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Comparing jsr166/src/main/java/util/Deque.java (file contents):
Revision 1.13 by jsr166, Wed May 18 03:45:35 2005 UTC vs.
Revision 1.26 by dl, Sat Jul 20 18:00:11 2013 UTC

# Line 1 | Line 1
1   /*
2   * Written by Doug Lea and Josh Bloch with assistance from members of
3   * JCP JSR-166 Expert Group and released to the public domain, as explained
4 < * at http://creativecommons.org/licenses/publicdomain
4 > * at http://creativecommons.org/publicdomain/zero/1.0/
5   */
6  
7   package java.util;
# Line 9 | Line 9 | package java.util;
9   /**
10   * A linear collection that supports element insertion and removal at
11   * both ends.  The name <i>deque</i> is short for "double ended queue"
12 < * and is usually pronounced "deck".  Most <tt>Deque</tt>
12 > * and is usually pronounced "deck".  Most {@code Deque}
13   * implementations place no fixed limits on the number of elements
14   * they may contain, but this interface supports capacity-restricted
15   * deques as well as those with no fixed size limit.
# Line 18 | Line 18 | package java.util;
18   * ends of the deque.  Methods are provided to insert, remove, and
19   * examine the element.  Each of these methods exists in two forms:
20   * one throws an exception if the operation fails, the other returns a
21 < * special value (either <tt>null</tt> or <tt>false</tt>, depending on
21 > * special value (either {@code null} or {@code false}, depending on
22   * the operation).  The latter form of the insert operation is
23   * designed specifically for use with capacity-restricted
24 < * <tt>Deque</tt> implementations; in most implementations, insert
24 > * {@code Deque} implementations; in most implementations, insert
25   * operations cannot fail.
26   *
27   * <p>The twelve methods described above are summarized in the
# Line 29 | Line 29 | package java.util;
29   *
30   * <p>
31   * <table BORDER CELLPADDING=3 CELLSPACING=1>
32 + * <caption>Summary of Deque methods</caption>
33   *  <tr>
34   *    <td></td>
35   *    <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
# Line 43 | Line 44 | package java.util;
44   *  </tr>
45   *  <tr>
46   *    <td><b>Insert</b></td>
47 < *    <td>{@link #addFirst addFirst(e)}</td>
48 < *    <td>{@link #offerFirst offerFirst(e)}</td>
49 < *    <td>{@link #addLast addLast(e)}</td>
50 < *    <td>{@link #offerLast offerLast(e)}</td>
47 > *    <td>{@link Deque#addFirst addFirst(e)}</td>
48 > *    <td>{@link Deque#offerFirst offerFirst(e)}</td>
49 > *    <td>{@link Deque#addLast addLast(e)}</td>
50 > *    <td>{@link Deque#offerLast offerLast(e)}</td>
51   *  </tr>
52   *  <tr>
53   *    <td><b>Remove</b></td>
54 < *    <td>{@link #removeFirst removeFirst()}</td>
55 < *    <td>{@link #pollFirst pollFirst()}</td>
56 < *    <td>{@link #removeLast removeLast()}</td>
57 < *    <td>{@link #pollLast pollLast()}</td>
54 > *    <td>{@link Deque#removeFirst removeFirst()}</td>
55 > *    <td>{@link Deque#pollFirst pollFirst()}</td>
56 > *    <td>{@link Deque#removeLast removeLast()}</td>
57 > *    <td>{@link Deque#pollLast pollLast()}</td>
58   *  </tr>
59   *  <tr>
60   *    <td><b>Examine</b></td>
61 < *    <td>{@link #getFirst getFirst()}</td>
62 < *    <td>{@link #peekFirst peekFirst()}</td>
63 < *    <td>{@link #getLast getLast()}</td>
64 < *    <td>{@link #peekLast peekLast()}</td>
61 > *    <td>{@link Deque#getFirst getFirst()}</td>
62 > *    <td>{@link Deque#peekFirst peekFirst()}</td>
63 > *    <td>{@link Deque#getLast getLast()}</td>
64 > *    <td>{@link Deque#peekLast peekLast()}</td>
65   *  </tr>
66   * </table>
67   *
68   * <p>This interface extends the {@link Queue} interface.  When a deque is
69   * used as a queue, FIFO (First-In-First-Out) behavior results.  Elements are
70   * added at the end of the deque and removed from the beginning.  The methods
71 < * inherited from the <tt>Queue</tt> interface are precisely equivalent to
72 < * <tt>Deque</tt> methods as indicated in the following table:
71 > * inherited from the {@code Queue} interface are precisely equivalent to
72 > * {@code Deque} methods as indicated in the following table:
73   *
74   * <p>
75   * <table BORDER CELLPADDING=3 CELLSPACING=1>
76 + * <caption>Comparison of Queue and Deque methods</caption>
77   *  <tr>
78 < *    <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
79 < *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
78 > *    <td ALIGN=CENTER> <b>{@code Queue} Method</b></td>
79 > *    <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td>
80   *  </tr>
81   *  <tr>
82   *    <td>{@link java.util.Queue#add add(e)}</td>
# Line 106 | Line 108 | package java.util;
108   * interface should be used in preference to the legacy {@link Stack} class.
109   * When a deque is used as a stack, elements are pushed and popped from the
110   * beginning of the deque.  Stack methods are precisely equivalent to
111 < * <tt>Deque</tt> methods as indicated in the table below:
111 > * {@code Deque} methods as indicated in the table below:
112   *
113   * <p>
114   * <table BORDER CELLPADDING=3 CELLSPACING=1>
115 + * <caption>Comparison of Stack and Deque methods</caption>
116   *  <tr>
117   *    <td ALIGN=CENTER> <b>Stack Method</b></td>
118 < *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
118 > *    <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td>
119   *  </tr>
120   *  <tr>
121   *    <td>{@link #push push(e)}</td>
# Line 139 | Line 142 | package java.util;
142   * <p>Unlike the {@link List} interface, this interface does not
143   * provide support for indexed access to elements.
144   *
145 < * <p>While <tt>Deque</tt> implementations are not strictly required
145 > * <p>While {@code Deque} implementations are not strictly required
146   * to prohibit the insertion of null elements, they are strongly
147 < * encouraged to do so.  Users of any <tt>Deque</tt> implementations
147 > * encouraged to do so.  Users of any {@code Deque} implementations
148   * that do allow null elements are strongly encouraged <i>not</i> to
149   * take advantage of the ability to insert nulls.  This is so because
150 < * <tt>null</tt> is used as a special return value by various methods
150 > * {@code null} is used as a special return value by various methods
151   * to indicated that the deque is empty.
152   *
153 < * <p><tt>Deque</tt> implementations generally do not define
154 < * element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
153 > * <p>{@code Deque} implementations generally do not define
154 > * element-based versions of the {@code equals} and {@code hashCode}
155   * methods, but instead inherit the identity-based versions from class
156 < * <tt>Object</tt>.
156 > * {@code Object}.
157   *
158   * <p>This interface is a member of the <a
159 < * href="{@docRoot}/../guide/collections/index.html"> Java Collections
159 > * href="{@docRoot}/../technotes/guides/collections/index.html"> Java Collections
160   * Framework</a>.
161   *
162   * @author Doug Lea
# Line 161 | Line 164 | package java.util;
164   * @since  1.6
165   * @param <E> the type of elements held in this collection
166   */
164 –
167   public interface Deque<E> extends Queue<E> {
168      /**
169       * Inserts the specified element at the front of this deque if it is
170 <     * possible to do so immediately without violating capacity restrictions.
171 <     * When using a capacity-restricted deque, it is generally preferable to
172 <     * use method {@link #offerFirst}.
170 >     * possible to do so immediately without violating capacity restrictions,
171 >     * throwing an {@code IllegalStateException} if no space is currently
172 >     * available.  When using a capacity-restricted deque, it is generally
173 >     * preferable to use method {@link #offerFirst}.
174       *
175       * @param e the element to add
176       * @throws IllegalStateException if the element cannot be added at this
# Line 183 | Line 186 | public interface Deque<E> extends Queue<
186  
187      /**
188       * Inserts the specified element at the end of this deque if it is
189 <     * possible to do so immediately without violating capacity restrictions.
190 <     * When using a capacity-restricted deque, it is generally preferable to
191 <     * use method {@link #offerLast}.
189 >     * possible to do so immediately without violating capacity restrictions,
190 >     * throwing an {@code IllegalStateException} if no space is currently
191 >     * available.  When using a capacity-restricted deque, it is generally
192 >     * preferable to use method {@link #offerLast}.
193 >     *
194 >     * <p>This method is equivalent to {@link #add}.
195       *
196       * @param e the element to add
197       * @throws IllegalStateException if the element cannot be added at this
# Line 206 | Line 212 | public interface Deque<E> extends Queue<
212       * which can fail to insert an element only by throwing an exception.
213       *
214       * @param e the element to add
215 <     * @return <tt>true</tt> if the element was added to this deque, else
216 <     *         <tt>false</tt>
215 >     * @return {@code true} if the element was added to this deque, else
216 >     *         {@code false}
217       * @throws ClassCastException if the class of the specified element
218       *         prevents it from being added to this deque
219       * @throws NullPointerException if the specified element is null and this
# Line 224 | Line 230 | public interface Deque<E> extends Queue<
230       * which can fail to insert an element only by throwing an exception.
231       *
232       * @param e the element to add
233 <     * @return <tt>true</tt> if the element was added to this deque, else
234 <     *         <tt>false</tt>
233 >     * @return {@code true} if the element was added to this deque, else
234 >     *         {@code false}
235       * @throws ClassCastException if the class of the specified element
236       *         prevents it from being added to this deque
237       * @throws NullPointerException if the specified element is null and this
# Line 237 | Line 243 | public interface Deque<E> extends Queue<
243  
244      /**
245       * Retrieves and removes the first element of this deque.  This method
246 <     * differs from {@link #pollFirst} only in that it throws an exception
247 <     * if this deque is empty.
246 >     * differs from {@link #pollFirst pollFirst} only in that it throws an
247 >     * exception if this deque is empty.
248       *
249       * @return the head of this deque
250       * @throws NoSuchElementException if this deque is empty
# Line 247 | Line 253 | public interface Deque<E> extends Queue<
253  
254      /**
255       * Retrieves and removes the last element of this deque.  This method
256 <     * differs from {@link #pollLast} only in that it throws an exception if
257 <     * this deque is empty.
256 >     * differs from {@link #pollLast pollLast} only in that it throws an
257 >     * exception if this deque is empty.
258       *
259       * @return the tail of this deque
260       * @throws NoSuchElementException if this deque is empty
# Line 257 | Line 263 | public interface Deque<E> extends Queue<
263  
264      /**
265       * Retrieves and removes the first element of this deque,
266 <     * or returns <tt>null</tt> if this deque is empty.
266 >     * or returns {@code null} if this deque is empty.
267       *
268 <     * @return the head of this deque, or <tt>null</tt> if this deque is empty
268 >     * @return the head of this deque, or {@code null} if this deque is empty
269       */
270      E pollFirst();
271  
272      /**
273       * Retrieves and removes the last element of this deque,
274 <     * or returns <tt>null</tt> if this deque is empty.
274 >     * or returns {@code null} if this deque is empty.
275       *
276 <     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
276 >     * @return the tail of this deque, or {@code null} if this deque is empty
277       */
278      E pollLast();
279  
280      /**
281       * Retrieves, but does not remove, the first element of this deque.
282 <     * This method differs from {@link #peekFirst} only in that it throws an
283 <     * exception if this deque is empty.
282 >     *
283 >     * This method differs from {@link #peekFirst peekFirst} only in that it
284 >     * throws an exception if this deque is empty.
285       *
286       * @return the head of this deque
287       * @throws NoSuchElementException if this deque is empty
# Line 283 | Line 290 | public interface Deque<E> extends Queue<
290  
291      /**
292       * Retrieves, but does not remove, the last element of this deque.
293 <     * This method differs from {@link #peekLast} only in that it throws an
294 <     * exception if this deque is empty.
293 >     * This method differs from {@link #peekLast peekLast} only in that it
294 >     * throws an exception if this deque is empty.
295       *
296       * @return the tail of this deque
297       * @throws NoSuchElementException if this deque is empty
# Line 293 | Line 300 | public interface Deque<E> extends Queue<
300  
301      /**
302       * Retrieves, but does not remove, the first element of this deque,
303 <     * or returns <tt>null</tt> if this deque is empty.
303 >     * or returns {@code null} if this deque is empty.
304       *
305 <     * @return the head of this deque, or <tt>null</tt> if this deque is empty
305 >     * @return the head of this deque, or {@code null} if this deque is empty
306       */
307      E peekFirst();
308  
309      /**
310       * Retrieves, but does not remove, the last element of this deque,
311 <     * or returns <tt>null</tt> if this deque is empty.
311 >     * or returns {@code null} if this deque is empty.
312       *
313 <     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
313 >     * @return the tail of this deque, or {@code null} if this deque is empty
314       */
315      E peekLast();
316  
317      /**
318       * Removes the first occurrence of the specified element from this deque.
319       * If the deque does not contain the element, it is unchanged.
320 <     * More formally, removes the first element <tt>e</tt> such that
320 >     * More formally, removes the first element {@code e} such that
321       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
322       * (if such an element exists).
323 <     * Returns <tt>true</tt> if this deque contained the specified element
323 >     * Returns {@code true} if this deque contained the specified element
324       * (or equivalently, if this deque changed as a result of the call).
325       *
326       * @param o element to be removed from this deque, if present
327 <     * @return <tt>true</tt> if an element was removed as a result of this call
327 >     * @return {@code true} if an element was removed as a result of this call
328       * @throws ClassCastException if the class of the specified element
329       *         is incompatible with this deque (optional)
330       * @throws NullPointerException if the specified element is null and this
# Line 328 | Line 335 | public interface Deque<E> extends Queue<
335      /**
336       * Removes the last occurrence of the specified element from this deque.
337       * If the deque does not contain the element, it is unchanged.
338 <     * More formally, removes the last element <tt>e</tt> such that
338 >     * More formally, removes the last element {@code e} such that
339       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
340       * (if such an element exists).
341 <     * Returns <tt>true</tt> if this deque contained the specified element
341 >     * Returns {@code true} if this deque contained the specified element
342       * (or equivalently, if this deque changed as a result of the call).
343       *
344       * @param o element to be removed from this deque, if present
345 <     * @return <tt>true</tt> if an element was removed as a result of this call
345 >     * @return {@code true} if an element was removed as a result of this call
346       * @throws ClassCastException if the class of the specified element
347       *         is incompatible with this deque (optional)
348       * @throws NullPointerException if the specified element is null and this
# Line 349 | Line 356 | public interface Deque<E> extends Queue<
356       * Inserts the specified element into the queue represented by this deque
357       * (in other words, at the tail of this deque) if it is possible to do so
358       * immediately without violating capacity restrictions, returning
359 <     * <tt>true</tt> upon success and throwing an
360 <     * <tt>IllegalStateException</tt> if no space is currently available.
359 >     * {@code true} upon success and throwing an
360 >     * {@code IllegalStateException} if no space is currently available.
361       * When using a capacity-restricted deque, it is generally preferable to
362       * use {@link #offer(Object) offer}.
363       *
364 <     * <p>This method is equivalent to {@link #addLast(Object) addLast}.
364 >     * <p>This method is equivalent to {@link #addLast}.
365       *
366       * @param e the element to add
367 <     * @return <tt>true</tt> (as per the spec for {@link Collection#add})
367 >     * @return {@code true} (as specified by {@link Collection#add})
368       * @throws IllegalStateException if the element cannot be added at this
369       *         time due to capacity restrictions
370       * @throws ClassCastException if the class of the specified element
# Line 373 | Line 380 | public interface Deque<E> extends Queue<
380       * Inserts the specified element into the queue represented by this deque
381       * (in other words, at the tail of this deque) if it is possible to do so
382       * immediately without violating capacity restrictions, returning
383 <     * <tt>true</tt> upon success and <tt>false</tt> if no space is currently
383 >     * {@code true} upon success and {@code false} if no space is currently
384       * available.  When using a capacity-restricted deque, this method is
385       * generally preferable to the {@link #add} method, which can fail to
386       * insert an element only by throwing an exception.
# Line 381 | Line 388 | public interface Deque<E> extends Queue<
388       * <p>This method is equivalent to {@link #offerLast}.
389       *
390       * @param e the element to add
391 <     * @return <tt>true</tt> if the element was added to this deque, else
392 <     *         <tt>false</tt>
391 >     * @return {@code true} if the element was added to this deque, else
392 >     *         {@code false}
393       * @throws ClassCastException if the class of the specified element
394       *         prevents it from being added to this deque
395       * @throws NullPointerException if the specified element is null and this
# Line 395 | Line 402 | public interface Deque<E> extends Queue<
402      /**
403       * Retrieves and removes the head of the queue represented by this deque
404       * (in other words, the first element of this deque).
405 <     * This method differs from {@link #poll} only in that it throws an
405 >     * This method differs from {@link #poll poll} only in that it throws an
406       * exception if this deque is empty.
407       *
408       * <p>This method is equivalent to {@link #removeFirst()}.
# Line 408 | Line 415 | public interface Deque<E> extends Queue<
415      /**
416       * Retrieves and removes the head of the queue represented by this deque
417       * (in other words, the first element of this deque), or returns
418 <     * <tt>null</tt> if this deque is empty.
418 >     * {@code null} if this deque is empty.
419       *
420       * <p>This method is equivalent to {@link #pollFirst()}.
421       *
422 <     * @return the first element of this deque, or <tt>null</tt> if
422 >     * @return the first element of this deque, or {@code null} if
423       *         this deque is empty
424       */
425      E poll();
# Line 420 | Line 427 | public interface Deque<E> extends Queue<
427      /**
428       * Retrieves, but does not remove, the head of the queue represented by
429       * this deque (in other words, the first element of this deque).
430 <     * This method differs from {@link #peek} only in that it throws an
430 >     * This method differs from {@link #peek peek} only in that it throws an
431       * exception if this deque is empty.
432       *
433       * <p>This method is equivalent to {@link #getFirst()}.
# Line 433 | Line 440 | public interface Deque<E> extends Queue<
440      /**
441       * Retrieves, but does not remove, the head of the queue represented by
442       * this deque (in other words, the first element of this deque), or
443 <     * returns <tt>null</tt> if this deque is empty.
443 >     * returns {@code null} if this deque is empty.
444       *
445       * <p>This method is equivalent to {@link #peekFirst()}.
446       *
447       * @return the head of the queue represented by this deque, or
448 <     *         <tt>null</tt> if this deque is empty
448 >     *         {@code null} if this deque is empty
449       */
450      E peek();
451  
# Line 448 | Line 455 | public interface Deque<E> extends Queue<
455      /**
456       * Pushes an element onto the stack represented by this deque (in other
457       * words, at the head of this deque) if it is possible to do so
458 <     * immediately without violating capacity restrictions, returning
459 <     * <tt>true</tt> upon success and throwing an
453 <     * <tt>IllegalStateException</tt> if no space is currently available.
458 >     * immediately without violating capacity restrictions, throwing an
459 >     * {@code IllegalStateException} if no space is currently available.
460       *
461       * <p>This method is equivalent to {@link #addFirst}.
462       *
# Line 484 | Line 490 | public interface Deque<E> extends Queue<
490      /**
491       * Removes the first occurrence of the specified element from this deque.
492       * If the deque does not contain the element, it is unchanged.
493 <     * More formally, removes the first element <tt>e</tt> such that
493 >     * More formally, removes the first element {@code e} such that
494       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
495       * (if such an element exists).
496 <     * Returns <tt>true</tt> if this deque contained the specified element
496 >     * Returns {@code true} if this deque contained the specified element
497       * (or equivalently, if this deque changed as a result of the call).
498       *
499 <     * <p>This method is equivalent to {@link #removeFirstOccurrence}.
499 >     * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
500       *
501       * @param o element to be removed from this deque, if present
502 <     * @return <tt>true</tt> if an element was removed as a result of this call
502 >     * @return {@code true} if an element was removed as a result of this call
503       * @throws ClassCastException if the class of the specified element
504       *         is incompatible with this deque (optional)
505       * @throws NullPointerException if the specified element is null and this
# Line 502 | Line 508 | public interface Deque<E> extends Queue<
508      boolean remove(Object o);
509  
510      /**
511 <     * Returns <tt>true</tt> if this deque contains the specified element.
512 <     * More formally, returns <tt>true</tt> if and only if this deque contains
513 <     * at least one element <tt>e</tt> such that
511 >     * Returns {@code true} if this deque contains the specified element.
512 >     * More formally, returns {@code true} if and only if this deque contains
513 >     * at least one element {@code e} such that
514       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
515       *
516       * @param o element whose presence in this deque is to be tested
517 <     * @return <tt>true</tt> if this deque contains the specified element
517 >     * @return {@code true} if this deque contains the specified element
518       * @throws ClassCastException if the type of the specified element
519       *         is incompatible with this deque (optional)
520       * @throws NullPointerException if the specified element is null and this
# Line 530 | Line 536 | public interface Deque<E> extends Queue<
536       * @return an iterator over the elements in this deque in proper sequence
537       */
538      Iterator<E> iterator();
539 +
540 +    /**
541 +     * Returns an iterator over the elements in this deque in reverse
542 +     * sequential order.  The elements will be returned in order from
543 +     * last (tail) to first (head).
544 +     *
545 +     * @return an iterator over the elements in this deque in reverse
546 +     * sequence
547 +     */
548 +    Iterator<E> descendingIterator();
549 +
550   }

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