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root/jsr166/jsr166/src/main/java/util/ArrayDeque.java

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.9 by jsr166, Mon May 16 06:16:12 2005 UTC vs.
Revision 1.30 by jsr166, Sun May 18 23:47:55 2008 UTC

#	Line 44 | Line 44 | import java.io.*;
44		* Iterator} interfaces.
45		*
46		* <p>This class is a member of the
47	<	* <a href="{@docRoot}/../guide/collections/index.html">
47	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
48		* Java Collections Framework</a>.
49		*
50		* @author  Josh Bloch and Doug Lea
#	Line 202 | Line 202 | public class ArrayDeque<E> extends Abstr
202
203		/**
204		* Inserts the specified element at the end of this deque.
205	<	* This method is equivalent to {@link #add} and {@link #push}.
205	>	*
206	>	* <p>This method is equivalent to {@link #add}.
207		*
208		* @param e the element to add
209		* @throws NullPointerException if the specified element is null
#	Line 219 | Line 220 | public class ArrayDeque<E> extends Abstr
220		* Inserts the specified element at the front of this deque.
221		*
222		* @param e the element to add
223	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
223	>	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
224		* @throws NullPointerException if the specified element is null
225		*/
226		public boolean offerFirst(E e) {
#	Line 231 | Line 232 | public class ArrayDeque<E> extends Abstr
232		* Inserts the specified element at the end of this deque.
233		*
234		* @param e the element to add
235	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
235	>	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
236		* @throws NullPointerException if the specified element is null
237		*/
238		public boolean offerLast(E e) {
#	Line 313 | Line 314 | public class ArrayDeque<E> extends Abstr
314		* If the deque does not contain the element, it is unchanged.
315		* More formally, removes the first element <tt>e</tt> such that
316		* <tt>o.equals(e)</tt> (if such an element exists).
317	<	* Returns true if this deque contained the specified element (or
318	<	* equivalently, if this deque changed as a result of the call).
317	>	* Returns <tt>true</tt> if this deque contained the specified element
318	>	* (or equivalently, if this deque changed as a result of the call).
319		*
320		* @param o element to be removed from this deque, if present
321		* @return <tt>true</tt> if the deque contained the specified element
#	Line 341 | Line 342 | public class ArrayDeque<E> extends Abstr
342		* If the deque does not contain the element, it is unchanged.
343		* More formally, removes the last element <tt>e</tt> such that
344		* <tt>o.equals(e)</tt> (if such an element exists).
345	<	* Returns true if this deque contained the specified element (or
346	<	* equivalently, if this deque changed as a result of the call).
345	>	* Returns <tt>true</tt> if this deque contained the specified element
346	>	* (or equivalently, if this deque changed as a result of the call).
347		*
348		* @param o element to be removed from this deque, if present
349		* @return <tt>true</tt> if the deque contained the specified element
#	Line 371 | Line 372 | public class ArrayDeque<E> extends Abstr
372		* <p>This method is equivalent to {@link #addLast}.
373		*
374		* @param e the element to add
375	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
375	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
376		* @throws NullPointerException if the specified element is null
377		*/
378		public boolean add(E e) {
#	Line 385 | Line 386 | public class ArrayDeque<E> extends Abstr
386		* <p>This method is equivalent to {@link #offerLast}.
387		*
388		* @param e the element to add
389	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
389	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
390		* @throws NullPointerException if the specified element is null
391		*/
392		public boolean offer(E e) {
#	Line 394 | Line 395 | public class ArrayDeque<E> extends Abstr
395
396		/**
397		* Retrieves and removes the head of the queue represented by this deque.
398	<	* This method differs from {@link #poll} only in that it throws an
398	>	*
399	>	* This method differs from {@link #poll poll} only in that it throws an
400		* exception if this deque is empty.
401		*
402		* <p>This method is equivalent to {@link #removeFirst}.
#	Line 422 | Line 424 | public class ArrayDeque<E> extends Abstr
424
425		/**
426		* Retrieves, but does not remove, the head of the queue represented by
427	<	* this deque.  This method differs from {@link #peek} only in that it
428	<	* throws an exception if this deque is empty.
427	>	* this deque.  This method differs from {@link #peek peek} only in
428	>	* that it throws an exception if this deque is empty.
429		*
430		* <p>This method is equivalent to {@link #getFirst}.
431		*
#	Line 476 | Line 478 | public class ArrayDeque<E> extends Abstr
478		return removeFirst();
479		}
480
481	+	private void checkInvariants() {
482	+	assert elements[tail] == null;
483	+	assert head == tail ? elements[head] == null :
484	+	(elements[head] != null &&
485	+	elements[(tail - 1) & (elements.length - 1)] != null);
486	+	assert elements[(head - 1) & (elements.length - 1)] == null;
487	+	}
488	+
489		/**
490		* Removes the element at the specified position in the elements array,
491		* adjusting head and tail as necessary.  This can result in motion of
#	Line 487 | Line 497 | public class ArrayDeque<E> extends Abstr
497		* @return true if elements moved backwards
498		*/
499		private boolean delete(int i) {
500	<	int mask = elements.length - 1;
501	<
502	<	// Invariant: head <= i < tail mod circularity
503	<	if (((i - head) & mask) >= ((tail - head) & mask))
504	<	throw new ConcurrentModificationException();
505	<
506	<	// Case 1: Deque doesn't wrap
507	<	// Case 2: Deque does wrap and removed element is in the head portion
508	<	if (i >= head) {
509	<	System.arraycopy(elements, head, elements, head + 1, i - head);
510	<	elements[head] = null;
511	<	head = (head + 1) & mask;
500	>	checkInvariants();
501	>	final E[] elements = this.elements;
502	>	final int mask = elements.length - 1;
503	>	final int h = head;
504	>	final int t = tail;
505	>	final int front = (i - h) & mask;
506	>	final int back  = (t - i) & mask;
507	>
508	>	// Invariant: head <= i < tail mod circularity
509	>	if (front >= ((t - h) & mask))
510	>	throw new ConcurrentModificationException();
511	>
512	>	// Optimize for least element motion
513	>	if (front < back) {
514	>	if (h <= i) {
515	>	System.arraycopy(elements, h, elements, h + 1, front);
516	>	} else { // Wrap around
517	>	System.arraycopy(elements, 0, elements, 1, i);
518	>	elements[0] = elements[mask];
519	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
520	>	}
521	>	elements[h] = null;
522	>	head = (h + 1) & mask;
523		return false;
524	+	} else {
525	+	if (i < t) { // Copy the null tail as well
526	+	System.arraycopy(elements, i + 1, elements, i, back);
527	+	tail = t - 1;
528	+	} else { // Wrap around
529	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
530	+	elements[mask] = elements[0];
531	+	System.arraycopy(elements, 1, elements, 0, t);
532	+	tail = (t - 1) & mask;
533	+	}
534	+	return true;
535		}
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;
536		}
537
538		// *** Collection Methods ***
#	Line 535 | Line 561 | public class ArrayDeque<E> extends Abstr
561		* order that elements would be dequeued (via successive calls to
562		* {@link #remove} or popped (via successive calls to {@link #pop}).
563		*
564	<	* @return an <tt>Iterator</tt> over the elements in this deque
564	>	* @return an iterator over the elements in this deque
565		*/
566		public Iterator<E> iterator() {
567		return new DeqIterator();
568		}
569
570	+	public Iterator<E> descendingIterator() {
571	+	return new DescendingIterator();
572	+	}
573	+
574		private class DeqIterator implements Iterator<E> {
575		/**
576		* Index of element to be returned by subsequent call to next.
#	Line 564 | Line 594 | public class ArrayDeque<E> extends Abstr
594		}
595
596		public E next() {
567	–	E result;
597		if (cursor == fence)
598		throw new NoSuchElementException();
599	+	E result = elements[cursor];
600		// This check doesn't catch all possible comodifications,
601		// but does catch the ones that corrupt traversal
602	<	if (tail != fence || (result = elements[cursor]) == null)
602	>	if (tail != fence || result == null)
603		throw new ConcurrentModificationException();
604		lastRet = cursor;
605		cursor = (cursor + 1) & (elements.length - 1);
#	Line 579 | Line 609 | public class ArrayDeque<E> extends Abstr
609		public void remove() {
610		if (lastRet < 0)
611		throw new IllegalStateException();
612	<	if (delete(lastRet))
613	<	cursor--;
612	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
613	>	cursor = (cursor - 1) & (elements.length - 1);
614	>	fence = tail;
615	>	}
616	>	lastRet = -1;
617	>	}
618	>	}
619	>
620	>	private class DescendingIterator implements Iterator<E> {
621	>	/*
622	>	* This class is nearly a mirror-image of DeqIterator, using
623	>	* tail instead of head for initial cursor, and head instead of
624	>	* tail for fence.
625	>	*/
626	>	private int cursor = tail;
627	>	private int fence = head;
628	>	private int lastRet = -1;
629	>
630	>	public boolean hasNext() {
631	>	return cursor != fence;
632	>	}
633	>
634	>	public E next() {
635	>	if (cursor == fence)
636	>	throw new NoSuchElementException();
637	>	cursor = (cursor - 1) & (elements.length - 1);
638	>	E result = elements[cursor];
639	>	if (head != fence || result == null)
640	>	throw new ConcurrentModificationException();
641	>	lastRet = cursor;
642	>	return result;
643	>	}
644	>
645	>	public void remove() {
646	>	if (lastRet < 0)
647	>	throw new IllegalStateException();
648	>	if (!delete(lastRet)) {
649	>	cursor = (cursor + 1) & (elements.length - 1);
650	>	fence = head;
651	>	}
652		lastRet = -1;
585	–	fence = tail;
653		}
654		}
655
#	Line 613 | Line 680 | public class ArrayDeque<E> extends Abstr
680		* If the deque does not contain the element, it is unchanged.
681		* More formally, removes the first element <tt>e</tt> such that
682		* <tt>o.equals(e)</tt> (if such an element exists).
683	<	* Returns true if this deque contained the specified element (or
684	<	* equivalently, if this deque changed as a result of the call).
683	>	* Returns <tt>true</tt> if this deque contained the specified element
684	>	* (or equivalently, if this deque changed as a result of the call).
685		*
686		* <p>This method is equivalent to {@link #removeFirstOccurrence}.
687		*
#	Line 645 | Line 712 | public class ArrayDeque<E> extends Abstr
712
713		/**
714		* Returns an array containing all of the elements in this deque
715	<	* in the correct order.
715	>	* in proper sequence (from first to last element).
716	>	*
717	>	* <p>The returned array will be "safe" in that no references to it are
718	>	* maintained by this deque.  (In other words, this method must allocate
719	>	* a new array).  The caller is thus free to modify the returned array.
720	>	*
721	>	* <p>This method acts as bridge between array-based and collection-based
722	>	* APIs.
723		*
724		* @return an array containing all of the elements in this deque
651	–	*         in the correct order
725		*/
726		public Object[] toArray() {
727	<	return copyElements(new Object[size()]);
727	>	return copyElements(new Object[size()]);
728		}
729
730		/**
731	<	* Returns an array containing all of the elements in this deque in the
732	<	* correct order; the runtime type of the returned array is that of the
733	<	* specified array.  If the deque fits in the specified array, it is
734	<	* returned therein.  Otherwise, a new array is allocated with the runtime
735	<	* type of the specified array and the size of this deque.
731	>	* Returns an array containing all of the elements in this deque in
732	>	* proper sequence (from first to last element); the runtime type of the
733	>	* returned array is that of the specified array.  If the deque fits in
734	>	* the specified array, it is returned therein.  Otherwise, a new array
735	>	* is allocated with the runtime type of the specified array and the
736	>	* size of this deque.
737	>	*
738	>	* <p>If this deque fits in the specified array with room to spare
739	>	* (i.e., the array has more elements than this deque), the element in
740	>	* the array immediately following the end of the deque is set to
741	>	* <tt>null</tt>.
742	>	*
743	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
744	>	* array-based and collection-based APIs.  Further, this method allows
745	>	* precise control over the runtime type of the output array, and may,
746	>	* under certain circumstances, be used to save allocation costs.
747		*
748	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
749	<	* the array has more elements than the deque), the element in the array
750	<	* immediately following the end of the collection is set to <tt>null</tt>.
748	>	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
749	>	* The following code can be used to dump the deque into a newly
750	>	* allocated array of <tt>String</tt>:
751	>	*
752	>	* <pre>
753	>	*     String[] y = x.toArray(new String[0]);</pre>
754	>	*
755	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
756	>	* <tt>toArray()</tt>.
757		*
758		* @param a the array into which the elements of the deque are to
759		*          be stored, if it is big enough; otherwise, a new array of the
760		*          same runtime type is allocated for this purpose
761	<	* @return an array containing the elements of the deque
762	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
763	<	*         of the runtime type of every element in this deque
761	>	* @return an array containing all of the elements in this deque
762	>	* @throws ArrayStoreException if the runtime type of the specified array
763	>	*         is not a supertype of the runtime type of every element in
764	>	*         this deque
765	>	* @throws NullPointerException if the specified array is null
766		*/
767		public <T> T[] toArray(T[] a) {
768		int size = size();
769		if (a.length < size)
770		a = (T[])java.lang.reflect.Array.newInstance(
771		a.getClass().getComponentType(), size);
772	<	copyElements(a);
772	>	copyElements(a);
773		if (a.length > size)
774		a[size] = null;
775		return a;
#	Line 693 | Line 785 | public class ArrayDeque<E> extends Abstr
785		public ArrayDeque<E> clone() {
786		try {
787		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
788	<	// These two lines are currently faster than cloning the array:
697	<	result.elements = (E[]) new Object[elements.length];
698	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
788	>	result.elements = Arrays.copyOf(elements, elements.length);
789		return result;
790
791		} catch (CloneNotSupportedException e) {
#	Line 719 | Line 809 | public class ArrayDeque<E> extends Abstr
809		s.defaultWriteObject();
810
811		// Write out size
812	<	int size = size();
723	<	s.writeInt(size);
812	>	s.writeInt(size());
813
814		// Write out elements in order.
726	–	int i = head;
815		int mask = elements.length - 1;
816	<	for (int j = 0; j < size; j++) {
816	>	for (int i = head; i != tail; i = (i + 1) & mask)
817		s.writeObject(elements[i]);
730	–	i = (i + 1) & mask;
731	–	}
818		}
819
820		/**
#	Line 747 | Line 833 | public class ArrayDeque<E> extends Abstr
833		// Read in all elements in the proper order.
834		for (int i = 0; i < size; i++)
835		elements[i] = (E)s.readObject();
750	–
836		}
837		}

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