mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-03 10:49:58 +00:00
840 lines
28 KiB
Java
840 lines
28 KiB
Java
/*
|
|
* Written by Josh Bloch of Google Inc. and released to the public domain,
|
|
* as explained at http://creativecommons.org/licenses/publicdomain.
|
|
*/
|
|
|
|
package java.util;
|
|
import java.io.*;
|
|
|
|
/**
|
|
* 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 <tt>ArrayDeque</tt> 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 <tt>iterator</tt> method are
|
|
* <i>fail-fast</i>: If the deque is modified at any time after the iterator
|
|
* is created, in any way except through the iterator's own <tt>remove</tt>
|
|
* 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 <tt>ConcurrentModificationException</tt> 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} and {@link
|
|
* Iterator} interfaces.
|
|
*
|
|
* <p>This class is a member of the
|
|
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
|
|
* Java Collections Framework</a>.
|
|
*
|
|
* @author Josh Bloch and Doug Lea
|
|
* @since 1.6
|
|
* @param <E> the type of elements held in this collection
|
|
*/
|
|
public class ArrayDeque<E> extends AbstractCollection<E>
|
|
implements Deque<E>, Cloneable, Serializable
|
|
{
|
|
/**
|
|
* The array in which the elements of the deque are stored.
|
|
* The capacity of the deque is the length of this array, which is
|
|
* always a power of two. The array is never allowed to become
|
|
* full, except transiently within an addX method where it is
|
|
* resized (see doubleCapacity) immediately upon becoming full,
|
|
* thus avoiding head and tail wrapping around to equal each
|
|
* other. We also guarantee that all array cells not holding
|
|
* deque elements are always null.
|
|
*/
|
|
private transient E[] 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 equal to tail if the deque is empty.
|
|
*/
|
|
private 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)).
|
|
*/
|
|
private transient int tail;
|
|
|
|
/**
|
|
* The minimum capacity that we'll use for a newly created deque.
|
|
* Must be a power of 2.
|
|
*/
|
|
private static final int MIN_INITIAL_CAPACITY = 8;
|
|
|
|
// ****** Array allocation and resizing utilities ******
|
|
|
|
/**
|
|
* Allocate empty array to hold the given number of elements.
|
|
*
|
|
* @param numElements the number of elements to hold
|
|
*/
|
|
private void allocateElements(int numElements) {
|
|
int initialCapacity = MIN_INITIAL_CAPACITY;
|
|
// Find the best power of two to hold elements.
|
|
// Tests "<=" because arrays aren't kept full.
|
|
if (numElements >= initialCapacity) {
|
|
initialCapacity = numElements;
|
|
initialCapacity |= (initialCapacity >>> 1);
|
|
initialCapacity |= (initialCapacity >>> 2);
|
|
initialCapacity |= (initialCapacity >>> 4);
|
|
initialCapacity |= (initialCapacity >>> 8);
|
|
initialCapacity |= (initialCapacity >>> 16);
|
|
initialCapacity++;
|
|
|
|
if (initialCapacity < 0) // Too many elements, must back off
|
|
initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
|
|
}
|
|
elements = (E[]) new Object[initialCapacity];
|
|
}
|
|
|
|
/**
|
|
* Double the capacity of this deque. Call only when full, i.e.,
|
|
* when head and tail have wrapped around to become equal.
|
|
*/
|
|
private void doubleCapacity() {
|
|
assert head == tail;
|
|
int p = head;
|
|
int n = elements.length;
|
|
int r = n - p; // number of elements to the right of p
|
|
int newCapacity = n << 1;
|
|
if (newCapacity < 0)
|
|
throw new IllegalStateException("Sorry, deque too big");
|
|
Object[] a = new Object[newCapacity];
|
|
System.arraycopy(elements, p, a, 0, r);
|
|
System.arraycopy(elements, 0, a, r, p);
|
|
elements = (E[])a;
|
|
head = 0;
|
|
tail = n;
|
|
}
|
|
|
|
/**
|
|
* Copies the elements from our element array into the specified array,
|
|
* in order (from first to last element in the deque). It is assumed
|
|
* that the array is large enough to hold all elements in the deque.
|
|
*
|
|
* @return its argument
|
|
*/
|
|
private <T> T[] copyElements(T[] a) {
|
|
if (head < tail) {
|
|
System.arraycopy(elements, head, a, 0, size());
|
|
} else if (head > tail) {
|
|
int headPortionLen = elements.length - head;
|
|
System.arraycopy(elements, head, a, 0, headPortionLen);
|
|
System.arraycopy(elements, 0, a, headPortionLen, tail);
|
|
}
|
|
return a;
|
|
}
|
|
|
|
/**
|
|
* Constructs an empty array deque with an initial capacity
|
|
* sufficient to hold 16 elements.
|
|
*/
|
|
public ArrayDeque() {
|
|
elements = (E[]) new Object[16];
|
|
}
|
|
|
|
/**
|
|
* 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) {
|
|
allocateElements(numElements);
|
|
}
|
|
|
|
/**
|
|
* 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) {
|
|
allocateElements(c.size());
|
|
addAll(c);
|
|
}
|
|
|
|
// 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();
|
|
elements[head = (head - 1) & (elements.length - 1)] = e;
|
|
if (head == tail)
|
|
doubleCapacity();
|
|
}
|
|
|
|
/**
|
|
* 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();
|
|
elements[tail] = e;
|
|
if ( (tail = (tail + 1) & (elements.length - 1)) == head)
|
|
doubleCapacity();
|
|
}
|
|
|
|
/**
|
|
* Inserts the specified element at the front of this deque.
|
|
*
|
|
* @param e the element to add
|
|
* @return <tt>true</tt> (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 <tt>true</tt> (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 x = pollFirst();
|
|
if (x == null)
|
|
throw new NoSuchElementException();
|
|
return x;
|
|
}
|
|
|
|
/**
|
|
* @throws NoSuchElementException {@inheritDoc}
|
|
*/
|
|
public E removeLast() {
|
|
E x = pollLast();
|
|
if (x == null)
|
|
throw new NoSuchElementException();
|
|
return x;
|
|
}
|
|
|
|
public E pollFirst() {
|
|
int h = head;
|
|
E result = elements[h]; // Element is null if deque empty
|
|
if (result == null)
|
|
return null;
|
|
elements[h] = null; // Must null out slot
|
|
head = (h + 1) & (elements.length - 1);
|
|
return result;
|
|
}
|
|
|
|
public E pollLast() {
|
|
int t = (tail - 1) & (elements.length - 1);
|
|
E result = elements[t];
|
|
if (result == null)
|
|
return null;
|
|
elements[t] = null;
|
|
tail = t;
|
|
return result;
|
|
}
|
|
|
|
/**
|
|
* @throws NoSuchElementException {@inheritDoc}
|
|
*/
|
|
public E getFirst() {
|
|
E x = elements[head];
|
|
if (x == null)
|
|
throw new NoSuchElementException();
|
|
return x;
|
|
}
|
|
|
|
/**
|
|
* @throws NoSuchElementException {@inheritDoc}
|
|
*/
|
|
public E getLast() {
|
|
E x = elements[(tail - 1) & (elements.length - 1)];
|
|
if (x == null)
|
|
throw new NoSuchElementException();
|
|
return x;
|
|
}
|
|
|
|
public E peekFirst() {
|
|
return elements[head]; // elements[head] is null if deque empty
|
|
}
|
|
|
|
public E peekLast() {
|
|
return elements[(tail - 1) & (elements.length - 1)];
|
|
}
|
|
|
|
/**
|
|
* 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 <tt>e</tt> such that
|
|
* <tt>o.equals(e)</tt> (if such an element exists).
|
|
* Returns <tt>true</tt> 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 <tt>true</tt> if the deque contained the specified element
|
|
*/
|
|
public boolean removeFirstOccurrence(Object o) {
|
|
if (o == null)
|
|
return false;
|
|
int mask = elements.length - 1;
|
|
int i = head;
|
|
E x;
|
|
while ( (x = elements[i]) != null) {
|
|
if (o.equals(x)) {
|
|
delete(i);
|
|
return true;
|
|
}
|
|
i = (i + 1) & mask;
|
|
}
|
|
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 <tt>e</tt> such that
|
|
* <tt>o.equals(e)</tt> (if such an element exists).
|
|
* Returns <tt>true</tt> 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 <tt>true</tt> if the deque contained the specified element
|
|
*/
|
|
public boolean removeLastOccurrence(Object o) {
|
|
if (o == null)
|
|
return false;
|
|
int mask = elements.length - 1;
|
|
int i = (tail - 1) & mask;
|
|
E x;
|
|
while ( (x = elements[i]) != null) {
|
|
if (o.equals(x)) {
|
|
delete(i);
|
|
return true;
|
|
}
|
|
i = (i - 1) & mask;
|
|
}
|
|
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 <tt>true</tt> (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 <tt>true</tt> (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
|
|
* <tt>null</tt> if this deque is empty.
|
|
*
|
|
* <p>This method is equivalent to {@link #pollFirst}.
|
|
*
|
|
* @return the head of the queue represented by this deque, or
|
|
* <tt>null</tt> 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 <tt>null</tt> if this deque is empty.
|
|
*
|
|
* <p>This method is equivalent to {@link #peekFirst}.
|
|
*
|
|
* @return the head of the queue represented by this deque, or
|
|
* <tt>null</tt> 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();
|
|
}
|
|
|
|
private void checkInvariants() {
|
|
assert elements[tail] == null;
|
|
assert head == tail ? elements[head] == null :
|
|
(elements[head] != null &&
|
|
elements[(tail - 1) & (elements.length - 1)] != null);
|
|
assert elements[(head - 1) & (elements.length - 1)] == null;
|
|
}
|
|
|
|
/**
|
|
* Removes the element at the specified position in the elements array,
|
|
* adjusting head and tail as necessary. This can result in motion of
|
|
* elements backwards or forwards in the array.
|
|
*
|
|
* <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 moved backwards
|
|
*/
|
|
private boolean delete(int i) {
|
|
checkInvariants();
|
|
final E[] elements = this.elements;
|
|
final int mask = elements.length - 1;
|
|
final int h = head;
|
|
final int t = tail;
|
|
final int front = (i - h) & mask;
|
|
final int back = (t - i) & mask;
|
|
|
|
// Invariant: head <= i < tail mod circularity
|
|
if (front >= ((t - h) & mask))
|
|
throw new ConcurrentModificationException();
|
|
|
|
// Optimize for least element motion
|
|
if (front < back) {
|
|
if (h <= i) {
|
|
System.arraycopy(elements, h, elements, h + 1, front);
|
|
} else { // Wrap around
|
|
System.arraycopy(elements, 0, elements, 1, i);
|
|
elements[0] = elements[mask];
|
|
System.arraycopy(elements, h, elements, h + 1, mask - h);
|
|
}
|
|
elements[h] = null;
|
|
head = (h + 1) & mask;
|
|
return false;
|
|
} else {
|
|
if (i < t) { // Copy the null tail as well
|
|
System.arraycopy(elements, i + 1, elements, i, back);
|
|
tail = t - 1;
|
|
} else { // Wrap around
|
|
System.arraycopy(elements, i + 1, elements, i, mask - i);
|
|
elements[mask] = elements[0];
|
|
System.arraycopy(elements, 1, elements, 0, t);
|
|
tail = (t - 1) & mask;
|
|
}
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// *** Collection Methods ***
|
|
|
|
/**
|
|
* Returns the number of elements in this deque.
|
|
*
|
|
* @return the number of elements in this deque
|
|
*/
|
|
public int size() {
|
|
return (tail - head) & (elements.length - 1);
|
|
}
|
|
|
|
/**
|
|
* Returns <tt>true</tt> if this deque contains no elements.
|
|
*
|
|
* @return <tt>true</tt> 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.
|
|
*/
|
|
private int cursor = head;
|
|
|
|
/**
|
|
* Tail recorded at construction (also in remove), to stop
|
|
* iterator and also to check for comodification.
|
|
*/
|
|
private int fence = tail;
|
|
|
|
/**
|
|
* Index of element returned by most recent call to next.
|
|
* Reset to -1 if element is deleted by a call to remove.
|
|
*/
|
|
private int lastRet = -1;
|
|
|
|
public boolean hasNext() {
|
|
return cursor != fence;
|
|
}
|
|
|
|
public E next() {
|
|
if (cursor == fence)
|
|
throw new NoSuchElementException();
|
|
E result = elements[cursor];
|
|
// This check doesn't catch all possible comodifications,
|
|
// but does catch the ones that corrupt traversal
|
|
if (tail != fence || result == null)
|
|
throw new ConcurrentModificationException();
|
|
lastRet = cursor;
|
|
cursor = (cursor + 1) & (elements.length - 1);
|
|
return result;
|
|
}
|
|
|
|
public void remove() {
|
|
if (lastRet < 0)
|
|
throw new IllegalStateException();
|
|
if (delete(lastRet)) { // if left-shifted, undo increment in next()
|
|
cursor = (cursor - 1) & (elements.length - 1);
|
|
fence = tail;
|
|
}
|
|
lastRet = -1;
|
|
}
|
|
}
|
|
|
|
private class DescendingIterator implements Iterator<E> {
|
|
/*
|
|
* This class is nearly a mirror-image of DeqIterator, using
|
|
* tail instead of head for initial cursor, and head instead of
|
|
* tail for fence.
|
|
*/
|
|
private int cursor = tail;
|
|
private int fence = head;
|
|
private int lastRet = -1;
|
|
|
|
public boolean hasNext() {
|
|
return cursor != fence;
|
|
}
|
|
|
|
public E next() {
|
|
if (cursor == fence)
|
|
throw new NoSuchElementException();
|
|
cursor = (cursor - 1) & (elements.length - 1);
|
|
E result = elements[cursor];
|
|
if (head != fence || result == null)
|
|
throw new ConcurrentModificationException();
|
|
lastRet = cursor;
|
|
return result;
|
|
}
|
|
|
|
public void remove() {
|
|
if (lastRet < 0)
|
|
throw new IllegalStateException();
|
|
if (!delete(lastRet)) {
|
|
cursor = (cursor + 1) & (elements.length - 1);
|
|
fence = head;
|
|
}
|
|
lastRet = -1;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns <tt>true</tt> if this deque contains the specified element.
|
|
* More formally, returns <tt>true</tt> if and only if this deque contains
|
|
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
|
|
*
|
|
* @param o object to be checked for containment in this deque
|
|
* @return <tt>true</tt> if this deque contains the specified element
|
|
*/
|
|
public boolean contains(Object o) {
|
|
if (o == null)
|
|
return false;
|
|
int mask = elements.length - 1;
|
|
int i = head;
|
|
E x;
|
|
while ( (x = elements[i]) != null) {
|
|
if (o.equals(x))
|
|
return true;
|
|
i = (i + 1) & mask;
|
|
}
|
|
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 <tt>e</tt> such that
|
|
* <tt>o.equals(e)</tt> (if such an element exists).
|
|
* Returns <tt>true</tt> 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}.
|
|
*
|
|
* @param o element to be removed from this deque, if present
|
|
* @return <tt>true</tt> 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() {
|
|
int h = head;
|
|
int t = tail;
|
|
if (h != t) { // clear all cells
|
|
head = tail = 0;
|
|
int i = h;
|
|
int mask = elements.length - 1;
|
|
do {
|
|
elements[i] = null;
|
|
i = (i + 1) & mask;
|
|
} while (i != t);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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 copyElements(new Object[size()]);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
* <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 deque known to contain only strings.
|
|
* The following code can be used to dump the deque 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 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
|
|
*/
|
|
public <T> T[] toArray(T[] a) {
|
|
int size = size();
|
|
if (a.length < size)
|
|
a = (T[])java.lang.reflect.Array.newInstance(
|
|
a.getClass().getComponentType(), size);
|
|
copyElements(a);
|
|
if (a.length > size)
|
|
a[size] = null;
|
|
return a;
|
|
}
|
|
|
|
// *** Object methods ***
|
|
|
|
/**
|
|
* Returns a copy of this deque.
|
|
*
|
|
* @return a copy of this deque
|
|
*/
|
|
public ArrayDeque<E> clone() {
|
|
try {
|
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
|
|
// Classpath local: we don't have Arrays.copyOf yet.
|
|
// result.elements = Arrays.copyOf(elements, elements.length);
|
|
result.elements = (E[]) elements.clone();
|
|
return result;
|
|
|
|
} catch (CloneNotSupportedException e) {
|
|
throw new AssertionError();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Appease the serialization gods.
|
|
*/
|
|
private static final long serialVersionUID = 2340985798034038923L;
|
|
|
|
/**
|
|
* Serialize this deque.
|
|
*
|
|
* @serialData The current size (<tt>int</tt>) of the deque,
|
|
* followed by all of its elements (each an object reference) in
|
|
* first-to-last order.
|
|
*/
|
|
private void writeObject(ObjectOutputStream s) throws IOException {
|
|
s.defaultWriteObject();
|
|
|
|
// Write out size
|
|
s.writeInt(size());
|
|
|
|
// Write out elements in order.
|
|
int mask = elements.length - 1;
|
|
for (int i = head; i != tail; i = (i + 1) & mask)
|
|
s.writeObject(elements[i]);
|
|
}
|
|
|
|
/**
|
|
* Deserialize this deque.
|
|
*/
|
|
private void readObject(ObjectInputStream s)
|
|
throws IOException, ClassNotFoundException {
|
|
s.defaultReadObject();
|
|
|
|
// Read in size and allocate array
|
|
int size = s.readInt();
|
|
allocateElements(size);
|
|
head = 0;
|
|
tail = size;
|
|
|
|
// Read in all elements in the proper order.
|
|
for (int i = 0; i < size; i++)
|
|
elements[i] = (E)s.readObject();
|
|
}
|
|
}
|