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* <pre> {@code
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* class FIFOEntry<E extends Comparable<? super E>>
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* implements Comparable<FIFOEntry<E>> {
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* static final AtomicLong seq = new AtomicLong();
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* final long seqNum;
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* final E entry;
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* public FIFOEntry(E entry) {
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* seqNum = seq.getAndIncrement();
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* this.entry = entry;
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* }
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* public E getEntry() { return entry; }
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* public int compareTo(FIFOEntry<E> other) {
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* int res = entry.compareTo(other.entry);
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* if (res == 0 && other.entry != this.entry)
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* res = (seqNum < other.seqNum ? -1 : 1);
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* return res;
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* }
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* }}</pre>
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*
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* <p>This class is a member of the
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* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
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* Java Collections Framework</a>.
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*
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* @since 1.5
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* @author Doug Lea
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* @param <E> the type of elements held in this queue
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*/
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@SuppressWarnings("unchecked")
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public class PriorityBlockingQueue<E> extends AbstractQueue<E>
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implements BlockingQueue<E>, java.io.Serializable {
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private static final long serialVersionUID = 5595510919245408276L;
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/*
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* The implementation uses an array-based binary heap, with public
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* operations protected with a single lock. However, allocation
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* during resizing uses a simple spinlock (used only while not
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* holding main lock) in order to allow takes to operate
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* concurrently with allocation. This avoids repeated
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* postponement of waiting consumers and consequent element
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* build-up. The need to back away from lock during allocation
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* makes it impossible to simply wrap delegated
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* java.util.PriorityQueue operations within a lock, as was done
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* in a previous version of this class. To maintain
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* interoperability, a plain PriorityQueue is still used during
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* serialization, which maintains compatibility at the expense of
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* transiently doubling overhead.
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*/
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/**
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* Default array capacity.
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*/
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private static final int DEFAULT_INITIAL_CAPACITY = 11;
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/**
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* Priority queue represented as a balanced binary heap: the two
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* children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The
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* priority queue is ordered by comparator, or by the elements'
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* natural ordering, if comparator is null: For each node n in the
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* heap and each descendant d of n, n <= d. The element with the
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* lowest value is in queue[0], assuming the queue is nonempty.
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*/
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private transient Object[] queue;
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/**
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* The number of elements in the priority queue.
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*/
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private transient int size;
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/**
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* The comparator, or null if priority queue uses elements'
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* natural ordering.
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*/
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private transient Comparator<? super E> comparator;
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/**
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* Lock used for all public operations.
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*/
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private final ReentrantLock lock = new ReentrantLock();
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/**
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* Condition for blocking when empty.
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*/
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@SuppressWarnings("serial") // Classes implementing Condition may be serializable.
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private final Condition notEmpty = lock.newCondition();
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/**
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* Spinlock for allocation, acquired via CAS.
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*/
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private transient volatile int allocationSpinLock;
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/**
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* A plain PriorityQueue used only for serialization,
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* to maintain compatibility with previous versions
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* of this class. Non-null only during serialization/deserialization.
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*/
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private PriorityQueue<E> q;
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/**
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* Creates a {@code PriorityBlockingQueue} with the default
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* initial capacity (11) that orders its elements according to
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* their {@linkplain Comparable natural ordering}.
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*/
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public PriorityBlockingQueue() {
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this(DEFAULT_INITIAL_CAPACITY, null);
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}
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/**
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* Creates a {@code PriorityBlockingQueue} with the specified
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* initial capacity that orders its elements according to their
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* {@linkplain Comparable natural ordering}.
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*
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* @param initialCapacity the initial capacity for this priority queue
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* @throws IllegalArgumentException if {@code initialCapacity} is less
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* than 1
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*/
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public PriorityBlockingQueue(int initialCapacity) {
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this(initialCapacity, null);
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}
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/**
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* Creates a {@code PriorityBlockingQueue} with the specified initial
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* capacity that orders its elements according to the specified
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* comparator.
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*
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* @param initialCapacity the initial capacity for this priority queue
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* @param comparator the comparator that will be used to order this
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* priority queue. If {@code null}, the {@linkplain Comparable
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* natural ordering} of the elements will be used.
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* @throws IllegalArgumentException if {@code initialCapacity} is less
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* than 1
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*/
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public PriorityBlockingQueue(int initialCapacity,
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Comparator<? super E> comparator) {
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if (initialCapacity < 1)
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throw new IllegalArgumentException();
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this.comparator = comparator;
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this.queue = new Object[Math.max(1, initialCapacity)];
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}
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/**
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* Creates a {@code PriorityBlockingQueue} containing the elements
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* in the specified collection. If the specified collection is a
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* {@link SortedSet} or a {@link PriorityBlockingQueue}, this
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* priority queue will be ordered according to the same ordering.
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* Otherwise, this priority queue will be ordered according to the
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* {@linkplain Comparable natural ordering} of its elements.
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*
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* @param c the collection whose elements are to be placed
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* into this priority queue
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* @throws ClassCastException if elements of the specified collection
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* cannot be compared to one another according to the priority
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* queue's ordering
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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 PriorityBlockingQueue(Collection<? extends E> c) {
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boolean heapify = true; // true if not known to be in heap order
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boolean screen = true; // true if must screen for nulls
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if (c instanceof SortedSet<?>) {
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SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
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this.comparator = (Comparator<? super E>) ss.comparator();
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heapify = false;
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}
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else if (c instanceof PriorityBlockingQueue<?>) {
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PriorityBlockingQueue<? extends E> pq =
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(PriorityBlockingQueue<? extends E>) c;
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this.comparator = (Comparator<? super E>) pq.comparator();
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screen = false;
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if (pq.getClass() == PriorityBlockingQueue.class) // exact match
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heapify = false;
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}
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Object[] es = c.toArray();
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int n = es.length;
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// Android-changed: Defend against c.toArray (incorrectly) not returning Object[]
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// (see b/204397945)
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// if (c.getClass() != java.util.ArrayList.class)
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if (es.getClass() != Object[].class)
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es = Arrays.copyOf(es, n, Object[].class);
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if (screen && (n == 1 || this.comparator != null)) {
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for (Object e : es)
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if (e == null)
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throw new NullPointerException();
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}
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this.queue = ensureNonEmpty(es);
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this.size = n;
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if (heapify)
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heapify();
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}
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/** Ensures that queue[0] exists, helping peek() and poll(). */
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private static Object[] ensureNonEmpty(Object[] es) {
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return (es.length > 0) ? es : new Object[1];
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}
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/**
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* Tries to grow array to accommodate at least one more element
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* (but normally expand by about 50%), giving up (allowing retry)
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* on contention (which we expect to be rare). Call only while
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* holding lock.
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*
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* @param array the heap array
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* @param oldCap the length of the array
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*/
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private void tryGrow(Object[] array, int oldCap) {
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lock.unlock(); // must release and then re-acquire main lock
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Object[] newArray = null;
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if (allocationSpinLock == 0 &&
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ALLOCATIONSPINLOCK.compareAndSet(this, 0, 1)) {
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try {
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int growth = (oldCap < 64)
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? (oldCap + 2) // grow faster if small
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: (oldCap >> 1);
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int newCap = ArraysSupport.newLength(oldCap, 1, growth);
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if (queue == array)
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newArray = new Object[newCap];
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} finally {
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allocationSpinLock = 0;
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}
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}
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if (newArray == null) // back off if another thread is allocating
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Thread.yield();
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lock.lock();
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if (newArray != null && queue == array) {
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queue = newArray;
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System.arraycopy(array, 0, newArray, 0, oldCap);
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}
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}
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/**
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* Mechanics for poll(). Call only while holding lock.
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*/
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private E dequeue() {
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// assert lock.isHeldByCurrentThread();
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final Object[] es;
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final E result;
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if ((result = (E) ((es = queue)[0])) != null) {
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final int n;
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final E x = (E) es[(n = --size)];
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es[n] = null;
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if (n > 0) {
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final Comparator<? super E> cmp;
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if ((cmp = comparator) == null)
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siftDownComparable(0, x, es, n);
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else
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siftDownUsingComparator(0, x, es, n, cmp);
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}
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}
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return result;
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}
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/**
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* Inserts item x at position k, maintaining heap invariant by
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* promoting x up the tree until it is greater than or equal to
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* its parent, or is the root.
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*
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* To simplify and speed up coercions and comparisons, the
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* Comparable and Comparator versions are separated into different
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* methods that are otherwise identical. (Similarly for siftDown.)
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*
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* @param k the position to fill
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* @param x the item to insert
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* @param es the heap array
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*/
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private static <T> void siftUpComparable(int k, T x, Object[] es) {
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Comparable<? super T> key = (Comparable<? super T>) x;
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while (k > 0) {
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int parent = (k - 1) >>> 1;
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Object e = es[parent];
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if (key.compareTo((T) e) >= 0)
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break;
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es[k] = e;
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k = parent;
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}
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es[k] = key;
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}
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private static <T> void siftUpUsingComparator(
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int k, T x, Object[] es, Comparator<? super T> cmp) {
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while (k > 0) {
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int parent = (k - 1) >>> 1;
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Object e = es[parent];
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if (cmp.compare(x, (T) e) >= 0)
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break;
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es[k] = e;
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k = parent;
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}
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es[k] = x;
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}
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/**
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* Inserts item x at position k, maintaining heap invariant by
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* demoting x down the tree repeatedly until it is less than or
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* equal to its children or is a leaf.
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*
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* @param k the position to fill
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* @param x the item to insert
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* @param es the heap array
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* @param n heap size
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*/
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private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
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// assert n > 0;
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Comparable<? super T> key = (Comparable<? super T>)x;
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int half = n >>> 1; // loop while a non-leaf
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while (k < half) {
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int child = (k << 1) + 1; // assume left child is least
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Object c = es[child];
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int right = child + 1;
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if (right < n &&
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((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
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c = es[child = right];
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if (key.compareTo((T) c) <= 0)
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break;
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es[k] = c;
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k = child;
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}
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es[k] = key;
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}
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private static <T> void siftDownUsingComparator(
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int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
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// assert n > 0;
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int half = n >>> 1;
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while (k < half) {
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int child = (k << 1) + 1;
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Object c = es[child];
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int right = child + 1;
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if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
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c = es[child = right];
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if (cmp.compare(x, (T) c) <= 0)
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break;
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es[k] = c;
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k = child;
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}
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es[k] = x;
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}
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/**
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* Establishes the heap invariant (described above) in the entire tree,
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* assuming nothing about the order of the elements prior to the call.
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* This classic algorithm due to Floyd (1964) is known to be O(size).
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*/
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private void heapify() {
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final Object[] es = queue;
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int n = size, i = (n >>> 1) - 1;
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final Comparator<? super E> cmp;
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if ((cmp = comparator) == null)
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for (; i >= 0; i--)
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siftDownComparable(i, (E) es[i], es, n);
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else
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for (; i >= 0; i--)
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siftDownUsingComparator(i, (E) es[i], es, n, cmp);
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}
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/**
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* Inserts the specified element into this priority queue.
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*
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* @param e the element to add
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* @return {@code true} (as specified by {@link Collection#add})
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* @throws ClassCastException if the specified element cannot be compared
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* with elements currently in the priority queue according to the
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* priority queue's ordering
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* @throws NullPointerException if the specified element is null
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*/
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public boolean add(E e) {
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return offer(e);
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}
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/**
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* Inserts the specified element into this priority queue.
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* As the queue is unbounded, this method will never return {@code false}.
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*
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* @param e the element to add
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* @return {@code true} (as specified by {@link Queue#offer})
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* @throws ClassCastException if the specified element cannot be compared
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* with elements currently in the priority queue according to the
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* priority queue's ordering
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* @throws NullPointerException if the specified element is null
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*/
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public boolean offer(E e) {
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if (e == null)
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throw new NullPointerException();
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final ReentrantLock lock = this.lock;
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lock.lock();
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int n, cap;
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Object[] es;
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while ((n = size) >= (cap = (es = queue).length))
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tryGrow(es, cap);
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try {
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final Comparator<? super E> cmp;
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if ((cmp = comparator) == null)
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siftUpComparable(n, e, es);
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else
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siftUpUsingComparator(n, e, es, cmp);
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size = n + 1;
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notEmpty.signal();
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} finally {
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lock.unlock();
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}
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return true;
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}
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|
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/**
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* Inserts the specified element into this priority queue.
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* As the queue is unbounded, this method will never block.
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*
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* @param e the element to add
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* @throws ClassCastException if the specified element cannot be compared
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* with elements currently in the priority queue according to the
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* priority queue's ordering
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* @throws NullPointerException if the specified element is null
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*/
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public void put(E e) {
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offer(e); // never need to block
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}
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/**
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* Inserts the specified element into this priority queue.
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|
* As the queue is unbounded, this method will never block or
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* return {@code false}.
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*
|
|
* @param e the element to add
|
|
* @param timeout This parameter is ignored as the method never blocks
|
|
* @param unit This parameter is ignored as the method never blocks
|
|
* @return {@code true} (as specified by
|
|
* {@link BlockingQueue#offer(Object,long,TimeUnit) BlockingQueue.offer})
|
|
* @throws ClassCastException if the specified element cannot be compared
|
|
* with elements currently in the priority queue according to the
|
|
* priority queue's ordering
|
|
* @throws NullPointerException if the specified element is null
|
|
*/
|
|
public boolean offer(E e, long timeout, TimeUnit unit) {
|
|
return offer(e); // never need to block
|
|
}
|
|
|
|
public E poll() {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
return dequeue();
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
public E take() throws InterruptedException {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lockInterruptibly();
|
|
E result;
|
|
try {
|
|
while ( (result = dequeue()) == null)
|
|
notEmpty.await();
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
return result;
|
|
}
|
|
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
|
|
long nanos = unit.toNanos(timeout);
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lockInterruptibly();
|
|
E result;
|
|
try {
|
|
while ( (result = dequeue()) == null && nanos > 0)
|
|
nanos = notEmpty.awaitNanos(nanos);
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
return result;
|
|
}
|
|
|
|
public E peek() {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
return (E) queue[0];
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns the comparator used to order the elements in this queue,
|
|
* or {@code null} if this queue uses the {@linkplain Comparable
|
|
* natural ordering} of its elements.
|
|
*
|
|
* @return the comparator used to order the elements in this queue,
|
|
* or {@code null} if this queue uses the natural
|
|
* ordering of its elements
|
|
*/
|
|
public Comparator<? super E> comparator() {
|
|
return comparator;
|
|
}
|
|
|
|
public int size() {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
return size;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Always returns {@code Integer.MAX_VALUE} because
|
|
* a {@code PriorityBlockingQueue} is not capacity constrained.
|
|
* @return {@code Integer.MAX_VALUE} always
|
|
*/
|
|
public int remainingCapacity() {
|
|
return Integer.MAX_VALUE;
|
|
}
|
|
|
|
private int indexOf(Object o) {
|
|
if (o != null) {
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
if (o.equals(es[i]))
|
|
return i;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/**
|
|
* Removes the ith element from queue.
|
|
*/
|
|
private void removeAt(int i) {
|
|
final Object[] es = queue;
|
|
final int n = size - 1;
|
|
if (n == i) // removed last element
|
|
es[i] = null;
|
|
else {
|
|
E moved = (E) es[n];
|
|
es[n] = null;
|
|
final Comparator<? super E> cmp;
|
|
if ((cmp = comparator) == null)
|
|
siftDownComparable(i, moved, es, n);
|
|
else
|
|
siftDownUsingComparator(i, moved, es, n, cmp);
|
|
if (es[i] == moved) {
|
|
if (cmp == null)
|
|
siftUpComparable(i, moved, es);
|
|
else
|
|
siftUpUsingComparator(i, moved, es, cmp);
|
|
}
|
|
}
|
|
size = n;
|
|
}
|
|
|
|
/**
|
|
* Removes a single instance of the specified element from this queue,
|
|
* if it is present. More formally, removes an element {@code e} such
|
|
* that {@code o.equals(e)}, if this queue contains one or more such
|
|
* elements. Returns {@code true} if and only if this queue contained
|
|
* the specified element (or equivalently, if this queue changed as a
|
|
* result of the call).
|
|
*
|
|
* @param o element to be removed from this queue, if present
|
|
* @return {@code true} if this queue changed as a result of the call
|
|
*/
|
|
public boolean remove(Object o) {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
int i = indexOf(o);
|
|
if (i == -1)
|
|
return false;
|
|
removeAt(i);
|
|
return true;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Identity-based version for use in Itr.remove.
|
|
*
|
|
* @param o element to be removed from this queue, if present
|
|
*/
|
|
void removeEq(Object o) {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++) {
|
|
if (o == es[i]) {
|
|
removeAt(i);
|
|
break;
|
|
}
|
|
}
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns {@code true} if this queue contains the specified element.
|
|
* More formally, returns {@code true} if and only if this queue contains
|
|
* at least one element {@code e} such that {@code o.equals(e)}.
|
|
*
|
|
* @param o object to be checked for containment in this queue
|
|
* @return {@code true} if this queue contains the specified element
|
|
*/
|
|
public boolean contains(Object o) {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
return indexOf(o) != -1;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
public String toString() {
|
|
return Helpers.collectionToString(this);
|
|
}
|
|
|
|
/**
|
|
* @throws UnsupportedOperationException {@inheritDoc}
|
|
* @throws ClassCastException {@inheritDoc}
|
|
* @throws NullPointerException {@inheritDoc}
|
|
* @throws IllegalArgumentException {@inheritDoc}
|
|
*/
|
|
public int drainTo(Collection<? super E> c) {
|
|
return drainTo(c, Integer.MAX_VALUE);
|
|
}
|
|
|
|
/**
|
|
* @throws UnsupportedOperationException {@inheritDoc}
|
|
* @throws ClassCastException {@inheritDoc}
|
|
* @throws NullPointerException {@inheritDoc}
|
|
* @throws IllegalArgumentException {@inheritDoc}
|
|
*/
|
|
public int drainTo(Collection<? super E> c, int maxElements) {
|
|
Objects.requireNonNull(c);
|
|
if (c == this)
|
|
throw new IllegalArgumentException();
|
|
if (maxElements <= 0)
|
|
return 0;
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
int n = Math.min(size, maxElements);
|
|
for (int i = 0; i < n; i++) {
|
|
c.add((E) queue[0]); // In this order, in case add() throws.
|
|
dequeue();
|
|
}
|
|
return n;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Atomically removes all of the elements from this queue.
|
|
* The queue will be empty after this call returns.
|
|
*/
|
|
public void clear() {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
es[i] = null;
|
|
size = 0;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns an array containing all of the elements in this queue.
|
|
* The returned array elements are in no particular order.
|
|
*
|
|
* <p>The returned array will be "safe" in that no references to it are
|
|
* maintained by this queue. (In other words, this method must allocate
|
|
* a new array). The caller is thus free to modify the returned array.
|
|
*
|
|
* <p>This method acts as bridge between array-based and collection-based
|
|
* APIs.
|
|
*
|
|
* @return an array containing all of the elements in this queue
|
|
*/
|
|
public Object[] toArray() {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
return Arrays.copyOf(queue, size);
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns an array containing all of the elements in this queue; the
|
|
* runtime type of the returned array is that of the specified array.
|
|
* The returned array elements are in no particular order.
|
|
* If the queue fits in the specified array, it is returned therein.
|
|
* Otherwise, a new array is allocated with the runtime type of the
|
|
* specified array and the size of this queue.
|
|
*
|
|
* <p>If this queue fits in the specified array with room to spare
|
|
* (i.e., the array has more elements than this queue), the element in
|
|
* the array immediately following the end of the queue is set to
|
|
* {@code null}.
|
|
*
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between
|
|
* array-based and collection-based APIs. Further, this method allows
|
|
* precise control over the runtime type of the output array, and may,
|
|
* under certain circumstances, be used to save allocation costs.
|
|
*
|
|
* <p>Suppose {@code x} is a queue known to contain only strings.
|
|
* The following code can be used to dump the queue into a newly
|
|
* allocated array of {@code String}:
|
|
*
|
|
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
|
|
*
|
|
* Note that {@code toArray(new Object[0])} is identical in function to
|
|
* {@code toArray()}.
|
|
*
|
|
* @param a the array into which the elements of the queue are to
|
|
* be stored, if it is big enough; otherwise, a new array of the
|
|
* same runtime type is allocated for this purpose
|
|
* @return an array containing all of the elements in this queue
|
|
* @throws ArrayStoreException if the runtime type of the specified array
|
|
* is not a supertype of the runtime type of every element in
|
|
* this queue
|
|
* @throws NullPointerException if the specified array is null
|
|
*/
|
|
public <T> T[] toArray(T[] a) {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
int n = size;
|
|
if (a.length < n)
|
|
// Make a new array of a's runtime type, but my contents:
|
|
return (T[]) Arrays.copyOf(queue, size, a.getClass());
|
|
System.arraycopy(queue, 0, a, 0, n);
|
|
if (a.length > n)
|
|
a[n] = null;
|
|
return a;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns an iterator over the elements in this queue. The
|
|
* iterator does not return the elements in any particular order.
|
|
*
|
|
* <p>The returned iterator is
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
|
|
*
|
|
* @return an iterator over the elements in this queue
|
|
*/
|
|
public Iterator<E> iterator() {
|
|
return new Itr(toArray());
|
|
}
|
|
|
|
/**
|
|
* Snapshot iterator that works off copy of underlying q array.
|
|
*/
|
|
final class Itr implements Iterator<E> {
|
|
final Object[] array; // Array of all elements
|
|
int cursor; // index of next element to return
|
|
int lastRet = -1; // index of last element, or -1 if no such
|
|
|
|
Itr(Object[] array) {
|
|
this.array = array;
|
|
}
|
|
|
|
public boolean hasNext() {
|
|
return cursor < array.length;
|
|
}
|
|
|
|
public E next() {
|
|
if (cursor >= array.length)
|
|
throw new NoSuchElementException();
|
|
return (E)array[lastRet = cursor++];
|
|
}
|
|
|
|
public void remove() {
|
|
if (lastRet < 0)
|
|
throw new IllegalStateException();
|
|
removeEq(array[lastRet]);
|
|
lastRet = -1;
|
|
}
|
|
|
|
public void forEachRemaining(Consumer<? super E> action) {
|
|
Objects.requireNonNull(action);
|
|
final Object[] es = array;
|
|
int i;
|
|
if ((i = cursor) < es.length) {
|
|
lastRet = -1;
|
|
cursor = es.length;
|
|
for (; i < es.length; i++)
|
|
action.accept((E) es[i]);
|
|
lastRet = es.length - 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Saves this queue to a stream (that is, serializes it).
|
|
*
|
|
* For compatibility with previous version of this class, elements
|
|
* are first copied to a java.util.PriorityQueue, which is then
|
|
* serialized.
|
|
*
|
|
* @param s the stream
|
|
* @throws java.io.IOException if an I/O error occurs
|
|
*/
|
|
private void writeObject(java.io.ObjectOutputStream s)
|
|
throws java.io.IOException {
|
|
lock.lock();
|
|
try {
|
|
// avoid zero capacity argument
|
|
q = new PriorityQueue<E>(Math.max(size, 1), comparator);
|
|
q.addAll(this);
|
|
s.defaultWriteObject();
|
|
} finally {
|
|
q = null;
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Reconstitutes this queue from a stream (that is, deserializes it).
|
|
* @param s the stream
|
|
* @throws ClassNotFoundException if the class of a serialized object
|
|
* could not be found
|
|
* @throws java.io.IOException if an I/O error occurs
|
|
*/
|
|
private void readObject(java.io.ObjectInputStream s)
|
|
throws java.io.IOException, ClassNotFoundException {
|
|
try {
|
|
s.defaultReadObject();
|
|
int sz = q.size();
|
|
SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, sz);
|
|
this.queue = new Object[Math.max(1, sz)];
|
|
comparator = q.comparator();
|
|
addAll(q);
|
|
} finally {
|
|
q = null;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Immutable snapshot spliterator that binds to elements "late".
|
|
*/
|
|
final class PBQSpliterator implements Spliterator<E> {
|
|
Object[] array; // null until late-bound-initialized
|
|
int index;
|
|
int fence;
|
|
|
|
PBQSpliterator() {}
|
|
|
|
PBQSpliterator(Object[] array, int index, int fence) {
|
|
this.array = array;
|
|
this.index = index;
|
|
this.fence = fence;
|
|
}
|
|
|
|
private int getFence() {
|
|
if (array == null)
|
|
fence = (array = toArray()).length;
|
|
return fence;
|
|
}
|
|
|
|
public PBQSpliterator trySplit() {
|
|
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
|
|
return (lo >= mid) ? null :
|
|
new PBQSpliterator(array, lo, index = mid);
|
|
}
|
|
|
|
public void forEachRemaining(Consumer<? super E> action) {
|
|
Objects.requireNonNull(action);
|
|
final int hi = getFence(), lo = index;
|
|
final Object[] es = array;
|
|
index = hi; // ensure exhaustion
|
|
for (int i = lo; i < hi; i++)
|
|
action.accept((E) es[i]);
|
|
}
|
|
|
|
public boolean tryAdvance(Consumer<? super E> action) {
|
|
Objects.requireNonNull(action);
|
|
if (getFence() > index && index >= 0) {
|
|
action.accept((E) array[index++]);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
public long estimateSize() { return getFence() - index; }
|
|
|
|
public int characteristics() {
|
|
return (Spliterator.NONNULL |
|
|
Spliterator.SIZED |
|
|
Spliterator.SUBSIZED);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a {@link Spliterator} over the elements in this queue.
|
|
* The spliterator does not traverse elements in any particular order
|
|
* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
|
|
*
|
|
* <p>The returned spliterator is
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
|
|
*
|
|
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
|
|
* {@link Spliterator#NONNULL}.
|
|
*
|
|
* @implNote
|
|
* The {@code Spliterator} additionally reports {@link Spliterator#SUBSIZED}.
|
|
*
|
|
* @return a {@code Spliterator} over the elements in this queue
|
|
* @since 1.8
|
|
*/
|
|
public Spliterator<E> spliterator() {
|
|
return new PBQSpliterator();
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean removeIf(Predicate<? super E> filter) {
|
|
Objects.requireNonNull(filter);
|
|
return bulkRemove(filter);
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean removeAll(Collection<?> c) {
|
|
Objects.requireNonNull(c);
|
|
return bulkRemove(e -> c.contains(e));
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public boolean retainAll(Collection<?> c) {
|
|
Objects.requireNonNull(c);
|
|
return bulkRemove(e -> !c.contains(e));
|
|
}
|
|
|
|
// A tiny bit set implementation
|
|
|
|
private static long[] nBits(int n) {
|
|
return new long[((n - 1) >> 6) + 1];
|
|
}
|
|
private static void setBit(long[] bits, int i) {
|
|
bits[i >> 6] |= 1L << i;
|
|
}
|
|
private static boolean isClear(long[] bits, int i) {
|
|
return (bits[i >> 6] & (1L << i)) == 0;
|
|
}
|
|
|
|
/** Implementation of bulk remove methods. */
|
|
private boolean bulkRemove(Predicate<? super E> filter) {
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
final Object[] es = queue;
|
|
final int end = size;
|
|
int i;
|
|
// Optimize for initial run of survivors
|
|
for (i = 0; i < end && !filter.test((E) es[i]); i++)
|
|
;
|
|
if (i >= end)
|
|
return false;
|
|
// Tolerate predicates that reentrantly access the
|
|
// collection for read, so traverse once to find elements
|
|
// to delete, a second pass to physically expunge.
|
|
final int beg = i;
|
|
final long[] deathRow = nBits(end - beg);
|
|
deathRow[0] = 1L; // set bit 0
|
|
for (i = beg + 1; i < end; i++)
|
|
if (filter.test((E) es[i]))
|
|
setBit(deathRow, i - beg);
|
|
int w = beg;
|
|
for (i = beg; i < end; i++)
|
|
if (isClear(deathRow, i - beg))
|
|
es[w++] = es[i];
|
|
for (i = size = w; i < end; i++)
|
|
es[i] = null;
|
|
heapify();
|
|
return true;
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @throws NullPointerException {@inheritDoc}
|
|
*/
|
|
public void forEach(Consumer<? super E> action) {
|
|
Objects.requireNonNull(action);
|
|
final ReentrantLock lock = this.lock;
|
|
lock.lock();
|
|
try {
|
|
final Object[] es = queue;
|
|
for (int i = 0, n = size; i < n; i++)
|
|
action.accept((E) es[i]);
|
|
} finally {
|
|
lock.unlock();
|
|
}
|
|
}
|
|
|
|
// VarHandle mechanics
|
|
private static final VarHandle ALLOCATIONSPINLOCK;
|
|
static {
|
|
try {
|
|
MethodHandles.Lookup l = MethodHandles.lookup();
|
|
ALLOCATIONSPINLOCK = l.findVarHandle(PriorityBlockingQueue.class,
|
|
"allocationSpinLock",
|
|
int.class);
|
|
} catch (ReflectiveOperationException e) {
|
|
throw new ExceptionInInitializerError(e);
|
|
}
|
|
}
|
|
}
|