1 /* 2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.util; 27 28 import java.util.function.Consumer; 29 import java.util.function.Predicate; 30 import java.util.function.UnaryOperator; 31 import jdk.internal.misc.SharedSecrets; 32 33 /** 34 * Resizable-array implementation of the {@code List} interface. Implements 35 * all optional list operations, and permits all elements, including 36 * {@code null}. In addition to implementing the {@code List} interface, 37 * this class provides methods to manipulate the size of the array that is 38 * used internally to store the list. (This class is roughly equivalent to 39 * {@code Vector}, except that it is unsynchronized.) 40 * 41 * <p>The {@code size}, {@code isEmpty}, {@code get}, {@code set}, 42 * {@code iterator}, and {@code listIterator} operations run in constant 43 * time. The {@code add} operation runs in <i>amortized constant time</i>, 44 * that is, adding n elements requires O(n) time. All of the other operations 45 * run in linear time (roughly speaking). The constant factor is low compared 46 * to that for the {@code LinkedList} implementation. 47 * 48 * <p>Each {@code ArrayList} instance has a <i>capacity</i>. The capacity is 49 * the size of the array used to store the elements in the list. It is always 50 * at least as large as the list size. As elements are added to an ArrayList, 51 * its capacity grows automatically. The details of the growth policy are not 52 * specified beyond the fact that adding an element has constant amortized 53 * time cost. 54 * 55 * <p>An application can increase the capacity of an {@code ArrayList} instance 56 * before adding a large number of elements using the {@code ensureCapacity} 57 * operation. This may reduce the amount of incremental reallocation. 58 * 59 * <p><strong>Note that this implementation is not synchronized.</strong> 60 * If multiple threads access an {@code ArrayList} instance concurrently, 61 * and at least one of the threads modifies the list structurally, it 62 * <i>must</i> be synchronized externally. (A structural modification is 63 * any operation that adds or deletes one or more elements, or explicitly 64 * resizes the backing array; merely setting the value of an element is not 65 * a structural modification.) This is typically accomplished by 66 * synchronizing on some object that naturally encapsulates the list. 67 * 68 * If no such object exists, the list should be "wrapped" using the 69 * {@link Collections#synchronizedList Collections.synchronizedList} 70 * method. This is best done at creation time, to prevent accidental 71 * unsynchronized access to the list:<pre> 72 * List list = Collections.synchronizedList(new ArrayList(...));</pre> 73 * 74 * <p id="fail-fast"> 75 * The iterators returned by this class's {@link #iterator() iterator} and 76 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>: 77 * if the list is structurally modified at any time after the iterator is 78 * created, in any way except through the iterator's own 79 * {@link ListIterator#remove() remove} or 80 * {@link ListIterator#add(Object) add} methods, the iterator will throw a 81 * {@link ConcurrentModificationException}. Thus, in the face of 82 * concurrent modification, the iterator fails quickly and cleanly, rather 83 * than risking arbitrary, non-deterministic behavior at an undetermined 84 * time in the future. 85 * 86 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed 87 * as it is, generally speaking, impossible to make any hard guarantees in the 88 * presence of unsynchronized concurrent modification. Fail-fast iterators 89 * throw {@code ConcurrentModificationException} on a best-effort basis. 90 * Therefore, it would be wrong to write a program that depended on this 91 * exception for its correctness: <i>the fail-fast behavior of iterators 92 * should be used only to detect bugs.</i> 93 * 94 * <p>This class is a member of the 95 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> 96 * Java Collections Framework</a>. 97 * 98 * @param <E> the type of elements in this list 99 * 100 * @author Josh Bloch 101 * @author Neal Gafter 102 * @see Collection 103 * @see List 104 * @see LinkedList 105 * @see Vector 106 * @since 1.2 107 */ 108 public class ArrayList<E> extends AbstractList<E> 109 implements List<E>, RandomAccess, Cloneable, java.io.Serializable 110 { 111 private static final long serialVersionUID = 8683452581122892189L; 112 113 /** 114 * Default initial capacity. 115 */ 116 private static final int DEFAULT_CAPACITY = 10; 117 118 /** 119 * Shared empty array instance used for empty instances. 120 */ 121 private static final Object[] EMPTY_ELEMENTDATA = {}; 122 123 /** 124 * Shared empty array instance used for default sized empty instances. We 125 * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when 126 * first element is added. 127 */ 128 private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; 129 130 /** 131 * The array buffer into which the elements of the ArrayList are stored. 132 * The capacity of the ArrayList is the length of this array buffer. Any 133 * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA 134 * will be expanded to DEFAULT_CAPACITY when the first element is added. 135 */ 136 transient Object[] elementData; // non-private to simplify nested class access 137 138 /** 139 * The size of the ArrayList (the number of elements it contains). 140 * 141 * @serial 142 */ 143 private int size; 144 145 /** 146 * Constructs an empty list with the specified initial capacity. 147 * 148 * @param initialCapacity the initial capacity of the list 149 * @throws IllegalArgumentException if the specified initial capacity 150 * is negative 151 */ 152 public ArrayList(int initialCapacity) { 153 if (initialCapacity > 0) { 154 this.elementData = new Object[initialCapacity]; 155 } else if (initialCapacity == 0) { 156 this.elementData = EMPTY_ELEMENTDATA; 157 } else { 158 throw new IllegalArgumentException("Illegal Capacity: "+ 159 initialCapacity); 160 } 161 } 162 163 /** 164 * Constructs an empty list with an initial capacity of ten. 165 */ 166 public ArrayList() { 167 this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; 168 } 169 170 /** 171 * Constructs a list containing the elements of the specified 172 * collection, in the order they are returned by the collection's 173 * iterator. 174 * 175 * @param c the collection whose elements are to be placed into this list 176 * @throws NullPointerException if the specified collection is null 177 */ 178 public ArrayList(Collection<? extends E> c) { 179 elementData = c.toArray(); 180 if ((size = elementData.length) != 0) { 181 // defend against c.toArray (incorrectly) not returning Object[] 182 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) 183 if (elementData.getClass() != Object[].class) 184 elementData = Arrays.copyOf(elementData, size, Object[].class); 185 } else { 186 // replace with empty array. 187 this.elementData = EMPTY_ELEMENTDATA; 188 } 189 } 190 191 /** 192 * Trims the capacity of this {@code ArrayList} instance to be the 193 * list's current size. An application can use this operation to minimize 194 * the storage of an {@code ArrayList} instance. 195 */ 196 public void trimToSize() { 197 modCount++; 198 if (size < elementData.length) { 199 elementData = (size == 0) 200 ? EMPTY_ELEMENTDATA 201 : Arrays.copyOf(elementData, size); 202 } 203 } 204 205 /** 206 * Increases the capacity of this {@code ArrayList} instance, if 207 * necessary, to ensure that it can hold at least the number of elements 208 * specified by the minimum capacity argument. 209 * 210 * @param minCapacity the desired minimum capacity 211 */ 212 public void ensureCapacity(int minCapacity) { 213 if (minCapacity > elementData.length 214 && !(elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA 215 && minCapacity <= DEFAULT_CAPACITY)) { 216 modCount++; 217 grow(minCapacity); 218 } 219 } 220 221 /** 222 * The maximum size of array to allocate (unless necessary). 223 * Some VMs reserve some header words in an array. 224 * Attempts to allocate larger arrays may result in 225 * OutOfMemoryError: Requested array size exceeds VM limit 226 */ 227 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; 228 229 /** 230 * Increases the capacity to ensure that it can hold at least the 231 * number of elements specified by the minimum capacity argument. 232 * 233 * @param minCapacity the desired minimum capacity 234 * @throws OutOfMemoryError if minCapacity is less than zero 235 */ 236 private Object[] grow(int minCapacity) { 237 return elementData = Arrays.copyOf(elementData, 238 newCapacity(minCapacity)); 239 } 240 241 private Object[] grow() { 242 return grow(size + 1); 243 } 244 245 /** 246 * Returns a capacity at least as large as the given minimum capacity. 247 * Returns the current capacity increased by 50% if that suffices. 248 * Will not return a capacity greater than MAX_ARRAY_SIZE unless 249 * the given minimum capacity is greater than MAX_ARRAY_SIZE. 250 * 251 * @param minCapacity the desired minimum capacity 252 * @throws OutOfMemoryError if minCapacity is less than zero 253 */ 254 private int newCapacity(int minCapacity) { 255 // overflow-conscious code 256 int oldCapacity = elementData.length; 257 int newCapacity = oldCapacity + (oldCapacity >> 1); 258 if (newCapacity - minCapacity <= 0) { 259 if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) 260 return Math.max(DEFAULT_CAPACITY, minCapacity); 261 if (minCapacity < 0) // overflow 262 throw new OutOfMemoryError(); 263 return minCapacity; 264 } 265 return (newCapacity - MAX_ARRAY_SIZE <= 0) 266 ? newCapacity 267 : hugeCapacity(minCapacity); 268 } 269 270 private static int hugeCapacity(int minCapacity) { 271 if (minCapacity < 0) // overflow 272 throw new OutOfMemoryError(); 273 return (minCapacity > MAX_ARRAY_SIZE) 274 ? Integer.MAX_VALUE 275 : MAX_ARRAY_SIZE; 276 } 277 278 /** 279 * Returns the number of elements in this list. 280 * 281 * @return the number of elements in this list 282 */ 283 public int size() { 284 return size; 285 } 286 287 /** 288 * Returns {@code true} if this list contains no elements. 289 * 290 * @return {@code true} if this list contains no elements 291 */ 292 public boolean isEmpty() { 293 return size == 0; 294 } 295 296 /** 297 * Returns {@code true} if this list contains the specified element. 298 * More formally, returns {@code true} if and only if this list contains 299 * at least one element {@code e} such that 300 * {@code Objects.equals(o, e)}. 301 * 302 * @param o element whose presence in this list is to be tested 303 * @return {@code true} if this list contains the specified element 304 */ 305 public boolean contains(Object o) { 306 return indexOf(o) >= 0; 307 } 308 309 /** 310 * Returns the index of the first occurrence of the specified element 311 * in this list, or -1 if this list does not contain the element. 312 * More formally, returns the lowest index {@code i} such that 313 * {@code Objects.equals(o, get(i))}, 314 * or -1 if there is no such index. 315 */ 316 public int indexOf(Object o) { 317 return indexOfRange(o, 0, size); 318 } 319 320 int indexOfRange(Object o, int start, int end) { 321 Object[] es = elementData; 322 if (o == null) { 323 for (int i = start; i < end; i++) { 324 if (es[i] == null) { 325 return i; 326 } 327 } 328 } else { 329 for (int i = start; i < end; i++) { 330 if (o.equals(es[i])) { 331 return i; 332 } 333 } 334 } 335 return -1; 336 } 337 338 /** 339 * Returns the index of the last occurrence of the specified element 340 * in this list, or -1 if this list does not contain the element. 341 * More formally, returns the highest index {@code i} such that 342 * {@code Objects.equals(o, get(i))}, 343 * or -1 if there is no such index. 344 */ 345 public int lastIndexOf(Object o) { 346 return lastIndexOfRange(o, 0, size); 347 } 348 349 int lastIndexOfRange(Object o, int start, int end) { 350 Object[] es = elementData; 351 if (o == null) { 352 for (int i = end - 1; i >= start; i--) { 353 if (es[i] == null) { 354 return i; 355 } 356 } 357 } else { 358 for (int i = end - 1; i >= start; i--) { 359 if (o.equals(es[i])) { 360 return i; 361 } 362 } 363 } 364 return -1; 365 } 366 367 /** 368 * Returns a shallow copy of this {@code ArrayList} instance. (The 369 * elements themselves are not copied.) 370 * 371 * @return a clone of this {@code ArrayList} instance 372 */ 373 public Object clone() { 374 try { 375 ArrayList<?> v = (ArrayList<?>) super.clone(); 376 v.elementData = Arrays.copyOf(elementData, size); 377 v.modCount = 0; 378 return v; 379 } catch (CloneNotSupportedException e) { 380 // this shouldn't happen, since we are Cloneable 381 throw new InternalError(e); 382 } 383 } 384 385 /** 386 * Returns an array containing all of the elements in this list 387 * in proper sequence (from first to last element). 388 * 389 * <p>The returned array will be "safe" in that no references to it are 390 * maintained by this list. (In other words, this method must allocate 391 * a new array). The caller is thus free to modify the returned array. 392 * 393 * <p>This method acts as bridge between array-based and collection-based 394 * APIs. 395 * 396 * @return an array containing all of the elements in this list in 397 * proper sequence 398 */ 399 public Object[] toArray() { 400 return Arrays.copyOf(elementData, size); 401 } 402 403 /** 404 * Returns an array containing all of the elements in this list in proper 405 * sequence (from first to last element); the runtime type of the returned 406 * array is that of the specified array. If the list fits in the 407 * specified array, it is returned therein. Otherwise, a new array is 408 * allocated with the runtime type of the specified array and the size of 409 * this list. 410 * 411 * <p>If the list fits in the specified array with room to spare 412 * (i.e., the array has more elements than the list), the element in 413 * the array immediately following the end of the collection is set to 414 * {@code null}. (This is useful in determining the length of the 415 * list <i>only</i> if the caller knows that the list does not contain 416 * any null elements.) 417 * 418 * @param a the array into which the elements of the list are to 419 * be stored, if it is big enough; otherwise, a new array of the 420 * same runtime type is allocated for this purpose. 421 * @return an array containing the elements of the list 422 * @throws ArrayStoreException if the runtime type of the specified array 423 * is not a supertype of the runtime type of every element in 424 * this list 425 * @throws NullPointerException if the specified array is null 426 */ 427 @SuppressWarnings("unchecked") 428 public <T> T[] toArray(T[] a) { 429 if (a.length < size) 430 // Make a new array of a's runtime type, but my contents: 431 return (T[]) Arrays.copyOf(elementData, size, a.getClass()); 432 System.arraycopy(elementData, 0, a, 0, size); 433 if (a.length > size) 434 a[size] = null; 435 return a; 436 } 437 438 // Positional Access Operations 439 440 @SuppressWarnings("unchecked") 441 E elementData(int index) { 442 return (E) elementData[index]; 443 } 444 445 @SuppressWarnings("unchecked") 446 static <E> E elementAt(Object[] es, int index) { 447 return (E) es[index]; 448 } 449 450 /** 451 * Returns the element at the specified position in this list. 452 * 453 * @param index index of the element to return 454 * @return the element at the specified position in this list 455 * @throws IndexOutOfBoundsException {@inheritDoc} 456 */ 457 public E get(int index) { 458 Objects.checkIndex(index, size); 459 return elementData(index); 460 } 461 462 /** 463 * Replaces the element at the specified position in this list with 464 * the specified element. 465 * 466 * @param index index of the element to replace 467 * @param element element to be stored at the specified position 468 * @return the element previously at the specified position 469 * @throws IndexOutOfBoundsException {@inheritDoc} 470 */ 471 public E set(int index, E element) { 472 Objects.checkIndex(index, size); 473 E oldValue = elementData(index); 474 elementData[index] = element; 475 return oldValue; 476 } 477 478 /** 479 * This helper method split out from add(E) to keep method 480 * bytecode size under 35 (the -XX:MaxInlineSize default value), 481 * which helps when add(E) is called in a C1-compiled loop. 482 */ 483 private void add(E e, Object[] elementData, int s) { 484 if (s == elementData.length) 485 elementData = grow(); 486 elementData[s] = e; 487 size = s + 1; 488 } 489 490 /** 491 * Appends the specified element to the end of this list. 492 * 493 * @param e element to be appended to this list 494 * @return {@code true} (as specified by {@link Collection#add}) 495 */ 496 public boolean add(E e) { 497 modCount++; 498 add(e, elementData, size); 499 return true; 500 } 501 502 /** 503 * Inserts the specified element at the specified position in this 504 * list. Shifts the element currently at that position (if any) and 505 * any subsequent elements to the right (adds one to their indices). 506 * 507 * @param index index at which the specified element is to be inserted 508 * @param element element to be inserted 509 * @throws IndexOutOfBoundsException {@inheritDoc} 510 */ 511 public void add(int index, E element) { 512 rangeCheckForAdd(index); 513 modCount++; 514 final int s; 515 Object[] elementData; 516 if ((s = size) == (elementData = this.elementData).length) 517 elementData = grow(); 518 System.arraycopy(elementData, index, 519 elementData, index + 1, 520 s - index); 521 elementData[index] = element; 522 size = s + 1; 523 } 524 525 /** 526 * Removes the element at the specified position in this list. 527 * Shifts any subsequent elements to the left (subtracts one from their 528 * indices). 529 * 530 * @param index the index of the element to be removed 531 * @return the element that was removed from the list 532 * @throws IndexOutOfBoundsException {@inheritDoc} 533 */ 534 public E remove(int index) { 535 Objects.checkIndex(index, size); 536 final Object[] es = elementData; 537 538 @SuppressWarnings("unchecked") E oldValue = (E) es[index]; 539 fastRemove(es, index); 540 541 return oldValue; 542 } 543 544 /** 545 * {@inheritDoc} 546 */ 547 public boolean equals(Object o) { 548 if (o == this) { 549 return true; 550 } 551 552 if (!(o instanceof List)) { 553 return false; 554 } 555 556 final int expectedModCount = modCount; 557 // ArrayList can be subclassed and given arbitrary behavior, but we can 558 // still deal with the common case where o is ArrayList precisely 559 boolean equal = (o.getClass() == ArrayList.class) 560 ? equalsArrayList((ArrayList<?>) o) 561 : equalsRange((List<?>) o, 0, size); 562 563 checkForComodification(expectedModCount); 564 return equal; 565 } 566 567 boolean equalsRange(List<?> other, int from, int to) { 568 final Object[] es = elementData; 569 if (to > es.length) { 570 throw new ConcurrentModificationException(); 571 } 572 var oit = other.iterator(); 573 for (; from < to; from++) { 574 if (!oit.hasNext() || !Objects.equals(es[from], oit.next())) { 575 return false; 576 } 577 } 578 return !oit.hasNext(); 579 } 580 581 private boolean equalsArrayList(ArrayList<?> other) { 582 final int otherModCount = other.modCount; 583 final int s = size; 584 boolean equal; 585 if (equal = (s == other.size)) { 586 final Object[] otherEs = other.elementData; 587 final Object[] es = elementData; 588 if (s > es.length || s > otherEs.length) { 589 throw new ConcurrentModificationException(); 590 } 591 for (int i = 0; i < s; i++) { 592 if (!Objects.equals(es[i], otherEs[i])) { 593 equal = false; 594 break; 595 } 596 } 597 } 598 other.checkForComodification(otherModCount); 599 return equal; 600 } 601 602 private void checkForComodification(final int expectedModCount) { 603 if (modCount != expectedModCount) { 604 throw new ConcurrentModificationException(); 605 } 606 } 607 608 /** 609 * {@inheritDoc} 610 */ 611 public int hashCode() { 612 int expectedModCount = modCount; 613 int hash = hashCodeRange(0, size); 614 checkForComodification(expectedModCount); 615 return hash; 616 } 617 618 int hashCodeRange(int from, int to) { 619 final Object[] es = elementData; 620 if (to > es.length) { 621 throw new ConcurrentModificationException(); 622 } 623 int hashCode = 1; 624 for (int i = from; i < to; i++) { 625 Object e = es[i]; 626 hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode()); 627 } 628 return hashCode; 629 } 630 631 /** 632 * Removes the first occurrence of the specified element from this list, 633 * if it is present. If the list does not contain the element, it is 634 * unchanged. More formally, removes the element with the lowest index 635 * {@code i} such that 636 * {@code Objects.equals(o, get(i))} 637 * (if such an element exists). Returns {@code true} if this list 638 * contained the specified element (or equivalently, if this list 639 * changed as a result of the call). 640 * 641 * @param o element to be removed from this list, if present 642 * @return {@code true} if this list contained the specified element 643 */ 644 public boolean remove(Object o) { 645 final Object[] es = elementData; 646 final int size = this.size; 647 int i = 0; 648 found: { 649 if (o == null) { 650 for (; i < size; i++) 651 if (es[i] == null) 652 break found; 653 } else { 654 for (; i < size; i++) 655 if (o.equals(es[i])) 656 break found; 657 } 658 return false; 659 } 660 fastRemove(es, i); 661 return true; 662 } 663 664 /** 665 * Private remove method that skips bounds checking and does not 666 * return the value removed. 667 */ 668 private void fastRemove(Object[] es, int i) { 669 modCount++; 670 final int newSize; 671 if ((newSize = size - 1) > i) 672 System.arraycopy(es, i + 1, es, i, newSize - i); 673 es[size = newSize] = null; 674 } 675 676 /** 677 * Removes all of the elements from this list. The list will 678 * be empty after this call returns. 679 */ 680 public void clear() { 681 modCount++; 682 final Object[] es = elementData; 683 for (int to = size, i = size = 0; i < to; i++) 684 es[i] = null; 685 } 686 687 /** 688 * Appends all of the elements in the specified collection to the end of 689 * this list, in the order that they are returned by the 690 * specified collection's Iterator. The behavior of this operation is 691 * undefined if the specified collection is modified while the operation 692 * is in progress. (This implies that the behavior of this call is 693 * undefined if the specified collection is this list, and this 694 * list is nonempty.) 695 * 696 * @param c collection containing elements to be added to this list 697 * @return {@code true} if this list changed as a result of the call 698 * @throws NullPointerException if the specified collection is null 699 */ 700 public boolean addAll(Collection<? extends E> c) { 701 Object[] a = c.toArray(); 702 modCount++; 703 int numNew = a.length; 704 if (numNew == 0) 705 return false; 706 Object[] elementData; 707 final int s; 708 if (numNew > (elementData = this.elementData).length - (s = size)) 709 elementData = grow(s + numNew); 710 System.arraycopy(a, 0, elementData, s, numNew); 711 size = s + numNew; 712 return true; 713 } 714 715 /** 716 * Inserts all of the elements in the specified collection into this 717 * list, starting at the specified position. Shifts the element 718 * currently at that position (if any) and any subsequent elements to 719 * the right (increases their indices). The new elements will appear 720 * in the list in the order that they are returned by the 721 * specified collection's iterator. 722 * 723 * @param index index at which to insert the first element from the 724 * specified collection 725 * @param c collection containing elements to be added to this list 726 * @return {@code true} if this list changed as a result of the call 727 * @throws IndexOutOfBoundsException {@inheritDoc} 728 * @throws NullPointerException if the specified collection is null 729 */ 730 public boolean addAll(int index, Collection<? extends E> c) { 731 rangeCheckForAdd(index); 732 733 Object[] a = c.toArray(); 734 modCount++; 735 int numNew = a.length; 736 if (numNew == 0) 737 return false; 738 Object[] elementData; 739 final int s; 740 if (numNew > (elementData = this.elementData).length - (s = size)) 741 elementData = grow(s + numNew); 742 743 int numMoved = s - index; 744 if (numMoved > 0) 745 System.arraycopy(elementData, index, 746 elementData, index + numNew, 747 numMoved); 748 System.arraycopy(a, 0, elementData, index, numNew); 749 size = s + numNew; 750 return true; 751 } 752 753 /** 754 * Removes from this list all of the elements whose index is between 755 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. 756 * Shifts any succeeding elements to the left (reduces their index). 757 * This call shortens the list by {@code (toIndex - fromIndex)} elements. 758 * (If {@code toIndex==fromIndex}, this operation has no effect.) 759 * 760 * @throws IndexOutOfBoundsException if {@code fromIndex} or 761 * {@code toIndex} is out of range 762 * ({@code fromIndex < 0 || 763 * toIndex > size() || 764 * toIndex < fromIndex}) 765 */ 766 protected void removeRange(int fromIndex, int toIndex) { 767 if (fromIndex > toIndex) { 768 throw new IndexOutOfBoundsException( 769 outOfBoundsMsg(fromIndex, toIndex)); 770 } 771 modCount++; 772 shiftTailOverGap(elementData, fromIndex, toIndex); 773 } 774 775 /** Erases the gap from lo to hi, by sliding down following elements. */ 776 private void shiftTailOverGap(Object[] es, int lo, int hi) { 777 System.arraycopy(es, hi, es, lo, size - hi); 778 for (int to = size, i = (size -= hi - lo); i < to; i++) 779 es[i] = null; 780 } 781 782 /** 783 * A version of rangeCheck used by add and addAll. 784 */ 785 private void rangeCheckForAdd(int index) { 786 if (index > size || index < 0) 787 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 788 } 789 790 /** 791 * Constructs an IndexOutOfBoundsException detail message. 792 * Of the many possible refactorings of the error handling code, 793 * this "outlining" performs best with both server and client VMs. 794 */ 795 private String outOfBoundsMsg(int index) { 796 return "Index: "+index+", Size: "+size; 797 } 798 799 /** 800 * A version used in checking (fromIndex > toIndex) condition 801 */ 802 private static String outOfBoundsMsg(int fromIndex, int toIndex) { 803 return "From Index: " + fromIndex + " > To Index: " + toIndex; 804 } 805 806 /** 807 * Removes from this list all of its elements that are contained in the 808 * specified collection. 809 * 810 * @param c collection containing elements to be removed from this list 811 * @return {@code true} if this list changed as a result of the call 812 * @throws ClassCastException if the class of an element of this list 813 * is incompatible with the specified collection 814 * (<a href="Collection.html#optional-restrictions">optional</a>) 815 * @throws NullPointerException if this list contains a null element and the 816 * specified collection does not permit null elements 817 * (<a href="Collection.html#optional-restrictions">optional</a>), 818 * or if the specified collection is null 819 * @see Collection#contains(Object) 820 */ 821 public boolean removeAll(Collection<?> c) { 822 return batchRemove(c, false, 0, size); 823 } 824 825 /** 826 * Retains only the elements in this list that are contained in the 827 * specified collection. In other words, removes from this list all 828 * of its elements that are not contained in the specified collection. 829 * 830 * @param c collection containing elements to be retained in this list 831 * @return {@code true} if this list changed as a result of the call 832 * @throws ClassCastException if the class of an element of this list 833 * is incompatible with the specified collection 834 * (<a href="Collection.html#optional-restrictions">optional</a>) 835 * @throws NullPointerException if this list contains a null element and the 836 * specified collection does not permit null elements 837 * (<a href="Collection.html#optional-restrictions">optional</a>), 838 * or if the specified collection is null 839 * @see Collection#contains(Object) 840 */ 841 public boolean retainAll(Collection<?> c) { 842 return batchRemove(c, true, 0, size); 843 } 844 845 boolean batchRemove(Collection<?> c, boolean complement, 846 final int from, final int end) { 847 Objects.requireNonNull(c); 848 final Object[] es = elementData; 849 int r; 850 // Optimize for initial run of survivors 851 for (r = from;; r++) { 852 if (r == end) 853 return false; 854 if (c.contains(es[r]) != complement) 855 break; 856 } 857 int w = r++; 858 try { 859 for (Object e; r < end; r++) 860 if (c.contains(e = es[r]) == complement) 861 es[w++] = e; 862 } catch (Throwable ex) { 863 // Preserve behavioral compatibility with AbstractCollection, 864 // even if c.contains() throws. 865 System.arraycopy(es, r, es, w, end - r); 866 w += end - r; 867 throw ex; 868 } finally { 869 modCount += end - w; 870 shiftTailOverGap(es, w, end); 871 } 872 return true; 873 } 874 875 /** 876 * Saves the state of the {@code ArrayList} instance to a stream 877 * (that is, serializes it). 878 * 879 * @param s the stream 880 * @throws java.io.IOException if an I/O error occurs 881 * @serialData The length of the array backing the {@code ArrayList} 882 * instance is emitted (int), followed by all of its elements 883 * (each an {@code Object}) in the proper order. 884 */ 885 private void writeObject(java.io.ObjectOutputStream s) 886 throws java.io.IOException { 887 // Write out element count, and any hidden stuff 888 int expectedModCount = modCount; 889 s.defaultWriteObject(); 890 891 // Write out size as capacity for behavioral compatibility with clone() 892 s.writeInt(size); 893 894 // Write out all elements in the proper order. 895 for (int i=0; i<size; i++) { 896 s.writeObject(elementData[i]); 897 } 898 899 if (modCount != expectedModCount) { 900 throw new ConcurrentModificationException(); 901 } 902 } 903 904 /** 905 * Reconstitutes the {@code ArrayList} instance from a stream (that is, 906 * deserializes it). 907 * @param s the stream 908 * @throws ClassNotFoundException if the class of a serialized object 909 * could not be found 910 * @throws java.io.IOException if an I/O error occurs 911 */ 912 private void readObject(java.io.ObjectInputStream s) 913 throws java.io.IOException, ClassNotFoundException { 914 915 // Read in size, and any hidden stuff 916 s.defaultReadObject(); 917 918 // Read in capacity 919 s.readInt(); // ignored 920 921 if (size > 0) { 922 // like clone(), allocate array based upon size not capacity 923 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size); 924 Object[] elements = new Object[size]; 925 926 // Read in all elements in the proper order. 927 for (int i = 0; i < size; i++) { 928 elements[i] = s.readObject(); 929 } 930 931 elementData = elements; 932 } else if (size == 0) { 933 elementData = EMPTY_ELEMENTDATA; 934 } else { 935 throw new java.io.InvalidObjectException("Invalid size: " + size); 936 } 937 } 938 939 /** 940 * Returns a list iterator over the elements in this list (in proper 941 * sequence), starting at the specified position in the list. 942 * The specified index indicates the first element that would be 943 * returned by an initial call to {@link ListIterator#next next}. 944 * An initial call to {@link ListIterator#previous previous} would 945 * return the element with the specified index minus one. 946 * 947 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 948 * 949 * @throws IndexOutOfBoundsException {@inheritDoc} 950 */ 951 public ListIterator<E> listIterator(int index) { 952 rangeCheckForAdd(index); 953 return new ListItr(index); 954 } 955 956 /** 957 * Returns a list iterator over the elements in this list (in proper 958 * sequence). 959 * 960 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 961 * 962 * @see #listIterator(int) 963 */ 964 public ListIterator<E> listIterator() { 965 return new ListItr(0); 966 } 967 968 /** 969 * Returns an iterator over the elements in this list in proper sequence. 970 * 971 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 972 * 973 * @return an iterator over the elements in this list in proper sequence 974 */ 975 public Iterator<E> iterator() { 976 return new Itr(); 977 } 978 979 /** 980 * An optimized version of AbstractList.Itr 981 */ 982 private class Itr implements Iterator<E> { 983 int cursor; // index of next element to return 984 int lastRet = -1; // index of last element returned; -1 if no such 985 int expectedModCount = modCount; 986 987 // prevent creating a synthetic constructor 988 Itr() {} 989 990 public boolean hasNext() { 991 return cursor != size; 992 } 993 994 @SuppressWarnings("unchecked") 995 public E next() { 996 checkForComodification(); 997 int i = cursor; 998 if (i >= size) 999 throw new NoSuchElementException(); 1000 Object[] elementData = ArrayList.this.elementData; 1001 if (i >= elementData.length) 1002 throw new ConcurrentModificationException(); 1003 cursor = i + 1; 1004 return (E) elementData[lastRet = i]; 1005 } 1006 1007 public void remove() { 1008 if (lastRet < 0) 1009 throw new IllegalStateException(); 1010 checkForComodification(); 1011 1012 try { 1013 ArrayList.this.remove(lastRet); 1014 cursor = lastRet; 1015 lastRet = -1; 1016 expectedModCount = modCount; 1017 } catch (IndexOutOfBoundsException ex) { 1018 throw new ConcurrentModificationException(); 1019 } 1020 } 1021 1022 @Override 1023 public void forEachRemaining(Consumer<? super E> action) { 1024 Objects.requireNonNull(action); 1025 final int size = ArrayList.this.size; 1026 int i = cursor; 1027 if (i < size) { 1028 final Object[] es = elementData; 1029 if (i >= es.length) 1030 throw new ConcurrentModificationException(); 1031 for (; i < size && modCount == expectedModCount; i++) 1032 action.accept(elementAt(es, i)); 1033 // update once at end to reduce heap write traffic 1034 cursor = i; 1035 lastRet = i - 1; 1036 checkForComodification(); 1037 } 1038 } 1039 1040 final void checkForComodification() { 1041 if (modCount != expectedModCount) 1042 throw new ConcurrentModificationException(); 1043 } 1044 } 1045 1046 /** 1047 * An optimized version of AbstractList.ListItr 1048 */ 1049 private class ListItr extends Itr implements ListIterator<E> { 1050 ListItr(int index) { 1051 super(); 1052 cursor = index; 1053 } 1054 1055 public boolean hasPrevious() { 1056 return cursor != 0; 1057 } 1058 1059 public int nextIndex() { 1060 return cursor; 1061 } 1062 1063 public int previousIndex() { 1064 return cursor - 1; 1065 } 1066 1067 @SuppressWarnings("unchecked") 1068 public E previous() { 1069 checkForComodification(); 1070 int i = cursor - 1; 1071 if (i < 0) 1072 throw new NoSuchElementException(); 1073 Object[] elementData = ArrayList.this.elementData; 1074 if (i >= elementData.length) 1075 throw new ConcurrentModificationException(); 1076 cursor = i; 1077 return (E) elementData[lastRet = i]; 1078 } 1079 1080 public void set(E e) { 1081 if (lastRet < 0) 1082 throw new IllegalStateException(); 1083 checkForComodification(); 1084 1085 try { 1086 ArrayList.this.set(lastRet, e); 1087 } catch (IndexOutOfBoundsException ex) { 1088 throw new ConcurrentModificationException(); 1089 } 1090 } 1091 1092 public void add(E e) { 1093 checkForComodification(); 1094 1095 try { 1096 int i = cursor; 1097 ArrayList.this.add(i, e); 1098 cursor = i + 1; 1099 lastRet = -1; 1100 expectedModCount = modCount; 1101 } catch (IndexOutOfBoundsException ex) { 1102 throw new ConcurrentModificationException(); 1103 } 1104 } 1105 } 1106 1107 /** 1108 * Returns a view of the portion of this list between the specified 1109 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If 1110 * {@code fromIndex} and {@code toIndex} are equal, the returned list is 1111 * empty.) The returned list is backed by this list, so non-structural 1112 * changes in the returned list are reflected in this list, and vice-versa. 1113 * The returned list supports all of the optional list operations. 1114 * 1115 * <p>This method eliminates the need for explicit range operations (of 1116 * the sort that commonly exist for arrays). Any operation that expects 1117 * a list can be used as a range operation by passing a subList view 1118 * instead of a whole list. For example, the following idiom 1119 * removes a range of elements from a list: 1120 * <pre> 1121 * list.subList(from, to).clear(); 1122 * </pre> 1123 * Similar idioms may be constructed for {@link #indexOf(Object)} and 1124 * {@link #lastIndexOf(Object)}, and all of the algorithms in the 1125 * {@link Collections} class can be applied to a subList. 1126 * 1127 * <p>The semantics of the list returned by this method become undefined if 1128 * the backing list (i.e., this list) is <i>structurally modified</i> in 1129 * any way other than via the returned list. (Structural modifications are 1130 * those that change the size of this list, or otherwise perturb it in such 1131 * a fashion that iterations in progress may yield incorrect results.) 1132 * 1133 * @throws IndexOutOfBoundsException {@inheritDoc} 1134 * @throws IllegalArgumentException {@inheritDoc} 1135 */ 1136 public List<E> subList(int fromIndex, int toIndex) { 1137 subListRangeCheck(fromIndex, toIndex, size); 1138 return new SubList<>(this, fromIndex, toIndex); 1139 } 1140 1141 private static class SubList<E> extends AbstractList<E> implements RandomAccess { 1142 private final ArrayList<E> root; 1143 private final SubList<E> parent; 1144 private final int offset; 1145 private int size; 1146 1147 /** 1148 * Constructs a sublist of an arbitrary ArrayList. 1149 */ 1150 public SubList(ArrayList<E> root, int fromIndex, int toIndex) { 1151 this.root = root; 1152 this.parent = null; 1153 this.offset = fromIndex; 1154 this.size = toIndex - fromIndex; 1155 this.modCount = root.modCount; 1156 } 1157 1158 /** 1159 * Constructs a sublist of another SubList. 1160 */ 1161 private SubList(SubList<E> parent, int fromIndex, int toIndex) { 1162 this.root = parent.root; 1163 this.parent = parent; 1164 this.offset = parent.offset + fromIndex; 1165 this.size = toIndex - fromIndex; 1166 this.modCount = root.modCount; 1167 } 1168 1169 public E set(int index, E element) { 1170 Objects.checkIndex(index, size); 1171 checkForComodification(); 1172 E oldValue = root.elementData(offset + index); 1173 root.elementData[offset + index] = element; 1174 return oldValue; 1175 } 1176 1177 public E get(int index) { 1178 Objects.checkIndex(index, size); 1179 checkForComodification(); 1180 return root.elementData(offset + index); 1181 } 1182 1183 public int size() { 1184 checkForComodification(); 1185 return size; 1186 } 1187 1188 public void add(int index, E element) { 1189 rangeCheckForAdd(index); 1190 checkForComodification(); 1191 root.add(offset + index, element); 1192 updateSizeAndModCount(1); 1193 } 1194 1195 public E remove(int index) { 1196 Objects.checkIndex(index, size); 1197 checkForComodification(); 1198 E result = root.remove(offset + index); 1199 updateSizeAndModCount(-1); 1200 return result; 1201 } 1202 1203 protected void removeRange(int fromIndex, int toIndex) { 1204 checkForComodification(); 1205 root.removeRange(offset + fromIndex, offset + toIndex); 1206 updateSizeAndModCount(fromIndex - toIndex); 1207 } 1208 1209 public boolean addAll(Collection<? extends E> c) { 1210 return addAll(this.size, c); 1211 } 1212 1213 public boolean addAll(int index, Collection<? extends E> c) { 1214 rangeCheckForAdd(index); 1215 int cSize = c.size(); 1216 if (cSize==0) 1217 return false; 1218 checkForComodification(); 1219 root.addAll(offset + index, c); 1220 updateSizeAndModCount(cSize); 1221 return true; 1222 } 1223 1224 public void replaceAll(UnaryOperator<E> operator) { 1225 root.replaceAllRange(operator, offset, offset + size); 1226 } 1227 1228 public boolean removeAll(Collection<?> c) { 1229 return batchRemove(c, false); 1230 } 1231 1232 public boolean retainAll(Collection<?> c) { 1233 return batchRemove(c, true); 1234 } 1235 1236 private boolean batchRemove(Collection<?> c, boolean complement) { 1237 checkForComodification(); 1238 int oldSize = root.size; 1239 boolean modified = 1240 root.batchRemove(c, complement, offset, offset + size); 1241 if (modified) 1242 updateSizeAndModCount(root.size - oldSize); 1243 return modified; 1244 } 1245 1246 public boolean removeIf(Predicate<? super E> filter) { 1247 checkForComodification(); 1248 int oldSize = root.size; 1249 boolean modified = root.removeIf(filter, offset, offset + size); 1250 if (modified) 1251 updateSizeAndModCount(root.size - oldSize); 1252 return modified; 1253 } 1254 1255 public Object[] toArray() { 1256 checkForComodification(); 1257 return Arrays.copyOfRange(root.elementData, offset, offset + size); 1258 } 1259 1260 @SuppressWarnings("unchecked") 1261 public <T> T[] toArray(T[] a) { 1262 checkForComodification(); 1263 if (a.length < size) 1264 return (T[]) Arrays.copyOfRange( 1265 root.elementData, offset, offset + size, a.getClass()); 1266 System.arraycopy(root.elementData, offset, a, 0, size); 1267 if (a.length > size) 1268 a[size] = null; 1269 return a; 1270 } 1271 1272 public boolean equals(Object o) { 1273 if (o == this) { 1274 return true; 1275 } 1276 1277 if (!(o instanceof List)) { 1278 return false; 1279 } 1280 1281 boolean equal = root.equalsRange((List<?>)o, offset, offset + size); 1282 checkForComodification(); 1283 return equal; 1284 } 1285 1286 public int hashCode() { 1287 int hash = root.hashCodeRange(offset, offset + size); 1288 checkForComodification(); 1289 return hash; 1290 } 1291 1292 public int indexOf(Object o) { 1293 int index = root.indexOfRange(o, offset, offset + size); 1294 checkForComodification(); 1295 return index >= 0 ? index - offset : -1; 1296 } 1297 1298 public int lastIndexOf(Object o) { 1299 int index = root.lastIndexOfRange(o, offset, offset + size); 1300 checkForComodification(); 1301 return index >= 0 ? index - offset : -1; 1302 } 1303 1304 public boolean contains(Object o) { 1305 return indexOf(o) >= 0; 1306 } 1307 1308 public Iterator<E> iterator() { 1309 return listIterator(); 1310 } 1311 1312 public ListIterator<E> listIterator(int index) { 1313 checkForComodification(); 1314 rangeCheckForAdd(index); 1315 1316 return new ListIterator<E>() { 1317 int cursor = index; 1318 int lastRet = -1; 1319 int expectedModCount = root.modCount; 1320 1321 public boolean hasNext() { 1322 return cursor != SubList.this.size; 1323 } 1324 1325 @SuppressWarnings("unchecked") 1326 public E next() { 1327 checkForComodification(); 1328 int i = cursor; 1329 if (i >= SubList.this.size) 1330 throw new NoSuchElementException(); 1331 Object[] elementData = root.elementData; 1332 if (offset + i >= elementData.length) 1333 throw new ConcurrentModificationException(); 1334 cursor = i + 1; 1335 return (E) elementData[offset + (lastRet = i)]; 1336 } 1337 1338 public boolean hasPrevious() { 1339 return cursor != 0; 1340 } 1341 1342 @SuppressWarnings("unchecked") 1343 public E previous() { 1344 checkForComodification(); 1345 int i = cursor - 1; 1346 if (i < 0) 1347 throw new NoSuchElementException(); 1348 Object[] elementData = root.elementData; 1349 if (offset + i >= elementData.length) 1350 throw new ConcurrentModificationException(); 1351 cursor = i; 1352 return (E) elementData[offset + (lastRet = i)]; 1353 } 1354 1355 public void forEachRemaining(Consumer<? super E> action) { 1356 Objects.requireNonNull(action); 1357 final int size = SubList.this.size; 1358 int i = cursor; 1359 if (i < size) { 1360 final Object[] es = root.elementData; 1361 if (offset + i >= es.length) 1362 throw new ConcurrentModificationException(); 1363 for (; i < size && modCount == expectedModCount; i++) 1364 action.accept(elementAt(es, offset + i)); 1365 // update once at end to reduce heap write traffic 1366 cursor = i; 1367 lastRet = i - 1; 1368 checkForComodification(); 1369 } 1370 } 1371 1372 public int nextIndex() { 1373 return cursor; 1374 } 1375 1376 public int previousIndex() { 1377 return cursor - 1; 1378 } 1379 1380 public void remove() { 1381 if (lastRet < 0) 1382 throw new IllegalStateException(); 1383 checkForComodification(); 1384 1385 try { 1386 SubList.this.remove(lastRet); 1387 cursor = lastRet; 1388 lastRet = -1; 1389 expectedModCount = root.modCount; 1390 } catch (IndexOutOfBoundsException ex) { 1391 throw new ConcurrentModificationException(); 1392 } 1393 } 1394 1395 public void set(E e) { 1396 if (lastRet < 0) 1397 throw new IllegalStateException(); 1398 checkForComodification(); 1399 1400 try { 1401 root.set(offset + lastRet, e); 1402 } catch (IndexOutOfBoundsException ex) { 1403 throw new ConcurrentModificationException(); 1404 } 1405 } 1406 1407 public void add(E e) { 1408 checkForComodification(); 1409 1410 try { 1411 int i = cursor; 1412 SubList.this.add(i, e); 1413 cursor = i + 1; 1414 lastRet = -1; 1415 expectedModCount = root.modCount; 1416 } catch (IndexOutOfBoundsException ex) { 1417 throw new ConcurrentModificationException(); 1418 } 1419 } 1420 1421 final void checkForComodification() { 1422 if (root.modCount != expectedModCount) 1423 throw new ConcurrentModificationException(); 1424 } 1425 }; 1426 } 1427 1428 public List<E> subList(int fromIndex, int toIndex) { 1429 subListRangeCheck(fromIndex, toIndex, size); 1430 return new SubList<>(this, fromIndex, toIndex); 1431 } 1432 1433 private void rangeCheckForAdd(int index) { 1434 if (index < 0 || index > this.size) 1435 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 1436 } 1437 1438 private String outOfBoundsMsg(int index) { 1439 return "Index: "+index+", Size: "+this.size; 1440 } 1441 1442 private void checkForComodification() { 1443 if (root.modCount != modCount) 1444 throw new ConcurrentModificationException(); 1445 } 1446 1447 private void updateSizeAndModCount(int sizeChange) { 1448 SubList<E> slist = this; 1449 do { 1450 slist.size += sizeChange; 1451 slist.modCount = root.modCount; 1452 slist = slist.parent; 1453 } while (slist != null); 1454 } 1455 1456 public Spliterator<E> spliterator() { 1457 checkForComodification(); 1458 1459 // ArrayListSpliterator not used here due to late-binding 1460 return new Spliterator<E>() { 1461 private int index = offset; // current index, modified on advance/split 1462 private int fence = -1; // -1 until used; then one past last index 1463 private int expectedModCount; // initialized when fence set 1464 1465 private int getFence() { // initialize fence to size on first use 1466 int hi; // (a specialized variant appears in method forEach) 1467 if ((hi = fence) < 0) { 1468 expectedModCount = modCount; 1469 hi = fence = offset + size; 1470 } 1471 return hi; 1472 } 1473 1474 public ArrayList<E>.ArrayListSpliterator trySplit() { 1475 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; 1476 // ArrayListSpliterator can be used here as the source is already bound 1477 return (lo >= mid) ? null : // divide range in half unless too small 1478 root.new ArrayListSpliterator(lo, index = mid, expectedModCount); 1479 } 1480 1481 public boolean tryAdvance(Consumer<? super E> action) { 1482 Objects.requireNonNull(action); 1483 int hi = getFence(), i = index; 1484 if (i < hi) { 1485 index = i + 1; 1486 @SuppressWarnings("unchecked") E e = (E)root.elementData[i]; 1487 action.accept(e); 1488 if (root.modCount != expectedModCount) 1489 throw new ConcurrentModificationException(); 1490 return true; 1491 } 1492 return false; 1493 } 1494 1495 public void forEachRemaining(Consumer<? super E> action) { 1496 Objects.requireNonNull(action); 1497 int i, hi, mc; // hoist accesses and checks from loop 1498 ArrayList<E> lst = root; 1499 Object[] a; 1500 if ((a = lst.elementData) != null) { 1501 if ((hi = fence) < 0) { 1502 mc = modCount; 1503 hi = offset + size; 1504 } 1505 else 1506 mc = expectedModCount; 1507 if ((i = index) >= 0 && (index = hi) <= a.length) { 1508 for (; i < hi; ++i) { 1509 @SuppressWarnings("unchecked") E e = (E) a[i]; 1510 action.accept(e); 1511 } 1512 if (lst.modCount == mc) 1513 return; 1514 } 1515 } 1516 throw new ConcurrentModificationException(); 1517 } 1518 1519 public long estimateSize() { 1520 return getFence() - index; 1521 } 1522 1523 public int characteristics() { 1524 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; 1525 } 1526 }; 1527 } 1528 } 1529 1530 /** 1531 * @throws NullPointerException {@inheritDoc} 1532 */ 1533 @Override 1534 public void forEach(Consumer<? super E> action) { 1535 Objects.requireNonNull(action); 1536 final int expectedModCount = modCount; 1537 final Object[] es = elementData; 1538 final int size = this.size; 1539 for (int i = 0; modCount == expectedModCount && i < size; i++) 1540 action.accept(elementAt(es, i)); 1541 if (modCount != expectedModCount) 1542 throw new ConcurrentModificationException(); 1543 } 1544 1545 /** 1546 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> 1547 * and <em>fail-fast</em> {@link Spliterator} over the elements in this 1548 * list. 1549 * 1550 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, 1551 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}. 1552 * Overriding implementations should document the reporting of additional 1553 * characteristic values. 1554 * 1555 * @return a {@code Spliterator} over the elements in this list 1556 * @since 1.8 1557 */ 1558 @Override 1559 public Spliterator<E> spliterator() { 1560 return new ArrayListSpliterator(0, -1, 0); 1561 } 1562 1563 /** Index-based split-by-two, lazily initialized Spliterator */ 1564 final class ArrayListSpliterator implements Spliterator<E> { 1565 1566 /* 1567 * If ArrayLists were immutable, or structurally immutable (no 1568 * adds, removes, etc), we could implement their spliterators 1569 * with Arrays.spliterator. Instead we detect as much 1570 * interference during traversal as practical without 1571 * sacrificing much performance. We rely primarily on 1572 * modCounts. These are not guaranteed to detect concurrency 1573 * violations, and are sometimes overly conservative about 1574 * within-thread interference, but detect enough problems to 1575 * be worthwhile in practice. To carry this out, we (1) lazily 1576 * initialize fence and expectedModCount until the latest 1577 * point that we need to commit to the state we are checking 1578 * against; thus improving precision. (This doesn't apply to 1579 * SubLists, that create spliterators with current non-lazy 1580 * values). (2) We perform only a single 1581 * ConcurrentModificationException check at the end of forEach 1582 * (the most performance-sensitive method). When using forEach 1583 * (as opposed to iterators), we can normally only detect 1584 * interference after actions, not before. Further 1585 * CME-triggering checks apply to all other possible 1586 * violations of assumptions for example null or too-small 1587 * elementData array given its size(), that could only have 1588 * occurred due to interference. This allows the inner loop 1589 * of forEach to run without any further checks, and 1590 * simplifies lambda-resolution. While this does entail a 1591 * number of checks, note that in the common case of 1592 * list.stream().forEach(a), no checks or other computation 1593 * occur anywhere other than inside forEach itself. The other 1594 * less-often-used methods cannot take advantage of most of 1595 * these streamlinings. 1596 */ 1597 1598 private int index; // current index, modified on advance/split 1599 private int fence; // -1 until used; then one past last index 1600 private int expectedModCount; // initialized when fence set 1601 1602 /** Creates new spliterator covering the given range. */ 1603 ArrayListSpliterator(int origin, int fence, int expectedModCount) { 1604 this.index = origin; 1605 this.fence = fence; 1606 this.expectedModCount = expectedModCount; 1607 } 1608 1609 private int getFence() { // initialize fence to size on first use 1610 int hi; // (a specialized variant appears in method forEach) 1611 if ((hi = fence) < 0) { 1612 expectedModCount = modCount; 1613 hi = fence = size; 1614 } 1615 return hi; 1616 } 1617 1618 public ArrayListSpliterator trySplit() { 1619 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; 1620 return (lo >= mid) ? null : // divide range in half unless too small 1621 new ArrayListSpliterator(lo, index = mid, expectedModCount); 1622 } 1623 1624 public boolean tryAdvance(Consumer<? super E> action) { 1625 if (action == null) 1626 throw new NullPointerException(); 1627 int hi = getFence(), i = index; 1628 if (i < hi) { 1629 index = i + 1; 1630 @SuppressWarnings("unchecked") E e = (E)elementData[i]; 1631 action.accept(e); 1632 if (modCount != expectedModCount) 1633 throw new ConcurrentModificationException(); 1634 return true; 1635 } 1636 return false; 1637 } 1638 1639 public void forEachRemaining(Consumer<? super E> action) { 1640 int i, hi, mc; // hoist accesses and checks from loop 1641 Object[] a; 1642 if (action == null) 1643 throw new NullPointerException(); 1644 if ((a = elementData) != null) { 1645 if ((hi = fence) < 0) { 1646 mc = modCount; 1647 hi = size; 1648 } 1649 else 1650 mc = expectedModCount; 1651 if ((i = index) >= 0 && (index = hi) <= a.length) { 1652 for (; i < hi; ++i) { 1653 @SuppressWarnings("unchecked") E e = (E) a[i]; 1654 action.accept(e); 1655 } 1656 if (modCount == mc) 1657 return; 1658 } 1659 } 1660 throw new ConcurrentModificationException(); 1661 } 1662 1663 public long estimateSize() { 1664 return getFence() - index; 1665 } 1666 1667 public int characteristics() { 1668 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; 1669 } 1670 } 1671 1672 // A tiny bit set implementation 1673 1674 private static long[] nBits(int n) { 1675 return new long[((n - 1) >> 6) + 1]; 1676 } 1677 private static void setBit(long[] bits, int i) { 1678 bits[i >> 6] |= 1L << i; 1679 } 1680 private static boolean isClear(long[] bits, int i) { 1681 return (bits[i >> 6] & (1L << i)) == 0; 1682 } 1683 1684 /** 1685 * @throws NullPointerException {@inheritDoc} 1686 */ 1687 @Override 1688 public boolean removeIf(Predicate<? super E> filter) { 1689 return removeIf(filter, 0, size); 1690 } 1691 1692 /** 1693 * Removes all elements satisfying the given predicate, from index 1694 * i (inclusive) to index end (exclusive). 1695 */ 1696 boolean removeIf(Predicate<? super E> filter, int i, final int end) { 1697 Objects.requireNonNull(filter); 1698 int expectedModCount = modCount; 1699 final Object[] es = elementData; 1700 // Optimize for initial run of survivors 1701 for (; i < end && !filter.test(elementAt(es, i)); i++) 1702 ; 1703 // Tolerate predicates that reentrantly access the collection for 1704 // read (but writers still get CME), so traverse once to find 1705 // elements to delete, a second pass to physically expunge. 1706 if (i < end) { 1707 final int beg = i; 1708 final long[] deathRow = nBits(end - beg); 1709 deathRow[0] = 1L; // set bit 0 1710 for (i = beg + 1; i < end; i++) 1711 if (filter.test(elementAt(es, i))) 1712 setBit(deathRow, i - beg); 1713 if (modCount != expectedModCount) 1714 throw new ConcurrentModificationException(); 1715 modCount++; 1716 int w = beg; 1717 for (i = beg; i < end; i++) 1718 if (isClear(deathRow, i - beg)) 1719 es[w++] = es[i]; 1720 shiftTailOverGap(es, w, end); 1721 return true; 1722 } else { 1723 if (modCount != expectedModCount) 1724 throw new ConcurrentModificationException(); 1725 return false; 1726 } 1727 } 1728 1729 @Override 1730 public void replaceAll(UnaryOperator<E> operator) { 1731 replaceAllRange(operator, 0, size); 1732 } 1733 1734 private void replaceAllRange(UnaryOperator<E> operator, int i, int end) { 1735 Objects.requireNonNull(operator); 1736 final int expectedModCount = modCount; 1737 final Object[] es = elementData; 1738 for (; modCount == expectedModCount && i < end; i++) 1739 es[i] = operator.apply(elementAt(es, i)); 1740 if (modCount != expectedModCount) 1741 throw new ConcurrentModificationException(); 1742 } 1743 1744 @Override 1745 @SuppressWarnings("unchecked") 1746 public void sort(Comparator<? super E> c) { 1747 final int expectedModCount = modCount; 1748 Arrays.sort((E[]) elementData, 0, size, c); 1749 if (modCount != expectedModCount) 1750 throw new ConcurrentModificationException(); 1751 modCount++; 1752 } 1753 1754 void checkInvariants() { 1755 // assert size >= 0; 1756 // assert size == elementData.length || elementData[size] == null; 1757 } 1758 }