--- jsr166/src/main/java/util/PriorityQueue.java 2016/11/30 18:12:52 1.114 +++ jsr166/src/main/java/util/PriorityQueue.java 2018/05/06 23:29:25 1.128 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -26,6 +26,8 @@ package java.util; import java.util.function.Consumer; +import java.util.function.Predicate; +import jdk.internal.misc.SharedSecrets; /** * An unbounded priority {@linkplain Queue queue} based on a priority heap. @@ -73,13 +75,14 @@ import java.util.function.Consumer; * ({@code peek}, {@code element}, and {@code size}). * *

This class is a member of the - * + * * Java Collections Framework. * * @since 1.5 * @author Josh Bloch, Doug Lea * @param the type of elements held in this queue */ +@SuppressWarnings("unchecked") public class PriorityQueue extends AbstractQueue implements java.io.Serializable { @@ -186,7 +189,6 @@ public class PriorityQueue extends Ab * @throws NullPointerException if the specified collection or any * of its elements are null */ - @SuppressWarnings("unchecked") public PriorityQueue(Collection c) { if (c instanceof SortedSet) { SortedSet ss = (SortedSet) c; @@ -218,7 +220,6 @@ public class PriorityQueue extends Ab * @throws NullPointerException if the specified priority queue or any * of its elements are null */ - @SuppressWarnings("unchecked") public PriorityQueue(PriorityQueue c) { this.comparator = (Comparator) c.comparator(); initFromPriorityQueue(c); @@ -237,15 +238,19 @@ public class PriorityQueue extends Ab * @throws NullPointerException if the specified sorted set or any * of its elements are null */ - @SuppressWarnings("unchecked") public PriorityQueue(SortedSet c) { this.comparator = (Comparator) c.comparator(); initElementsFromCollection(c); } + /** Ensures that queue[0] exists, helping peek() and poll(). */ + private static Object[] ensureNonEmpty(Object[] es) { + return (es.length > 0) ? es : new Object[1]; + } + private void initFromPriorityQueue(PriorityQueue c) { if (c.getClass() == PriorityQueue.class) { - this.queue = c.toArray(); + this.queue = ensureNonEmpty(c.toArray()); this.size = c.size(); } else { initFromCollection(c); @@ -253,17 +258,17 @@ public class PriorityQueue extends Ab } private void initElementsFromCollection(Collection c) { - Object[] a = c.toArray(); + Object[] es = c.toArray(); + int len = es.length; // If c.toArray incorrectly doesn't return Object[], copy it. - if (a.getClass() != Object[].class) - a = Arrays.copyOf(a, a.length, Object[].class); - int len = a.length; + if (es.getClass() != Object[].class) + es = Arrays.copyOf(es, len, Object[].class); if (len == 1 || this.comparator != null) - for (Object e : a) + for (Object e : es) if (e == null) throw new NullPointerException(); - this.queue = a; - this.size = a.length; + this.queue = ensureNonEmpty(es); + this.size = len; } /** @@ -343,15 +348,15 @@ public class PriorityQueue extends Ab return true; } - @SuppressWarnings("unchecked") public E peek() { - return (size == 0) ? null : (E) queue[0]; + return (E) queue[0]; } private int indexOf(Object o) { if (o != null) { - for (int i = 0; i < size; i++) - if (o.equals(queue[i])) + final Object[] es = queue; + for (int i = 0, n = size; i < n; i++) + if (o.equals(es[i])) return i; } return -1; @@ -379,20 +384,18 @@ public class PriorityQueue extends Ab } /** - * Version of remove using reference equality, not equals. - * Needed by iterator.remove. + * Identity-based version for use in Itr.remove. * * @param o element to be removed from this queue, if present - * @return {@code true} if removed */ - boolean removeEq(Object o) { - for (int i = 0; i < size; i++) { - if (o == queue[i]) { + void removeEq(Object o) { + final Object[] es = queue; + for (int i = 0, n = size; i < n; i++) { + if (o == es[i]) { removeAt(i); - return true; + break; } } - return false; } /** @@ -460,7 +463,6 @@ public class PriorityQueue extends Ab * this queue * @throws NullPointerException if the specified array is null */ - @SuppressWarnings("unchecked") public T[] toArray(T[] a) { final int size = this.size; if (a.length < size) @@ -522,12 +524,13 @@ public class PriorityQueue extends Ab */ private int expectedModCount = modCount; + Itr() {} // prevent access constructor creation + public boolean hasNext() { return cursor < size || (forgetMeNot != null && !forgetMeNot.isEmpty()); } - @SuppressWarnings("unchecked") public E next() { if (expectedModCount != modCount) throw new ConcurrentModificationException(); @@ -575,22 +578,29 @@ public class PriorityQueue extends Ab */ public void clear() { modCount++; - for (int i = 0; i < size; i++) - queue[i] = null; + final Object[] es = queue; + for (int i = 0, n = size; i < n; i++) + es[i] = null; size = 0; } - @SuppressWarnings("unchecked") public E poll() { - if (size == 0) - return null; - int s = --size; - modCount++; - E result = (E) queue[0]; - E x = (E) queue[s]; - queue[s] = null; - if (s != 0) - siftDown(0, x); + final Object[] es; + final E result; + + if ((result = (E) ((es = queue)[0])) != null) { + modCount++; + final int n; + final E x = (E) es[(n = --size)]; + es[n] = null; + if (n > 0) { + final Comparator cmp; + if ((cmp = comparator) == null) + siftDownComparable(0, x, es, n); + else + siftDownUsingComparator(0, x, es, n, cmp); + } + } return result; } @@ -606,20 +616,20 @@ public class PriorityQueue extends Ab * position before i. This fact is used by iterator.remove so as to * avoid missing traversing elements. */ - @SuppressWarnings("unchecked") E removeAt(int i) { // assert i >= 0 && i < size; + final Object[] es = queue; modCount++; int s = --size; if (s == i) // removed last element - queue[i] = null; + es[i] = null; else { - E moved = (E) queue[s]; - queue[s] = null; + E moved = (E) es[s]; + es[s] = null; siftDown(i, moved); - if (queue[i] == moved) { + if (es[i] == moved) { siftUp(i, moved); - if (queue[i] != moved) + if (es[i] != moved) return moved; } } @@ -631,7 +641,7 @@ public class PriorityQueue extends Ab * 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 + * 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.) * @@ -640,36 +650,35 @@ public class PriorityQueue extends Ab */ private void siftUp(int k, E x) { if (comparator != null) - siftUpUsingComparator(k, x); + siftUpUsingComparator(k, x, queue, comparator); else - siftUpComparable(k, x); + siftUpComparable(k, x, queue); } - @SuppressWarnings("unchecked") - private void siftUpComparable(int k, E x) { - Comparable key = (Comparable) x; + private static void siftUpComparable(int k, T x, Object[] es) { + Comparable key = (Comparable) x; while (k > 0) { int parent = (k - 1) >>> 1; - Object e = queue[parent]; - if (key.compareTo((E) e) >= 0) + Object e = es[parent]; + if (key.compareTo((T) e) >= 0) break; - queue[k] = e; + es[k] = e; k = parent; } - queue[k] = key; + es[k] = key; } - @SuppressWarnings("unchecked") - private void siftUpUsingComparator(int k, E x) { + private static void siftUpUsingComparator( + int k, T x, Object[] es, Comparator cmp) { while (k > 0) { int parent = (k - 1) >>> 1; - Object e = queue[parent]; - if (comparator.compare(x, (E) e) >= 0) + Object e = es[parent]; + if (cmp.compare(x, (T) e) >= 0) break; - queue[k] = e; + es[k] = e; k = parent; } - queue[k] = x; + es[k] = x; } /** @@ -682,46 +691,46 @@ public class PriorityQueue extends Ab */ private void siftDown(int k, E x) { if (comparator != null) - siftDownUsingComparator(k, x); + siftDownUsingComparator(k, x, queue, size, comparator); else - siftDownComparable(k, x); + siftDownComparable(k, x, queue, size); } - @SuppressWarnings("unchecked") - private void siftDownComparable(int k, E x) { - Comparable key = (Comparable)x; - int half = size >>> 1; // loop while a non-leaf + private static void siftDownComparable(int k, T x, Object[] es, int n) { + // assert n > 0; + Comparable key = (Comparable)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 = queue[child]; + Object c = es[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) + if (right < n && + ((Comparable) c).compareTo((T) es[right]) > 0) + c = es[child = right]; + if (key.compareTo((T) c) <= 0) break; - queue[k] = c; + es[k] = c; k = child; } - queue[k] = key; + es[k] = key; } - @SuppressWarnings("unchecked") - private void siftDownUsingComparator(int k, E x) { - int half = size >>> 1; + private static void siftDownUsingComparator( + int k, T x, Object[] es, int n, Comparator cmp) { + // assert n > 0; + int half = n >>> 1; while (k < half) { int child = (k << 1) + 1; - Object c = queue[child]; + Object c = es[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) + if (right < n && cmp.compare((T) c, (T) es[right]) > 0) + c = es[child = right]; + if (cmp.compare(x, (T) c) <= 0) break; - queue[k] = c; + es[k] = c; k = child; } - queue[k] = x; + es[k] = x; } /** @@ -729,16 +738,16 @@ public class PriorityQueue extends Ab * assuming nothing about the order of the elements prior to the call. * This classic algorithm due to Floyd (1964) is known to be O(size). */ - @SuppressWarnings("unchecked") private void heapify() { final Object[] es = queue; - final int half = (size >>> 1) - 1; - if (comparator == null) - for (int i = half; i >= 0; i--) - siftDownComparable(i, (E) es[i]); + int n = size, i = (n >>> 1) - 1; + final Comparator cmp; + if ((cmp = comparator) == null) + for (; i >= 0; i--) + siftDownComparable(i, (E) es[i], es, n); else - for (int i = half; i >= 0; i--) - siftDownUsingComparator(i, (E) es[i]); + for (; i >= 0; i--) + siftDownUsingComparator(i, (E) es[i], es, n, cmp); } /** @@ -772,8 +781,9 @@ public class PriorityQueue extends Ab s.writeInt(Math.max(2, size + 1)); // Write out all elements in the "proper order". - for (int i = 0; i < size; i++) - s.writeObject(queue[i]); + final Object[] es = queue; + for (int i = 0, n = size; i < n; i++) + s.writeObject(es[i]); } /** @@ -793,11 +803,12 @@ public class PriorityQueue extends Ab // Read in (and discard) array length s.readInt(); - queue = new Object[size]; + SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size); + final Object[] es = queue = new Object[Math.max(size, 1)]; // Read in all elements. - for (int i = 0; i < size; i++) - queue[i] = s.readObject(); + for (int i = 0, n = size; i < n; i++) + es[i] = s.readObject(); // Elements are guaranteed to be in "proper order", but the // spec has never explained what that might be. @@ -823,10 +834,6 @@ public class PriorityQueue extends Ab } final class PriorityQueueSpliterator implements Spliterator { - /* - * This is very similar to ArrayList Spliterator, except for - * extra null checks. - */ private int index; // current index, modified on advance/split private int fence; // -1 until first use private int expectedModCount; // initialized when fence set @@ -853,48 +860,33 @@ public class PriorityQueue extends Ab new PriorityQueueSpliterator(lo, index = mid, expectedModCount); } - @SuppressWarnings("unchecked") public void forEachRemaining(Consumer action) { - int i, hi, mc; // hoist accesses and checks from loop - final Object[] a; if (action == null) throw new NullPointerException(); - if ((a = queue) != null) { - if ((hi = fence) < 0) { - mc = modCount; - hi = size; - } - else - mc = expectedModCount; - if ((i = index) >= 0 && (index = hi) <= a.length) { - for (E e;; ++i) { - if (i < hi) { - if ((e = (E) a[i]) == null) // must be CME - break; - action.accept(e); - } - else if (modCount != mc) - break; - else - return; - } - } + if (fence < 0) { fence = size; expectedModCount = modCount; } + final Object[] es = queue; + int i, hi; E e; + for (i = index, index = hi = fence; i < hi; i++) { + if ((e = (E) es[i]) == null) + break; // must be CME + action.accept(e); } - throw new ConcurrentModificationException(); + if (modCount != expectedModCount) + throw new ConcurrentModificationException(); } public boolean tryAdvance(Consumer action) { if (action == null) throw new NullPointerException(); - int hi = getFence(), lo = index; - if (lo >= 0 && lo < hi) { - index = lo + 1; - @SuppressWarnings("unchecked") E e = (E)queue[lo]; - if (e == null) + if (fence < 0) { fence = size; expectedModCount = modCount; } + int i; + if ((i = index) < fence) { + index = i + 1; + E e; + if ((e = (E) queue[i]) == null + || modCount != expectedModCount) throw new ConcurrentModificationException(); action.accept(e); - if (modCount != expectedModCount) - throw new ConcurrentModificationException(); return true; } return false; @@ -908,4 +900,88 @@ public class PriorityQueue extends Ab return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; } } + + /** + * @throws NullPointerException {@inheritDoc} + */ + public boolean removeIf(Predicate 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 filter) { + final int expectedModCount = ++modCount; + 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) { + if (modCount != expectedModCount) + throw new ConcurrentModificationException(); + return false; + } + // Tolerate predicates that reentrantly access the collection for + // read (but writers still get CME), 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); + if (modCount != expectedModCount) + throw new ConcurrentModificationException(); + 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; + } + + /** + * @throws NullPointerException {@inheritDoc} + */ + public void forEach(Consumer action) { + Objects.requireNonNull(action); + final int expectedModCount = modCount; + final Object[] es = queue; + for (int i = 0, n = size; i < n; i++) + action.accept((E) es[i]); + if (expectedModCount != modCount) + throw new ConcurrentModificationException(); + } }