| /* |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * This file is available under and governed by the GNU General Public |
| * License version 2 only, as published by the Free Software Foundation. |
| * However, the following notice accompanied the original version of this |
| * file: |
| * |
| * Written by Josh Bloch of Google Inc. and released to the public domain, |
| * as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
| */ |
| |
| package java.util; |
| |
| import java.io.Serializable; |
| import java.util.function.Consumer; |
| import java.util.function.Predicate; |
| import jdk.internal.access.SharedSecrets; |
| |
| /** |
| * Resizable-array implementation of the {@link Deque} interface. Array |
| * deques have no capacity restrictions; they grow as necessary to support |
| * usage. They are not thread-safe; in the absence of external |
| * synchronization, they do not support concurrent access by multiple threads. |
| * Null elements are prohibited. This class is likely to be faster than |
| * {@link Stack} when used as a stack, and faster than {@link LinkedList} |
| * when used as a queue. |
| * |
| * <p>Most {@code ArrayDeque} operations run in amortized constant time. |
| * Exceptions include |
| * {@link #remove(Object) remove}, |
| * {@link #removeFirstOccurrence removeFirstOccurrence}, |
| * {@link #removeLastOccurrence removeLastOccurrence}, |
| * {@link #contains contains}, |
| * {@link #iterator iterator.remove()}, |
| * and the bulk operations, all of which run in linear time. |
| * |
| * <p>The iterators returned by this class's {@link #iterator() iterator} |
| * method are <em>fail-fast</em>: If the deque is modified at any time after |
| * the iterator is created, in any way except through the iterator's own |
| * {@code remove} method, the iterator will generally throw a {@link |
| * ConcurrentModificationException}. Thus, in the face of concurrent |
| * modification, the iterator fails quickly and cleanly, rather than risking |
| * arbitrary, non-deterministic behavior at an undetermined time in the |
| * future. |
| * |
| * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
| * as it is, generally speaking, impossible to make any hard guarantees in the |
| * presence of unsynchronized concurrent modification. Fail-fast iterators |
| * throw {@code ConcurrentModificationException} on a best-effort basis. |
| * Therefore, it would be wrong to write a program that depended on this |
| * exception for its correctness: <i>the fail-fast behavior of iterators |
| * should be used only to detect bugs.</i> |
| * |
| * <p>This class and its iterator implement all of the <em>optional</em> methods of the |
| * {@link Collection}, {@link SequencedCollection}, and {@link Iterator} interfaces. |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> |
| * Java Collections Framework</a>. |
| * |
| * @author Josh Bloch and Doug Lea |
| * @param <E> the type of elements held in this deque |
| * @since 1.6 |
| */ |
| public class ArrayDeque<E> extends AbstractCollection<E> |
| implements Deque<E>, Cloneable, Serializable |
| { |
| /* |
| * VMs excel at optimizing simple array loops where indices are |
| * incrementing or decrementing over a valid slice, e.g. |
| * |
| * for (int i = start; i < end; i++) ... elements[i] |
| * |
| * Because in a circular array, elements are in general stored in |
| * two disjoint such slices, we help the VM by writing unusual |
| * nested loops for all traversals over the elements. Having only |
| * one hot inner loop body instead of two or three eases human |
| * maintenance and encourages VM loop inlining into the caller. |
| */ |
| |
| /** |
| * The array in which the elements of the deque are stored. |
| * All array cells not holding deque elements are always null. |
| * The array always has at least one null slot (at tail). |
| */ |
| transient Object[] elements; |
| |
| /** |
| * The index of the element at the head of the deque (which is the |
| * element that would be removed by remove() or pop()); or an |
| * arbitrary number 0 <= head < elements.length equal to tail if |
| * the deque is empty. |
| */ |
| transient int head; |
| |
| /** |
| * The index at which the next element would be added to the tail |
| * of the deque (via addLast(E), add(E), or push(E)); |
| * elements[tail] is always null. |
| */ |
| transient int tail; |
| |
| /** |
| * 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; |
| |
| /** |
| * Increases the capacity of this deque by at least the given amount. |
| * |
| * @param needed the required minimum extra capacity; must be positive |
| */ |
| private void grow(int needed) { |
| // overflow-conscious code |
| final int oldCapacity = elements.length; |
| int newCapacity; |
| // Double capacity if small; else grow by 50% |
| int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1); |
| if (jump < needed |
| || (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0) |
| newCapacity = newCapacity(needed, jump); |
| // Android-added: preserve reference to the old storage to nullify it later. |
| final Object[] oldElements = elements; |
| final Object[] es = elements = Arrays.copyOf(elements, newCapacity); |
| // Exceptionally, here tail == head needs to be disambiguated |
| if (tail < head || (tail == head && es[head] != null)) { |
| // wrap around; slide first leg forward to end of array |
| int newSpace = newCapacity - oldCapacity; |
| System.arraycopy(es, head, |
| es, head + newSpace, |
| oldCapacity - head); |
| for (int i = head, to = (head += newSpace); i < to; i++) |
| es[i] = null; |
| } |
| // Android-added: Clear old array instance that's about to become eligible for GC. |
| // This ensures that array elements can be eligible for garbage collection even |
| // before the array itself is recognized as being eligible; the latter might |
| // take a while in some GC implementations, if the array instance is longer lived |
| // (its liveness rarely checked) than some of its contents. |
| Arrays.fill(oldElements, null); |
| } |
| |
| /** Capacity calculation for edge conditions, especially overflow. */ |
| private int newCapacity(int needed, int jump) { |
| final int oldCapacity = elements.length, minCapacity; |
| if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) { |
| if (minCapacity < 0) |
| throw new IllegalStateException("Sorry, deque too big"); |
| return Integer.MAX_VALUE; |
| } |
| if (needed > jump) |
| return minCapacity; |
| return (oldCapacity + jump - MAX_ARRAY_SIZE < 0) |
| ? oldCapacity + jump |
| : MAX_ARRAY_SIZE; |
| } |
| |
| /** |
| * Constructs an empty array deque with an initial capacity |
| * sufficient to hold 16 elements. |
| */ |
| public ArrayDeque() { |
| elements = new Object[16 + 1]; |
| } |
| |
| /** |
| * Constructs an empty array deque with an initial capacity |
| * sufficient to hold the specified number of elements. |
| * |
| * @param numElements lower bound on initial capacity of the deque |
| */ |
| public ArrayDeque(int numElements) { |
| elements = |
| new Object[(numElements < 1) ? 1 : |
| (numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE : |
| numElements + 1]; |
| } |
| |
| /** |
| * Constructs a deque containing the elements of the specified |
| * collection, in the order they are returned by the collection's |
| * iterator. (The first element returned by the collection's |
| * iterator becomes the first element, or <i>front</i> of the |
| * deque.) |
| * |
| * @param c the collection whose elements are to be placed into the deque |
| * @throws NullPointerException if the specified collection is null |
| */ |
| public ArrayDeque(Collection<? extends E> c) { |
| this(c.size()); |
| copyElements(c); |
| } |
| |
| /** |
| * Circularly increments i, mod modulus. |
| * Precondition and postcondition: 0 <= i < modulus. |
| */ |
| static final int inc(int i, int modulus) { |
| if (++i >= modulus) i = 0; |
| return i; |
| } |
| |
| /** |
| * Circularly decrements i, mod modulus. |
| * Precondition and postcondition: 0 <= i < modulus. |
| */ |
| static final int dec(int i, int modulus) { |
| if (--i < 0) i = modulus - 1; |
| return i; |
| } |
| |
| /** |
| * Circularly adds the given distance to index i, mod modulus. |
| * Precondition: 0 <= i < modulus, 0 <= distance <= modulus. |
| * @return index 0 <= i < modulus |
| */ |
| static final int inc(int i, int distance, int modulus) { |
| if ((i += distance) - modulus >= 0) i -= modulus; |
| return i; |
| } |
| |
| /** |
| * Subtracts j from i, mod modulus. |
| * Index i must be logically ahead of index j. |
| * Precondition: 0 <= i < modulus, 0 <= j < modulus. |
| * @return the "circular distance" from j to i; corner case i == j |
| * is disambiguated to "empty", returning 0. |
| */ |
| static final int sub(int i, int j, int modulus) { |
| if ((i -= j) < 0) i += modulus; |
| return i; |
| } |
| |
| /** |
| * Returns element at array index i. |
| * This is a slight abuse of generics, accepted by javac. |
| */ |
| @SuppressWarnings("unchecked") |
| static final <E> E elementAt(Object[] es, int i) { |
| return (E) es[i]; |
| } |
| |
| /** |
| * A version of elementAt that checks for null elements. |
| * This check doesn't catch all possible comodifications, |
| * but does catch ones that corrupt traversal. |
| */ |
| static final <E> E nonNullElementAt(Object[] es, int i) { |
| @SuppressWarnings("unchecked") E e = (E) es[i]; |
| if (e == null) |
| throw new ConcurrentModificationException(); |
| return e; |
| } |
| |
| // The main insertion and extraction methods are addFirst, |
| // addLast, pollFirst, pollLast. The other methods are defined in |
| // terms of these. |
| |
| /** |
| * Inserts the specified element at the front of this deque. |
| * |
| * @param e the element to add |
| * @throws NullPointerException if the specified element is null |
| */ |
| public void addFirst(E e) { |
| if (e == null) |
| throw new NullPointerException(); |
| final Object[] es = elements; |
| es[head = dec(head, es.length)] = e; |
| if (head == tail) |
| grow(1); |
| } |
| |
| /** |
| * Inserts the specified element at the end of this deque. |
| * |
| * <p>This method is equivalent to {@link #add}. |
| * |
| * @param e the element to add |
| * @throws NullPointerException if the specified element is null |
| */ |
| public void addLast(E e) { |
| if (e == null) |
| throw new NullPointerException(); |
| final Object[] es = elements; |
| es[tail] = e; |
| if (head == (tail = inc(tail, es.length))) |
| grow(1); |
| } |
| |
| /** |
| * Adds all of the elements in the specified collection at the end |
| * of this deque, as if by calling {@link #addLast} on each one, |
| * in the order that they are returned by the collection's iterator. |
| * |
| * @param c the elements to be inserted into this deque |
| * @return {@code true} if this deque changed as a result of the call |
| * @throws NullPointerException if the specified collection or any |
| * of its elements are null |
| */ |
| public boolean addAll(Collection<? extends E> c) { |
| final int s, needed; |
| if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0) |
| grow(needed); |
| copyElements(c); |
| return size() > s; |
| } |
| |
| private void copyElements(Collection<? extends E> c) { |
| c.forEach(this::addLast); |
| } |
| |
| /** |
| * Inserts the specified element at the front of this deque. |
| * |
| * @param e the element to add |
| * @return {@code true} (as specified by {@link Deque#offerFirst}) |
| * @throws NullPointerException if the specified element is null |
| */ |
| public boolean offerFirst(E e) { |
| addFirst(e); |
| return true; |
| } |
| |
| /** |
| * Inserts the specified element at the end of this deque. |
| * |
| * @param e the element to add |
| * @return {@code true} (as specified by {@link Deque#offerLast}) |
| * @throws NullPointerException if the specified element is null |
| */ |
| public boolean offerLast(E e) { |
| addLast(e); |
| return true; |
| } |
| |
| /** |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E removeFirst() { |
| E e = pollFirst(); |
| if (e == null) |
| throw new NoSuchElementException(); |
| return e; |
| } |
| |
| /** |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E removeLast() { |
| E e = pollLast(); |
| if (e == null) |
| throw new NoSuchElementException(); |
| return e; |
| } |
| |
| public E pollFirst() { |
| final Object[] es; |
| final int h; |
| E e = elementAt(es = elements, h = head); |
| if (e != null) { |
| es[h] = null; |
| head = inc(h, es.length); |
| } |
| return e; |
| } |
| |
| public E pollLast() { |
| final Object[] es; |
| final int t; |
| E e = elementAt(es = elements, t = dec(tail, es.length)); |
| if (e != null) |
| es[tail = t] = null; |
| return e; |
| } |
| |
| /** |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E getFirst() { |
| E e = elementAt(elements, head); |
| if (e == null) |
| throw new NoSuchElementException(); |
| return e; |
| } |
| |
| /** |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E getLast() { |
| final Object[] es = elements; |
| E e = elementAt(es, dec(tail, es.length)); |
| if (e == null) |
| throw new NoSuchElementException(); |
| return e; |
| } |
| |
| public E peekFirst() { |
| return elementAt(elements, head); |
| } |
| |
| public E peekLast() { |
| final Object[] es; |
| return elementAt(es = elements, dec(tail, es.length)); |
| } |
| |
| /** |
| * Removes the first occurrence of the specified element in this |
| * deque (when traversing the deque from head to tail). |
| * If the deque does not contain the element, it is unchanged. |
| * More formally, removes the first element {@code e} such that |
| * {@code o.equals(e)} (if such an element exists). |
| * Returns {@code true} if this deque contained the specified element |
| * (or equivalently, if this deque changed as a result of the call). |
| * |
| * @param o element to be removed from this deque, if present |
| * @return {@code true} if the deque contained the specified element |
| */ |
| public boolean removeFirstOccurrence(Object o) { |
| if (o != null) { |
| final Object[] es = elements; |
| for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| if (o.equals(es[i])) { |
| delete(i); |
| return true; |
| } |
| if (to == end) break; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Removes the last occurrence of the specified element in this |
| * deque (when traversing the deque from head to tail). |
| * If the deque does not contain the element, it is unchanged. |
| * More formally, removes the last element {@code e} such that |
| * {@code o.equals(e)} (if such an element exists). |
| * Returns {@code true} if this deque contained the specified element |
| * (or equivalently, if this deque changed as a result of the call). |
| * |
| * @param o element to be removed from this deque, if present |
| * @return {@code true} if the deque contained the specified element |
| */ |
| public boolean removeLastOccurrence(Object o) { |
| if (o != null) { |
| final Object[] es = elements; |
| for (int i = tail, end = head, to = (i >= end) ? end : 0; |
| ; i = es.length, to = end) { |
| for (i--; i > to - 1; i--) |
| if (o.equals(es[i])) { |
| delete(i); |
| return true; |
| } |
| if (to == end) break; |
| } |
| } |
| return false; |
| } |
| |
| // *** Queue methods *** |
| |
| /** |
| * Inserts the specified element at the end of this deque. |
| * |
| * <p>This method is equivalent to {@link #addLast}. |
| * |
| * @param e the element to add |
| * @return {@code true} (as specified by {@link Collection#add}) |
| * @throws NullPointerException if the specified element is null |
| */ |
| public boolean add(E e) { |
| addLast(e); |
| return true; |
| } |
| |
| /** |
| * Inserts the specified element at the end of this deque. |
| * |
| * <p>This method is equivalent to {@link #offerLast}. |
| * |
| * @param e the element to add |
| * @return {@code true} (as specified by {@link Queue#offer}) |
| * @throws NullPointerException if the specified element is null |
| */ |
| public boolean offer(E e) { |
| return offerLast(e); |
| } |
| |
| /** |
| * Retrieves and removes the head of the queue represented by this deque. |
| * |
| * This method differs from {@link #poll() poll()} only in that it |
| * throws an exception if this deque is empty. |
| * |
| * <p>This method is equivalent to {@link #removeFirst}. |
| * |
| * @return the head of the queue represented by this deque |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E remove() { |
| return removeFirst(); |
| } |
| |
| /** |
| * Retrieves and removes the head of the queue represented by this deque |
| * (in other words, the first element of this deque), or returns |
| * {@code null} if this deque is empty. |
| * |
| * <p>This method is equivalent to {@link #pollFirst}. |
| * |
| * @return the head of the queue represented by this deque, or |
| * {@code null} if this deque is empty |
| */ |
| public E poll() { |
| return pollFirst(); |
| } |
| |
| /** |
| * Retrieves, but does not remove, the head of the queue represented by |
| * this deque. This method differs from {@link #peek peek} only in |
| * that it throws an exception if this deque is empty. |
| * |
| * <p>This method is equivalent to {@link #getFirst}. |
| * |
| * @return the head of the queue represented by this deque |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E element() { |
| return getFirst(); |
| } |
| |
| /** |
| * Retrieves, but does not remove, the head of the queue represented by |
| * this deque, or returns {@code null} if this deque is empty. |
| * |
| * <p>This method is equivalent to {@link #peekFirst}. |
| * |
| * @return the head of the queue represented by this deque, or |
| * {@code null} if this deque is empty |
| */ |
| public E peek() { |
| return peekFirst(); |
| } |
| |
| // *** Stack methods *** |
| |
| /** |
| * Pushes an element onto the stack represented by this deque. In other |
| * words, inserts the element at the front of this deque. |
| * |
| * <p>This method is equivalent to {@link #addFirst}. |
| * |
| * @param e the element to push |
| * @throws NullPointerException if the specified element is null |
| */ |
| public void push(E e) { |
| addFirst(e); |
| } |
| |
| /** |
| * Pops an element from the stack represented by this deque. In other |
| * words, removes and returns the first element of this deque. |
| * |
| * <p>This method is equivalent to {@link #removeFirst()}. |
| * |
| * @return the element at the front of this deque (which is the top |
| * of the stack represented by this deque) |
| * @throws NoSuchElementException {@inheritDoc} |
| */ |
| public E pop() { |
| return removeFirst(); |
| } |
| |
| /** |
| * Removes the element at the specified position in the elements array. |
| * This can result in forward or backwards motion of array elements. |
| * We optimize for least element motion. |
| * |
| * <p>This method is called delete rather than remove to emphasize |
| * that its semantics differ from those of {@link List#remove(int)}. |
| * |
| * @return true if elements near tail moved backwards |
| */ |
| boolean delete(int i) { |
| final Object[] es = elements; |
| final int capacity = es.length; |
| final int h, t; |
| // number of elements before to-be-deleted elt |
| final int front = sub(i, h = head, capacity); |
| // number of elements after to-be-deleted elt |
| final int back = sub(t = tail, i, capacity) - 1; |
| if (front < back) { |
| // move front elements forwards |
| if (h <= i) { |
| System.arraycopy(es, h, es, h + 1, front); |
| } else { // Wrap around |
| System.arraycopy(es, 0, es, 1, i); |
| es[0] = es[capacity - 1]; |
| System.arraycopy(es, h, es, h + 1, front - (i + 1)); |
| } |
| es[h] = null; |
| head = inc(h, capacity); |
| return false; |
| } else { |
| // move back elements backwards |
| tail = dec(t, capacity); |
| if (i <= tail) { |
| System.arraycopy(es, i + 1, es, i, back); |
| } else { // Wrap around |
| System.arraycopy(es, i + 1, es, i, capacity - (i + 1)); |
| es[capacity - 1] = es[0]; |
| System.arraycopy(es, 1, es, 0, t - 1); |
| } |
| es[tail] = null; |
| return true; |
| } |
| } |
| |
| // *** Collection Methods *** |
| |
| /** |
| * Returns the number of elements in this deque. |
| * |
| * @return the number of elements in this deque |
| */ |
| public int size() { |
| return sub(tail, head, elements.length); |
| } |
| |
| /** |
| * Returns {@code true} if this deque contains no elements. |
| * |
| * @return {@code true} if this deque contains no elements |
| */ |
| public boolean isEmpty() { |
| return head == tail; |
| } |
| |
| /** |
| * Returns an iterator over the elements in this deque. The elements |
| * will be ordered from first (head) to last (tail). This is the same |
| * order that elements would be dequeued (via successive calls to |
| * {@link #remove} or popped (via successive calls to {@link #pop}). |
| * |
| * @return an iterator over the elements in this deque |
| */ |
| public Iterator<E> iterator() { |
| return new DeqIterator(); |
| } |
| |
| public Iterator<E> descendingIterator() { |
| return new DescendingIterator(); |
| } |
| |
| private class DeqIterator implements Iterator<E> { |
| /** Index of element to be returned by subsequent call to next. */ |
| int cursor; |
| |
| /** Number of elements yet to be returned. */ |
| int remaining = size(); |
| |
| /** |
| * Index of element returned by most recent call to next. |
| * Reset to -1 if element is deleted by a call to remove. |
| */ |
| int lastRet = -1; |
| |
| DeqIterator() { cursor = head; } |
| |
| public final boolean hasNext() { |
| return remaining > 0; |
| } |
| |
| public E next() { |
| if (remaining <= 0) |
| throw new NoSuchElementException(); |
| final Object[] es = elements; |
| E e = nonNullElementAt(es, cursor); |
| cursor = inc(lastRet = cursor, es.length); |
| remaining--; |
| return e; |
| } |
| |
| void postDelete(boolean leftShifted) { |
| if (leftShifted) |
| cursor = dec(cursor, elements.length); |
| } |
| |
| public final void remove() { |
| if (lastRet < 0) |
| throw new IllegalStateException(); |
| postDelete(delete(lastRet)); |
| lastRet = -1; |
| } |
| |
| @Override |
| public void forEachRemaining(Consumer<? super E> action) { |
| Objects.requireNonNull(action); |
| int r; |
| if ((r = remaining) <= 0) |
| return; |
| remaining = 0; |
| final Object[] es = elements; |
| if (es[cursor] == null || sub(tail, cursor, es.length) != r) |
| throw new ConcurrentModificationException(); |
| for (int i = cursor, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| action.accept(elementAt(es, i)); |
| if (to == end) { |
| if (end != tail) |
| throw new ConcurrentModificationException(); |
| lastRet = dec(end, es.length); |
| break; |
| } |
| } |
| } |
| } |
| |
| private class DescendingIterator extends DeqIterator { |
| DescendingIterator() { cursor = dec(tail, elements.length); } |
| |
| public final E next() { |
| if (remaining <= 0) |
| throw new NoSuchElementException(); |
| final Object[] es = elements; |
| E e = nonNullElementAt(es, cursor); |
| cursor = dec(lastRet = cursor, es.length); |
| remaining--; |
| return e; |
| } |
| |
| void postDelete(boolean leftShifted) { |
| if (!leftShifted) |
| cursor = inc(cursor, elements.length); |
| } |
| |
| public final void forEachRemaining(Consumer<? super E> action) { |
| Objects.requireNonNull(action); |
| int r; |
| if ((r = remaining) <= 0) |
| return; |
| remaining = 0; |
| final Object[] es = elements; |
| if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r) |
| throw new ConcurrentModificationException(); |
| for (int i = cursor, end = head, to = (i >= end) ? end : 0; |
| ; i = es.length - 1, to = end) { |
| // hotspot generates faster code than for: i >= to ! |
| for (; i > to - 1; i--) |
| action.accept(elementAt(es, i)); |
| if (to == end) { |
| if (end != head) |
| throw new ConcurrentModificationException(); |
| lastRet = end; |
| break; |
| } |
| } |
| } |
| } |
| |
| /** |
| * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
| * and <em>fail-fast</em> {@link Spliterator} over the elements in this |
| * deque. |
| * |
| * <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
| * {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
| * {@link Spliterator#NONNULL}. Overriding implementations should document |
| * the reporting of additional characteristic values. |
| * |
| * @return a {@code Spliterator} over the elements in this deque |
| * @since 1.8 |
| */ |
| public Spliterator<E> spliterator() { |
| return new DeqSpliterator(); |
| } |
| |
| final class DeqSpliterator implements Spliterator<E> { |
| private int fence; // -1 until first use |
| private int cursor; // current index, modified on traverse/split |
| |
| /** Constructs late-binding spliterator over all elements. */ |
| DeqSpliterator() { |
| this.fence = -1; |
| } |
| |
| /** Constructs spliterator over the given range. */ |
| DeqSpliterator(int origin, int fence) { |
| // assert 0 <= origin && origin < elements.length; |
| // assert 0 <= fence && fence < elements.length; |
| this.cursor = origin; |
| this.fence = fence; |
| } |
| |
| /** Ensures late-binding initialization; then returns fence. */ |
| private int getFence() { // force initialization |
| int t; |
| if ((t = fence) < 0) { |
| t = fence = tail; |
| cursor = head; |
| } |
| return t; |
| } |
| |
| public DeqSpliterator trySplit() { |
| final Object[] es = elements; |
| final int i, n; |
| return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0) |
| ? null |
| : new DeqSpliterator(i, cursor = inc(i, n, es.length)); |
| } |
| |
| public void forEachRemaining(Consumer<? super E> action) { |
| if (action == null) |
| throw new NullPointerException(); |
| final int end = getFence(), cursor = this.cursor; |
| final Object[] es = elements; |
| if (cursor != end) { |
| this.cursor = end; |
| // null check at both ends of range is sufficient |
| if (es[cursor] == null || es[dec(end, es.length)] == null) |
| throw new ConcurrentModificationException(); |
| for (int i = cursor, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| action.accept(elementAt(es, i)); |
| if (to == end) break; |
| } |
| } |
| } |
| |
| public boolean tryAdvance(Consumer<? super E> action) { |
| Objects.requireNonNull(action); |
| final Object[] es = elements; |
| if (fence < 0) { fence = tail; cursor = head; } // late-binding |
| final int i; |
| if ((i = cursor) == fence) |
| return false; |
| E e = nonNullElementAt(es, i); |
| cursor = inc(i, es.length); |
| action.accept(e); |
| return true; |
| } |
| |
| public long estimateSize() { |
| return sub(getFence(), cursor, elements.length); |
| } |
| |
| public int characteristics() { |
| return Spliterator.NONNULL |
| | Spliterator.ORDERED |
| | Spliterator.SIZED |
| | Spliterator.SUBSIZED; |
| } |
| } |
| |
| /** |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public void forEach(Consumer<? super E> action) { |
| Objects.requireNonNull(action); |
| final Object[] es = elements; |
| for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| action.accept(elementAt(es, i)); |
| if (to == end) { |
| if (end != tail) throw new ConcurrentModificationException(); |
| break; |
| } |
| } |
| } |
| |
| /** |
| * @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)); |
| } |
| |
| /** Implementation of bulk remove methods. */ |
| private boolean bulkRemove(Predicate<? super E> filter) { |
| final Object[] es = elements; |
| // Optimize for initial run of survivors |
| for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| if (filter.test(elementAt(es, i))) |
| return bulkRemoveModified(filter, i); |
| if (to == end) { |
| if (end != tail) throw new ConcurrentModificationException(); |
| break; |
| } |
| } |
| return false; |
| } |
| |
| // 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; |
| } |
| |
| /** |
| * Helper for bulkRemove, in case of at least one deletion. |
| * 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. |
| * |
| * @param beg valid index of first element to be deleted |
| */ |
| private boolean bulkRemoveModified( |
| Predicate<? super E> filter, final int beg) { |
| final Object[] es = elements; |
| final int capacity = es.length; |
| final int end = tail; |
| final long[] deathRow = nBits(sub(end, beg, capacity)); |
| deathRow[0] = 1L; // set bit 0 |
| for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
| ; i = 0, to = end, k -= capacity) { |
| for (; i < to; i++) |
| if (filter.test(elementAt(es, i))) |
| setBit(deathRow, i - k); |
| if (to == end) break; |
| } |
| // a two-finger traversal, with hare i reading, tortoise w writing |
| int w = beg; |
| for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
| ; w = 0) { // w rejoins i on second leg |
| // In this loop, i and w are on the same leg, with i > w |
| for (; i < to; i++) |
| if (isClear(deathRow, i - k)) |
| es[w++] = es[i]; |
| if (to == end) break; |
| // In this loop, w is on the first leg, i on the second |
| for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++) |
| if (isClear(deathRow, i - k)) |
| es[w++] = es[i]; |
| if (i >= to) { |
| if (w == capacity) w = 0; // "corner" case |
| break; |
| } |
| } |
| if (end != tail) throw new ConcurrentModificationException(); |
| circularClear(es, tail = w, end); |
| return true; |
| } |
| |
| /** |
| * Returns {@code true} if this deque contains the specified element. |
| * More formally, returns {@code true} if and only if this deque contains |
| * at least one element {@code e} such that {@code o.equals(e)}. |
| * |
| * @param o object to be checked for containment in this deque |
| * @return {@code true} if this deque contains the specified element |
| */ |
| public boolean contains(Object o) { |
| if (o != null) { |
| final Object[] es = elements; |
| for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| if (o.equals(es[i])) |
| return true; |
| if (to == end) break; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Removes a single instance of the specified element from this deque. |
| * If the deque does not contain the element, it is unchanged. |
| * More formally, removes the first element {@code e} such that |
| * {@code o.equals(e)} (if such an element exists). |
| * Returns {@code true} if this deque contained the specified element |
| * (or equivalently, if this deque changed as a result of the call). |
| * |
| * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
| * |
| * @param o element to be removed from this deque, if present |
| * @return {@code true} if this deque contained the specified element |
| */ |
| public boolean remove(Object o) { |
| return removeFirstOccurrence(o); |
| } |
| |
| /** |
| * Removes all of the elements from this deque. |
| * The deque will be empty after this call returns. |
| */ |
| public void clear() { |
| circularClear(elements, head, tail); |
| head = tail = 0; |
| } |
| |
| /** |
| * Nulls out slots starting at array index i, up to index end. |
| * Condition i == end means "empty" - nothing to do. |
| */ |
| private static void circularClear(Object[] es, int i, int end) { |
| // assert 0 <= i && i < es.length; |
| // assert 0 <= end && end < es.length; |
| for (int to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) es[i] = null; |
| if (to == end) break; |
| } |
| } |
| |
| /** |
| * Returns an array containing all of the elements in this deque |
| * in proper sequence (from first to last element). |
| * |
| * <p>The returned array will be "safe" in that no references to it are |
| * maintained by this deque. (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 deque |
| */ |
| public Object[] toArray() { |
| return toArray(Object[].class); |
| } |
| |
| private <T> T[] toArray(Class<T[]> klazz) { |
| final Object[] es = elements; |
| final T[] a; |
| final int head = this.head, tail = this.tail, end; |
| if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) { |
| // Uses null extension feature of copyOfRange |
| a = Arrays.copyOfRange(es, head, end, klazz); |
| } else { |
| // integer overflow! |
| a = Arrays.copyOfRange(es, 0, end - head, klazz); |
| System.arraycopy(es, head, a, 0, es.length - head); |
| } |
| if (end != tail) |
| System.arraycopy(es, 0, a, es.length - head, tail); |
| return a; |
| } |
| |
| /** |
| * Returns an array containing all of the elements in this deque in |
| * proper sequence (from first to last element); the runtime type of the |
| * returned array is that of the specified array. If the deque 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 deque. |
| * |
| * <p>If this deque fits in the specified array with room to spare |
| * (i.e., the array has more elements than this deque), the element in |
| * the array immediately following the end of the deque 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 deque known to contain only strings. |
| * The following code can be used to dump the deque 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 deque 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 deque |
| * @throws ArrayStoreException if the runtime type of the specified array |
| * is not a supertype of the runtime type of every element in |
| * this deque |
| * @throws NullPointerException if the specified array is null |
| */ |
| @SuppressWarnings("unchecked") |
| public <T> T[] toArray(T[] a) { |
| final int size; |
| if ((size = size()) > a.length) |
| return toArray((Class<T[]>) a.getClass()); |
| final Object[] es = elements; |
| for (int i = head, j = 0, len = Math.min(size, es.length - i); |
| ; i = 0, len = tail) { |
| System.arraycopy(es, i, a, j, len); |
| if ((j += len) == size) break; |
| } |
| if (size < a.length) |
| a[size] = null; |
| return a; |
| } |
| |
| // *** Object methods *** |
| |
| /** |
| * Returns a copy of this deque. |
| * |
| * @return a copy of this deque |
| */ |
| public ArrayDeque<E> clone() { |
| try { |
| @SuppressWarnings("unchecked") |
| ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
| result.elements = Arrays.copyOf(elements, elements.length); |
| return result; |
| } catch (CloneNotSupportedException e) { |
| throw new AssertionError(); |
| } |
| } |
| |
| @java.io.Serial |
| private static final long serialVersionUID = 2340985798034038923L; |
| |
| /** |
| * Saves this deque to a stream (that is, serializes it). |
| * |
| * @param s the stream |
| * @throws java.io.IOException if an I/O error occurs |
| * @serialData The current size ({@code int}) of the deque, |
| * followed by all of its elements (each an object reference) in |
| * first-to-last order. |
| */ |
| @java.io.Serial |
| private void writeObject(java.io.ObjectOutputStream s) |
| throws java.io.IOException { |
| s.defaultWriteObject(); |
| |
| // Write out size |
| s.writeInt(size()); |
| |
| // Write out elements in order. |
| final Object[] es = elements; |
| for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
| ; i = 0, to = end) { |
| for (; i < to; i++) |
| s.writeObject(es[i]); |
| if (to == end) break; |
| } |
| } |
| |
| /** |
| * Reconstitutes this deque 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 |
| */ |
| @java.io.Serial |
| private void readObject(java.io.ObjectInputStream s) |
| throws java.io.IOException, ClassNotFoundException { |
| s.defaultReadObject(); |
| |
| // Read in size and allocate array |
| int size = s.readInt(); |
| SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size + 1); |
| elements = new Object[size + 1]; |
| this.tail = size; |
| |
| // Read in all elements in the proper order. |
| for (int i = 0; i < size; i++) |
| elements[i] = s.readObject(); |
| } |
| |
| /** debugging */ |
| void checkInvariants() { |
| // Use head and tail fields with empty slot at tail strategy. |
| // head == tail disambiguates to "empty". |
| try { |
| int capacity = elements.length; |
| // assert 0 <= head && head < capacity; |
| // assert 0 <= tail && tail < capacity; |
| // assert capacity > 0; |
| // assert size() < capacity; |
| // assert head == tail || elements[head] != null; |
| // assert elements[tail] == null; |
| // assert head == tail || elements[dec(tail, capacity)] != null; |
| } catch (Throwable t) { |
| System.err.printf("head=%d tail=%d capacity=%d%n", |
| head, tail, elements.length); |
| System.err.printf("elements=%s%n", |
| Arrays.toString(elements)); |
| throw t; |
| } |
| } |
| |
| } |
