--- jsr166/src/main/java/util/PriorityQueue.java 2005/11/23 05:33:25 1.53 +++ jsr166/src/main/java/util/PriorityQueue.java 2005/12/05 02:56:59 1.60 @@ -1,7 +1,7 @@ /* - * @(#)PriorityQueue.java 1.8 05/08/27 + * %W% %E% * - * Copyright 2005 Sun Microsystems, Inc. All rights reserved. + * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ @@ -68,17 +68,12 @@ public class PriorityQueue extends Ab private static final int DEFAULT_INITIAL_CAPACITY = 11; /** - * Priority queue represented as a balanced binary heap: the two children - * of queue[n] are queue[2*n] 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[1], assuming the queue is - * nonempty. (A one-based array is used in preference to the traditional - * zero-based array to simplify parent and child calculations.) - * - * queue.length must be >= 2, even if size == 0. + * 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; @@ -134,60 +129,17 @@ public class PriorityQueue extends Ab */ public PriorityQueue(int initialCapacity, Comparator comparator) { + // Note: This restriction of at least one is not actually needed, + // but continues for 1.5 compatibility if (initialCapacity < 1) throw new IllegalArgumentException(); - this.queue = new Object[initialCapacity + 1]; + this.queue = new Object[initialCapacity]; this.comparator = comparator; } /** - * Common code to initialize underlying queue array across - * constructors below. - */ - private void initializeArray(Collection c) { - int sz = c.size(); - int initialCapacity = (int)Math.min((sz * 110L) / 100, - Integer.MAX_VALUE - 1); - if (initialCapacity < 1) - initialCapacity = 1; - - this.queue = new Object[initialCapacity + 1]; - } - - /** - * Initially fill elements of the queue array under the - * knowledge that it is sorted or is another PQ, in which - * case we can just place the elements in the order presented. - */ - private void fillFromSorted(Collection c) { - for (Iterator i = c.iterator(); i.hasNext(); ) { - int k = ++size; - if (k >= queue.length) - grow(k); - queue[k] = i.next(); - } - } - - /** - * Initially fill elements of the queue array that is not to our knowledge - * sorted, so we must rearrange the elements to guarantee the heap - * invariant. - */ - private void fillFromUnsorted(Collection c) { - for (Iterator i = c.iterator(); i.hasNext(); ) { - int k = ++size; - if (k >= queue.length) - grow(k); - queue[k] = i.next(); - } - heapify(); - } - - /** * Creates a PriorityQueue containing the elements in the - * specified collection. The priority queue has an initial - * capacity of 110% of the size of the specified collection or 1 - * if the collection is empty. If the specified collection is an + * specified collection. If the specified collection is an * instance of a {@link java.util.SortedSet} or is another * PriorityQueue, the priority queue will be ordered * according to the same ordering. Otherwise, this priority queue @@ -202,26 +154,22 @@ public class PriorityQueue extends Ab * of its elements are null */ public PriorityQueue(Collection c) { - initializeArray(c); - if (c instanceof SortedSet) { - SortedSet s = (SortedSet)c; - comparator = (Comparator)s.comparator(); - fillFromSorted(s); - } else if (c instanceof PriorityQueue) { - PriorityQueue s = (PriorityQueue) c; - comparator = (Comparator)s.comparator(); - fillFromSorted(s); - } else { + initFromCollection(c); + if (c instanceof SortedSet) + comparator = (Comparator) + ((SortedSet)c).comparator(); + else if (c instanceof PriorityQueue) + comparator = (Comparator) + ((PriorityQueue)c).comparator(); + else { comparator = null; - fillFromUnsorted(c); + heapify(); } } /** * Creates a PriorityQueue containing the elements in the - * specified priority queue. The priority queue has an initial - * capacity of 110% of the size of the specified priority queue or - * 1 if the priority queue is empty. This priority queue will be + * specified priority queue. This priority queue will be * ordered according to the same ordering as the given priority * queue. * @@ -234,16 +182,13 @@ public class PriorityQueue extends Ab * of its elements are null */ public PriorityQueue(PriorityQueue c) { - initializeArray(c); comparator = (Comparator)c.comparator(); - fillFromSorted(c); + initFromCollection(c); } /** * Creates a PriorityQueue containing the elements in the - * specified sorted set. The priority queue has an initial - * capacity of 110% of the size of the specified sorted set or 1 - * if the sorted set is empty. This priority queue will be ordered + * specified sorted set. This priority queue will be ordered * according to the same ordering as the given sorted set. * * @param c the sorted set whose elements are to be placed @@ -255,27 +200,41 @@ public class PriorityQueue extends Ab * of its elements are null */ public PriorityQueue(SortedSet c) { - initializeArray(c); comparator = (Comparator)c.comparator(); - fillFromSorted(c); + initFromCollection(c); } /** - * Resize array, if necessary, to be able to hold given index. + * Initialize queue array with elements from the given Collection. + * @param c the collection */ - private void grow(int index) { - int newlen = queue.length; - if (index < newlen) // don't need to grow - return; - if (index == Integer.MAX_VALUE) + private void initFromCollection(Collection c) { + Object[] a = c.toArray(); + // If c.toArray incorrectly doesn't return Object[], copy it. + if (a.getClass() != Object[].class) + a = Arrays.copyOf(a, a.length, Object[].class); + queue = a; + size = a.length; + } + + /** + * Increases the capacity of the array. + * + * @param minCapacity the desired minimum capacity + */ + private void grow(int minCapacity) { + if (minCapacity < 0) // overflow throw new OutOfMemoryError(); - while (newlen <= index) { - if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow - newlen = Integer.MAX_VALUE; - else - newlen <<= 2; - } - queue = Arrays.copyOf(queue, newlen); + int oldCapacity = queue.length; + // Double size if small; else grow by 50% + int newCapacity = ((oldCapacity < 64)? + ((oldCapacity + 1) * 2): + ((oldCapacity / 2) * 3)); + if (newCapacity < 0) // overflow + newCapacity = Integer.MAX_VALUE; + if (newCapacity < minCapacity) + newCapacity = minCapacity; + queue = Arrays.copyOf(queue, newCapacity); } /** @@ -304,29 +263,29 @@ public class PriorityQueue extends Ab if (e == null) throw new NullPointerException(); modCount++; - ++size; - - // Grow backing store if necessary - if (size >= queue.length) - grow(size); - - queue[size] = e; - fixUp(size); + int i = size; + if (i >= queue.length) + grow(i + 1); + size = i + 1; + if (i == 0) + queue[0] = e; + else + siftUp(i, e); return true; } public E peek() { if (size == 0) return null; - return (E) queue[1]; + return (E) queue[0]; } private int indexOf(Object o) { - if (o == null) - return -1; - for (int i = 1; i <= size; i++) - if (o.equals(queue[i])) - return i; + if (o != null) { + for (int i = 0; i < size; i++) + if (o.equals(queue[i])) + return i; + } return -1; } @@ -351,6 +310,23 @@ public class PriorityQueue extends Ab } /** + * Version of remove using reference equality, not equals. + * Needed by iterator.remove. + * + * @param o element to be removed from this queue, if present + * @return true if removed + */ + boolean removeEq(Object o) { + for (int i = 0; i < size; i++) { + if (o == queue[i]) { + removeAt(i); + return true; + } + } + return false; + } + + /** * Returns true if this queue contains the specified element. * More formally, returns true if and only if this queue contains * at least one element e such that o.equals(e). @@ -370,10 +346,10 @@ public class PriorityQueue extends Ab * maintained by this list. (In other words, this method must allocate * a new array). The caller is thus free to modify the returned array. * - * @return an array containing all of the elements in this queue. + * @return an array containing all of the elements in this queue */ public Object[] toArray() { - return Arrays.copyOfRange(queue, 1, size+1); + return Arrays.copyOf(queue, size); } /** @@ -403,8 +379,8 @@ public class PriorityQueue extends Ab public T[] toArray(T[] a) { if (a.length < size) // Make a new array of a's runtime type, but my contents: - return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass()); - System.arraycopy(queue, 1, a, 0, size); + return (T[]) Arrays.copyOf(queue, size, a.getClass()); + System.arraycopy(queue, 0, a, 0, size); if (a.length > size) a[size] = null; return a; @@ -420,98 +396,87 @@ public class PriorityQueue extends Ab return new Itr(); } - private class Itr implements Iterator { - + private final class Itr implements Iterator { /** * Index (into queue array) of element to be returned by * subsequent call to next. */ - private int cursor = 1; + private int cursor = 0; /** * Index of element returned by most recent call to next, * unless that element came from the forgetMeNot list. - * Reset to 0 if element is deleted by a call to remove. - */ - private int lastRet = 0; - - /** - * The modCount value that the iterator believes that the backing - * List should have. If this expectation is violated, the iterator - * has detected concurrent modification. + * Set to -1 if element is deleted by a call to remove. */ - private int expectedModCount = modCount; + private int lastRet = -1; /** - * A list of elements that were moved from the unvisited portion of + * A queue of elements that were moved from the unvisited portion of * the heap into the visited portion as a result of "unlucky" element * removals during the iteration. (Unlucky element removals are those - * that require a fixup instead of a fixdown.) We must visit all of + * that require a siftup instead of a siftdown.) We must visit all of * the elements in this list to complete the iteration. We do this * after we've completed the "normal" iteration. * * We expect that most iterations, even those involving removals, * will not use need to store elements in this field. */ - private ArrayList forgetMeNot = null; + private ArrayDeque forgetMeNot = null; /** * Element returned by the most recent call to next iff that * element was drawn from the forgetMeNot list. */ - private Object lastRetElt = null; + private E lastRetElt = null; + + /** + * The modCount value that the iterator believes that the backing + * List should have. If this expectation is violated, the iterator + * has detected concurrent modification. + */ + private int expectedModCount = modCount; public boolean hasNext() { - return cursor <= size || forgetMeNot != null; + return cursor < size || + (forgetMeNot != null && !forgetMeNot.isEmpty()); } public E next() { - checkForComodification(); - E result; - if (cursor <= size) { - result = (E) queue[cursor]; - lastRet = cursor++; - } - else if (forgetMeNot == null) - throw new NoSuchElementException(); - else { - int remaining = forgetMeNot.size(); - result = forgetMeNot.remove(remaining - 1); - if (remaining == 1) - forgetMeNot = null; - lastRet = 0; - lastRetElt = result; + if (expectedModCount != modCount) + throw new ConcurrentModificationException(); + if (cursor < size) + return (E) queue[lastRet = cursor++]; + if (forgetMeNot != null) { + lastRet = -1; + lastRetElt = forgetMeNot.poll(); + if (lastRetElt != null) + return lastRetElt; } - return result; + throw new NoSuchElementException(); } public void remove() { - checkForComodification(); - - if (lastRet != 0) { + if (expectedModCount != modCount) + throw new ConcurrentModificationException(); + if (lastRet == -1 && lastRetElt == null) + throw new IllegalStateException(); + if (lastRet != -1) { E moved = PriorityQueue.this.removeAt(lastRet); - lastRet = 0; - if (moved == null) { + lastRet = -1; + if (moved == null) cursor--; - } else { + else { if (forgetMeNot == null) - forgetMeNot = new ArrayList(); + forgetMeNot = new ArrayDeque(); forgetMeNot.add(moved); } - } else if (lastRetElt != null) { - PriorityQueue.this.remove(lastRetElt); - lastRetElt = null; } else { - throw new IllegalStateException(); + PriorityQueue.this.removeEq(lastRetElt); + lastRetElt = null; } - expectedModCount = modCount; } - final void checkForComodification() { - if (modCount != expectedModCount) - throw new ConcurrentModificationException(); - } } public int size() { @@ -524,52 +489,48 @@ public class PriorityQueue extends Ab */ public void clear() { modCount++; - - // Null out element references to prevent memory leak - for (int i=1; i<=size; i++) + for (int i = 0; i < size; i++) queue[i] = null; - size = 0; } public E poll() { if (size == 0) return null; + int s = --size; modCount++; - - E result = (E) queue[1]; - queue[1] = queue[size]; - queue[size--] = null; // Drop extra ref to prevent memory leak - if (size > 1) - fixDown(1); - + E result = (E)queue[0]; + E x = (E)queue[s]; + queue[s] = null; + if (s != 0) + siftDown(0, x); return result; } /** - * Removes and returns the ith element from queue. (Recall that queue - * is one-based, so 1 <= i <= size.) + * Removes the ith element from queue. * - * Normally this method leaves the elements at positions from 1 up to i-1, - * inclusive, untouched. Under these circumstances, it returns null. - * Occasionally, in order to maintain the heap invariant, it must move - * the last element of the list to some index in the range [2, i-1], - * and move the element previously at position (i/2) to position i. - * Under these circumstances, this method returns the element that was - * previously at the end of the list and is now at some position between - * 2 and i-1 inclusive. + * Normally this method leaves the elements at up to i-1, + * inclusive, untouched. Under these circumstances, it returns + * null. Occasionally, in order to maintain the heap invariant, + * it must swap a later element of the list with one earlier than + * i. Under these circumstances, this method returns the element + * that was previously at the end of the list and is now at some + * position before i. This fact is used by iterator.remove so as to + * avoid missing traverseing elements. */ private E removeAt(int i) { - assert i > 0 && i <= size; + assert i >= 0 && i < size; modCount++; - - E moved = (E) queue[size]; - queue[i] = moved; - queue[size--] = null; // Drop extra ref to prevent memory leak - if (i <= size) { - fixDown(i); + int s = --size; + if (s == i) // removed last element + queue[i] = null; + else { + E moved = (E) queue[s]; + queue[s] = null; + siftDown(i, moved); if (queue[i] == moved) { - fixUp(i); + siftUp(i, moved); if (queue[i] != moved) return moved; } @@ -578,67 +539,97 @@ public class PriorityQueue extends Ab } /** - * Establishes the heap invariant (described above) assuming the heap - * satisfies the invariant except possibly for the leaf-node indexed by k - * (which may have a nextExecutionTime less than its parent's). - * - * This method functions by "promoting" queue[k] up the hierarchy - * (by swapping it with its parent) repeatedly until queue[k] - * is greater than or equal to its parent. - */ - private void fixUp(int k) { - if (comparator == null) { - while (k > 1) { - int j = k >> 1; - if (((Comparable)queue[j]).compareTo((E)queue[k]) <= 0) - break; - Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; - k = j; - } - } else { - while (k > 1) { - int j = k >>> 1; - if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) - break; - Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; - k = j; - } - } - } - - /** - * Establishes the heap invariant (described above) in the subtree - * rooted at k, which is assumed to satisfy the heap invariant except - * possibly for node k itself (which may be greater than its children). - * - * This method functions by "demoting" queue[k] down the hierarchy - * (by swapping it with its smaller child) repeatedly until queue[k] - * is less than or equal to its children. - */ - private void fixDown(int k) { - int j; - if (comparator == null) { - while ((j = k << 1) <= size && (j > 0)) { - if (j)queue[j]).compareTo((E)queue[j+1]) > 0) - j++; // j indexes smallest kid - - if (((Comparable)queue[k]).compareTo((E)queue[j]) <= 0) - break; - Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; - k = j; - } - } else { - while ((j = k << 1) <= size && (j > 0)) { - if (j 0) - j++; // j indexes smallest kid - if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) - break; - Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; - k = j; - } + * 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.) + * + * @param k the position to fill + * @param x the item to insert + */ + private void siftUp(int k, E x) { + if (comparator != null) + siftUpUsingComparator(k, x); + else + siftUpComparable(k, x); + } + + private void siftUpComparable(int k, E x) { + Comparable key = (Comparable) x; + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = queue[parent]; + if (key.compareTo((E)e) >= 0) + break; + queue[k] = e; + k = parent; + } + queue[k] = key; + } + + private void siftUpUsingComparator(int k, E x) { + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = queue[parent]; + if (comparator.compare(x, (E)e) >= 0) + break; + queue[k] = e; + k = parent; + } + queue[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 + */ + private void siftDown(int k, E x) { + if (comparator != null) + siftDownUsingComparator(k, x); + else + siftDownComparable(k, x); + } + + private void siftDownComparable(int k, E x) { + Comparable key = (Comparable)x; + int half = size >>> 1; // loop while a non-leaf + while (k < half) { + int child = (k << 1) + 1; // assume left child is least + Object c = queue[child]; + int right = child + 1; + if (right < size && + ((Comparable)c).compareTo((E)queue[right]) > 0) + c = queue[child = right]; + if (key.compareTo((E)c) <= 0) + break; + queue[k] = c; + k = child; + } + queue[k] = key; + } + + private void siftDownUsingComparator(int k, E x) { + int half = size >>> 1; + while (k < half) { + int child = (k << 1) + 1; + Object c = queue[child]; + int right = child + 1; + if (right < size && + comparator.compare((E)c, (E)queue[right]) > 0) + c = queue[child = right]; + if (comparator.compare(x, (E)c) <= 0) + break; + queue[k] = c; + k = child; } + queue[k] = x; } /** @@ -646,8 +637,8 @@ public class PriorityQueue extends Ab * assuming nothing about the order of the elements prior to the call. */ private void heapify() { - for (int i = size/2; i >= 1; i--) - fixDown(i); + for (int i = (size >>> 1) - 1; i >= 0; i--) + siftDown(i, (E)queue[i]); } /** @@ -678,10 +669,11 @@ public class PriorityQueue extends Ab s.defaultWriteObject(); // Write out array length - s.writeInt(queue.length); + // For compatibility with 1.5 version, must be at least 2. + s.writeInt(Math.max(2, queue.length)); // Write out all elements in the proper order. - for (int i=1; i<=size; i++) + for (int i=0; i extends Ab queue = new Object[arrayLength]; // Read in all elements in the proper order. - for (int i=1; i<=size; i++) + for (int i=0; i