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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 1.14 by jsr166, Sat Jun 18 01:56:01 2005 UTC

#	Line 4 | Line 4
4		*/
5
6		package java.util;
7	+	import java.util.*; // for javadoc
8		import java.io.*;
9
10		/**
#	Line 18 | Line 19 | import java.io.*;
19		* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
20		* Exceptions include {@link #remove(Object) remove}, {@link
21		* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
22	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
22	>	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
23		* iterator.remove()}, and the bulk operations, all of which run in linear
24		* time.
25		*
26		* <p>The iterators returned by this class's <tt>iterator</tt> method are
27		* <i>fail-fast</i>: If the deque is modified at any time after the iterator
28	<	* is created, in any way except through the iterator's own remove method, the
29	<	* iterator will generally throw a {@link ConcurrentModificationException}.
30	<	* Thus, in the face of concurrent modification, the iterator fails quickly
31	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
32	<	* an undetermined time in the future.
28	>	* is created, in any way except through the iterator's own <tt>remove</tt>
29	>	* method, the iterator will generally throw a {@link
30	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
31	>	* modification, the iterator fails quickly and cleanly, rather than risking
32	>	* arbitrary, non-deterministic behavior at an undetermined time in the
33	>	* future.
34		*
35		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
36		* as it is, generally speaking, impossible to make any hard guarantees in the
#	Line 39 | Line 41 | import java.io.*;
41		* should be used only to detect bugs.</i>
42		*
43		* <p>This class and its iterator implement all of the
44	<	* optional methods of the {@link Collection} and {@link
45	<	* Iterator} interfaces.  This class is a member of the <a
46	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
47	<	* Framework</a>.
44	>	* <em>optional</em> methods of the {@link Collection} and {@link
45	>	* Iterator} interfaces.
46	>	*
47	>	* <p>This class is a member of the
48	>	* <a href="{@docRoot}/../guide/collections/index.html">
49	>	* Java Collections Framework</a>.
50		*
51		* @author  Josh Bloch and Doug Lea
52		* @since   1.6
#	Line 87 | Line 91 | public class ArrayDeque<E> extends Abstr
91		/**
92		* Allocate empty array to hold the given number of elements.
93		*
94	<	* @param numElements  the number of elements to hold.
94	>	* @param numElements  the number of elements to hold
95		*/
96		private void allocateElements(int numElements) {
97		int initialCapacity = MIN_INITIAL_CAPACITY;
#	Line 129 | Line 133 | public class ArrayDeque<E> extends Abstr
133		}
134
135		/**
136	<	* Copy the elements from our element array into the specified array,
136	>	* Copies the elements from our element array into the specified array,
137		* in order (from first to last element in the deque).  It is assumed
138		* that the array is large enough to hold all elements in the deque.
139		*
#	Line 186 | Line 190 | public class ArrayDeque<E> extends Abstr
190		/**
191		* Inserts the specified element at the front of this deque.
192		*
193	<	* @param e the element to insert
194	<	* @throws NullPointerException if <tt>e</tt> is null
193	>	* @param e the element to add
194	>	* @throws NullPointerException if the specified element is null
195		*/
196		public void addFirst(E e) {
197		if (e == null)
#	Line 199 | Line 203 | public class ArrayDeque<E> extends Abstr
203
204		/**
205		* Inserts the specified element at the end of this deque.
202	–	* This method is equivalent to {@link Collection#add} and
203	–	* {@link #push}.
206		*
207	<	* @param e the element to insert
208	<	* @throws NullPointerException if <tt>e</tt> is null
207	>	* <p>This method is equivalent to {@link #add}.
208	>	*
209	>	* @param e the element to add
210	>	* @throws NullPointerException if the specified element is null
211		*/
212		public void addLast(E e) {
213		if (e == null)
#	Line 214 | Line 218 | public class ArrayDeque<E> extends Abstr
218		}
219
220		/**
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	–	/**
221		* Inserts the specified element at the front of this deque.
222		*
223	<	* @param e the element to insert
223	>	* @param e the element to add
224		* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
225	<	* @throws NullPointerException if <tt>e</tt> is null
225	>	* @throws NullPointerException if the specified element is null
226		*/
227		public boolean offerFirst(E e) {
228		addFirst(e);
#	Line 262 | Line 232 | public class ArrayDeque<E> extends Abstr
232		/**
233		* Inserts the specified element at the end of this deque.
234		*
235	<	* @param e the element to insert
235	>	* @param e the element to add
236		* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
237	<	* @throws NullPointerException if <tt>e</tt> is null
237	>	* @throws NullPointerException if the specified element is null
238		*/
239		public boolean offerLast(E e) {
240		addLast(e);
#	Line 272 | Line 242 | public class ArrayDeque<E> extends Abstr
242		}
243
244		/**
245	<	* 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
245	>	* @throws NoSuchElementException {@inheritDoc}
246		*/
247		public E removeFirst() {
248		E x = pollFirst();
#	Line 287 | Line 252 | public class ArrayDeque<E> extends Abstr
252		}
253
254		/**
255	<	* 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
255	>	* @throws NoSuchElementException {@inheritDoc}
256		*/
257		public E removeLast() {
258		E x = pollLast();
#	Line 301 | Line 261 | public class ArrayDeque<E> extends Abstr
261		return x;
262		}
263
264	<	/**
265	<	* Retrieves, but does not remove, the first element of this deque,
266	<	* returning <tt>null</tt> if this deque is empty.
267	<	*
268	<	* @return the first element of this deque, or <tt>null</tt> if
269	<	*     this deque is empty
270	<	*/
271	<	public E peekFirst() {
312	<	return elements[head]; // elements[head] is null if deque empty
264	>	public E pollFirst() {
265	>	int h = head;
266	>	E result = elements[h]; // Element is null if deque empty
267	>	if (result == null)
268	>	return null;
269	>	elements[h] = null;     // Must null out slot
270	>	head = (h + 1) & (elements.length - 1);
271	>	return result;
272		}
273
274	<	/**
275	<	* Retrieves, but does not remove, the last element of this deque,
276	<	* returning <tt>null</tt> if this deque is empty.
277	<	*
278	<	* @return the last element of this deque, or <tt>null</tt> if this deque
279	<	*     is empty
280	<	*/
281	<	public E peekLast() {
323	<	return elements[(tail - 1) & (elements.length - 1)];
274	>	public E pollLast() {
275	>	int t = (tail - 1) & (elements.length - 1);
276	>	E result = elements[t];
277	>	if (result == null)
278	>	return null;
279	>	elements[t] = null;
280	>	tail = t;
281	>	return result;
282		}
283
284		/**
285	<	* 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
285	>	* @throws NoSuchElementException {@inheritDoc}
286		*/
287		public E getFirst() {
288		E x = elements[head];
#	Line 339 | Line 292 | public class ArrayDeque<E> extends Abstr
292		}
293
294		/**
295	<	* 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
295	>	* @throws NoSuchElementException {@inheritDoc}
296		*/
297		public E getLast() {
298		E x = elements[(tail - 1) & (elements.length - 1)];
#	Line 353 | Line 301 | public class ArrayDeque<E> extends Abstr
301		return x;
302		}
303
304	+	public E peekFirst() {
305	+	return elements[head]; // elements[head] is null if deque empty
306	+	}
307	+
308	+	public E peekLast() {
309	+	return elements[(tail - 1) & (elements.length - 1)];
310	+	}
311	+
312		/**
313		* Removes the first occurrence of the specified element in this
314	<	* deque (when traversing the deque from head to tail).  More
315	<	* formally, removes the first element e such that (o==null ?
316	<	* e==null : o.equals(e)). If the deque does not contain the
317	<	* element, it is unchanged.
314	>	* deque (when traversing the deque from head to tail).
315	>	* If the deque does not contain the element, it is unchanged.
316	>	* More formally, removes the first element <tt>e</tt> such that
317	>	* <tt>o.equals(e)</tt> (if such an element exists).
318	>	* Returns <tt>true</tt> if this deque contained the specified element
319	>	* (or equivalently, if this deque changed as a result of the call).
320		*
321		* @param o element to be removed from this deque, if present
322		* @return <tt>true</tt> if the deque contained the specified element
#	Line 381 | Line 339 | public class ArrayDeque<E> extends Abstr
339
340		/**
341		* Removes the last occurrence of the specified element in this
342	<	* deque (when traversing the deque from head to tail). More
343	<	* formally, removes the last element e such that (o==null ?
344	<	* e==null : o.equals(e)). If the deque
345	<	* does not contain the element, it is unchanged.
342	>	* deque (when traversing the deque from head to tail).
343	>	* If the deque does not contain the element, it is unchanged.
344	>	* More formally, removes the last element <tt>e</tt> such that
345	>	* <tt>o.equals(e)</tt> (if such an element exists).
346	>	* Returns <tt>true</tt> if this deque contained the specified element
347	>	* (or equivalently, if this deque changed as a result of the call).
348		*
349		* @param o element to be removed from this deque, if present
350		* @return <tt>true</tt> if the deque contained the specified element
#	Line 410 | Line 370 | public class ArrayDeque<E> extends Abstr
370		/**
371		* Inserts the specified element at the end of this deque.
372		*
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	–	*
373		* <p>This method is equivalent to {@link #addLast}.
374		*
375	<	* @param e the element to insert
375	>	* @param e the element to add
376		* @return <tt>true</tt> (as per the spec for {@link Collection#add})
377	<	* @throws NullPointerException if <tt>e</tt> is null
377	>	* @throws NullPointerException if the specified element is null
378		*/
379		public boolean add(E e) {
380		addLast(e);
#	Line 435 | Line 382 | public class ArrayDeque<E> extends Abstr
382		}
383
384		/**
385	<	* 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.
385	>	* Inserts the specified element at the end of this deque.
386		*
387	<	* <p>This method is equivalent to {@link #pollFirst}.
387	>	* <p>This method is equivalent to {@link #offerLast}.
388		*
389	<	* @return the first element of this deque, or <tt>null</tt> if
390	<	*     this deque is empty
389	>	* @param e the element to add
390	>	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
391	>	* @throws NullPointerException if the specified element is null
392		*/
393	<	public E poll() {
394	<	return pollFirst();
393	>	public boolean offer(E e) {
394	>	return offerLast(e);
395		}
396
397		/**
398		* Retrieves and removes the head of the queue represented by this deque.
399	<	* This method differs from the <tt>poll</tt> method in that it throws an
399	>	* This method differs from {@link #poll} only in that it throws an
400		* exception if this deque is empty.
401		*
402		* <p>This method is equivalent to {@link #removeFirst}.
403		*
404		* @return the head of the queue represented by this deque
405	<	* @throws NoSuchElementException if this deque is empty
405	>	* @throws NoSuchElementException {@inheritDoc}
406		*/
407		public E remove() {
408		return removeFirst();
409		}
410
411		/**
412	<	* Retrieves, but does not remove, the head of the queue represented by
413	<	* this deque, returning <tt>null</tt> if this deque is empty.
412	>	* Retrieves and removes the head of the queue represented by this deque
413	>	* (in other words, the first element of this deque), or returns
414	>	* <tt>null</tt> if this deque is empty.
415		*
416	<	* <p>This method is equivalent to {@link #peekFirst}
416	>	* <p>This method is equivalent to {@link #pollFirst}.
417		*
418		* @return the head of the queue represented by this deque, or
419	<	*     <tt>null</tt> if this deque is empty
419	>	*         <tt>null</tt> if this deque is empty
420		*/
421	<	public E peek() {
422	<	return peekFirst();
421	>	public E poll() {
422	>	return pollFirst();
423		}
424
425		/**
426		* Retrieves, but does not remove, the head of the queue represented by
427	<	* this deque.  This method differs from the <tt>peek</tt> method only in
428	<	* that it throws an exception if this deque is empty.
427	>	* this deque.  This method differs from {@link #peek} only in that it
428	>	* throws an exception if this deque is empty.
429		*
430	<	* <p>This method is equivalent to {@link #getFirst}
430	>	* <p>This method is equivalent to {@link #getFirst}.
431		*
432		* @return the head of the queue represented by this deque
433	<	* @throws NoSuchElementException if this deque is empty
433	>	* @throws NoSuchElementException {@inheritDoc}
434		*/
435		public E element() {
436		return getFirst();
437		}
438
439	+	/**
440	+	* Retrieves, but does not remove, the head of the queue represented by
441	+	* this deque, or returns <tt>null</tt> if this deque is empty.
442	+	*
443	+	* <p>This method is equivalent to {@link #peekFirst}.
444	+	*
445	+	* @return the head of the queue represented by this deque, or
446	+	*         <tt>null</tt> if this deque is empty
447	+	*/
448	+	public E peek() {
449	+	return peekFirst();
450	+	}
451	+
452		// *** Stack methods ***
453
454		/**
#	Line 499 | Line 458 | public class ArrayDeque<E> extends Abstr
458		* <p>This method is equivalent to {@link #addFirst}.
459		*
460		* @param e the element to push
461	<	* @throws NullPointerException if <tt>e</tt> is null
461	>	* @throws NullPointerException if the specified element is null
462		*/
463		public void push(E e) {
464		addFirst(e);
#	Line 512 | Line 471 | public class ArrayDeque<E> extends Abstr
471		* <p>This method is equivalent to {@link #removeFirst()}.
472		*
473		* @return the element at the front of this deque (which is the top
474	<	*     of the stack represented by this deque)
475	<	* @throws NoSuchElementException if this deque is empty
474	>	*         of the stack represented by this deque)
475	>	* @throws NoSuchElementException {@inheritDoc}
476		*/
477		public E pop() {
478		return removeFirst();
479		}
480
481		/**
482	<	* Remove the element at the specified position in the elements array,
483	<	* adjusting head, tail, and size as necessary.  This can result in
484	<	* motion of elements backwards or forwards in the array.
482	>	* Removes the element at the specified position in the elements array,
483	>	* adjusting head and tail as necessary.  This can result in motion of
484	>	* elements backwards or forwards in the array.
485		*
486		* <p>This method is called delete rather than remove to emphasize
487	<	* that its semantics differ from those of List.remove(int).
487	>	* that its semantics differ from those of {@link List#remove(int)}.
488		*
489		* @return true if elements moved backwards
490		*/
491		private boolean delete(int i) {
492	+	int mask = elements.length - 1;
493	+
494	+	// Invariant: head <= i < tail mod circularity
495	+	if (((i - head) & mask) >= ((tail - head) & mask))
496	+	throw new ConcurrentModificationException();
497	+
498		// Case 1: Deque doesn't wrap
499		// Case 2: Deque does wrap and removed element is in the head portion
500	<	if ((head < tail || tail == 0) || i >= head) {
500	>	if (i >= head) {
501		System.arraycopy(elements, head, elements, head + 1, i - head);
502		elements[head] = null;
503	<	head = (head + 1) & (elements.length - 1);
503	>	head = (head + 1) & mask;
504		return false;
505		}
506
#	Line 558 | Line 523 | public class ArrayDeque<E> extends Abstr
523		}
524
525		/**
526	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
526	>	* Returns <tt>true</tt> if this deque contains no elements.
527		*
528	<	* @return <tt>true</tt> if this collection contains no elements.
528	>	* @return <tt>true</tt> if this deque contains no elements
529		*/
530		public boolean isEmpty() {
531		return head == tail;
#	Line 624 | Line 589 | public class ArrayDeque<E> extends Abstr
589		}
590
591		/**
592	<	* Returns <tt>true</tt> if this deque contains the specified
593	<	* element.  More formally, returns <tt>true</tt> if and only if this
594	<	* deque contains at least one element <tt>e</tt> such that
630	<	* <tt>e.equals(o)</tt>.
592	>	* Returns <tt>true</tt> if this deque contains the specified element.
593	>	* More formally, returns <tt>true</tt> if and only if this deque contains
594	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
595		*
596		* @param o object to be checked for containment in this deque
597		* @return <tt>true</tt> if this deque contains the specified element
#	Line 648 | Line 612 | public class ArrayDeque<E> extends Abstr
612
613		/**
614		* Removes a single instance of the specified element from this deque.
615	<	* This method is equivalent to {@link #removeFirstOccurrence}.
615	>	* If the deque does not contain the element, it is unchanged.
616	>	* More formally, removes the first element <tt>e</tt> such that
617	>	* <tt>o.equals(e)</tt> (if such an element exists).
618	>	* Returns <tt>true</tt> if this deque contained the specified element
619	>	* (or equivalently, if this deque changed as a result of the call).
620		*
621	<	* @param e element to be removed from this deque, if present
621	>	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
622	>	*
623	>	* @param o element to be removed from this deque, if present
624		* @return <tt>true</tt> if this deque contained the specified element
625		*/
626	<	public boolean remove(Object e) {
627	<	return removeFirstOccurrence(e);
626	>	public boolean remove(Object o) {
627	>	return removeFirstOccurrence(o);
628		}
629
630		/**
631		* Removes all of the elements from this deque.
632	+	* The deque will be empty after this call returns.
633		*/
634		public void clear() {
635		int h = head;
#	Line 670 | Line 641 | public class ArrayDeque<E> extends Abstr
641		do {
642		elements[i] = null;
643		i = (i + 1) & mask;
644	<	} while(i != t);
644	>	} while (i != t);
645		}
646		}
647
648		/**
649		* Returns an array containing all of the elements in this deque
650	<	* in the correct order.
650	>	* in proper sequence (from first to last element).
651	>	*
652	>	* <p>The returned array will be "safe" in that no references to it are
653	>	* maintained by this deque.  (In other words, this method must allocate
654	>	* a new array).  The caller is thus free to modify the returned array.
655	>	*
656	>	* <p>This method acts as bridge between array-based and collection-based
657	>	* APIs.
658		*
659		* @return an array containing all of the elements in this deque
682	–	*         in the correct order
660		*/
661		public Object[] toArray() {
662		return copyElements(new Object[size()]);
663		}
664
665		/**
666	<	* Returns an array containing all of the elements in this deque in the
667	<	* correct order; the runtime type of the returned array is that of the
668	<	* specified array.  If the deque fits in the specified array, it is
669	<	* returned therein.  Otherwise, a new array is allocated with the runtime
670	<	* type of the specified array and the size of this deque.
671	<	*
672	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
673	<	* the array has more elements than the deque), the element in the array
674	<	* immediately following the end of the collection is set to <tt>null</tt>.
666	>	* Returns an array containing all of the elements in this deque in
667	>	* proper sequence (from first to last element); the runtime type of the
668	>	* returned array is that of the specified array.  If the deque fits in
669	>	* the specified array, it is returned therein.  Otherwise, a new array
670	>	* is allocated with the runtime type of the specified array and the
671	>	* size of this deque.
672	>	*
673	>	* <p>If this deque fits in the specified array with room to spare
674	>	* (i.e., the array has more elements than this deque), the element in
675	>	* the array immediately following the end of the deque is set to
676	>	* <tt>null</tt>.
677	>	*
678	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
679	>	* array-based and collection-based APIs.  Further, this method allows
680	>	* precise control over the runtime type of the output array, and may,
681	>	* under certain circumstances, be used to save allocation costs.
682	>	*
683	>	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
684	>	* The following code can be used to dump the deque into a newly
685	>	* allocated array of <tt>String</tt>:
686	>	*
687	>	* <pre>
688	>	*     String[] y = x.toArray(new String[0]);</pre>
689	>	*
690	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
691	>	* <tt>toArray()</tt>.
692		*
693		* @param a the array into which the elements of the deque are to
694	<	*          be stored, if it is big enough; otherwise, a new array of the
695	<	*          same runtime type is allocated for this purpose
696	<	* @return an array containing the elements of the deque
697	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
698	<	*         of the runtime type of every element in this deque
694	>	*          be stored, if it is big enough; otherwise, a new array of the
695	>	*          same runtime type is allocated for this purpose
696	>	* @return an array containing all of the elements in this deque
697	>	* @throws ArrayStoreException if the runtime type of the specified array
698	>	*         is not a supertype of the runtime type of every element in
699	>	*         this deque
700	>	* @throws NullPointerException if the specified array is null
701		*/
702		public <T> T[] toArray(T[] a) {
703		int size = size();

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