src/share/classes/java/util/concurrent/PriorityBlockingQueue.java

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*** 41,92 **** /** * An unbounded {@linkplain BlockingQueue blocking queue} that uses * the same ordering rules as class {@link PriorityQueue} and supplies * blocking retrieval operations. While this queue is logically * unbounded, attempted additions may fail due to resource exhaustion ! * (causing <tt>OutOfMemoryError</tt>). This class does not permit ! * <tt>null</tt> elements. A priority queue relying on {@linkplain * Comparable natural ordering} also does not permit insertion of * non-comparable objects (doing so results in ! * <tt>ClassCastException</tt>). * * <p>This class and its iterator implement all of the * <em>optional</em> methods of the {@link Collection} and {@link * Iterator} interfaces. The Iterator provided in method {@link * #iterator()} is <em>not</em> guaranteed to traverse the elements of * the PriorityBlockingQueue in any particular order. If you need * ordered traversal, consider using ! * <tt>Arrays.sort(pq.toArray())</tt>. Also, method <tt>drainTo</tt> * can be used to <em>remove</em> some or all elements in priority * order and place them in another collection. * * <p>Operations on this class make no guarantees about the ordering * of elements with equal priority. If you need to enforce an * ordering, you can define custom classes or comparators that use a * secondary key to break ties in primary priority values. For * example, here is a class that applies first-in-first-out * tie-breaking to comparable elements. To use it, you would insert a ! * <tt>new FIFOEntry(anEntry)</tt> instead of a plain entry object. * ! * <pre> ! * class FIFOEntry&lt;E extends Comparable&lt;? super E&gt;&gt; ! * implements Comparable&lt;FIFOEntry&lt;E&gt;&gt; { ! * final static AtomicLong seq = new AtomicLong(); * final long seqNum; * final E entry; * public FIFOEntry(E entry) { * seqNum = seq.getAndIncrement(); * this.entry = entry; * } * public E getEntry() { return entry; } ! * public int compareTo(FIFOEntry&lt;E&gt; other) { * int res = entry.compareTo(other.entry); ! * if (res == 0 &amp;&amp; other.entry != this.entry) ! * res = (seqNum &lt; other.seqNum ? -1 : 1); * return res; * } ! * }</pre> * * <p>This class is a member of the * <a href="{@docRoot}/../technotes/guides/collections/index.html"> * Java Collections Framework</a>. * --- 41,92 ---- /** * An unbounded {@linkplain BlockingQueue blocking queue} that uses * the same ordering rules as class {@link PriorityQueue} and supplies * blocking retrieval operations. While this queue is logically * unbounded, attempted additions may fail due to resource exhaustion ! * (causing {@code OutOfMemoryError}). This class does not permit ! * {@code null} elements. A priority queue relying on {@linkplain * Comparable natural ordering} also does not permit insertion of * non-comparable objects (doing so results in ! * {@code ClassCastException}). * * <p>This class and its iterator implement all of the * <em>optional</em> methods of the {@link Collection} and {@link * Iterator} interfaces. The Iterator provided in method {@link * #iterator()} is <em>not</em> guaranteed to traverse the elements of * the PriorityBlockingQueue in any particular order. If you need * ordered traversal, consider using ! * {@code Arrays.sort(pq.toArray())}. Also, method {@code drainTo} * can be used to <em>remove</em> some or all elements in priority * order and place them in another collection. * * <p>Operations on this class make no guarantees about the ordering * of elements with equal priority. If you need to enforce an * ordering, you can define custom classes or comparators that use a * secondary key to break ties in primary priority values. For * example, here is a class that applies first-in-first-out * tie-breaking to comparable elements. To use it, you would insert a ! * {@code new FIFOEntry(anEntry)} instead of a plain entry object. * ! * <pre> {@code ! * class FIFOEntry<E extends Comparable<? super E>> ! * implements Comparable<FIFOEntry<E>> { ! * static final AtomicLong seq = new AtomicLong(0); * final long seqNum; * final E entry; * public FIFOEntry(E entry) { * seqNum = seq.getAndIncrement(); * this.entry = entry; * } * public E getEntry() { return entry; } ! * public int compareTo(FIFOEntry<E> other) { * int res = entry.compareTo(other.entry); ! * if (res == 0 && other.entry != this.entry) ! * res = (seqNum < other.seqNum ? -1 : 1); * return res; * } ! * }}</pre> * * <p>This class is a member of the * <a href="{@docRoot}/../technotes/guides/collections/index.html"> * Java Collections Framework</a>. *
*** 96,150 **** */ public class PriorityBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, java.io.Serializable { private static final long serialVersionUID = 5595510919245408276L; ! private final PriorityQueue<E> q; ! private final ReentrantLock lock = new ReentrantLock(true); ! private final Condition notEmpty = lock.newCondition(); /** ! * Creates a <tt>PriorityBlockingQueue</tt> with the default * initial capacity (11) that orders its elements according to * their {@linkplain Comparable natural ordering}. */ public PriorityBlockingQueue() { ! q = new PriorityQueue<E>(); } /** ! * Creates a <tt>PriorityBlockingQueue</tt> with the specified * initial capacity that orders its elements according to their * {@linkplain Comparable natural ordering}. * * @param initialCapacity the initial capacity for this priority queue ! * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less * than 1 */ public PriorityBlockingQueue(int initialCapacity) { ! q = new PriorityQueue<E>(initialCapacity, null); } /** ! * Creates a <tt>PriorityBlockingQueue</tt> with the specified initial * capacity that orders its elements according to the specified * comparator. * * @param initialCapacity the initial capacity for this priority queue * @param comparator the comparator that will be used to order this * priority queue. If {@code null}, the {@linkplain Comparable * natural ordering} of the elements will be used. ! * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less * than 1 */ public PriorityBlockingQueue(int initialCapacity, Comparator<? super E> comparator) { ! q = new PriorityQueue<E>(initialCapacity, comparator); } /** ! * Creates a <tt>PriorityBlockingQueue</tt> containing the elements * in the specified collection. If the specified collection is a * {@link SortedSet} or a {@link PriorityQueue}, this * priority queue will be ordered according to the same ordering. * Otherwise, this priority queue will be ordered according to the * {@linkplain Comparable natural ordering} of its elements. --- 96,223 ---- */ public class PriorityBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, java.io.Serializable { private static final long serialVersionUID = 5595510919245408276L; ! /* ! * The implementation uses an array-based binary heap, with public ! * operations protected with a single lock. However, allocation ! * during resizing uses a simple spinlock (used only while not ! * holding main lock) in order to allow takes to operate ! * concurrently with allocation. This avoids repeated ! * postponement of waiting consumers and consequent element ! * build-up. The need to back away from lock during allocation ! * makes it impossible to simply wrap delegated ! * java.util.PriorityQueue operations within a lock, as was done ! * in a previous version of this class. To maintain ! * interoperability, a plain PriorityQueue is still used during ! * serialization, which maintains compatibility at the espense of ! * transiently doubling overhead. ! */ /** ! * Default array capacity. ! */ ! private static final int DEFAULT_INITIAL_CAPACITY = 11; ! ! /** ! * The maximum size of array to allocate. ! * Some VMs reserve some header words in an array. ! * Attempts to allocate larger arrays may result in ! * OutOfMemoryError: Requested array size exceeds VM limit ! */ ! private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; ! ! /** ! * Priority queue represented as a balanced binary heap: the two ! * children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The ! * priority queue is ordered by comparator, or by the elements' ! * natural ordering, if comparator is null: For each node n in the ! * heap and each descendant d of n, n <= d. The element with the ! * lowest value is in queue[0], assuming the queue is nonempty. ! */ ! private transient Object[] queue; ! ! /** ! * The number of elements in the priority queue. ! */ ! private transient int size; ! ! /** ! * The comparator, or null if priority queue uses elements' ! * natural ordering. ! */ ! private transient Comparator<? super E> comparator; ! ! /** ! * Lock used for all public operations ! */ ! private final ReentrantLock lock; ! ! /** ! * Condition for blocking when empty ! */ ! private final Condition notEmpty; ! ! /** ! * Spinlock for allocation, acquired via CAS. ! */ ! private transient volatile int allocationSpinLock; ! ! /** ! * A plain PriorityQueue used only for serialization, ! * to maintain compatibility with previous versions ! * of this class. Non-null only during serialization/deserialization. ! */ ! private PriorityQueue q; ! ! /** ! * Creates a {@code PriorityBlockingQueue} with the default * initial capacity (11) that orders its elements according to * their {@linkplain Comparable natural ordering}. */ public PriorityBlockingQueue() { ! this(DEFAULT_INITIAL_CAPACITY, null); } /** ! * Creates a {@code PriorityBlockingQueue} with the specified * initial capacity that orders its elements according to their * {@linkplain Comparable natural ordering}. * * @param initialCapacity the initial capacity for this priority queue ! * @throws IllegalArgumentException if {@code initialCapacity} is less * than 1 */ public PriorityBlockingQueue(int initialCapacity) { ! this(initialCapacity, null); } /** ! * Creates a {@code PriorityBlockingQueue} with the specified initial * capacity that orders its elements according to the specified * comparator. * * @param initialCapacity the initial capacity for this priority queue * @param comparator the comparator that will be used to order this * priority queue. If {@code null}, the {@linkplain Comparable * natural ordering} of the elements will be used. ! * @throws IllegalArgumentException if {@code initialCapacity} is less * than 1 */ public PriorityBlockingQueue(int initialCapacity, Comparator<? super E> comparator) { ! if (initialCapacity < 1) ! throw new IllegalArgumentException(); ! this.lock = new ReentrantLock(); ! this.notEmpty = lock.newCondition(); ! this.comparator = comparator; ! this.queue = new Object[initialCapacity]; } /** ! * Creates a {@code PriorityBlockingQueue} containing the elements * in the specified collection. If the specified collection is a * {@link SortedSet} or a {@link PriorityQueue}, this * priority queue will be ordered according to the same ordering. * Otherwise, this priority queue will be ordered according to the * {@linkplain Comparable natural ordering} of its elements.
*** 156,173 **** * queue's ordering * @throws NullPointerException if the specified collection or any * of its elements are null */ public PriorityBlockingQueue(Collection<? extends E> c) { ! q = new PriorityQueue<E>(c); } /** * Inserts the specified element into this priority queue. * * @param e the element to add ! * @return <tt>true</tt> (as specified by {@link Collection#add}) * @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 */ --- 229,447 ---- * queue's ordering * @throws NullPointerException if the specified collection or any * of its elements are null */ public PriorityBlockingQueue(Collection<? extends E> c) { ! this.lock = new ReentrantLock(); ! this.notEmpty = lock.newCondition(); ! boolean heapify = true; // true if not known to be in heap order ! boolean screen = true; // true if must screen for nulls ! if (c instanceof SortedSet<?>) { ! SortedSet<? extends E> ss = (SortedSet<? extends E>) c; ! this.comparator = (Comparator<? super E>) ss.comparator(); ! heapify = false; } + else if (c instanceof PriorityBlockingQueue<?>) { + PriorityBlockingQueue<? extends E> pq = + (PriorityBlockingQueue<? extends E>) c; + this.comparator = (Comparator<? super E>) pq.comparator(); + screen = false; + if (pq.getClass() == PriorityBlockingQueue.class) // exact match + heapify = false; + } + Object[] a = c.toArray(); + int n = a.length; + // If c.toArray incorrectly doesn't return Object[], copy it. + if (a.getClass() != Object[].class) + a = Arrays.copyOf(a, n, Object[].class); + if (screen && (n == 1 || this.comparator != null)) { + for (int i = 0; i < n; ++i) + if (a[i] == null) + throw new NullPointerException(); + } + this.queue = a; + this.size = n; + if (heapify) + heapify(); + } /** + * Tries to grow array to accommodate at least one more element + * (but normally expand by about 50%), giving up (allowing retry) + * on contention (which we expect to be rare). Call only while + * holding lock. + * + * @param array the heap array + * @param oldCap the length of the array + */ + private void tryGrow(Object[] array, int oldCap) { + lock.unlock(); // must release and then re-acquire main lock + Object[] newArray = null; + if (allocationSpinLock == 0 && + UNSAFE.compareAndSwapInt(this, allocationSpinLockOffset, + 0, 1)) { + try { + int newCap = oldCap + ((oldCap < 64) ? + (oldCap + 2) : // grow faster if small + (oldCap >> 1)); + if (newCap - MAX_ARRAY_SIZE > 0) { // possible overflow + int minCap = oldCap + 1; + if (minCap < 0 || minCap > MAX_ARRAY_SIZE) + throw new OutOfMemoryError(); + newCap = MAX_ARRAY_SIZE; + } + if (newCap > oldCap && queue == array) + newArray = new Object[newCap]; + } finally { + allocationSpinLock = 0; + } + } + if (newArray == null) // back off if another thread is allocating + Thread.yield(); + lock.lock(); + if (newArray != null && queue == array) { + queue = newArray; + System.arraycopy(array, 0, newArray, 0, oldCap); + } + } + + /** + * Mechanics for poll(). Call only while holding lock. + */ + private E extract() { + E result; + int n = size - 1; + if (n < 0) + result = null; + else { + Object[] array = queue; + result = (E) array[0]; + E x = (E) array[n]; + array[n] = null; + Comparator<? super E> cmp = comparator; + if (cmp == null) + siftDownComparable(0, x, array, n); + else + siftDownUsingComparator(0, x, array, n, cmp); + size = n; + } + return result; + } + + /** + * Inserts item x at position k, maintaining heap invariant by + * promoting x up the tree until it is greater than or equal to + * its parent, or is the root. + * + * To simplify and speed up coercions and comparisons. the + * Comparable and Comparator versions are separated into different + * methods that are otherwise identical. (Similarly for siftDown.) + * These methods are static, with heap state as arguments, to + * simplify use in light of possible comparator exceptions. + * + * @param k the position to fill + * @param x the item to insert + * @param array the heap array + * @param n heap size + */ + private static <T> void siftUpComparable(int k, T x, Object[] array) { + Comparable<? super T> key = (Comparable<? super T>) x; + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = array[parent]; + if (key.compareTo((T) e) >= 0) + break; + array[k] = e; + k = parent; + } + array[k] = key; + } + + private static <T> void siftUpUsingComparator(int k, T x, Object[] array, + Comparator<? super T> cmp) { + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = array[parent]; + if (cmp.compare(x, (T) e) >= 0) + break; + array[k] = e; + k = parent; + } + array[k] = x; + } + + /** + * Inserts item x at position k, maintaining heap invariant by + * demoting x down the tree repeatedly until it is less than or + * equal to its children or is a leaf. + * + * @param k the position to fill + * @param x the item to insert + * @param array the heap array + * @param n heap size + */ + private static <T> void siftDownComparable(int k, T x, Object[] array, + int n) { + Comparable<? super T> key = (Comparable<? super T>)x; + int half = n >>> 1; // loop while a non-leaf + while (k < half) { + int child = (k << 1) + 1; // assume left child is least + Object c = array[child]; + int right = child + 1; + if (right < n && + ((Comparable<? super T>) c).compareTo((T) array[right]) > 0) + c = array[child = right]; + if (key.compareTo((T) c) <= 0) + break; + array[k] = c; + k = child; + } + array[k] = key; + } + + private static <T> void siftDownUsingComparator(int k, T x, Object[] array, + int n, + Comparator<? super T> cmp) { + int half = n >>> 1; + while (k < half) { + int child = (k << 1) + 1; + Object c = array[child]; + int right = child + 1; + if (right < n && cmp.compare((T) c, (T) array[right]) > 0) + c = array[child = right]; + if (cmp.compare(x, (T) c) <= 0) + break; + array[k] = c; + k = child; + } + array[k] = x; + } + + /** + * Establishes the heap invariant (described above) in the entire tree, + * assuming nothing about the order of the elements prior to the call. + */ + private void heapify() { + Object[] array = queue; + int n = size; + int half = (n >>> 1) - 1; + Comparator<? super E> cmp = comparator; + if (cmp == null) { + for (int i = half; i >= 0; i--) + siftDownComparable(i, (E) array[i], array, n); + } + else { + for (int i = half; i >= 0; i--) + siftDownUsingComparator(i, (E) array[i], array, n, cmp); + } + } + + /** * Inserts the specified element into this priority queue. * * @param e the element to add ! * @return {@code true} (as specified by {@link Collection#add}) * @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 */
*** 175,208 **** return offer(e); } /** * Inserts the specified element into this priority queue. * * @param e the element to add ! * @return <tt>true</tt> (as specified by {@link Queue#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) { final ReentrantLock lock = this.lock; lock.lock(); try { ! boolean ok = q.offer(e); ! assert ok; notEmpty.signal(); - return true; } finally { lock.unlock(); } } /** ! * Inserts the specified element into this priority queue. As the queue is ! * unbounded this method will never block. * * @param e the element to add * @throws ClassCastException if the specified element cannot be compared * with elements currently in the priority queue according to the * priority queue's ordering --- 449,493 ---- return offer(e); } /** * Inserts the specified element into this priority queue. + * As the queue is unbounded, this method will never return {@code false}. * * @param e the element to add ! * @return {@code true} (as specified by {@link Queue#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) { + if (e == null) + throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); + int n, cap; + Object[] array; + while ((n = size) >= (cap = (array = queue).length)) + tryGrow(array, cap); try { ! Comparator<? super E> cmp = comparator; ! if (cmp == null) ! siftUpComparable(n, e, array); ! else ! siftUpUsingComparator(n, e, array, cmp); ! size = n + 1; notEmpty.signal(); } finally { lock.unlock(); } + return true; } /** ! * Inserts the specified element into this priority queue. ! * As the queue is unbounded, this method will never block. * * @param e the element to add * @throws ClassCastException if the specified element cannot be compared * with elements currently in the priority queue according to the * priority queue's ordering
*** 211,227 **** public void put(E e) { offer(e); // never need to block } /** ! * Inserts the specified element into this priority queue. As the queue is ! * unbounded this method will never block. * * @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 <tt>true</tt> * @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 */ --- 496,514 ---- public void put(E e) { offer(e); // never need to block } /** ! * Inserts the specified element into this priority queue. ! * As the queue is unbounded, this method will never block or ! * return {@code false}. * * @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 */
*** 230,367 **** } public E poll() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.poll(); } finally { lock.unlock(); } } public E take() throws InterruptedException { final ReentrantLock lock = this.lock; lock.lockInterruptibly(); try { ! try { ! while (q.size() == 0) notEmpty.await(); - } catch (InterruptedException ie) { - notEmpty.signal(); // propagate to non-interrupted thread - throw ie; - } - E x = q.poll(); - assert x != null; - return x; } finally { lock.unlock(); } } public E poll(long timeout, TimeUnit unit) throws InterruptedException { long nanos = unit.toNanos(timeout); final ReentrantLock lock = this.lock; lock.lockInterruptibly(); try { ! for (;;) { ! E x = q.poll(); ! if (x != null) ! return x; ! if (nanos <= 0) ! return null; ! try { nanos = notEmpty.awaitNanos(nanos); - } catch (InterruptedException ie) { - notEmpty.signal(); // propagate to non-interrupted thread - throw ie; - } - } } finally { lock.unlock(); } } public E peek() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.peek(); } finally { lock.unlock(); } } /** * Returns the comparator used to order the elements in this queue, ! * or <tt>null</tt> if this queue uses the {@linkplain Comparable * natural ordering} of its elements. * * @return the comparator used to order the elements in this queue, ! * or <tt>null</tt> if this queue uses the natural * ordering of its elements */ public Comparator<? super E> comparator() { ! return q.comparator(); } public int size() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.size(); } finally { lock.unlock(); } } /** ! * Always returns <tt>Integer.MAX_VALUE</tt> because ! * a <tt>PriorityBlockingQueue</tt> is not capacity constrained. ! * @return <tt>Integer.MAX_VALUE</tt> */ public int remainingCapacity() { return Integer.MAX_VALUE; } /** * 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 <tt>true</tt> if this queue changed as a result of the call */ public boolean remove(Object o) { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.remove(o); } 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 <tt>true</tt> if this queue contains the specified element */ public boolean contains(Object o) { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.contains(o); } finally { lock.unlock(); } } /** * Returns an array containing all of the elements in this queue. * The returned array elements are in no particular order. --- 517,709 ---- } public E poll() { final ReentrantLock lock = this.lock; lock.lock(); + E result; try { ! result = extract(); } finally { lock.unlock(); } + return result; } public E take() throws InterruptedException { final ReentrantLock lock = this.lock; lock.lockInterruptibly(); + E result; try { ! while ( (result = extract()) == 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 = extract()) == null && nanos > 0) nanos = notEmpty.awaitNanos(nanos); } finally { lock.unlock(); } + return result; } public E peek() { final ReentrantLock lock = this.lock; lock.lock(); + E result; try { ! result = size > 0 ? (E) queue[0] : null; } finally { lock.unlock(); } + return result; } /** * 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) { + Object[] array = queue; + int n = size; + for (int i = 0; i < n; i++) + if (o.equals(array[i])) + return i; + } + return -1; + } + /** + * Removes the ith element from queue. + */ + private void removeAt(int i) { + Object[] array = queue; + int n = size - 1; + if (n == i) // removed last element + array[i] = null; + else { + E moved = (E) array[n]; + array[n] = null; + Comparator<? super E> cmp = comparator; + if (cmp == null) + siftDownComparable(i, moved, array, n); + else + siftDownUsingComparator(i, moved, array, n, cmp); + if (array[i] == moved) { + if (cmp == null) + siftUpComparable(i, moved, array); + else + siftUpUsingComparator(i, moved, array, 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) { + boolean removed = false; final ReentrantLock lock = this.lock; lock.lock(); try { ! int i = indexOf(o); ! if (i != -1) { ! removeAt(i); ! removed = true; ! } } finally { lock.unlock(); } + return removed; } + /** + * Identity-based version for use in Itr.remove + */ + private void removeEQ(Object o) { + final ReentrantLock lock = this.lock; + lock.lock(); + try { + Object[] array = queue; + int n = size; + for (int i = 0; i < n; i++) { + if (o == array[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) { + int index; final ReentrantLock lock = this.lock; lock.lock(); try { ! index = indexOf(o); } finally { lock.unlock(); } + return index != -1; } /** * Returns an array containing all of the elements in this queue. * The returned array elements are in no particular order.
*** 377,387 **** */ public Object[] toArray() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.toArray(); } finally { lock.unlock(); } } --- 719,729 ---- */ public Object[] toArray() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return Arrays.copyOf(queue, size); } finally { lock.unlock(); } }
*** 388,398 **** public String toString() { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.toString(); } finally { lock.unlock(); } } --- 730,751 ---- public String toString() { final ReentrantLock lock = this.lock; lock.lock(); try { ! int n = size; ! if (n == 0) ! return "[]"; ! StringBuilder sb = new StringBuilder(); ! sb.append('['); ! for (int i = 0; i < n; ++i) { ! E e = (E)queue[i]; ! sb.append(e == this ? "(this Collection)" : e); ! if (i != n - 1) ! sb.append(',').append(' '); ! } ! return sb.append(']').toString(); } finally { lock.unlock(); } }
*** 410,420 **** final ReentrantLock lock = this.lock; lock.lock(); try { int n = 0; E e; ! while ( (e = q.poll()) != null) { c.add(e); ++n; } return n; } finally { --- 763,773 ---- final ReentrantLock lock = this.lock; lock.lock(); try { int n = 0; E e; ! while ( (e = extract()) != null) { c.add(e); ++n; } return n; } finally {
*** 438,448 **** final ReentrantLock lock = this.lock; lock.lock(); try { int n = 0; E e; ! while (n < maxElements && (e = q.poll()) != null) { c.add(e); ++n; } return n; } finally { --- 791,801 ---- final ReentrantLock lock = this.lock; lock.lock(); try { int n = 0; E e; ! while (n < maxElements && (e = extract()) != null) { c.add(e); ++n; } return n; } finally {
*** 456,466 **** */ public void clear() { final ReentrantLock lock = this.lock; lock.lock(); try { ! q.clear(); } finally { lock.unlock(); } } --- 809,823 ---- */ public void clear() { final ReentrantLock lock = this.lock; lock.lock(); try { ! Object[] array = queue; ! int n = size; ! size = 0; ! for (int i = 0; i < n; i++) ! array[i] = null; } finally { lock.unlock(); } }
*** 473,498 **** * 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 ! * <tt>null</tt>. * * <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 <tt>x</tt> is a queue known to contain only strings. * The following code can be used to dump the queue into a newly ! * allocated array of <tt>String</tt>: * * <pre> * String[] y = x.toArray(new String[0]);</pre> * ! * Note that <tt>toArray(new Object[0])</tt> is identical in function to ! * <tt>toArray()</tt>. * * @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 --- 830,855 ---- * 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> * 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
*** 503,523 **** */ public <T> T[] toArray(T[] a) { final ReentrantLock lock = this.lock; lock.lock(); try { ! return q.toArray(a); } finally { lock.unlock(); } } /** * Returns an iterator over the elements in this queue. The * iterator does not return the elements in any particular order. ! * The returned <tt>Iterator</tt> is a "weakly consistent" ! * iterator that will never throw {@link * ConcurrentModificationException}, and guarantees to traverse * elements as they existed upon construction of the iterator, and * may (but is not guaranteed to) reflect any modifications * subsequent to construction. * --- 860,888 ---- */ 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 "weakly consistent" iterator that ! * will never throw {@link java.util.ConcurrentModificationException * ConcurrentModificationException}, and guarantees to traverse * elements as they existed upon construction of the iterator, and * may (but is not guaranteed to) reflect any modifications * subsequent to construction. *
*** 528,538 **** } /** * Snapshot iterator that works off copy of underlying q array. */ ! private class Itr implements Iterator<E> { final Object[] array; // Array of all elements int cursor; // index of next element to return; int lastRet; // index of last element, or -1 if no such Itr(Object[] array) { --- 893,903 ---- } /** * 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; // index of last element, or -1 if no such Itr(Object[] array) {
*** 552,592 **** } public void remove() { if (lastRet < 0) throw new IllegalStateException(); ! Object x = array[lastRet]; lastRet = -1; - // Traverse underlying queue to find == element, - // not just a .equals element. - lock.lock(); - try { - for (Iterator it = q.iterator(); it.hasNext(); ) { - if (it.next() == x) { - it.remove(); - return; } } - } finally { - lock.unlock(); - } - } - } /** ! * Saves the state to a stream (that is, serializes it). This ! * merely wraps default serialization within lock. The ! * serialization strategy for items is left to underlying ! * Queue. Note that locking is not needed on deserialization, so ! * readObject is not defined, just relying on default. */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { lock.lock(); try { s.defaultWriteObject(); } finally { lock.unlock(); } } } --- 917,983 ---- } public void remove() { if (lastRet < 0) throw new IllegalStateException(); ! removeEQ(array[lastRet]); lastRet = -1; } } /** ! * Saves the state 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. */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { lock.lock(); try { + int n = size; // avoid zero capacity argument + q = new PriorityQueue<E>(n == 0 ? 1 : n, comparator); + q.addAll(this); s.defaultWriteObject(); } finally { + q = null; lock.unlock(); } } + + /** + * Reconstitutes the {@code PriorityBlockingQueue} instance from a stream + * (that is, deserializes it). + * + * @param s the stream + */ + private void readObject(java.io.ObjectInputStream s) + throws java.io.IOException, ClassNotFoundException { + try { + s.defaultReadObject(); + this.queue = new Object[q.size()]; + comparator = q.comparator(); + addAll(q); + } finally { + q = null; + } + } + + // Unsafe mechanics + private static final sun.misc.Unsafe UNSAFE = sun.misc.Unsafe.getUnsafe(); + private static final long allocationSpinLockOffset = + objectFieldOffset(UNSAFE, "allocationSpinLock", + PriorityBlockingQueue.class); + + static long objectFieldOffset(sun.misc.Unsafe UNSAFE, + String field, Class<?> klazz) { + try { + return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); + } catch (NoSuchFieldException e) { + // Convert Exception to corresponding Error + NoSuchFieldError error = new NoSuchFieldError(field); + error.initCause(e); + throw error; + } + } }