Added conversion to long for JavaScript implementation of System.currentTimeMillis
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31 * Written by Doug Lea and Josh Bloch with assistance from members of
32 * JCP JSR-166 Expert Group and released to the public domain, as explained
33 * at http://creativecommons.org/publicdomain/zero/1.0/
39 * A linear collection that supports element insertion and removal at
40 * both ends. The name <i>deque</i> is short for "double ended queue"
41 * and is usually pronounced "deck". Most <tt>Deque</tt>
42 * implementations place no fixed limits on the number of elements
43 * they may contain, but this interface supports capacity-restricted
44 * deques as well as those with no fixed size limit.
46 * <p>This interface defines methods to access the elements at both
47 * ends of the deque. Methods are provided to insert, remove, and
48 * examine the element. Each of these methods exists in two forms:
49 * one throws an exception if the operation fails, the other returns a
50 * special value (either <tt>null</tt> or <tt>false</tt>, depending on
51 * the operation). The latter form of the insert operation is
52 * designed specifically for use with capacity-restricted
53 * <tt>Deque</tt> implementations; in most implementations, insert
54 * operations cannot fail.
56 * <p>The twelve methods described above are summarized in the
60 * <table BORDER CELLPADDING=3 CELLSPACING=1>
63 * <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
64 * <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td>
68 * <td ALIGN=CENTER><em>Throws exception</em></td>
69 * <td ALIGN=CENTER><em>Special value</em></td>
70 * <td ALIGN=CENTER><em>Throws exception</em></td>
71 * <td ALIGN=CENTER><em>Special value</em></td>
74 * <td><b>Insert</b></td>
75 * <td>{@link #addFirst addFirst(e)}</td>
76 * <td>{@link #offerFirst offerFirst(e)}</td>
77 * <td>{@link #addLast addLast(e)}</td>
78 * <td>{@link #offerLast offerLast(e)}</td>
81 * <td><b>Remove</b></td>
82 * <td>{@link #removeFirst removeFirst()}</td>
83 * <td>{@link #pollFirst pollFirst()}</td>
84 * <td>{@link #removeLast removeLast()}</td>
85 * <td>{@link #pollLast pollLast()}</td>
88 * <td><b>Examine</b></td>
89 * <td>{@link #getFirst getFirst()}</td>
90 * <td>{@link #peekFirst peekFirst()}</td>
91 * <td>{@link #getLast getLast()}</td>
92 * <td>{@link #peekLast peekLast()}</td>
96 * <p>This interface extends the {@link Queue} interface. When a deque is
97 * used as a queue, FIFO (First-In-First-Out) behavior results. Elements are
98 * added at the end of the deque and removed from the beginning. The methods
99 * inherited from the <tt>Queue</tt> interface are precisely equivalent to
100 * <tt>Deque</tt> methods as indicated in the following table:
103 * <table BORDER CELLPADDING=3 CELLSPACING=1>
105 * <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
106 * <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
109 * <td>{@link java.util.Queue#add add(e)}</td>
110 * <td>{@link #addLast addLast(e)}</td>
113 * <td>{@link java.util.Queue#offer offer(e)}</td>
114 * <td>{@link #offerLast offerLast(e)}</td>
117 * <td>{@link java.util.Queue#remove remove()}</td>
118 * <td>{@link #removeFirst removeFirst()}</td>
121 * <td>{@link java.util.Queue#poll poll()}</td>
122 * <td>{@link #pollFirst pollFirst()}</td>
125 * <td>{@link java.util.Queue#element element()}</td>
126 * <td>{@link #getFirst getFirst()}</td>
129 * <td>{@link java.util.Queue#peek peek()}</td>
130 * <td>{@link #peek peekFirst()}</td>
134 * <p>Deques can also be used as LIFO (Last-In-First-Out) stacks. This
135 * interface should be used in preference to the legacy {@link Stack} class.
136 * When a deque is used as a stack, elements are pushed and popped from the
137 * beginning of the deque. Stack methods are precisely equivalent to
138 * <tt>Deque</tt> methods as indicated in the table below:
141 * <table BORDER CELLPADDING=3 CELLSPACING=1>
143 * <td ALIGN=CENTER> <b>Stack Method</b></td>
144 * <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
147 * <td>{@link #push push(e)}</td>
148 * <td>{@link #addFirst addFirst(e)}</td>
151 * <td>{@link #pop pop()}</td>
152 * <td>{@link #removeFirst removeFirst()}</td>
155 * <td>{@link #peek peek()}</td>
156 * <td>{@link #peekFirst peekFirst()}</td>
160 * <p>Note that the {@link #peek peek} method works equally well when
161 * a deque is used as a queue or a stack; in either case, elements are
162 * drawn from the beginning of the deque.
164 * <p>This interface provides two methods to remove interior
165 * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
166 * {@link #removeLastOccurrence removeLastOccurrence}.
168 * <p>Unlike the {@link List} interface, this interface does not
169 * provide support for indexed access to elements.
171 * <p>While <tt>Deque</tt> implementations are not strictly required
172 * to prohibit the insertion of null elements, they are strongly
173 * encouraged to do so. Users of any <tt>Deque</tt> implementations
174 * that do allow null elements are strongly encouraged <i>not</i> to
175 * take advantage of the ability to insert nulls. This is so because
176 * <tt>null</tt> is used as a special return value by various methods
177 * to indicated that the deque is empty.
179 * <p><tt>Deque</tt> implementations generally do not define
180 * element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
181 * methods, but instead inherit the identity-based versions from class
184 * <p>This interface is a member of the <a
185 * href="{@docRoot}/../technotes/guides/collections/index.html"> Java Collections
191 * @param <E> the type of elements held in this collection
194 public interface Deque<E> extends Queue<E> {
196 * Inserts the specified element at the front of this deque if it is
197 * possible to do so immediately without violating capacity restrictions.
198 * When using a capacity-restricted deque, it is generally preferable to
199 * use method {@link #offerFirst}.
201 * @param e the element to add
202 * @throws IllegalStateException if the element cannot be added at this
203 * time due to capacity restrictions
204 * @throws ClassCastException if the class of the specified element
205 * prevents it from being added to this deque
206 * @throws NullPointerException if the specified element is null and this
207 * deque does not permit null elements
208 * @throws IllegalArgumentException if some property of the specified
209 * element prevents it from being added to this deque
214 * Inserts the specified element at the end of this deque if it is
215 * possible to do so immediately without violating capacity restrictions.
216 * When using a capacity-restricted deque, it is generally preferable to
217 * use method {@link #offerLast}.
219 * <p>This method is equivalent to {@link #add}.
221 * @param e the element to add
222 * @throws IllegalStateException if the element cannot be added at this
223 * time due to capacity restrictions
224 * @throws ClassCastException if the class of the specified element
225 * prevents it from being added to this deque
226 * @throws NullPointerException if the specified element is null and this
227 * deque does not permit null elements
228 * @throws IllegalArgumentException if some property of the specified
229 * element prevents it from being added to this deque
234 * Inserts the specified element at the front of this deque unless it would
235 * violate capacity restrictions. When using a capacity-restricted deque,
236 * this method is generally preferable to the {@link #addFirst} method,
237 * which can fail to insert an element only by throwing an exception.
239 * @param e the element to add
240 * @return <tt>true</tt> if the element was added to this deque, else
242 * @throws ClassCastException if the class of the specified element
243 * prevents it from being added to this deque
244 * @throws NullPointerException if the specified element is null and this
245 * deque does not permit null elements
246 * @throws IllegalArgumentException if some property of the specified
247 * element prevents it from being added to this deque
249 boolean offerFirst(E e);
252 * Inserts the specified element at the end of this deque unless it would
253 * violate capacity restrictions. When using a capacity-restricted deque,
254 * this method is generally preferable to the {@link #addLast} method,
255 * which can fail to insert an element only by throwing an exception.
257 * @param e the element to add
258 * @return <tt>true</tt> if the element was added to this deque, else
260 * @throws ClassCastException if the class of the specified element
261 * prevents it from being added to this deque
262 * @throws NullPointerException if the specified element is null and this
263 * deque does not permit null elements
264 * @throws IllegalArgumentException if some property of the specified
265 * element prevents it from being added to this deque
267 boolean offerLast(E e);
270 * Retrieves and removes the first element of this deque. This method
271 * differs from {@link #pollFirst pollFirst} only in that it throws an
272 * exception if this deque is empty.
274 * @return the head of this deque
275 * @throws NoSuchElementException if this deque is empty
280 * Retrieves and removes the last element of this deque. This method
281 * differs from {@link #pollLast pollLast} only in that it throws an
282 * exception if this deque is empty.
284 * @return the tail of this deque
285 * @throws NoSuchElementException if this deque is empty
290 * Retrieves and removes the first element of this deque,
291 * or returns <tt>null</tt> if this deque is empty.
293 * @return the head of this deque, or <tt>null</tt> if this deque is empty
298 * Retrieves and removes the last element of this deque,
299 * or returns <tt>null</tt> if this deque is empty.
301 * @return the tail of this deque, or <tt>null</tt> if this deque is empty
306 * Retrieves, but does not remove, the first element of this deque.
308 * This method differs from {@link #peekFirst peekFirst} only in that it
309 * throws an exception if this deque is empty.
311 * @return the head of this deque
312 * @throws NoSuchElementException if this deque is empty
317 * Retrieves, but does not remove, the last element of this deque.
318 * This method differs from {@link #peekLast peekLast} only in that it
319 * throws an exception if this deque is empty.
321 * @return the tail of this deque
322 * @throws NoSuchElementException if this deque is empty
327 * Retrieves, but does not remove, the first element of this deque,
328 * or returns <tt>null</tt> if this deque is empty.
330 * @return the head of this deque, or <tt>null</tt> if this deque is empty
335 * Retrieves, but does not remove, the last element of this deque,
336 * or returns <tt>null</tt> if this deque is empty.
338 * @return the tail of this deque, or <tt>null</tt> if this deque is empty
343 * Removes the first occurrence of the specified element from this deque.
344 * If the deque does not contain the element, it is unchanged.
345 * More formally, removes the first element <tt>e</tt> such that
346 * <tt>(o==null ? e==null : o.equals(e))</tt>
347 * (if such an element exists).
348 * Returns <tt>true</tt> if this deque contained the specified element
349 * (or equivalently, if this deque changed as a result of the call).
351 * @param o element to be removed from this deque, if present
352 * @return <tt>true</tt> if an element was removed as a result of this call
353 * @throws ClassCastException if the class of the specified element
354 * is incompatible with this deque
355 * (<a href="Collection.html#optional-restrictions">optional</a>)
356 * @throws NullPointerException if the specified element is null and this
357 * deque does not permit null elements
358 * (<a href="Collection.html#optional-restrictions">optional</a>)
360 boolean removeFirstOccurrence(Object o);
363 * Removes the last occurrence of the specified element from this deque.
364 * If the deque does not contain the element, it is unchanged.
365 * More formally, removes the last element <tt>e</tt> such that
366 * <tt>(o==null ? e==null : o.equals(e))</tt>
367 * (if such an element exists).
368 * Returns <tt>true</tt> if this deque contained the specified element
369 * (or equivalently, if this deque changed as a result of the call).
371 * @param o element to be removed from this deque, if present
372 * @return <tt>true</tt> if an element was removed as a result of this call
373 * @throws ClassCastException if the class of the specified element
374 * is incompatible with this deque
375 * (<a href="Collection.html#optional-restrictions">optional</a>)
376 * @throws NullPointerException if the specified element is null and this
377 * deque does not permit null elements
378 * (<a href="Collection.html#optional-restrictions">optional</a>)
380 boolean removeLastOccurrence(Object o);
382 // *** Queue methods ***
385 * Inserts the specified element into the queue represented by this deque
386 * (in other words, at the tail of this deque) if it is possible to do so
387 * immediately without violating capacity restrictions, returning
388 * <tt>true</tt> upon success and throwing an
389 * <tt>IllegalStateException</tt> if no space is currently available.
390 * When using a capacity-restricted deque, it is generally preferable to
391 * use {@link #offer(Object) offer}.
393 * <p>This method is equivalent to {@link #addLast}.
395 * @param e the element to add
396 * @return <tt>true</tt> (as specified by {@link Collection#add})
397 * @throws IllegalStateException if the element cannot be added at this
398 * time due to capacity restrictions
399 * @throws ClassCastException if the class of the specified element
400 * prevents it from being added to this deque
401 * @throws NullPointerException if the specified element is null and this
402 * deque does not permit null elements
403 * @throws IllegalArgumentException if some property of the specified
404 * element prevents it from being added to this deque
409 * Inserts the specified element into the queue represented by this deque
410 * (in other words, at the tail of this deque) if it is possible to do so
411 * immediately without violating capacity restrictions, returning
412 * <tt>true</tt> upon success and <tt>false</tt> if no space is currently
413 * available. When using a capacity-restricted deque, this method is
414 * generally preferable to the {@link #add} method, which can fail to
415 * insert an element only by throwing an exception.
417 * <p>This method is equivalent to {@link #offerLast}.
419 * @param e the element to add
420 * @return <tt>true</tt> if the element was added to this deque, else
422 * @throws ClassCastException if the class of the specified element
423 * prevents it from being added to this deque
424 * @throws NullPointerException if the specified element is null and this
425 * deque does not permit null elements
426 * @throws IllegalArgumentException if some property of the specified
427 * element prevents it from being added to this deque
432 * Retrieves and removes the head of the queue represented by this deque
433 * (in other words, the first element of this deque).
434 * This method differs from {@link #poll poll} only in that it throws an
435 * exception if this deque is empty.
437 * <p>This method is equivalent to {@link #removeFirst()}.
439 * @return the head of the queue represented by this deque
440 * @throws NoSuchElementException if this deque is empty
445 * Retrieves and removes the head of the queue represented by this deque
446 * (in other words, the first element of this deque), or returns
447 * <tt>null</tt> if this deque is empty.
449 * <p>This method is equivalent to {@link #pollFirst()}.
451 * @return the first element of this deque, or <tt>null</tt> if
452 * this deque is empty
457 * Retrieves, but does not remove, the head of the queue represented by
458 * this deque (in other words, the first element of this deque).
459 * This method differs from {@link #peek peek} only in that it throws an
460 * exception if this deque is empty.
462 * <p>This method is equivalent to {@link #getFirst()}.
464 * @return the head of the queue represented by this deque
465 * @throws NoSuchElementException if this deque is empty
470 * Retrieves, but does not remove, the head of the queue represented by
471 * this deque (in other words, the first element of this deque), or
472 * returns <tt>null</tt> if this deque is empty.
474 * <p>This method is equivalent to {@link #peekFirst()}.
476 * @return the head of the queue represented by this deque, or
477 * <tt>null</tt> if this deque is empty
482 // *** Stack methods ***
485 * Pushes an element onto the stack represented by this deque (in other
486 * words, at the head of this deque) if it is possible to do so
487 * immediately without violating capacity restrictions, returning
488 * <tt>true</tt> upon success and throwing an
489 * <tt>IllegalStateException</tt> if no space is currently available.
491 * <p>This method is equivalent to {@link #addFirst}.
493 * @param e the element to push
494 * @throws IllegalStateException if the element cannot be added at this
495 * time due to capacity restrictions
496 * @throws ClassCastException if the class of the specified element
497 * prevents it from being added to this deque
498 * @throws NullPointerException if the specified element is null and this
499 * deque does not permit null elements
500 * @throws IllegalArgumentException if some property of the specified
501 * element prevents it from being added to this deque
506 * Pops an element from the stack represented by this deque. In other
507 * words, removes and returns the first element of this deque.
509 * <p>This method is equivalent to {@link #removeFirst()}.
511 * @return the element at the front of this deque (which is the top
512 * of the stack represented by this deque)
513 * @throws NoSuchElementException if this deque is empty
518 // *** Collection methods ***
521 * Removes the first occurrence of the specified element from this deque.
522 * If the deque does not contain the element, it is unchanged.
523 * More formally, removes the first element <tt>e</tt> such that
524 * <tt>(o==null ? e==null : o.equals(e))</tt>
525 * (if such an element exists).
526 * Returns <tt>true</tt> if this deque contained the specified element
527 * (or equivalently, if this deque changed as a result of the call).
529 * <p>This method is equivalent to {@link #removeFirstOccurrence}.
531 * @param o element to be removed from this deque, if present
532 * @return <tt>true</tt> if an element was removed as a result of this call
533 * @throws ClassCastException if the class of the specified element
534 * is incompatible with this deque
535 * (<a href="Collection.html#optional-restrictions">optional</a>)
536 * @throws NullPointerException if the specified element is null and this
537 * deque does not permit null elements
538 * (<a href="Collection.html#optional-restrictions">optional</a>)
540 boolean remove(Object o);
543 * Returns <tt>true</tt> if this deque contains the specified element.
544 * More formally, returns <tt>true</tt> if and only if this deque contains
545 * at least one element <tt>e</tt> such that
546 * <tt>(o==null ? e==null : o.equals(e))</tt>.
548 * @param o element whose presence in this deque is to be tested
549 * @return <tt>true</tt> if this deque contains the specified element
550 * @throws ClassCastException if the type of the specified element
551 * is incompatible with this deque
552 * (<a href="Collection.html#optional-restrictions">optional</a>)
553 * @throws NullPointerException if the specified element is null and this
554 * deque does not permit null elements
555 * (<a href="Collection.html#optional-restrictions">optional</a>)
557 boolean contains(Object o);
560 * Returns the number of elements in this deque.
562 * @return the number of elements in this deque
567 * Returns an iterator over the elements in this deque in proper sequence.
568 * The elements will be returned in order from first (head) to last (tail).
570 * @return an iterator over the elements in this deque in proper sequence
572 Iterator<E> iterator();
575 * Returns an iterator over the elements in this deque in reverse
576 * sequential order. The elements will be returned in order from
577 * last (tail) to first (head).
579 * @return an iterator over the elements in this deque in reverse
582 Iterator<E> descendingIterator();