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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.6 by dl, Tue Mar 22 16:48:32 2005 UTC vs.
Revision 1.12 by jsr166, Tue May 17 16:14:34 2005 UTC

#	Line 18 | Line 18 | import java.io.*;
18		* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
19		* Exceptions include {@link #remove(Object) remove}, {@link
20		* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
21	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
21	>	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
22		* iterator.remove()}, and the bulk operations, all of which run in linear
23		* time.
24		*
25		* <p>The iterators returned by this class's <tt>iterator</tt> method are
26		* <i>fail-fast</i>: If the deque is modified at any time after the iterator
27	<	* is created, in any way except through the iterator's own remove method, the
28	<	* iterator will generally throw a {@link ConcurrentModificationException}.
29	<	* Thus, in the face of concurrent modification, the iterator fails quickly
30	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
31	<	* an undetermined time in the future.
27	>	* is created, in any way except through the iterator's own <tt>remove</tt>
28	>	* method, the iterator will generally throw a {@link
29	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
30	>	* modification, the iterator fails quickly and cleanly, rather than risking
31	>	* arbitrary, non-deterministic behavior at an undetermined time in the
32	>	* future.
33		*
34		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
35		* as it is, generally speaking, impossible to make any hard guarantees in the
#	Line 39 | Line 40 | import java.io.*;
40		* should be used only to detect bugs.</i>
41		*
42		* <p>This class and its iterator implement all of the
43	<	* optional methods of the {@link Collection} and {@link
44	<	* Iterator} interfaces.  This class is a member of the <a
45	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
46	<	* Framework</a>.
43	>	* <em>optional</em> methods of the {@link Collection} and {@link
44	>	* Iterator} interfaces.
45	>	*
46	>	* <p>This class is a member of the
47	>	* <a href="{@docRoot}/../guide/collections/index.html">
48	>	* Java Collections Framework</a>.
49		*
50		* @author  Josh Bloch and Doug Lea
51		* @since   1.6
#	Line 87 | Line 90 | public class ArrayDeque<E> extends Abstr
90		/**
91		* Allocate empty array to hold the given number of elements.
92		*
93	<	* @param numElements  the number of elements to hold.
93	>	* @param numElements  the number of elements to hold
94		*/
95		private void allocateElements(int numElements) {
96		int initialCapacity = MIN_INITIAL_CAPACITY;
#	Line 129 | Line 132 | public class ArrayDeque<E> extends Abstr
132		}
133
134		/**
135	<	* Copy the elements from our element array into the specified array,
135	>	* Copies the elements from our element array into the specified array,
136		* in order (from first to last element in the deque).  It is assumed
137		* that the array is large enough to hold all elements in the deque.
138		*
#	Line 186 | Line 189 | public class ArrayDeque<E> extends Abstr
189		/**
190		* Inserts the specified element at the front of this deque.
191		*
192	<	* @param e the element to insert
193	<	* @throws NullPointerException if <tt>e</tt> is null
192	>	* @param e the element to add
193	>	* @throws NullPointerException if the specified element is null
194		*/
195		public void addFirst(E e) {
196		if (e == null)
#	Line 199 | 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 Collection#add} and
203	<	* {@link #push}.
205	>	* This method is equivalent to {@link #add} and {@link #push}.
206		*
207	<	* @param e the element to insert
208	<	* @throws NullPointerException if <tt>e</tt> is null
207	>	* @param e the element to add
208	>	* @throws NullPointerException if the specified element is null
209		*/
210		public void addLast(E e) {
211		if (e == null)
#	Line 214 | Line 216 | public class ArrayDeque<E> extends Abstr
216		}
217
218		/**
217	–	* Retrieves and removes the first element of this deque, or
218	–	* <tt>null</tt> if this deque is empty.
219	–	*
220	–	* @return the first element of this deque, or <tt>null</tt> if
221	–	*     this deque is empty
222	–	*/
223	–	public E pollFirst() {
224	–	int h = head;
225	–	E result = elements[h]; // Element is null if deque empty
226	–	if (result == null)
227	–	return null;
228	–	elements[h] = null;     // Must null out slot
229	–	head = (h + 1) & (elements.length - 1);
230	–	return result;
231	–	}
232	–
233	–	/**
234	–	* Retrieves and removes the last element of this deque, or
235	–	* <tt>null</tt> if this deque is empty.
236	–	*
237	–	* @return the last element of this deque, or <tt>null</tt> if
238	–	*     this deque is empty
239	–	*/
240	–	public E pollLast() {
241	–	int t = (tail - 1) & (elements.length - 1);
242	–	E result = elements[t];
243	–	if (result == null)
244	–	return null;
245	–	elements[t] = null;
246	–	tail = t;
247	–	return result;
248	–	}
249	–
250	–	/**
219		* Inserts the specified element at the front of this deque.
220		*
221	<	* @param e the element to insert
221	>	* @param e the element to add
222		* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
223	<	* @throws NullPointerException if <tt>e</tt> is null
223	>	* @throws NullPointerException if the specified element is null
224		*/
225		public boolean offerFirst(E e) {
226		addFirst(e);
#	Line 262 | Line 230 | public class ArrayDeque<E> extends Abstr
230		/**
231		* Inserts the specified element at the end of this deque.
232		*
233	<	* @param e the element to insert
233	>	* @param e the element to add
234		* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
235	<	* @throws NullPointerException if <tt>e</tt> is null
235	>	* @throws NullPointerException if the specified element is null
236		*/
237		public boolean offerLast(E e) {
238		addLast(e);
#	Line 272 | Line 240 | public class ArrayDeque<E> extends Abstr
240		}
241
242		/**
243	<	* Retrieves and removes the first element of this deque.  This method
276	<	* differs from the <tt>pollFirst</tt> method in that it throws an
277	<	* exception if this deque is empty.
278	<	*
279	<	* @return the first element of this deque
280	<	* @throws NoSuchElementException if this deque is empty
243	>	* @throws NoSuchElementException {@inheritDoc}
244		*/
245		public E removeFirst() {
246		E x = pollFirst();
#	Line 287 | Line 250 | public class ArrayDeque<E> extends Abstr
250		}
251
252		/**
253	<	* Retrieves and removes the last element of this deque.  This method
291	<	* differs from the <tt>pollLast</tt> method in that it throws an
292	<	* exception if this deque is empty.
293	<	*
294	<	* @return the last element of this deque
295	<	* @throws NoSuchElementException if this deque is empty
253	>	* @throws NoSuchElementException {@inheritDoc}
254		*/
255		public E removeLast() {
256		E x = pollLast();
#	Line 301 | Line 259 | public class ArrayDeque<E> extends Abstr
259		return x;
260		}
261
262	<	/**
263	<	* Retrieves, but does not remove, the first element of this deque,
264	<	* returning <tt>null</tt> if this deque is empty.
265	<	*
266	<	* @return the first element of this deque, or <tt>null</tt> if
267	<	*     this deque is empty
268	<	*/
269	<	public E peekFirst() {
312	<	return elements[head]; // elements[head] is null if deque empty
262	>	public E pollFirst() {
263	>	int h = head;
264	>	E result = elements[h]; // Element is null if deque empty
265	>	if (result == null)
266	>	return null;
267	>	elements[h] = null;     // Must null out slot
268	>	head = (h + 1) & (elements.length - 1);
269	>	return result;
270		}
271
272	<	/**
273	<	* Retrieves, but does not remove, the last element of this deque,
274	<	* returning <tt>null</tt> if this deque is empty.
275	<	*
276	<	* @return the last element of this deque, or <tt>null</tt> if this deque
277	<	*     is empty
278	<	*/
279	<	public E peekLast() {
323	<	return elements[(tail - 1) & (elements.length - 1)];
272	>	public E pollLast() {
273	>	int t = (tail - 1) & (elements.length - 1);
274	>	E result = elements[t];
275	>	if (result == null)
276	>	return null;
277	>	elements[t] = null;
278	>	tail = t;
279	>	return result;
280		}
281
282		/**
283	<	* Retrieves, but does not remove, the first element of this
328	<	* deque.  This method differs from the <tt>peekFirst</tt> method only
329	<	* in that it throws an exception if this deque is empty.
330	<	*
331	<	* @return the first element of this deque
332	<	* @throws NoSuchElementException if this deque is empty
283	>	* @throws NoSuchElementException {@inheritDoc}
284		*/
285		public E getFirst() {
286		E x = elements[head];
#	Line 339 | Line 290 | public class ArrayDeque<E> extends Abstr
290		}
291
292		/**
293	<	* Retrieves, but does not remove, the last element of this
343	<	* deque.  This method differs from the <tt>peekLast</tt> method only
344	<	* in that it throws an exception if this deque is empty.
345	<	*
346	<	* @return the last element of this deque
347	<	* @throws NoSuchElementException if this deque is empty
293	>	* @throws NoSuchElementException {@inheritDoc}
294		*/
295		public E getLast() {
296		E x = elements[(tail - 1) & (elements.length - 1)];
#	Line 353 | Line 299 | public class ArrayDeque<E> extends Abstr
299		return x;
300		}
301
302	+	public E peekFirst() {
303	+	return elements[head]; // elements[head] is null if deque empty
304	+	}
305	+
306	+	public E peekLast() {
307	+	return elements[(tail - 1) & (elements.length - 1)];
308	+	}
309	+
310		/**
311		* Removes the first occurrence of the specified element in this
312	<	* deque (when traversing the deque from head to tail).  More
313	<	* formally, removes the first element e such that (o==null ?
314	<	* e==null : o.equals(e)). If the deque does not contain the
315	<	* element, it is unchanged.
312	>	* deque (when traversing the deque from head to tail).
313	>	* If the deque does not contain the element, it is unchanged.
314	>	* More formally, removes the first element <tt>e</tt> such that
315	>	* <tt>o.equals(e)</tt> (if such an element exists).
316	>	* Returns <tt>true</tt> if this deque contained the specified element
317	>	* (or equivalently, if this deque changed as a result of the call).
318		*
319		* @param o element to be removed from this deque, if present
320		* @return <tt>true</tt> if the deque contained the specified element
#	Line 381 | Line 337 | public class ArrayDeque<E> extends Abstr
337
338		/**
339		* Removes the last occurrence of the specified element in this
340	<	* deque (when traversing the deque from head to tail). More
341	<	* formally, removes the last element e such that (o==null ?
342	<	* e==null : o.equals(e)). If the deque
343	<	* does not contain the element, it is unchanged.
340	>	* deque (when traversing the deque from head to tail).
341	>	* If the deque does not contain the element, it is unchanged.
342	>	* More formally, removes the last element <tt>e</tt> such that
343	>	* <tt>o.equals(e)</tt> (if such an element exists).
344	>	* Returns <tt>true</tt> if this deque contained the specified element
345	>	* (or equivalently, if this deque changed as a result of the call).
346		*
347		* @param o element to be removed from this deque, if present
348		* @return <tt>true</tt> if the deque contained the specified element
#	Line 410 | Line 368 | public class ArrayDeque<E> extends Abstr
368		/**
369		* Inserts the specified element at the end of this deque.
370		*
413	–	* <p>This method is equivalent to {@link #offerLast}.
414	–	*
415	–	* @param e the element to insert
416	–	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
417	–	* @throws NullPointerException if <tt>e</tt> is null
418	–	*/
419	–	public boolean offer(E e) {
420	–	return offerLast(e);
421	–	}
422	–
423	–	/**
424	–	* Inserts the specified element at the end of this deque.
425	–	*
371		* <p>This method is equivalent to {@link #addLast}.
372		*
373	<	* @param e the element to insert
373	>	* @param e the element to add
374		* @return <tt>true</tt> (as per the spec for {@link Collection#add})
375	<	* @throws NullPointerException if <tt>e</tt> is null
375	>	* @throws NullPointerException if the specified element is null
376		*/
377		public boolean add(E e) {
378		addLast(e);
#	Line 435 | Line 380 | public class ArrayDeque<E> extends Abstr
380		}
381
382		/**
383	<	* Retrieves and removes the head of the queue represented by
439	<	* this deque, or <tt>null</tt> if this deque is empty.  In other words,
440	<	* retrieves and removes the first element of this deque, or <tt>null</tt>
441	<	* if this deque is empty.
383	>	* Inserts the specified element at the end of this deque.
384		*
385	<	* <p>This method is equivalent to {@link #pollFirst}.
385	>	* <p>This method is equivalent to {@link #offerLast}.
386		*
387	<	* @return the first element of this deque, or <tt>null</tt> if
388	<	*     this deque is empty
387	>	* @param e the element to add
388	>	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
389	>	* @throws NullPointerException if the specified element is null
390		*/
391	<	public E poll() {
392	<	return pollFirst();
391	>	public boolean offer(E e) {
392	>	return offerLast(e);
393		}
394
395		/**
396		* Retrieves and removes the head of the queue represented by this deque.
397	<	* This method differs from the <tt>poll</tt> method in that it throws an
397	>	* This method differs from {@link #poll} only in that it throws an
398		* exception if this deque is empty.
399		*
400		* <p>This method is equivalent to {@link #removeFirst}.
401		*
402		* @return the head of the queue represented by this deque
403	<	* @throws NoSuchElementException if this deque is empty
403	>	* @throws NoSuchElementException {@inheritDoc}
404		*/
405		public E remove() {
406		return removeFirst();
407		}
408
409		/**
410	<	* Retrieves, but does not remove, the head of the queue represented by
411	<	* this deque, returning <tt>null</tt> if this deque is empty.
410	>	* Retrieves and removes the head of the queue represented by this deque
411	>	* (in other words, the first element of this deque), or returns
412	>	* <tt>null</tt> if this deque is empty.
413		*
414	<	* <p>This method is equivalent to {@link #peekFirst}
414	>	* <p>This method is equivalent to {@link #pollFirst}.
415		*
416		* @return the head of the queue represented by this deque, or
417	<	*     <tt>null</tt> if this deque is empty
417	>	*         <tt>null</tt> if this deque is empty
418		*/
419	<	public E peek() {
420	<	return peekFirst();
419	>	public E poll() {
420	>	return pollFirst();
421		}
422
423		/**
424		* Retrieves, but does not remove, the head of the queue represented by
425	<	* this deque.  This method differs from the <tt>peek</tt> method only in
426	<	* that it throws an exception if this deque is empty.
425	>	* this deque.  This method differs from {@link #peek} only in that it
426	>	* throws an exception if this deque is empty.
427		*
428	<	* <p>This method is equivalent to {@link #getFirst}
428	>	* <p>This method is equivalent to {@link #getFirst}.
429		*
430		* @return the head of the queue represented by this deque
431	<	* @throws NoSuchElementException if this deque is empty
431	>	* @throws NoSuchElementException {@inheritDoc}
432		*/
433		public E element() {
434		return getFirst();
435		}
436
437	+	/**
438	+	* Retrieves, but does not remove, the head of the queue represented by
439	+	* this deque, or returns <tt>null</tt> if this deque is empty.
440	+	*
441	+	* <p>This method is equivalent to {@link #peekFirst}.
442	+	*
443	+	* @return the head of the queue represented by this deque, or
444	+	*         <tt>null</tt> if this deque is empty
445	+	*/
446	+	public E peek() {
447	+	return peekFirst();
448	+	}
449	+
450		// *** Stack methods ***
451
452		/**
#	Line 499 | Line 456 | public class ArrayDeque<E> extends Abstr
456		* <p>This method is equivalent to {@link #addFirst}.
457		*
458		* @param e the element to push
459	<	* @throws NullPointerException if <tt>e</tt> is null
459	>	* @throws NullPointerException if the specified element is null
460		*/
461		public void push(E e) {
462		addFirst(e);
#	Line 512 | Line 469 | public class ArrayDeque<E> extends Abstr
469		* <p>This method is equivalent to {@link #removeFirst()}.
470		*
471		* @return the element at the front of this deque (which is the top
472	<	*     of the stack represented by this deque)
473	<	* @throws NoSuchElementException if this deque is empty
472	>	*         of the stack represented by this deque)
473	>	* @throws NoSuchElementException {@inheritDoc}
474		*/
475		public E pop() {
476		return removeFirst();
477		}
478
479		/**
480	<	* Remove the element at the specified position in the elements array,
481	<	* adjusting head, tail, and size as necessary.  This can result in
482	<	* motion of elements backwards or forwards in the array.
480	>	* Removes the element at the specified position in the elements array,
481	>	* adjusting head and tail as necessary.  This can result in motion of
482	>	* elements backwards or forwards in the array.
483		*
484		* <p>This method is called delete rather than remove to emphasize
485	<	* that its semantics differ from those of List.remove(int).
485	>	* that its semantics differ from those of {@link List#remove(int)}.
486		*
487		* @return true if elements moved backwards
488		*/
489		private boolean delete(int i) {
490	+	int mask = elements.length - 1;
491	+
492	+	// Invariant: head <= i < tail mod circularity
493	+	if (((i - head) & mask) >= ((tail - head) & mask))
494	+	throw new ConcurrentModificationException();
495	+
496		// Case 1: Deque doesn't wrap
497		// Case 2: Deque does wrap and removed element is in the head portion
498	<	if ((head < tail || tail == 0) || i >= head) {
498	>	if (i >= head) {
499		System.arraycopy(elements, head, elements, head + 1, i - head);
500		elements[head] = null;
501	<	head = (head + 1) & (elements.length - 1);
501	>	head = (head + 1) & mask;
502		return false;
503		}
504
#	Line 558 | Line 521 | public class ArrayDeque<E> extends Abstr
521		}
522
523		/**
524	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
524	>	* Returns <tt>true</tt> if this deque contains no elements.
525		*
526	<	* @return <tt>true</tt> if this collection contains no elements.
526	>	* @return <tt>true</tt> if this deque contains no elements
527		*/
528		public boolean isEmpty() {
529		return head == tail;
#	Line 624 | Line 587 | public class ArrayDeque<E> extends Abstr
587		}
588
589		/**
590	<	* Returns <tt>true</tt> if this deque contains the specified
591	<	* element.  More formally, returns <tt>true</tt> if and only if this
592	<	* deque contains at least one element <tt>e</tt> such that
630	<	* <tt>e.equals(o)</tt>.
590	>	* Returns <tt>true</tt> if this deque contains the specified element.
591	>	* More formally, returns <tt>true</tt> if and only if this deque contains
592	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
593		*
594		* @param o object to be checked for containment in this deque
595		* @return <tt>true</tt> if this deque contains the specified element
#	Line 648 | Line 610 | public class ArrayDeque<E> extends Abstr
610
611		/**
612		* Removes a single instance of the specified element from this deque.
613	<	* This method is equivalent to {@link #removeFirstOccurrence}.
613	>	* If the deque does not contain the element, it is unchanged.
614	>	* More formally, removes the first element <tt>e</tt> such that
615	>	* <tt>o.equals(e)</tt> (if such an element exists).
616	>	* Returns <tt>true</tt> if this deque contained the specified element
617	>	* (or equivalently, if this deque changed as a result of the call).
618	>	*
619	>	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
620		*
621	<	* @param e element to be removed from this deque, if present
621	>	* @param o element to be removed from this deque, if present
622		* @return <tt>true</tt> if this deque contained the specified element
623		*/
624	<	public boolean remove(Object e) {
625	<	return removeFirstOccurrence(e);
624	>	public boolean remove(Object o) {
625	>	return removeFirstOccurrence(o);
626		}
627
628		/**
629		* Removes all of the elements from this deque.
630	+	* The deque will be empty after this call returns.
631		*/
632		public void clear() {
633		int h = head;
#	Line 670 | Line 639 | public class ArrayDeque<E> extends Abstr
639		do {
640		elements[i] = null;
641		i = (i + 1) & mask;
642	<	} while(i != t);
642	>	} while (i != t);
643		}
644		}
645
646		/**
647		* Returns an array containing all of the elements in this deque
648	<	* in the correct order.
648	>	* in proper sequence (from first to last element).
649	>	*
650	>	* <p>The returned array will be "safe" in that no references to it are
651	>	* maintained by this deque.  (In other words, this method must allocate
652	>	* a new array).  The caller is thus free to modify the returned array.
653	>	*
654	>	* <p>This method acts as bridge between array-based and collection-based
655	>	* APIs.
656		*
657		* @return an array containing all of the elements in this deque
682	–	*         in the correct order
658		*/
659		public Object[] toArray() {
660		return copyElements(new Object[size()]);
661		}
662
663		/**
664	<	* Returns an array containing all of the elements in this deque in the
665	<	* correct order; the runtime type of the returned array is that of the
666	<	* specified array.  If the deque fits in the specified array, it is
667	<	* returned therein.  Otherwise, a new array is allocated with the runtime
668	<	* type of the specified array and the size of this deque.
669	<	*
670	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
671	<	* the array has more elements than the deque), the element in the array
672	<	* immediately following the end of the collection is set to <tt>null</tt>.
664	>	* Returns an array containing all of the elements in this deque in
665	>	* proper sequence (from first to last element); the runtime type of the
666	>	* returned array is that of the specified array.  If the deque fits in
667	>	* the specified array, it is returned therein.  Otherwise, a new array
668	>	* is allocated with the runtime type of the specified array and the
669	>	* size of this deque.
670	>	*
671	>	* <p>If this deque fits in the specified array with room to spare
672	>	* (i.e., the array has more elements than this deque), the element in
673	>	* the array immediately following the end of the deque is set to
674	>	* <tt>null</tt>.
675	>	*
676	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
677	>	* array-based and collection-based APIs.  Further, this method allows
678	>	* precise control over the runtime type of the output array, and may,
679	>	* under certain circumstances, be used to save allocation costs.
680	>	*
681	>	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
682	>	* The following code can be used to dump the deque into a newly
683	>	* allocated array of <tt>String</tt>:
684	>	*
685	>	* <pre>
686	>	*     String[] y = x.toArray(new String[0]);</pre>
687	>	*
688	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
689	>	* <tt>toArray()</tt>.
690		*
691		* @param a the array into which the elements of the deque are to
692	<	*          be stored, if it is big enough; otherwise, a new array of the
693	<	*          same runtime type is allocated for this purpose
694	<	* @return an array containing the elements of the deque
695	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
696	<	*         of the runtime type of every element in this deque
692	>	*          be stored, if it is big enough; otherwise, a new array of the
693	>	*          same runtime type is allocated for this purpose
694	>	* @return an array containing all of the elements in this deque
695	>	* @throws ArrayStoreException if the runtime type of the specified array
696	>	*         is not a supertype of the runtime type of every element in
697	>	*         this deque
698	>	* @throws NullPointerException if the specified array is null
699		*/
700		public <T> T[] toArray(T[] a) {
701		int size = size();

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