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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.11 by jsr166, Tue May 17 06:36:47 2005 UTC vs.
Revision 1.36 by jsr166, Fri Dec 2 15:51:56 2011 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Josh Bloch of Google Inc. and released to the public domain,
3	<	* as explained at http://creativecommons.org/licenses/publicdomain.
3	>	* as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4		*/
5
6		package java.util;
7	–	import java.io.*;
7
8		/**
9		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 44 | Line 43 | import java.io.*;
43		* Iterator} interfaces.
44		*
45		* <p>This class is a member of the
46	<	* <a href="{@docRoot}/../guide/collections/index.html">
46	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
47		* Java Collections Framework</a>.
48		*
49		* @author  Josh Bloch and Doug Lea
#	Line 52 | Line 51 | import java.io.*;
51		* @param <E> the type of elements held in this collection
52		*/
53		public class ArrayDeque<E> extends AbstractCollection<E>
54	<	implements Deque<E>, Cloneable, Serializable
54	>	implements Deque<E>, Cloneable, java.io.Serializable
55		{
56		/**
57		* The array in which the elements of the deque are stored.
#	Line 64 | Line 63 | public class ArrayDeque<E> extends Abstr
63		* other.  We also guarantee that all array cells not holding
64		* deque elements are always null.
65		*/
66	<	private transient E[] elements;
66	>	private transient Object[] elements;
67
68		/**
69		* The index of the element at the head of the deque (which is the
#	Line 108 | Line 107 | public class ArrayDeque<E> extends Abstr
107		if (initialCapacity < 0)   // Too many elements, must back off
108		initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
109		}
110	<	elements = (E[]) new Object[initialCapacity];
110	>	elements = new Object[initialCapacity];
111		}
112
113		/**
#	Line 126 | Line 125 | public class ArrayDeque<E> extends Abstr
125		Object[] a = new Object[newCapacity];
126		System.arraycopy(elements, p, a, 0, r);
127		System.arraycopy(elements, 0, a, r, p);
128	<	elements = (E[])a;
128	>	elements = a;
129		head = 0;
130		tail = n;
131		}
#	Line 154 | Line 153 | public class ArrayDeque<E> extends Abstr
153		* sufficient to hold 16 elements.
154		*/
155		public ArrayDeque() {
156	<	elements = (E[]) new Object[16];
156	>	elements = new Object[16];
157		}
158
159		/**
#	Line 202 | Line 201 | public class ArrayDeque<E> extends Abstr
201
202		/**
203		* Inserts the specified element at the end of this deque.
204	<	* This method is equivalent to {@link #add} and {@link #push}.
204	>	*
205	>	* <p>This method is equivalent to {@link #add}.
206		*
207		* @param e the element to add
208		* @throws NullPointerException if the specified element is null
#	Line 219 | Line 219 | public class ArrayDeque<E> extends Abstr
219		* Inserts the specified element at the front of this deque.
220		*
221		* @param e the element to add
222	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
222	>	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
223		* @throws NullPointerException if the specified element is null
224		*/
225		public boolean offerFirst(E e) {
#	Line 231 | Line 231 | public class ArrayDeque<E> extends Abstr
231		* Inserts the specified element at the end of this deque.
232		*
233		* @param e the element to add
234	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
234	>	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
235		* @throws NullPointerException if the specified element is null
236		*/
237		public boolean offerLast(E e) {
#	Line 261 | Line 261 | public class ArrayDeque<E> extends Abstr
261
262		public E pollFirst() {
263		int h = head;
264	<	E result = elements[h]; // Element is null if deque empty
264	>	@SuppressWarnings("unchecked") E result = (E) elements[h];
265	>	// Element is null if deque empty
266		if (result == null)
267		return null;
268		elements[h] = null;     // Must null out slot
#	Line 271 | Line 272 | public class ArrayDeque<E> extends Abstr
272
273		public E pollLast() {
274		int t = (tail - 1) & (elements.length - 1);
275	<	E result = elements[t];
275	>	@SuppressWarnings("unchecked") E result = (E) elements[t];
276		if (result == null)
277		return null;
278		elements[t] = null;
#	Line 283 | Line 284 | public class ArrayDeque<E> extends Abstr
284		* @throws NoSuchElementException {@inheritDoc}
285		*/
286		public E getFirst() {
287	<	E x = elements[head];
288	<	if (x == null)
287	>	@SuppressWarnings("unchecked") E result = (E) elements[head];
288	>	if (result == null)
289		throw new NoSuchElementException();
290	<	return x;
290	>	return result;
291		}
292
293		/**
294		* @throws NoSuchElementException {@inheritDoc}
295		*/
296		public E getLast() {
297	<	E x = elements[(tail - 1) & (elements.length - 1)];
298	<	if (x == null)
297	>	@SuppressWarnings("unchecked")
298	>	E result = (E) elements[(tail - 1) & (elements.length - 1)];
299	>	if (result == null)
300		throw new NoSuchElementException();
301	<	return x;
301	>	return result;
302		}
303
304	+	@SuppressWarnings("unchecked")
305		public E peekFirst() {
306	<	return elements[head]; // elements[head] is null if deque empty
306	>	// elements[head] is null if deque empty
307	>	return (E) elements[head];
308		}
309
310	+	@SuppressWarnings("unchecked")
311		public E peekLast() {
312	<	return elements[(tail - 1) & (elements.length - 1)];
312	>	return (E) elements[(tail - 1) & (elements.length - 1)];
313		}
314
315		/**
#	Line 313 | Line 318 | public class ArrayDeque<E> extends Abstr
318		* If the deque does not contain the element, it is unchanged.
319		* More formally, removes the first element <tt>e</tt> such that
320		* <tt>o.equals(e)</tt> (if such an element exists).
321	<	* Returns true if this deque contained the specified element (or
322	<	* equivalently, if this deque changed as a result of the call).
321	>	* Returns <tt>true</tt> if this deque contained the specified element
322	>	* (or equivalently, if this deque changed as a result of the call).
323		*
324		* @param o element to be removed from this deque, if present
325		* @return <tt>true</tt> if the deque contained the specified element
#	Line 324 | Line 329 | public class ArrayDeque<E> extends Abstr
329		return false;
330		int mask = elements.length - 1;
331		int i = head;
332	<	E x;
332	>	Object x;
333		while ( (x = elements[i]) != null) {
334		if (o.equals(x)) {
335		delete(i);
#	Line 341 | Line 346 | public class ArrayDeque<E> extends Abstr
346		* If the deque does not contain the element, it is unchanged.
347		* More formally, removes the last element <tt>e</tt> such that
348		* <tt>o.equals(e)</tt> (if such an element exists).
349	<	* Returns true if this deque contained the specified element (or
350	<	* equivalently, if this deque changed as a result of the call).
349	>	* Returns <tt>true</tt> if this deque contained the specified element
350	>	* (or equivalently, if this deque changed as a result of the call).
351		*
352		* @param o element to be removed from this deque, if present
353		* @return <tt>true</tt> if the deque contained the specified element
#	Line 352 | Line 357 | public class ArrayDeque<E> extends Abstr
357		return false;
358		int mask = elements.length - 1;
359		int i = (tail - 1) & mask;
360	<	E x;
360	>	Object x;
361		while ( (x = elements[i]) != null) {
362		if (o.equals(x)) {
363		delete(i);
#	Line 371 | Line 376 | public class ArrayDeque<E> extends Abstr
376		* <p>This method is equivalent to {@link #addLast}.
377		*
378		* @param e the element to add
379	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
379	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
380		* @throws NullPointerException if the specified element is null
381		*/
382		public boolean add(E e) {
#	Line 385 | Line 390 | public class ArrayDeque<E> extends Abstr
390		* <p>This method is equivalent to {@link #offerLast}.
391		*
392		* @param e the element to add
393	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
393	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
394		* @throws NullPointerException if the specified element is null
395		*/
396		public boolean offer(E e) {
#	Line 394 | Line 399 | public class ArrayDeque<E> extends Abstr
399
400		/**
401		* Retrieves and removes the head of the queue represented by this deque.
402	<	* This method differs from {@link #poll} only in that it throws an
402	>	*
403	>	* This method differs from {@link #poll poll} only in that it throws an
404		* exception if this deque is empty.
405		*
406		* <p>This method is equivalent to {@link #removeFirst}.
#	Line 422 | Line 428 | public class ArrayDeque<E> extends Abstr
428
429		/**
430		* Retrieves, but does not remove, the head of the queue represented by
431	<	* this deque.  This method differs from {@link #peek} only in that it
432	<	* throws an exception if this deque is empty.
431	>	* this deque.  This method differs from {@link #peek peek} only in
432	>	* that it throws an exception if this deque is empty.
433		*
434		* <p>This method is equivalent to {@link #getFirst}.
435		*
#	Line 476 | Line 482 | public class ArrayDeque<E> extends Abstr
482		return removeFirst();
483		}
484
485	+	private void checkInvariants() {
486	+	assert elements[tail] == null;
487	+	assert head == tail ? elements[head] == null :
488	+	(elements[head] != null &&
489	+	elements[(tail - 1) & (elements.length - 1)] != null);
490	+	assert elements[(head - 1) & (elements.length - 1)] == null;
491	+	}
492	+
493		/**
494		* Removes the element at the specified position in the elements array,
495		* adjusting head and tail as necessary.  This can result in motion of
#	Line 487 | Line 501 | public class ArrayDeque<E> extends Abstr
501		* @return true if elements moved backwards
502		*/
503		private boolean delete(int i) {
504	<	int mask = elements.length - 1;
505	<
506	<	// Invariant: head <= i < tail mod circularity
507	<	if (((i - head) & mask) >= ((tail - head) & mask))
508	<	throw new ConcurrentModificationException();
509	<
510	<	// Case 1: Deque doesn't wrap
511	<	// Case 2: Deque does wrap and removed element is in the head portion
512	<	if (i >= head) {
513	<	System.arraycopy(elements, head, elements, head + 1, i - head);
514	<	elements[head] = null;
515	<	head = (head + 1) & mask;
504	>	checkInvariants();
505	>	final Object[] elements = this.elements;
506	>	final int mask = elements.length - 1;
507	>	final int h = head;
508	>	final int t = tail;
509	>	final int front = (i - h) & mask;
510	>	final int back  = (t - i) & mask;
511	>
512	>	// Invariant: head <= i < tail mod circularity
513	>	if (front >= ((t - h) & mask))
514	>	throw new ConcurrentModificationException();
515	>
516	>	// Optimize for least element motion
517	>	if (front < back) {
518	>	if (h <= i) {
519	>	System.arraycopy(elements, h, elements, h + 1, front);
520	>	} else { // Wrap around
521	>	System.arraycopy(elements, 0, elements, 1, i);
522	>	elements[0] = elements[mask];
523	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
524	>	}
525	>	elements[h] = null;
526	>	head = (h + 1) & mask;
527		return false;
528	+	} else {
529	+	if (i < t) { // Copy the null tail as well
530	+	System.arraycopy(elements, i + 1, elements, i, back);
531	+	tail = t - 1;
532	+	} else { // Wrap around
533	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
534	+	elements[mask] = elements[0];
535	+	System.arraycopy(elements, 1, elements, 0, t);
536	+	tail = (t - 1) & mask;
537	+	}
538	+	return true;
539		}
504	–
505	–	// Case 3: Deque wraps and removed element is in the tail portion
506	–	tail--;
507	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
508	–	elements[tail] = null;
509	–	return true;
540		}
541
542		// *** Collection Methods ***
#	Line 535 | Line 565 | public class ArrayDeque<E> extends Abstr
565		* order that elements would be dequeued (via successive calls to
566		* {@link #remove} or popped (via successive calls to {@link #pop}).
567		*
568	<	* @return an <tt>Iterator</tt> over the elements in this deque
568	>	* @return an iterator over the elements in this deque
569		*/
570		public Iterator<E> iterator() {
571		return new DeqIterator();
572		}
573
574	+	public Iterator<E> descendingIterator() {
575	+	return new DescendingIterator();
576	+	}
577	+
578		private class DeqIterator implements Iterator<E> {
579		/**
580		* Index of element to be returned by subsequent call to next.
#	Line 564 | Line 598 | public class ArrayDeque<E> extends Abstr
598		}
599
600		public E next() {
567	–	E result;
601		if (cursor == fence)
602		throw new NoSuchElementException();
603	+	@SuppressWarnings("unchecked") E result = (E) elements[cursor];
604		// This check doesn't catch all possible comodifications,
605		// but does catch the ones that corrupt traversal
606	<	if (tail != fence || (result = elements[cursor]) == null)
606	>	if (tail != fence || result == null)
607		throw new ConcurrentModificationException();
608		lastRet = cursor;
609		cursor = (cursor + 1) & (elements.length - 1);
#	Line 579 | Line 613 | public class ArrayDeque<E> extends Abstr
613		public void remove() {
614		if (lastRet < 0)
615		throw new IllegalStateException();
616	<	if (delete(lastRet))
617	<	cursor--;
616	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
617	>	cursor = (cursor - 1) & (elements.length - 1);
618	>	fence = tail;
619	>	}
620	>	lastRet = -1;
621	>	}
622	>	}
623	>
624	>	private class DescendingIterator implements Iterator<E> {
625	>	/*
626	>	* This class is nearly a mirror-image of DeqIterator, using
627	>	* tail instead of head for initial cursor, and head instead of
628	>	* tail for fence.
629	>	*/
630	>	private int cursor = tail;
631	>	private int fence = head;
632	>	private int lastRet = -1;
633	>
634	>	public boolean hasNext() {
635	>	return cursor != fence;
636	>	}
637	>
638	>	public E next() {
639	>	if (cursor == fence)
640	>	throw new NoSuchElementException();
641	>	cursor = (cursor - 1) & (elements.length - 1);
642	>	@SuppressWarnings("unchecked") E result = (E) elements[cursor];
643	>	if (head != fence || result == null)
644	>	throw new ConcurrentModificationException();
645	>	lastRet = cursor;
646	>	return result;
647	>	}
648	>
649	>	public void remove() {
650	>	if (lastRet < 0)
651	>	throw new IllegalStateException();
652	>	if (!delete(lastRet)) {
653	>	cursor = (cursor + 1) & (elements.length - 1);
654	>	fence = head;
655	>	}
656		lastRet = -1;
585	–	fence = tail;
657		}
658		}
659
#	Line 599 | Line 670 | public class ArrayDeque<E> extends Abstr
670		return false;
671		int mask = elements.length - 1;
672		int i = head;
673	<	E x;
673	>	Object x;
674		while ( (x = elements[i]) != null) {
675		if (o.equals(x))
676		return true;
#	Line 613 | Line 684 | public class ArrayDeque<E> extends Abstr
684		* If the deque does not contain the element, it is unchanged.
685		* More formally, removes the first element <tt>e</tt> such that
686		* <tt>o.equals(e)</tt> (if such an element exists).
687	<	* Returns true if this deque contained the specified element (or
688	<	* equivalently, if this deque changed as a result of the call).
687	>	* Returns <tt>true</tt> if this deque contained the specified element
688	>	* (or equivalently, if this deque changed as a result of the call).
689		*
690		* <p>This method is equivalent to {@link #removeFirstOccurrence}.
691		*
#	Line 650 | Line 721 | public class ArrayDeque<E> extends Abstr
721		* <p>The returned array will be "safe" in that no references to it are
722		* maintained by this deque.  (In other words, this method must allocate
723		* a new array).  The caller is thus free to modify the returned array.
724	<	*
724	>	*
725		* <p>This method acts as bridge between array-based and collection-based
726		* APIs.
727		*
728		* @return an array containing all of the elements in this deque
729		*/
730		public Object[] toArray() {
731	<	return copyElements(new Object[size()]);
731	>	return copyElements(new Object[size()]);
732		}
733
734		/**
#	Line 682 | Line 753 | public class ArrayDeque<E> extends Abstr
753		* The following code can be used to dump the deque into a newly
754		* allocated array of <tt>String</tt>:
755		*
756	<	* <pre>
686	<	*     String[] y = x.toArray(new String[0]);</pre>
756	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
757		*
758		* Note that <tt>toArray(new Object[0])</tt> is identical in function to
759		* <tt>toArray()</tt>.
#	Line 697 | Line 767 | public class ArrayDeque<E> extends Abstr
767		*         this deque
768		* @throws NullPointerException if the specified array is null
769		*/
770	+	@SuppressWarnings("unchecked")
771		public <T> T[] toArray(T[] a) {
772		int size = size();
773		if (a.length < size)
774		a = (T[])java.lang.reflect.Array.newInstance(
775		a.getClass().getComponentType(), size);
776	<	copyElements(a);
776	>	copyElements(a);
777		if (a.length > size)
778		a[size] = null;
779		return a;
#	Line 717 | Line 788 | public class ArrayDeque<E> extends Abstr
788		*/
789		public ArrayDeque<E> clone() {
790		try {
791	+	@SuppressWarnings("unchecked")
792		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
793	<	// These two lines are currently faster than cloning the array:
722	<	result.elements = (E[]) new Object[elements.length];
723	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
793	>	result.elements = Arrays.copyOf(elements, elements.length);
794		return result;
725	–
795		} catch (CloneNotSupportedException e) {
796		throw new AssertionError();
797		}
#	Line 740 | Line 809 | public class ArrayDeque<E> extends Abstr
809		* followed by all of its elements (each an object reference) in
810		* first-to-last order.
811		*/
812	<	private void writeObject(ObjectOutputStream s) throws IOException {
812	>	private void writeObject(java.io.ObjectOutputStream s)
813	>	throws java.io.IOException {
814		s.defaultWriteObject();
815
816		// Write out size
817	<	int size = size();
748	<	s.writeInt(size);
817	>	s.writeInt(size());
818
819		// Write out elements in order.
751	–	int i = head;
820		int mask = elements.length - 1;
821	<	for (int j = 0; j < size; j++) {
821	>	for (int i = head; i != tail; i = (i + 1) & mask)
822		s.writeObject(elements[i]);
755	–	i = (i + 1) & mask;
756	–	}
823		}
824
825		/**
826		* Deserialize this deque.
827		*/
828	<	private void readObject(ObjectInputStream s)
829	<	throws IOException, ClassNotFoundException {
828	>	private void readObject(java.io.ObjectInputStream s)
829	>	throws java.io.IOException, ClassNotFoundException {
830		s.defaultReadObject();
831
832		// Read in size and allocate array
#	Line 771 | Line 837 | public class ArrayDeque<E> extends Abstr
837
838		// Read in all elements in the proper order.
839		for (int i = 0; i < size; i++)
840	<	elements[i] = (E)s.readObject();
775	<
840	>	elements[i] = s.readObject();
841		}
842		}

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