J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 3 | * |
| 4 | * This code is free software; you can redistribute it and/or modify it |
| 5 | * under the terms of the GNU General Public License version 2 only, as |
| 6 | * published by the Free Software Foundation. Sun designates this |
| 7 | * particular file as subject to the "Classpath" exception as provided |
| 8 | * by Sun in the LICENSE file that accompanied this code. |
| 9 | * |
| 10 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 11 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 12 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 13 | * version 2 for more details (a copy is included in the LICENSE file that |
| 14 | * accompanied this code). |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License version |
| 17 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 18 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 19 | * |
| 20 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 21 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 22 | * have any questions. |
| 23 | */ |
| 24 | |
| 25 | /* |
| 26 | * This file is available under and governed by the GNU General Public |
| 27 | * License version 2 only, as published by the Free Software Foundation. |
| 28 | * However, the following notice accompanied the original version of this |
| 29 | * file: |
| 30 | * |
| 31 | * Written by Doug Lea with assistance from members of JCP JSR-166 |
| 32 | * Expert Group and released to the public domain, as explained at |
| 33 | * http://creativecommons.org/licenses/publicdomain |
| 34 | */ |
| 35 | |
| 36 | package java.util.concurrent; |
| 37 | import java.util.*; |
| 38 | import java.util.concurrent.locks.*; |
| 39 | |
| 40 | /** |
| 41 | * An optionally-bounded {@linkplain BlockingDeque blocking deque} based on |
| 42 | * linked nodes. |
| 43 | * |
| 44 | * <p> The optional capacity bound constructor argument serves as a |
| 45 | * way to prevent excessive expansion. The capacity, if unspecified, |
| 46 | * is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
| 47 | * dynamically created upon each insertion unless this would bring the |
| 48 | * deque above capacity. |
| 49 | * |
| 50 | * <p>Most operations run in constant time (ignoring time spent |
| 51 | * blocking). Exceptions include {@link #remove(Object) remove}, |
| 52 | * {@link #removeFirstOccurrence removeFirstOccurrence}, {@link |
| 53 | * #removeLastOccurrence removeLastOccurrence}, {@link #contains |
| 54 | * contains}, {@link #iterator iterator.remove()}, and the bulk |
| 55 | * operations, all of which run in linear time. |
| 56 | * |
| 57 | * <p>This class and its iterator implement all of the |
| 58 | * <em>optional</em> methods of the {@link Collection} and {@link |
| 59 | * Iterator} interfaces. |
| 60 | * |
| 61 | * <p>This class is a member of the |
| 62 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| 63 | * Java Collections Framework</a>. |
| 64 | * |
| 65 | * @since 1.6 |
| 66 | * @author Doug Lea |
| 67 | * @param <E> the type of elements held in this collection |
| 68 | */ |
| 69 | public class LinkedBlockingDeque<E> |
| 70 | extends AbstractQueue<E> |
| 71 | implements BlockingDeque<E>, java.io.Serializable { |
| 72 | |
| 73 | /* |
| 74 | * Implemented as a simple doubly-linked list protected by a |
| 75 | * single lock and using conditions to manage blocking. |
| 76 | */ |
| 77 | |
| 78 | /* |
| 79 | * We have "diamond" multiple interface/abstract class inheritance |
| 80 | * here, and that introduces ambiguities. Often we want the |
| 81 | * BlockingDeque javadoc combined with the AbstractQueue |
| 82 | * implementation, so a lot of method specs are duplicated here. |
| 83 | */ |
| 84 | |
| 85 | private static final long serialVersionUID = -387911632671998426L; |
| 86 | |
| 87 | /** Doubly-linked list node class */ |
| 88 | static final class Node<E> { |
| 89 | E item; |
| 90 | Node<E> prev; |
| 91 | Node<E> next; |
| 92 | Node(E x, Node<E> p, Node<E> n) { |
| 93 | item = x; |
| 94 | prev = p; |
| 95 | next = n; |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | /** Pointer to first node */ |
| 100 | private transient Node<E> first; |
| 101 | /** Pointer to last node */ |
| 102 | private transient Node<E> last; |
| 103 | /** Number of items in the deque */ |
| 104 | private transient int count; |
| 105 | /** Maximum number of items in the deque */ |
| 106 | private final int capacity; |
| 107 | /** Main lock guarding all access */ |
| 108 | private final ReentrantLock lock = new ReentrantLock(); |
| 109 | /** Condition for waiting takes */ |
| 110 | private final Condition notEmpty = lock.newCondition(); |
| 111 | /** Condition for waiting puts */ |
| 112 | private final Condition notFull = lock.newCondition(); |
| 113 | |
| 114 | /** |
| 115 | * Creates a <tt>LinkedBlockingDeque</tt> with a capacity of |
| 116 | * {@link Integer#MAX_VALUE}. |
| 117 | */ |
| 118 | public LinkedBlockingDeque() { |
| 119 | this(Integer.MAX_VALUE); |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * Creates a <tt>LinkedBlockingDeque</tt> with the given (fixed) capacity. |
| 124 | * |
| 125 | * @param capacity the capacity of this deque |
| 126 | * @throws IllegalArgumentException if <tt>capacity</tt> is less than 1 |
| 127 | */ |
| 128 | public LinkedBlockingDeque(int capacity) { |
| 129 | if (capacity <= 0) throw new IllegalArgumentException(); |
| 130 | this.capacity = capacity; |
| 131 | } |
| 132 | |
| 133 | /** |
| 134 | * Creates a <tt>LinkedBlockingDeque</tt> with a capacity of |
| 135 | * {@link Integer#MAX_VALUE}, initially containing the elements of |
| 136 | * the given collection, added in traversal order of the |
| 137 | * collection's iterator. |
| 138 | * |
| 139 | * @param c the collection of elements to initially contain |
| 140 | * @throws NullPointerException if the specified collection or any |
| 141 | * of its elements are null |
| 142 | */ |
| 143 | public LinkedBlockingDeque(Collection<? extends E> c) { |
| 144 | this(Integer.MAX_VALUE); |
| 145 | for (E e : c) |
| 146 | add(e); |
| 147 | } |
| 148 | |
| 149 | |
| 150 | // Basic linking and unlinking operations, called only while holding lock |
| 151 | |
| 152 | /** |
| 153 | * Links e as first element, or returns false if full. |
| 154 | */ |
| 155 | private boolean linkFirst(E e) { |
| 156 | if (count >= capacity) |
| 157 | return false; |
| 158 | ++count; |
| 159 | Node<E> f = first; |
| 160 | Node<E> x = new Node<E>(e, null, f); |
| 161 | first = x; |
| 162 | if (last == null) |
| 163 | last = x; |
| 164 | else |
| 165 | f.prev = x; |
| 166 | notEmpty.signal(); |
| 167 | return true; |
| 168 | } |
| 169 | |
| 170 | /** |
| 171 | * Links e as last element, or returns false if full. |
| 172 | */ |
| 173 | private boolean linkLast(E e) { |
| 174 | if (count >= capacity) |
| 175 | return false; |
| 176 | ++count; |
| 177 | Node<E> l = last; |
| 178 | Node<E> x = new Node<E>(e, l, null); |
| 179 | last = x; |
| 180 | if (first == null) |
| 181 | first = x; |
| 182 | else |
| 183 | l.next = x; |
| 184 | notEmpty.signal(); |
| 185 | return true; |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * Removes and returns first element, or null if empty. |
| 190 | */ |
| 191 | private E unlinkFirst() { |
| 192 | Node<E> f = first; |
| 193 | if (f == null) |
| 194 | return null; |
| 195 | Node<E> n = f.next; |
| 196 | first = n; |
| 197 | if (n == null) |
| 198 | last = null; |
| 199 | else |
| 200 | n.prev = null; |
| 201 | --count; |
| 202 | notFull.signal(); |
| 203 | return f.item; |
| 204 | } |
| 205 | |
| 206 | /** |
| 207 | * Removes and returns last element, or null if empty. |
| 208 | */ |
| 209 | private E unlinkLast() { |
| 210 | Node<E> l = last; |
| 211 | if (l == null) |
| 212 | return null; |
| 213 | Node<E> p = l.prev; |
| 214 | last = p; |
| 215 | if (p == null) |
| 216 | first = null; |
| 217 | else |
| 218 | p.next = null; |
| 219 | --count; |
| 220 | notFull.signal(); |
| 221 | return l.item; |
| 222 | } |
| 223 | |
| 224 | /** |
| 225 | * Unlink e |
| 226 | */ |
| 227 | private void unlink(Node<E> x) { |
| 228 | Node<E> p = x.prev; |
| 229 | Node<E> n = x.next; |
| 230 | if (p == null) { |
| 231 | if (n == null) |
| 232 | first = last = null; |
| 233 | else { |
| 234 | n.prev = null; |
| 235 | first = n; |
| 236 | } |
| 237 | } else if (n == null) { |
| 238 | p.next = null; |
| 239 | last = p; |
| 240 | } else { |
| 241 | p.next = n; |
| 242 | n.prev = p; |
| 243 | } |
| 244 | --count; |
| 245 | notFull.signalAll(); |
| 246 | } |
| 247 | |
| 248 | // BlockingDeque methods |
| 249 | |
| 250 | /** |
| 251 | * @throws IllegalStateException {@inheritDoc} |
| 252 | * @throws NullPointerException {@inheritDoc} |
| 253 | */ |
| 254 | public void addFirst(E e) { |
| 255 | if (!offerFirst(e)) |
| 256 | throw new IllegalStateException("Deque full"); |
| 257 | } |
| 258 | |
| 259 | /** |
| 260 | * @throws IllegalStateException {@inheritDoc} |
| 261 | * @throws NullPointerException {@inheritDoc} |
| 262 | */ |
| 263 | public void addLast(E e) { |
| 264 | if (!offerLast(e)) |
| 265 | throw new IllegalStateException("Deque full"); |
| 266 | } |
| 267 | |
| 268 | /** |
| 269 | * @throws NullPointerException {@inheritDoc} |
| 270 | */ |
| 271 | public boolean offerFirst(E e) { |
| 272 | if (e == null) throw new NullPointerException(); |
| 273 | lock.lock(); |
| 274 | try { |
| 275 | return linkFirst(e); |
| 276 | } finally { |
| 277 | lock.unlock(); |
| 278 | } |
| 279 | } |
| 280 | |
| 281 | /** |
| 282 | * @throws NullPointerException {@inheritDoc} |
| 283 | */ |
| 284 | public boolean offerLast(E e) { |
| 285 | if (e == null) throw new NullPointerException(); |
| 286 | lock.lock(); |
| 287 | try { |
| 288 | return linkLast(e); |
| 289 | } finally { |
| 290 | lock.unlock(); |
| 291 | } |
| 292 | } |
| 293 | |
| 294 | /** |
| 295 | * @throws NullPointerException {@inheritDoc} |
| 296 | * @throws InterruptedException {@inheritDoc} |
| 297 | */ |
| 298 | public void putFirst(E e) throws InterruptedException { |
| 299 | if (e == null) throw new NullPointerException(); |
| 300 | lock.lock(); |
| 301 | try { |
| 302 | while (!linkFirst(e)) |
| 303 | notFull.await(); |
| 304 | } finally { |
| 305 | lock.unlock(); |
| 306 | } |
| 307 | } |
| 308 | |
| 309 | /** |
| 310 | * @throws NullPointerException {@inheritDoc} |
| 311 | * @throws InterruptedException {@inheritDoc} |
| 312 | */ |
| 313 | public void putLast(E e) throws InterruptedException { |
| 314 | if (e == null) throw new NullPointerException(); |
| 315 | lock.lock(); |
| 316 | try { |
| 317 | while (!linkLast(e)) |
| 318 | notFull.await(); |
| 319 | } finally { |
| 320 | lock.unlock(); |
| 321 | } |
| 322 | } |
| 323 | |
| 324 | /** |
| 325 | * @throws NullPointerException {@inheritDoc} |
| 326 | * @throws InterruptedException {@inheritDoc} |
| 327 | */ |
| 328 | public boolean offerFirst(E e, long timeout, TimeUnit unit) |
| 329 | throws InterruptedException { |
| 330 | if (e == null) throw new NullPointerException(); |
| 331 | long nanos = unit.toNanos(timeout); |
| 332 | lock.lockInterruptibly(); |
| 333 | try { |
| 334 | for (;;) { |
| 335 | if (linkFirst(e)) |
| 336 | return true; |
| 337 | if (nanos <= 0) |
| 338 | return false; |
| 339 | nanos = notFull.awaitNanos(nanos); |
| 340 | } |
| 341 | } finally { |
| 342 | lock.unlock(); |
| 343 | } |
| 344 | } |
| 345 | |
| 346 | /** |
| 347 | * @throws NullPointerException {@inheritDoc} |
| 348 | * @throws InterruptedException {@inheritDoc} |
| 349 | */ |
| 350 | public boolean offerLast(E e, long timeout, TimeUnit unit) |
| 351 | throws InterruptedException { |
| 352 | if (e == null) throw new NullPointerException(); |
| 353 | long nanos = unit.toNanos(timeout); |
| 354 | lock.lockInterruptibly(); |
| 355 | try { |
| 356 | for (;;) { |
| 357 | if (linkLast(e)) |
| 358 | return true; |
| 359 | if (nanos <= 0) |
| 360 | return false; |
| 361 | nanos = notFull.awaitNanos(nanos); |
| 362 | } |
| 363 | } finally { |
| 364 | lock.unlock(); |
| 365 | } |
| 366 | } |
| 367 | |
| 368 | /** |
| 369 | * @throws NoSuchElementException {@inheritDoc} |
| 370 | */ |
| 371 | public E removeFirst() { |
| 372 | E x = pollFirst(); |
| 373 | if (x == null) throw new NoSuchElementException(); |
| 374 | return x; |
| 375 | } |
| 376 | |
| 377 | /** |
| 378 | * @throws NoSuchElementException {@inheritDoc} |
| 379 | */ |
| 380 | public E removeLast() { |
| 381 | E x = pollLast(); |
| 382 | if (x == null) throw new NoSuchElementException(); |
| 383 | return x; |
| 384 | } |
| 385 | |
| 386 | public E pollFirst() { |
| 387 | lock.lock(); |
| 388 | try { |
| 389 | return unlinkFirst(); |
| 390 | } finally { |
| 391 | lock.unlock(); |
| 392 | } |
| 393 | } |
| 394 | |
| 395 | public E pollLast() { |
| 396 | lock.lock(); |
| 397 | try { |
| 398 | return unlinkLast(); |
| 399 | } finally { |
| 400 | lock.unlock(); |
| 401 | } |
| 402 | } |
| 403 | |
| 404 | public E takeFirst() throws InterruptedException { |
| 405 | lock.lock(); |
| 406 | try { |
| 407 | E x; |
| 408 | while ( (x = unlinkFirst()) == null) |
| 409 | notEmpty.await(); |
| 410 | return x; |
| 411 | } finally { |
| 412 | lock.unlock(); |
| 413 | } |
| 414 | } |
| 415 | |
| 416 | public E takeLast() throws InterruptedException { |
| 417 | lock.lock(); |
| 418 | try { |
| 419 | E x; |
| 420 | while ( (x = unlinkLast()) == null) |
| 421 | notEmpty.await(); |
| 422 | return x; |
| 423 | } finally { |
| 424 | lock.unlock(); |
| 425 | } |
| 426 | } |
| 427 | |
| 428 | public E pollFirst(long timeout, TimeUnit unit) |
| 429 | throws InterruptedException { |
| 430 | long nanos = unit.toNanos(timeout); |
| 431 | lock.lockInterruptibly(); |
| 432 | try { |
| 433 | for (;;) { |
| 434 | E x = unlinkFirst(); |
| 435 | if (x != null) |
| 436 | return x; |
| 437 | if (nanos <= 0) |
| 438 | return null; |
| 439 | nanos = notEmpty.awaitNanos(nanos); |
| 440 | } |
| 441 | } finally { |
| 442 | lock.unlock(); |
| 443 | } |
| 444 | } |
| 445 | |
| 446 | public E pollLast(long timeout, TimeUnit unit) |
| 447 | throws InterruptedException { |
| 448 | long nanos = unit.toNanos(timeout); |
| 449 | lock.lockInterruptibly(); |
| 450 | try { |
| 451 | for (;;) { |
| 452 | E x = unlinkLast(); |
| 453 | if (x != null) |
| 454 | return x; |
| 455 | if (nanos <= 0) |
| 456 | return null; |
| 457 | nanos = notEmpty.awaitNanos(nanos); |
| 458 | } |
| 459 | } finally { |
| 460 | lock.unlock(); |
| 461 | } |
| 462 | } |
| 463 | |
| 464 | /** |
| 465 | * @throws NoSuchElementException {@inheritDoc} |
| 466 | */ |
| 467 | public E getFirst() { |
| 468 | E x = peekFirst(); |
| 469 | if (x == null) throw new NoSuchElementException(); |
| 470 | return x; |
| 471 | } |
| 472 | |
| 473 | /** |
| 474 | * @throws NoSuchElementException {@inheritDoc} |
| 475 | */ |
| 476 | public E getLast() { |
| 477 | E x = peekLast(); |
| 478 | if (x == null) throw new NoSuchElementException(); |
| 479 | return x; |
| 480 | } |
| 481 | |
| 482 | public E peekFirst() { |
| 483 | lock.lock(); |
| 484 | try { |
| 485 | return (first == null) ? null : first.item; |
| 486 | } finally { |
| 487 | lock.unlock(); |
| 488 | } |
| 489 | } |
| 490 | |
| 491 | public E peekLast() { |
| 492 | lock.lock(); |
| 493 | try { |
| 494 | return (last == null) ? null : last.item; |
| 495 | } finally { |
| 496 | lock.unlock(); |
| 497 | } |
| 498 | } |
| 499 | |
| 500 | public boolean removeFirstOccurrence(Object o) { |
| 501 | if (o == null) return false; |
| 502 | lock.lock(); |
| 503 | try { |
| 504 | for (Node<E> p = first; p != null; p = p.next) { |
| 505 | if (o.equals(p.item)) { |
| 506 | unlink(p); |
| 507 | return true; |
| 508 | } |
| 509 | } |
| 510 | return false; |
| 511 | } finally { |
| 512 | lock.unlock(); |
| 513 | } |
| 514 | } |
| 515 | |
| 516 | public boolean removeLastOccurrence(Object o) { |
| 517 | if (o == null) return false; |
| 518 | lock.lock(); |
| 519 | try { |
| 520 | for (Node<E> p = last; p != null; p = p.prev) { |
| 521 | if (o.equals(p.item)) { |
| 522 | unlink(p); |
| 523 | return true; |
| 524 | } |
| 525 | } |
| 526 | return false; |
| 527 | } finally { |
| 528 | lock.unlock(); |
| 529 | } |
| 530 | } |
| 531 | |
| 532 | // BlockingQueue methods |
| 533 | |
| 534 | /** |
| 535 | * Inserts the specified element at the end of this deque unless it would |
| 536 | * violate capacity restrictions. When using a capacity-restricted deque, |
| 537 | * it is generally preferable to use method {@link #offer(Object) offer}. |
| 538 | * |
| 539 | * <p>This method is equivalent to {@link #addLast}. |
| 540 | * |
| 541 | * @throws IllegalStateException if the element cannot be added at this |
| 542 | * time due to capacity restrictions |
| 543 | * @throws NullPointerException if the specified element is null |
| 544 | */ |
| 545 | public boolean add(E e) { |
| 546 | addLast(e); |
| 547 | return true; |
| 548 | } |
| 549 | |
| 550 | /** |
| 551 | * @throws NullPointerException if the specified element is null |
| 552 | */ |
| 553 | public boolean offer(E e) { |
| 554 | return offerLast(e); |
| 555 | } |
| 556 | |
| 557 | /** |
| 558 | * @throws NullPointerException {@inheritDoc} |
| 559 | * @throws InterruptedException {@inheritDoc} |
| 560 | */ |
| 561 | public void put(E e) throws InterruptedException { |
| 562 | putLast(e); |
| 563 | } |
| 564 | |
| 565 | /** |
| 566 | * @throws NullPointerException {@inheritDoc} |
| 567 | * @throws InterruptedException {@inheritDoc} |
| 568 | */ |
| 569 | public boolean offer(E e, long timeout, TimeUnit unit) |
| 570 | throws InterruptedException { |
| 571 | return offerLast(e, timeout, unit); |
| 572 | } |
| 573 | |
| 574 | /** |
| 575 | * Retrieves and removes the head of the queue represented by this deque. |
| 576 | * This method differs from {@link #poll poll} only in that it throws an |
| 577 | * exception if this deque is empty. |
| 578 | * |
| 579 | * <p>This method is equivalent to {@link #removeFirst() removeFirst}. |
| 580 | * |
| 581 | * @return the head of the queue represented by this deque |
| 582 | * @throws NoSuchElementException if this deque is empty |
| 583 | */ |
| 584 | public E remove() { |
| 585 | return removeFirst(); |
| 586 | } |
| 587 | |
| 588 | public E poll() { |
| 589 | return pollFirst(); |
| 590 | } |
| 591 | |
| 592 | public E take() throws InterruptedException { |
| 593 | return takeFirst(); |
| 594 | } |
| 595 | |
| 596 | public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
| 597 | return pollFirst(timeout, unit); |
| 598 | } |
| 599 | |
| 600 | /** |
| 601 | * Retrieves, but does not remove, the head of the queue represented by |
| 602 | * this deque. This method differs from {@link #peek peek} only in that |
| 603 | * it throws an exception if this deque is empty. |
| 604 | * |
| 605 | * <p>This method is equivalent to {@link #getFirst() getFirst}. |
| 606 | * |
| 607 | * @return the head of the queue represented by this deque |
| 608 | * @throws NoSuchElementException if this deque is empty |
| 609 | */ |
| 610 | public E element() { |
| 611 | return getFirst(); |
| 612 | } |
| 613 | |
| 614 | public E peek() { |
| 615 | return peekFirst(); |
| 616 | } |
| 617 | |
| 618 | /** |
| 619 | * Returns the number of additional elements that this deque can ideally |
| 620 | * (in the absence of memory or resource constraints) accept without |
| 621 | * blocking. This is always equal to the initial capacity of this deque |
| 622 | * less the current <tt>size</tt> of this deque. |
| 623 | * |
| 624 | * <p>Note that you <em>cannot</em> always tell if an attempt to insert |
| 625 | * an element will succeed by inspecting <tt>remainingCapacity</tt> |
| 626 | * because it may be the case that another thread is about to |
| 627 | * insert or remove an element. |
| 628 | */ |
| 629 | public int remainingCapacity() { |
| 630 | lock.lock(); |
| 631 | try { |
| 632 | return capacity - count; |
| 633 | } finally { |
| 634 | lock.unlock(); |
| 635 | } |
| 636 | } |
| 637 | |
| 638 | /** |
| 639 | * @throws UnsupportedOperationException {@inheritDoc} |
| 640 | * @throws ClassCastException {@inheritDoc} |
| 641 | * @throws NullPointerException {@inheritDoc} |
| 642 | * @throws IllegalArgumentException {@inheritDoc} |
| 643 | */ |
| 644 | public int drainTo(Collection<? super E> c) { |
| 645 | if (c == null) |
| 646 | throw new NullPointerException(); |
| 647 | if (c == this) |
| 648 | throw new IllegalArgumentException(); |
| 649 | lock.lock(); |
| 650 | try { |
| 651 | for (Node<E> p = first; p != null; p = p.next) |
| 652 | c.add(p.item); |
| 653 | int n = count; |
| 654 | count = 0; |
| 655 | first = last = null; |
| 656 | notFull.signalAll(); |
| 657 | return n; |
| 658 | } finally { |
| 659 | lock.unlock(); |
| 660 | } |
| 661 | } |
| 662 | |
| 663 | /** |
| 664 | * @throws UnsupportedOperationException {@inheritDoc} |
| 665 | * @throws ClassCastException {@inheritDoc} |
| 666 | * @throws NullPointerException {@inheritDoc} |
| 667 | * @throws IllegalArgumentException {@inheritDoc} |
| 668 | */ |
| 669 | public int drainTo(Collection<? super E> c, int maxElements) { |
| 670 | if (c == null) |
| 671 | throw new NullPointerException(); |
| 672 | if (c == this) |
| 673 | throw new IllegalArgumentException(); |
| 674 | lock.lock(); |
| 675 | try { |
| 676 | int n = 0; |
| 677 | while (n < maxElements && first != null) { |
| 678 | c.add(first.item); |
| 679 | first.prev = null; |
| 680 | first = first.next; |
| 681 | --count; |
| 682 | ++n; |
| 683 | } |
| 684 | if (first == null) |
| 685 | last = null; |
| 686 | notFull.signalAll(); |
| 687 | return n; |
| 688 | } finally { |
| 689 | lock.unlock(); |
| 690 | } |
| 691 | } |
| 692 | |
| 693 | // Stack methods |
| 694 | |
| 695 | /** |
| 696 | * @throws IllegalStateException {@inheritDoc} |
| 697 | * @throws NullPointerException {@inheritDoc} |
| 698 | */ |
| 699 | public void push(E e) { |
| 700 | addFirst(e); |
| 701 | } |
| 702 | |
| 703 | /** |
| 704 | * @throws NoSuchElementException {@inheritDoc} |
| 705 | */ |
| 706 | public E pop() { |
| 707 | return removeFirst(); |
| 708 | } |
| 709 | |
| 710 | // Collection methods |
| 711 | |
| 712 | /** |
| 713 | * Removes the first occurrence of the specified element from this deque. |
| 714 | * If the deque does not contain the element, it is unchanged. |
| 715 | * More formally, removes the first element <tt>e</tt> such that |
| 716 | * <tt>o.equals(e)</tt> (if such an element exists). |
| 717 | * Returns <tt>true</tt> if this deque contained the specified element |
| 718 | * (or equivalently, if this deque changed as a result of the call). |
| 719 | * |
| 720 | * <p>This method is equivalent to |
| 721 | * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. |
| 722 | * |
| 723 | * @param o element to be removed from this deque, if present |
| 724 | * @return <tt>true</tt> if this deque changed as a result of the call |
| 725 | */ |
| 726 | public boolean remove(Object o) { |
| 727 | return removeFirstOccurrence(o); |
| 728 | } |
| 729 | |
| 730 | /** |
| 731 | * Returns the number of elements in this deque. |
| 732 | * |
| 733 | * @return the number of elements in this deque |
| 734 | */ |
| 735 | public int size() { |
| 736 | lock.lock(); |
| 737 | try { |
| 738 | return count; |
| 739 | } finally { |
| 740 | lock.unlock(); |
| 741 | } |
| 742 | } |
| 743 | |
| 744 | /** |
| 745 | * Returns <tt>true</tt> if this deque contains the specified element. |
| 746 | * More formally, returns <tt>true</tt> if and only if this deque contains |
| 747 | * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 748 | * |
| 749 | * @param o object to be checked for containment in this deque |
| 750 | * @return <tt>true</tt> if this deque contains the specified element |
| 751 | */ |
| 752 | public boolean contains(Object o) { |
| 753 | if (o == null) return false; |
| 754 | lock.lock(); |
| 755 | try { |
| 756 | for (Node<E> p = first; p != null; p = p.next) |
| 757 | if (o.equals(p.item)) |
| 758 | return true; |
| 759 | return false; |
| 760 | } finally { |
| 761 | lock.unlock(); |
| 762 | } |
| 763 | } |
| 764 | |
| 765 | /** |
| 766 | * Variant of removeFirstOccurrence needed by iterator.remove. |
| 767 | * Searches for the node, not its contents. |
| 768 | */ |
| 769 | boolean removeNode(Node<E> e) { |
| 770 | lock.lock(); |
| 771 | try { |
| 772 | for (Node<E> p = first; p != null; p = p.next) { |
| 773 | if (p == e) { |
| 774 | unlink(p); |
| 775 | return true; |
| 776 | } |
| 777 | } |
| 778 | return false; |
| 779 | } finally { |
| 780 | lock.unlock(); |
| 781 | } |
| 782 | } |
| 783 | |
| 784 | /** |
| 785 | * Returns an array containing all of the elements in this deque, in |
| 786 | * proper sequence (from first to last element). |
| 787 | * |
| 788 | * <p>The returned array will be "safe" in that no references to it are |
| 789 | * maintained by this deque. (In other words, this method must allocate |
| 790 | * a new array). The caller is thus free to modify the returned array. |
| 791 | * |
| 792 | * <p>This method acts as bridge between array-based and collection-based |
| 793 | * APIs. |
| 794 | * |
| 795 | * @return an array containing all of the elements in this deque |
| 796 | */ |
| 797 | public Object[] toArray() { |
| 798 | lock.lock(); |
| 799 | try { |
| 800 | Object[] a = new Object[count]; |
| 801 | int k = 0; |
| 802 | for (Node<E> p = first; p != null; p = p.next) |
| 803 | a[k++] = p.item; |
| 804 | return a; |
| 805 | } finally { |
| 806 | lock.unlock(); |
| 807 | } |
| 808 | } |
| 809 | |
| 810 | /** |
| 811 | * Returns an array containing all of the elements in this deque, in |
| 812 | * proper sequence; the runtime type of the returned array is that of |
| 813 | * the specified array. If the deque fits in the specified array, it |
| 814 | * is returned therein. Otherwise, a new array is allocated with the |
| 815 | * runtime type of the specified array and the size of this deque. |
| 816 | * |
| 817 | * <p>If this deque fits in the specified array with room to spare |
| 818 | * (i.e., the array has more elements than this deque), the element in |
| 819 | * the array immediately following the end of the deque is set to |
| 820 | * <tt>null</tt>. |
| 821 | * |
| 822 | * <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 823 | * array-based and collection-based APIs. Further, this method allows |
| 824 | * precise control over the runtime type of the output array, and may, |
| 825 | * under certain circumstances, be used to save allocation costs. |
| 826 | * |
| 827 | * <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
| 828 | * The following code can be used to dump the deque into a newly |
| 829 | * allocated array of <tt>String</tt>: |
| 830 | * |
| 831 | * <pre> |
| 832 | * String[] y = x.toArray(new String[0]);</pre> |
| 833 | * |
| 834 | * Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 835 | * <tt>toArray()</tt>. |
| 836 | * |
| 837 | * @param a the array into which the elements of the deque are to |
| 838 | * be stored, if it is big enough; otherwise, a new array of the |
| 839 | * same runtime type is allocated for this purpose |
| 840 | * @return an array containing all of the elements in this deque |
| 841 | * @throws ArrayStoreException if the runtime type of the specified array |
| 842 | * is not a supertype of the runtime type of every element in |
| 843 | * this deque |
| 844 | * @throws NullPointerException if the specified array is null |
| 845 | */ |
| 846 | public <T> T[] toArray(T[] a) { |
| 847 | lock.lock(); |
| 848 | try { |
| 849 | if (a.length < count) |
| 850 | a = (T[])java.lang.reflect.Array.newInstance( |
| 851 | a.getClass().getComponentType(), |
| 852 | count |
| 853 | ); |
| 854 | |
| 855 | int k = 0; |
| 856 | for (Node<E> p = first; p != null; p = p.next) |
| 857 | a[k++] = (T)p.item; |
| 858 | if (a.length > k) |
| 859 | a[k] = null; |
| 860 | return a; |
| 861 | } finally { |
| 862 | lock.unlock(); |
| 863 | } |
| 864 | } |
| 865 | |
| 866 | public String toString() { |
| 867 | lock.lock(); |
| 868 | try { |
| 869 | return super.toString(); |
| 870 | } finally { |
| 871 | lock.unlock(); |
| 872 | } |
| 873 | } |
| 874 | |
| 875 | /** |
| 876 | * Atomically removes all of the elements from this deque. |
| 877 | * The deque will be empty after this call returns. |
| 878 | */ |
| 879 | public void clear() { |
| 880 | lock.lock(); |
| 881 | try { |
| 882 | first = last = null; |
| 883 | count = 0; |
| 884 | notFull.signalAll(); |
| 885 | } finally { |
| 886 | lock.unlock(); |
| 887 | } |
| 888 | } |
| 889 | |
| 890 | /** |
| 891 | * Returns an iterator over the elements in this deque in proper sequence. |
| 892 | * The elements will be returned in order from first (head) to last (tail). |
| 893 | * The returned <tt>Iterator</tt> is a "weakly consistent" iterator that |
| 894 | * will never throw {@link ConcurrentModificationException}, |
| 895 | * and guarantees to traverse elements as they existed upon |
| 896 | * construction of the iterator, and may (but is not guaranteed to) |
| 897 | * reflect any modifications subsequent to construction. |
| 898 | * |
| 899 | * @return an iterator over the elements in this deque in proper sequence |
| 900 | */ |
| 901 | public Iterator<E> iterator() { |
| 902 | return new Itr(); |
| 903 | } |
| 904 | |
| 905 | /** |
| 906 | * Returns an iterator over the elements in this deque in reverse |
| 907 | * sequential order. The elements will be returned in order from |
| 908 | * last (tail) to first (head). |
| 909 | * The returned <tt>Iterator</tt> is a "weakly consistent" iterator that |
| 910 | * will never throw {@link ConcurrentModificationException}, |
| 911 | * and guarantees to traverse elements as they existed upon |
| 912 | * construction of the iterator, and may (but is not guaranteed to) |
| 913 | * reflect any modifications subsequent to construction. |
| 914 | */ |
| 915 | public Iterator<E> descendingIterator() { |
| 916 | return new DescendingItr(); |
| 917 | } |
| 918 | |
| 919 | /** |
| 920 | * Base class for Iterators for LinkedBlockingDeque |
| 921 | */ |
| 922 | private abstract class AbstractItr implements Iterator<E> { |
| 923 | /** |
| 924 | * The next node to return in next |
| 925 | */ |
| 926 | Node<E> next; |
| 927 | |
| 928 | /** |
| 929 | * nextItem holds on to item fields because once we claim that |
| 930 | * an element exists in hasNext(), we must return item read |
| 931 | * under lock (in advance()) even if it was in the process of |
| 932 | * being removed when hasNext() was called. |
| 933 | */ |
| 934 | E nextItem; |
| 935 | |
| 936 | /** |
| 937 | * Node returned by most recent call to next. Needed by remove. |
| 938 | * Reset to null if this element is deleted by a call to remove. |
| 939 | */ |
| 940 | private Node<E> lastRet; |
| 941 | |
| 942 | AbstractItr() { |
| 943 | advance(); // set to initial position |
| 944 | } |
| 945 | |
| 946 | /** |
| 947 | * Advances next, or if not yet initialized, sets to first node. |
| 948 | * Implemented to move forward vs backward in the two subclasses. |
| 949 | */ |
| 950 | abstract void advance(); |
| 951 | |
| 952 | public boolean hasNext() { |
| 953 | return next != null; |
| 954 | } |
| 955 | |
| 956 | public E next() { |
| 957 | if (next == null) |
| 958 | throw new NoSuchElementException(); |
| 959 | lastRet = next; |
| 960 | E x = nextItem; |
| 961 | advance(); |
| 962 | return x; |
| 963 | } |
| 964 | |
| 965 | public void remove() { |
| 966 | Node<E> n = lastRet; |
| 967 | if (n == null) |
| 968 | throw new IllegalStateException(); |
| 969 | lastRet = null; |
| 970 | // Note: removeNode rescans looking for this node to make |
| 971 | // sure it was not already removed. Otherwise, trying to |
| 972 | // re-remove could corrupt list. |
| 973 | removeNode(n); |
| 974 | } |
| 975 | } |
| 976 | |
| 977 | /** Forward iterator */ |
| 978 | private class Itr extends AbstractItr { |
| 979 | void advance() { |
| 980 | final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
| 981 | lock.lock(); |
| 982 | try { |
| 983 | next = (next == null)? first : next.next; |
| 984 | nextItem = (next == null)? null : next.item; |
| 985 | } finally { |
| 986 | lock.unlock(); |
| 987 | } |
| 988 | } |
| 989 | } |
| 990 | |
| 991 | /** |
| 992 | * Descending iterator for LinkedBlockingDeque |
| 993 | */ |
| 994 | private class DescendingItr extends AbstractItr { |
| 995 | void advance() { |
| 996 | final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
| 997 | lock.lock(); |
| 998 | try { |
| 999 | next = (next == null)? last : next.prev; |
| 1000 | nextItem = (next == null)? null : next.item; |
| 1001 | } finally { |
| 1002 | lock.unlock(); |
| 1003 | } |
| 1004 | } |
| 1005 | } |
| 1006 | |
| 1007 | /** |
| 1008 | * Save the state of this deque to a stream (that is, serialize it). |
| 1009 | * |
| 1010 | * @serialData The capacity (int), followed by elements (each an |
| 1011 | * <tt>Object</tt>) in the proper order, followed by a null |
| 1012 | * @param s the stream |
| 1013 | */ |
| 1014 | private void writeObject(java.io.ObjectOutputStream s) |
| 1015 | throws java.io.IOException { |
| 1016 | lock.lock(); |
| 1017 | try { |
| 1018 | // Write out capacity and any hidden stuff |
| 1019 | s.defaultWriteObject(); |
| 1020 | // Write out all elements in the proper order. |
| 1021 | for (Node<E> p = first; p != null; p = p.next) |
| 1022 | s.writeObject(p.item); |
| 1023 | // Use trailing null as sentinel |
| 1024 | s.writeObject(null); |
| 1025 | } finally { |
| 1026 | lock.unlock(); |
| 1027 | } |
| 1028 | } |
| 1029 | |
| 1030 | /** |
| 1031 | * Reconstitute this deque from a stream (that is, |
| 1032 | * deserialize it). |
| 1033 | * @param s the stream |
| 1034 | */ |
| 1035 | private void readObject(java.io.ObjectInputStream s) |
| 1036 | throws java.io.IOException, ClassNotFoundException { |
| 1037 | s.defaultReadObject(); |
| 1038 | count = 0; |
| 1039 | first = null; |
| 1040 | last = null; |
| 1041 | // Read in all elements and place in queue |
| 1042 | for (;;) { |
| 1043 | E item = (E)s.readObject(); |
| 1044 | if (item == null) |
| 1045 | break; |
| 1046 | add(item); |
| 1047 | } |
| 1048 | } |
| 1049 | |
| 1050 | } |