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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.14 by jsr166, Sat Jun 18 01:56:01 2005 UTC vs.
Revision 1.38 by jsr166, Mon Dec 12 20:53:11 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.util.*; // for javadoc
8	–	import java.io.*;
7
8		/**
9		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 45 | 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 53 | 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 65 | 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 109 | 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 127 | 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 155 | 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 221 | 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 233 | 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 263 | 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")
265	>	E result = (E) elements[h];
266	>	// Element is null if deque empty
267		if (result == null)
268		return null;
269		elements[h] = null;     // Must null out slot
#	Line 273 | Line 273 | public class ArrayDeque<E> extends Abstr
273
274		public E pollLast() {
275		int t = (tail - 1) & (elements.length - 1);
276	<	E result = elements[t];
276	>	@SuppressWarnings("unchecked")
277	>	E result = (E) elements[t];
278		if (result == null)
279		return null;
280		elements[t] = null;
#	Line 285 | Line 286 | public class ArrayDeque<E> extends Abstr
286		* @throws NoSuchElementException {@inheritDoc}
287		*/
288		public E getFirst() {
289	<	E x = elements[head];
290	<	if (x == null)
289	>	@SuppressWarnings("unchecked")
290	>	E result = (E) elements[head];
291	>	if (result == null)
292		throw new NoSuchElementException();
293	<	return x;
293	>	return result;
294		}
295
296		/**
297		* @throws NoSuchElementException {@inheritDoc}
298		*/
299		public E getLast() {
300	<	E x = elements[(tail - 1) & (elements.length - 1)];
301	<	if (x == null)
300	>	@SuppressWarnings("unchecked")
301	>	E result = (E) elements[(tail - 1) & (elements.length - 1)];
302	>	if (result == null)
303		throw new NoSuchElementException();
304	<	return x;
304	>	return result;
305		}
306
307	+	@SuppressWarnings("unchecked")
308		public E peekFirst() {
309	<	return elements[head]; // elements[head] is null if deque empty
309	>	// elements[head] is null if deque empty
310	>	return (E) elements[head];
311		}
312
313	+	@SuppressWarnings("unchecked")
314		public E peekLast() {
315	<	return elements[(tail - 1) & (elements.length - 1)];
315	>	return (E) elements[(tail - 1) & (elements.length - 1)];
316		}
317
318		/**
#	Line 326 | Line 332 | public class ArrayDeque<E> extends Abstr
332		return false;
333		int mask = elements.length - 1;
334		int i = head;
335	<	E x;
335	>	Object x;
336		while ( (x = elements[i]) != null) {
337		if (o.equals(x)) {
338		delete(i);
#	Line 354 | Line 360 | public class ArrayDeque<E> extends Abstr
360		return false;
361		int mask = elements.length - 1;
362		int i = (tail - 1) & mask;
363	<	E x;
363	>	Object x;
364		while ( (x = elements[i]) != null) {
365		if (o.equals(x)) {
366		delete(i);
#	Line 373 | Line 379 | public class ArrayDeque<E> extends Abstr
379		* <p>This method is equivalent to {@link #addLast}.
380		*
381		* @param e the element to add
382	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
382	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
383		* @throws NullPointerException if the specified element is null
384		*/
385		public boolean add(E e) {
#	Line 387 | Line 393 | public class ArrayDeque<E> extends Abstr
393		* <p>This method is equivalent to {@link #offerLast}.
394		*
395		* @param e the element to add
396	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
396	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
397		* @throws NullPointerException if the specified element is null
398		*/
399		public boolean offer(E e) {
#	Line 396 | Line 402 | public class ArrayDeque<E> extends Abstr
402
403		/**
404		* Retrieves and removes the head of the queue represented by this deque.
405	<	* This method differs from {@link #poll} only in that it throws an
405	>	*
406	>	* This method differs from {@link #poll poll} only in that it throws an
407		* exception if this deque is empty.
408		*
409		* <p>This method is equivalent to {@link #removeFirst}.
#	Line 424 | Line 431 | public class ArrayDeque<E> extends Abstr
431
432		/**
433		* Retrieves, but does not remove, the head of the queue represented by
434	<	* this deque.  This method differs from {@link #peek} only in that it
435	<	* throws an exception if this deque is empty.
434	>	* this deque.  This method differs from {@link #peek peek} only in
435	>	* that it throws an exception if this deque is empty.
436		*
437		* <p>This method is equivalent to {@link #getFirst}.
438		*
#	Line 478 | Line 485 | public class ArrayDeque<E> extends Abstr
485		return removeFirst();
486		}
487
488	+	private void checkInvariants() {
489	+	assert elements[tail] == null;
490	+	assert head == tail ? elements[head] == null :
491	+	(elements[head] != null &&
492	+	elements[(tail - 1) & (elements.length - 1)] != null);
493	+	assert elements[(head - 1) & (elements.length - 1)] == null;
494	+	}
495	+
496		/**
497		* Removes the element at the specified position in the elements array,
498		* adjusting head and tail as necessary.  This can result in motion of
#	Line 489 | Line 504 | public class ArrayDeque<E> extends Abstr
504		* @return true if elements moved backwards
505		*/
506		private boolean delete(int i) {
507	<	int mask = elements.length - 1;
508	<
509	<	// Invariant: head <= i < tail mod circularity
510	<	if (((i - head) & mask) >= ((tail - head) & mask))
511	<	throw new ConcurrentModificationException();
512	<
513	<	// Case 1: Deque doesn't wrap
514	<	// Case 2: Deque does wrap and removed element is in the head portion
515	<	if (i >= head) {
516	<	System.arraycopy(elements, head, elements, head + 1, i - head);
517	<	elements[head] = null;
518	<	head = (head + 1) & mask;
507	>	checkInvariants();
508	>	final Object[] elements = this.elements;
509	>	final int mask = elements.length - 1;
510	>	final int h = head;
511	>	final int t = tail;
512	>	final int front = (i - h) & mask;
513	>	final int back  = (t - i) & mask;
514	>
515	>	// Invariant: head <= i < tail mod circularity
516	>	if (front >= ((t - h) & mask))
517	>	throw new ConcurrentModificationException();
518	>
519	>	// Optimize for least element motion
520	>	if (front < back) {
521	>	if (h <= i) {
522	>	System.arraycopy(elements, h, elements, h + 1, front);
523	>	} else { // Wrap around
524	>	System.arraycopy(elements, 0, elements, 1, i);
525	>	elements[0] = elements[mask];
526	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
527	>	}
528	>	elements[h] = null;
529	>	head = (h + 1) & mask;
530		return false;
531	+	} else {
532	+	if (i < t) { // Copy the null tail as well
533	+	System.arraycopy(elements, i + 1, elements, i, back);
534	+	tail = t - 1;
535	+	} else { // Wrap around
536	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
537	+	elements[mask] = elements[0];
538	+	System.arraycopy(elements, 1, elements, 0, t);
539	+	tail = (t - 1) & mask;
540	+	}
541	+	return true;
542		}
506	–
507	–	// Case 3: Deque wraps and removed element is in the tail portion
508	–	tail--;
509	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
510	–	elements[tail] = null;
511	–	return true;
543		}
544
545		// *** Collection Methods ***
#	Line 537 | Line 568 | public class ArrayDeque<E> extends Abstr
568		* order that elements would be dequeued (via successive calls to
569		* {@link #remove} or popped (via successive calls to {@link #pop}).
570		*
571	<	* @return an <tt>Iterator</tt> over the elements in this deque
571	>	* @return an iterator over the elements in this deque
572		*/
573		public Iterator<E> iterator() {
574		return new DeqIterator();
575		}
576
577	+	public Iterator<E> descendingIterator() {
578	+	return new DescendingIterator();
579	+	}
580	+
581		private class DeqIterator implements Iterator<E> {
582		/**
583		* Index of element to be returned by subsequent call to next.
#	Line 566 | Line 601 | public class ArrayDeque<E> extends Abstr
601		}
602
603		public E next() {
569	–	E result;
604		if (cursor == fence)
605		throw new NoSuchElementException();
606	+	@SuppressWarnings("unchecked")
607	+	E result = (E) elements[cursor];
608		// This check doesn't catch all possible comodifications,
609		// but does catch the ones that corrupt traversal
610	<	if (tail != fence || (result = elements[cursor]) == null)
610	>	if (tail != fence || result == null)
611		throw new ConcurrentModificationException();
612		lastRet = cursor;
613		cursor = (cursor + 1) & (elements.length - 1);
#	Line 581 | Line 617 | public class ArrayDeque<E> extends Abstr
617		public void remove() {
618		if (lastRet < 0)
619		throw new IllegalStateException();
620	<	if (delete(lastRet))
621	<	cursor--;
620	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
621	>	cursor = (cursor - 1) & (elements.length - 1);
622	>	fence = tail;
623	>	}
624	>	lastRet = -1;
625	>	}
626	>	}
627	>
628	>	private class DescendingIterator implements Iterator<E> {
629	>	/*
630	>	* This class is nearly a mirror-image of DeqIterator, using
631	>	* tail instead of head for initial cursor, and head instead of
632	>	* tail for fence.
633	>	*/
634	>	private int cursor = tail;
635	>	private int fence = head;
636	>	private int lastRet = -1;
637	>
638	>	public boolean hasNext() {
639	>	return cursor != fence;
640	>	}
641	>
642	>	public E next() {
643	>	if (cursor == fence)
644	>	throw new NoSuchElementException();
645	>	cursor = (cursor - 1) & (elements.length - 1);
646	>	@SuppressWarnings("unchecked")
647	>	E result = (E) elements[cursor];
648	>	if (head != fence || result == null)
649	>	throw new ConcurrentModificationException();
650	>	lastRet = cursor;
651	>	return result;
652	>	}
653	>
654	>	public void remove() {
655	>	if (lastRet < 0)
656	>	throw new IllegalStateException();
657	>	if (!delete(lastRet)) {
658	>	cursor = (cursor + 1) & (elements.length - 1);
659	>	fence = head;
660	>	}
661		lastRet = -1;
587	–	fence = tail;
662		}
663		}
664
#	Line 601 | Line 675 | public class ArrayDeque<E> extends Abstr
675		return false;
676		int mask = elements.length - 1;
677		int i = head;
678	<	E x;
678	>	Object x;
679		while ( (x = elements[i]) != null) {
680		if (o.equals(x))
681		return true;
#	Line 659 | Line 733 | public class ArrayDeque<E> extends Abstr
733		* @return an array containing all of the elements in this deque
734		*/
735		public Object[] toArray() {
736	<	return copyElements(new Object[size()]);
736	>	return copyElements(new Object[size()]);
737		}
738
739		/**
#	Line 684 | Line 758 | public class ArrayDeque<E> extends Abstr
758		* The following code can be used to dump the deque into a newly
759		* allocated array of <tt>String</tt>:
760		*
761	<	* <pre>
688	<	*     String[] y = x.toArray(new String[0]);</pre>
761	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
762		*
763		* Note that <tt>toArray(new Object[0])</tt> is identical in function to
764		* <tt>toArray()</tt>.
#	Line 699 | Line 772 | public class ArrayDeque<E> extends Abstr
772		*         this deque
773		* @throws NullPointerException if the specified array is null
774		*/
775	+	@SuppressWarnings("unchecked")
776		public <T> T[] toArray(T[] a) {
777		int size = size();
778		if (a.length < size)
779		a = (T[])java.lang.reflect.Array.newInstance(
780		a.getClass().getComponentType(), size);
781	<	copyElements(a);
781	>	copyElements(a);
782		if (a.length > size)
783		a[size] = null;
784		return a;
#	Line 719 | Line 793 | public class ArrayDeque<E> extends Abstr
793		*/
794		public ArrayDeque<E> clone() {
795		try {
796	+	@SuppressWarnings("unchecked")
797		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
798	<	// These two lines are currently faster than cloning the array:
724	<	result.elements = (E[]) new Object[elements.length];
725	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
798	>	result.elements = Arrays.copyOf(elements, elements.length);
799		return result;
727	–
800		} catch (CloneNotSupportedException e) {
801		throw new AssertionError();
802		}
803		}
804
733	–	/**
734	–	* Appease the serialization gods.
735	–	*/
805		private static final long serialVersionUID = 2340985798034038923L;
806
807		/**
808	<	* Serialize this deque.
808	>	* Saves this deque to a stream (that is, serializes it).
809		*
810		* @serialData The current size (<tt>int</tt>) of the deque,
811		* followed by all of its elements (each an object reference) in
812		* first-to-last order.
813		*/
814	<	private void writeObject(ObjectOutputStream s) throws IOException {
814	>	private void writeObject(java.io.ObjectOutputStream s)
815	>	throws java.io.IOException {
816		s.defaultWriteObject();
817
818		// Write out size
819	<	int size = size();
750	<	s.writeInt(size);
819	>	s.writeInt(size());
820
821		// Write out elements in order.
753	–	int i = head;
822		int mask = elements.length - 1;
823	<	for (int j = 0; j < size; j++) {
823	>	for (int i = head; i != tail; i = (i + 1) & mask)
824		s.writeObject(elements[i]);
757	–	i = (i + 1) & mask;
758	–	}
825		}
826
827		/**
828	<	* Deserialize this deque.
828	>	* Reconstitutes this deque from a stream (that is, deserializes it).
829		*/
830	<	private void readObject(ObjectInputStream s)
831	<	throws IOException, ClassNotFoundException {
830	>	private void readObject(java.io.ObjectInputStream s)
831	>	throws java.io.IOException, ClassNotFoundException {
832		s.defaultReadObject();
833
834		// Read in size and allocate array
#	Line 773 | Line 839 | public class ArrayDeque<E> extends Abstr
839
840		// Read in all elements in the proper order.
841		for (int i = 0; i < size; i++)
842	<	elements[i] = (E)s.readObject();
777	<
842	>	elements[i] = s.readObject();
843		}
844		}

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