1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.util; 28 29 import java.util.function.Consumer; 30 import java.util.function.Predicate; 31 import java.util.function.UnaryOperator; 32 import jdk.internal.misc.SharedSecrets; 33 import jdk.internal.util.ArraysSupport; 34 35 /** 36 * Resizable-array implementation of the {@code List} interface. Implements 37 * all optional list operations, and permits all elements, including 38 * {@code null}. In addition to implementing the {@code List} interface, 39 * this class provides methods to manipulate the size of the array that is 40 * used internally to store the list. (This class is roughly equivalent to 41 * {@code Vector}, except that it is unsynchronized.) 42 * 43 * <p>The {@code size}, {@code isEmpty}, {@code get}, {@code set}, 44 * {@code iterator}, and {@code listIterator} operations run in constant 45 * time. The {@code add} operation runs in <i>amortized constant time</i>, 46 * that is, adding n elements requires O(n) time. All of the other operations 47 * run in linear time (roughly speaking). The constant factor is low compared 48 * to that for the {@code LinkedList} implementation. 49 * 50 * <p>Each {@code ArrayList} instance has a <i>capacity</i>. The capacity is 51 * the size of the array used to store the elements in the list. It is always 52 * at least as large as the list size. As elements are added to an ArrayList, 53 * its capacity grows automatically. The details of the growth policy are not 54 * specified beyond the fact that adding an element has constant amortized 55 * time cost. 56 * 57 * <p>An application can increase the capacity of an {@code ArrayList} instance 58 * before adding a large number of elements using the {@code ensureCapacity} 59 * operation. This may reduce the amount of incremental reallocation. 60 * 61 * <p><strong>Note that this implementation is not synchronized.</strong> 62 * If multiple threads access an {@code ArrayList} instance concurrently, 63 * and at least one of the threads modifies the list structurally, it 64 * <i>must</i> be synchronized externally. (A structural modification is 65 * any operation that adds or deletes one or more elements, or explicitly 66 * resizes the backing array; merely setting the value of an element is not 67 * a structural modification.) This is typically accomplished by 68 * synchronizing on some object that naturally encapsulates the list. 69 * 70 * If no such object exists, the list should be "wrapped" using the 71 * {@link Collections#synchronizedList Collections.synchronizedList} 72 * method. This is best done at creation time, to prevent accidental 73 * unsynchronized access to the list:<pre> 74 * List list = Collections.synchronizedList(new ArrayList(...));</pre> 75 * 76 * <p id="fail-fast"> 77 * The iterators returned by this class's {@link #iterator() iterator} and 78 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>: 79 * if the list is structurally modified at any time after the iterator is 80 * created, in any way except through the iterator's own 81 * {@link ListIterator#remove() remove} or 82 * {@link ListIterator#add(Object) add} methods, the iterator will throw a 83 * {@link ConcurrentModificationException}. Thus, in the face of 84 * concurrent modification, the iterator fails quickly and cleanly, rather 85 * than risking arbitrary, non-deterministic behavior at an undetermined 86 * time in the future. 87 * 88 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed 89 * as it is, generally speaking, impossible to make any hard guarantees in the 90 * presence of unsynchronized concurrent modification. Fail-fast iterators 91 * throw {@code ConcurrentModificationException} on a best-effort basis. 92 * Therefore, it would be wrong to write a program that depended on this 93 * exception for its correctness: <i>the fail-fast behavior of iterators 94 * should be used only to detect bugs.</i> 95 * 96 * <p>This class is a member of the 97 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> 98 * Java Collections Framework</a>. 99 * 100 * @param <E> the type of elements in this list 101 * 102 * @author Josh Bloch 103 * @author Neal Gafter 104 * @see Collection 105 * @see List 106 * @see LinkedList 107 * @see Vector 108 * @since 1.2 109 */ 110 // Android-changed: CME in iterators; 111 /* 112 * - AOSP commit b10b2a3ab693cfd6156d06ffe4e00ce69b9c9194 113 * Fix ConcurrentModificationException in ArrayList iterators. 114 */ 115 public class ArrayList<E> extends AbstractList<E> 116 implements List<E>, RandomAccess, Cloneable, java.io.Serializable 117 { 118 @java.io.Serial 119 private static final long serialVersionUID = 8683452581122892189L; 120 121 /** 122 * Default initial capacity. 123 */ 124 private static final int DEFAULT_CAPACITY = 10; 125 126 /** 127 * Shared empty array instance used for empty instances. 128 */ 129 private static final Object[] EMPTY_ELEMENTDATA = {}; 130 131 /** 132 * Shared empty array instance used for default sized empty instances. We 133 * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when 134 * first element is added. 135 */ 136 private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; 137 138 /** 139 * The array buffer into which the elements of the ArrayList are stored. 140 * The capacity of the ArrayList is the length of this array buffer. Any 141 * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA 142 * will be expanded to DEFAULT_CAPACITY when the first element is added. 143 */ 144 // Android-note: Also accessed from java.util.Collections 145 transient Object[] elementData; // non-private to simplify nested class access 146 147 /** 148 * The size of the ArrayList (the number of elements it contains). 149 * 150 * @serial 151 */ 152 private int size; 153 154 /** 155 * Constructs an empty list with the specified initial capacity. 156 * 157 * @param initialCapacity the initial capacity of the list 158 * @throws IllegalArgumentException if the specified initial capacity 159 * is negative 160 */ ArrayList(int initialCapacity)161 public ArrayList(int initialCapacity) { 162 if (initialCapacity > 0) { 163 this.elementData = new Object[initialCapacity]; 164 } else if (initialCapacity == 0) { 165 this.elementData = EMPTY_ELEMENTDATA; 166 } else { 167 throw new IllegalArgumentException("Illegal Capacity: "+ 168 initialCapacity); 169 } 170 } 171 172 /** 173 * Constructs an empty list with an initial capacity of ten. 174 */ ArrayList()175 public ArrayList() { 176 this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; 177 } 178 179 /** 180 * Constructs a list containing the elements of the specified 181 * collection, in the order they are returned by the collection's 182 * iterator. 183 * 184 * @param c the collection whose elements are to be placed into this list 185 * @throws NullPointerException if the specified collection is null 186 */ ArrayList(Collection<? extends E> c)187 public ArrayList(Collection<? extends E> c) { 188 Object[] a = c.toArray(); 189 if ((size = a.length) != 0) { 190 if (c.getClass() == ArrayList.class) { 191 elementData = a; 192 } else { 193 elementData = Arrays.copyOf(a, size, Object[].class); 194 } 195 } else { 196 // replace with empty array. 197 elementData = EMPTY_ELEMENTDATA; 198 } 199 } 200 201 /** 202 * Trims the capacity of this {@code ArrayList} instance to be the 203 * list's current size. An application can use this operation to minimize 204 * the storage of an {@code ArrayList} instance. 205 */ trimToSize()206 public void trimToSize() { 207 modCount++; 208 if (size < elementData.length) { 209 elementData = (size == 0) 210 ? EMPTY_ELEMENTDATA 211 : Arrays.copyOf(elementData, size); 212 } 213 } 214 215 /** 216 * Increases the capacity of this {@code ArrayList} instance, if 217 * necessary, to ensure that it can hold at least the number of elements 218 * specified by the minimum capacity argument. 219 * 220 * @param minCapacity the desired minimum capacity 221 */ ensureCapacity(int minCapacity)222 public void ensureCapacity(int minCapacity) { 223 if (minCapacity > elementData.length 224 && !(elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA 225 && minCapacity <= DEFAULT_CAPACITY)) { 226 modCount++; 227 grow(minCapacity); 228 } 229 } 230 231 /** 232 * Increases the capacity to ensure that it can hold at least the 233 * number of elements specified by the minimum capacity argument. 234 * 235 * @param minCapacity the desired minimum capacity 236 * @throws OutOfMemoryError if minCapacity is less than zero 237 */ grow(int minCapacity)238 private Object[] grow(int minCapacity) { 239 int oldCapacity = elementData.length; 240 if (oldCapacity > 0 || elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA) { 241 int newCapacity = ArraysSupport.newLength(oldCapacity, 242 minCapacity - oldCapacity, /* minimum growth */ 243 oldCapacity >> 1 /* preferred growth */); 244 return elementData = Arrays.copyOf(elementData, newCapacity); 245 } else { 246 return elementData = new Object[Math.max(DEFAULT_CAPACITY, minCapacity)]; 247 } 248 } 249 grow()250 private Object[] grow() { 251 return grow(size + 1); 252 } 253 254 /** 255 * Returns the number of elements in this list. 256 * 257 * @return the number of elements in this list 258 */ size()259 public int size() { 260 return size; 261 } 262 263 /** 264 * Returns {@code true} if this list contains no elements. 265 * 266 * @return {@code true} if this list contains no elements 267 */ isEmpty()268 public boolean isEmpty() { 269 return size == 0; 270 } 271 272 /** 273 * Returns {@code true} if this list contains the specified element. 274 * More formally, returns {@code true} if and only if this list contains 275 * at least one element {@code e} such that 276 * {@code Objects.equals(o, e)}. 277 * 278 * @param o element whose presence in this list is to be tested 279 * @return {@code true} if this list contains the specified element 280 */ contains(Object o)281 public boolean contains(Object o) { 282 return indexOf(o) >= 0; 283 } 284 285 /** 286 * Returns the index of the first occurrence of the specified element 287 * in this list, or -1 if this list does not contain the element. 288 * More formally, returns the lowest index {@code i} such that 289 * {@code Objects.equals(o, get(i))}, 290 * or -1 if there is no such index. 291 */ indexOf(Object o)292 public int indexOf(Object o) { 293 return indexOfRange(o, 0, size); 294 } 295 indexOfRange(Object o, int start, int end)296 int indexOfRange(Object o, int start, int end) { 297 Object[] es = elementData; 298 if (o == null) { 299 for (int i = start; i < end; i++) { 300 if (es[i] == null) { 301 return i; 302 } 303 } 304 } else { 305 for (int i = start; i < end; i++) { 306 if (o.equals(es[i])) { 307 return i; 308 } 309 } 310 } 311 return -1; 312 } 313 314 /** 315 * Returns the index of the last occurrence of the specified element 316 * in this list, or -1 if this list does not contain the element. 317 * More formally, returns the highest index {@code i} such that 318 * {@code Objects.equals(o, get(i))}, 319 * or -1 if there is no such index. 320 */ lastIndexOf(Object o)321 public int lastIndexOf(Object o) { 322 return lastIndexOfRange(o, 0, size); 323 } 324 lastIndexOfRange(Object o, int start, int end)325 int lastIndexOfRange(Object o, int start, int end) { 326 Object[] es = elementData; 327 if (o == null) { 328 for (int i = end - 1; i >= start; i--) { 329 if (es[i] == null) { 330 return i; 331 } 332 } 333 } else { 334 for (int i = end - 1; i >= start; i--) { 335 if (o.equals(es[i])) { 336 return i; 337 } 338 } 339 } 340 return -1; 341 } 342 343 /** 344 * Returns a shallow copy of this {@code ArrayList} instance. (The 345 * elements themselves are not copied.) 346 * 347 * @return a clone of this {@code ArrayList} instance 348 */ clone()349 public Object clone() { 350 try { 351 ArrayList<?> v = (ArrayList<?>) super.clone(); 352 v.elementData = Arrays.copyOf(elementData, size); 353 v.modCount = 0; 354 return v; 355 } catch (CloneNotSupportedException e) { 356 // this shouldn't happen, since we are Cloneable 357 throw new InternalError(e); 358 } 359 } 360 361 /** 362 * Returns an array containing all of the elements in this list 363 * in proper sequence (from first to last element). 364 * 365 * <p>The returned array will be "safe" in that no references to it are 366 * maintained by this list. (In other words, this method must allocate 367 * a new array). The caller is thus free to modify the returned array. 368 * 369 * <p>This method acts as bridge between array-based and collection-based 370 * APIs. 371 * 372 * @return an array containing all of the elements in this list in 373 * proper sequence 374 */ toArray()375 public Object[] toArray() { 376 return Arrays.copyOf(elementData, size); 377 } 378 379 /** 380 * Returns an array containing all of the elements in this list in proper 381 * sequence (from first to last element); the runtime type of the returned 382 * array is that of the specified array. If the list fits in the 383 * specified array, it is returned therein. Otherwise, a new array is 384 * allocated with the runtime type of the specified array and the size of 385 * this list. 386 * 387 * <p>If the list fits in the specified array with room to spare 388 * (i.e., the array has more elements than the list), the element in 389 * the array immediately following the end of the collection is set to 390 * {@code null}. (This is useful in determining the length of the 391 * list <i>only</i> if the caller knows that the list does not contain 392 * any null elements.) 393 * 394 * @param a the array into which the elements of the list are to 395 * be stored, if it is big enough; otherwise, a new array of the 396 * same runtime type is allocated for this purpose. 397 * @return an array containing the elements of the list 398 * @throws ArrayStoreException if the runtime type of the specified array 399 * is not a supertype of the runtime type of every element in 400 * this list 401 * @throws NullPointerException if the specified array is null 402 */ 403 @SuppressWarnings("unchecked") toArray(T[] a)404 public <T> T[] toArray(T[] a) { 405 if (a.length < size) 406 // Make a new array of a's runtime type, but my contents: 407 return (T[]) Arrays.copyOf(elementData, size, a.getClass()); 408 System.arraycopy(elementData, 0, a, 0, size); 409 if (a.length > size) 410 a[size] = null; 411 return a; 412 } 413 414 // Positional Access Operations 415 416 @SuppressWarnings("unchecked") elementData(int index)417 E elementData(int index) { 418 return (E) elementData[index]; 419 } 420 421 @SuppressWarnings("unchecked") elementAt(Object[] es, int index)422 static <E> E elementAt(Object[] es, int index) { 423 return (E) es[index]; 424 } 425 426 /** 427 * Returns the element at the specified position in this list. 428 * 429 * @param index index of the element to return 430 * @return the element at the specified position in this list 431 * @throws IndexOutOfBoundsException {@inheritDoc} 432 */ get(int index)433 public E get(int index) { 434 Objects.checkIndex(index, size); 435 return elementData(index); 436 } 437 438 /** 439 * Replaces the element at the specified position in this list with 440 * the specified element. 441 * 442 * @param index index of the element to replace 443 * @param element element to be stored at the specified position 444 * @return the element previously at the specified position 445 * @throws IndexOutOfBoundsException {@inheritDoc} 446 */ set(int index, E element)447 public E set(int index, E element) { 448 Objects.checkIndex(index, size); 449 E oldValue = elementData(index); 450 elementData[index] = element; 451 return oldValue; 452 } 453 454 /** 455 * This helper method split out from add(E) to keep method 456 * bytecode size under 35 (the -XX:MaxInlineSize default value), 457 * which helps when add(E) is called in a C1-compiled loop. 458 */ add(E e, Object[] elementData, int s)459 private void add(E e, Object[] elementData, int s) { 460 if (s == elementData.length) 461 elementData = grow(); 462 elementData[s] = e; 463 size = s + 1; 464 } 465 466 /** 467 * Appends the specified element to the end of this list. 468 * 469 * @param e element to be appended to this list 470 * @return {@code true} (as specified by {@link Collection#add}) 471 */ add(E e)472 public boolean add(E e) { 473 modCount++; 474 add(e, elementData, size); 475 return true; 476 } 477 478 /** 479 * Inserts the specified element at the specified position in this 480 * list. Shifts the element currently at that position (if any) and 481 * any subsequent elements to the right (adds one to their indices). 482 * 483 * @param index index at which the specified element is to be inserted 484 * @param element element to be inserted 485 * @throws IndexOutOfBoundsException {@inheritDoc} 486 */ add(int index, E element)487 public void add(int index, E element) { 488 rangeCheckForAdd(index); 489 modCount++; 490 final int s; 491 Object[] elementData; 492 if ((s = size) == (elementData = this.elementData).length) 493 elementData = grow(); 494 System.arraycopy(elementData, index, 495 elementData, index + 1, 496 s - index); 497 elementData[index] = element; 498 size = s + 1; 499 } 500 501 /** 502 * Removes the element at the specified position in this list. 503 * Shifts any subsequent elements to the left (subtracts one from their 504 * indices). 505 * 506 * @param index the index of the element to be removed 507 * @return the element that was removed from the list 508 * @throws IndexOutOfBoundsException {@inheritDoc} 509 */ remove(int index)510 public E remove(int index) { 511 Objects.checkIndex(index, size); 512 final Object[] es = elementData; 513 514 @SuppressWarnings("unchecked") E oldValue = (E) es[index]; 515 fastRemove(es, index); 516 517 return oldValue; 518 } 519 520 /** 521 * {@inheritDoc} 522 */ equals(Object o)523 public boolean equals(Object o) { 524 if (o == this) { 525 return true; 526 } 527 528 if (!(o instanceof List)) { 529 return false; 530 } 531 532 final int expectedModCount = modCount; 533 // ArrayList can be subclassed and given arbitrary behavior, but we can 534 // still deal with the common case where o is ArrayList precisely 535 boolean equal = (o.getClass() == ArrayList.class) 536 ? equalsArrayList((ArrayList<?>) o) 537 : equalsRange((List<?>) o, 0, size); 538 539 checkForComodification(expectedModCount); 540 return equal; 541 } 542 equalsRange(List<?> other, int from, int to)543 boolean equalsRange(List<?> other, int from, int to) { 544 final Object[] es = elementData; 545 if (to > es.length) { 546 throw new ConcurrentModificationException(); 547 } 548 var oit = other.iterator(); 549 for (; from < to; from++) { 550 if (!oit.hasNext() || !Objects.equals(es[from], oit.next())) { 551 return false; 552 } 553 } 554 return !oit.hasNext(); 555 } 556 equalsArrayList(ArrayList<?> other)557 private boolean equalsArrayList(ArrayList<?> other) { 558 final int otherModCount = other.modCount; 559 final int s = size; 560 boolean equal; 561 if (equal = (s == other.size)) { 562 final Object[] otherEs = other.elementData; 563 final Object[] es = elementData; 564 if (s > es.length || s > otherEs.length) { 565 throw new ConcurrentModificationException(); 566 } 567 for (int i = 0; i < s; i++) { 568 if (!Objects.equals(es[i], otherEs[i])) { 569 equal = false; 570 break; 571 } 572 } 573 } 574 other.checkForComodification(otherModCount); 575 return equal; 576 } 577 checkForComodification(final int expectedModCount)578 private void checkForComodification(final int expectedModCount) { 579 if (modCount != expectedModCount) { 580 throw new ConcurrentModificationException(); 581 } 582 } 583 584 /** 585 * {@inheritDoc} 586 */ hashCode()587 public int hashCode() { 588 int expectedModCount = modCount; 589 int hash = hashCodeRange(0, size); 590 checkForComodification(expectedModCount); 591 return hash; 592 } 593 hashCodeRange(int from, int to)594 int hashCodeRange(int from, int to) { 595 final Object[] es = elementData; 596 if (to > es.length) { 597 throw new ConcurrentModificationException(); 598 } 599 int hashCode = 1; 600 for (int i = from; i < to; i++) { 601 Object e = es[i]; 602 hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode()); 603 } 604 return hashCode; 605 } 606 607 /** 608 * Removes the first occurrence of the specified element from this list, 609 * if it is present. If the list does not contain the element, it is 610 * unchanged. More formally, removes the element with the lowest index 611 * {@code i} such that 612 * {@code Objects.equals(o, get(i))} 613 * (if such an element exists). Returns {@code true} if this list 614 * contained the specified element (or equivalently, if this list 615 * changed as a result of the call). 616 * 617 * @param o element to be removed from this list, if present 618 * @return {@code true} if this list contained the specified element 619 */ remove(Object o)620 public boolean remove(Object o) { 621 final Object[] es = elementData; 622 final int size = this.size; 623 int i = 0; 624 found: { 625 if (o == null) { 626 for (; i < size; i++) 627 if (es[i] == null) 628 break found; 629 } else { 630 for (; i < size; i++) 631 if (o.equals(es[i])) 632 break found; 633 } 634 return false; 635 } 636 fastRemove(es, i); 637 return true; 638 } 639 640 /** 641 * Private remove method that skips bounds checking and does not 642 * return the value removed. 643 */ fastRemove(Object[] es, int i)644 private void fastRemove(Object[] es, int i) { 645 modCount++; 646 final int newSize; 647 if ((newSize = size - 1) > i) 648 System.arraycopy(es, i + 1, es, i, newSize - i); 649 es[size = newSize] = null; 650 } 651 652 /** 653 * Removes all of the elements from this list. The list will 654 * be empty after this call returns. 655 */ clear()656 public void clear() { 657 modCount++; 658 final Object[] es = elementData; 659 for (int to = size, i = size = 0; i < to; i++) 660 es[i] = null; 661 } 662 663 /** 664 * Appends all of the elements in the specified collection to the end of 665 * this list, in the order that they are returned by the 666 * specified collection's Iterator. The behavior of this operation is 667 * undefined if the specified collection is modified while the operation 668 * is in progress. (This implies that the behavior of this call is 669 * undefined if the specified collection is this list, and this 670 * list is nonempty.) 671 * 672 * @param c collection containing elements to be added to this list 673 * @return {@code true} if this list changed as a result of the call 674 * @throws NullPointerException if the specified collection is null 675 */ addAll(Collection<? extends E> c)676 public boolean addAll(Collection<? extends E> c) { 677 Object[] a = c.toArray(); 678 modCount++; 679 int numNew = a.length; 680 if (numNew == 0) 681 return false; 682 Object[] elementData; 683 final int s; 684 if (numNew > (elementData = this.elementData).length - (s = size)) 685 elementData = grow(s + numNew); 686 System.arraycopy(a, 0, elementData, s, numNew); 687 size = s + numNew; 688 return true; 689 } 690 691 /** 692 * Inserts all of the elements in the specified collection into this 693 * list, starting at the specified position. Shifts the element 694 * currently at that position (if any) and any subsequent elements to 695 * the right (increases their indices). The new elements will appear 696 * in the list in the order that they are returned by the 697 * specified collection's iterator. 698 * 699 * @param index index at which to insert the first element from the 700 * specified collection 701 * @param c collection containing elements to be added to this list 702 * @return {@code true} if this list changed as a result of the call 703 * @throws IndexOutOfBoundsException {@inheritDoc} 704 * @throws NullPointerException if the specified collection is null 705 */ addAll(int index, Collection<? extends E> c)706 public boolean addAll(int index, Collection<? extends E> c) { 707 rangeCheckForAdd(index); 708 709 Object[] a = c.toArray(); 710 modCount++; 711 int numNew = a.length; 712 if (numNew == 0) 713 return false; 714 Object[] elementData; 715 final int s; 716 if (numNew > (elementData = this.elementData).length - (s = size)) 717 elementData = grow(s + numNew); 718 719 int numMoved = s - index; 720 if (numMoved > 0) 721 System.arraycopy(elementData, index, 722 elementData, index + numNew, 723 numMoved); 724 System.arraycopy(a, 0, elementData, index, numNew); 725 size = s + numNew; 726 return true; 727 } 728 729 /** 730 * Removes from this list all of the elements whose index is between 731 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. 732 * Shifts any succeeding elements to the left (reduces their index). 733 * This call shortens the list by {@code (toIndex - fromIndex)} elements. 734 * (If {@code toIndex==fromIndex}, this operation has no effect.) 735 * 736 * @throws IndexOutOfBoundsException if {@code fromIndex} or 737 * {@code toIndex} is out of range 738 * ({@code fromIndex < 0 || 739 * toIndex > size() || 740 * toIndex < fromIndex}) 741 */ removeRange(int fromIndex, int toIndex)742 protected void removeRange(int fromIndex, int toIndex) { 743 if (fromIndex > toIndex) { 744 throw new IndexOutOfBoundsException( 745 outOfBoundsMsg(fromIndex, toIndex)); 746 } 747 modCount++; 748 shiftTailOverGap(elementData, fromIndex, toIndex); 749 } 750 751 /** Erases the gap from lo to hi, by sliding down following elements. */ shiftTailOverGap(Object[] es, int lo, int hi)752 private void shiftTailOverGap(Object[] es, int lo, int hi) { 753 System.arraycopy(es, hi, es, lo, size - hi); 754 for (int to = size, i = (size -= hi - lo); i < to; i++) 755 es[i] = null; 756 } 757 758 /** 759 * A version of rangeCheck used by add and addAll. 760 */ rangeCheckForAdd(int index)761 private void rangeCheckForAdd(int index) { 762 if (index > size || index < 0) 763 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 764 } 765 766 /** 767 * Constructs an IndexOutOfBoundsException detail message. 768 * Of the many possible refactorings of the error handling code, 769 * this "outlining" performs best with both server and client VMs. 770 */ outOfBoundsMsg(int index)771 private String outOfBoundsMsg(int index) { 772 return "Index: "+index+", Size: "+size; 773 } 774 775 /** 776 * A version used in checking (fromIndex > toIndex) condition 777 */ outOfBoundsMsg(int fromIndex, int toIndex)778 private static String outOfBoundsMsg(int fromIndex, int toIndex) { 779 return "From Index: " + fromIndex + " > To Index: " + toIndex; 780 } 781 782 /** 783 * Removes from this list all of its elements that are contained in the 784 * specified collection. 785 * 786 * @param c collection containing elements to be removed from this list 787 * @return {@code true} if this list changed as a result of the call 788 * @throws ClassCastException if the class of an element of this list 789 * is incompatible with the specified collection 790 * (<a href="Collection.html#optional-restrictions">optional</a>) 791 * @throws NullPointerException if this list contains a null element and the 792 * specified collection does not permit null elements 793 * (<a href="Collection.html#optional-restrictions">optional</a>), 794 * or if the specified collection is null 795 * @see Collection#contains(Object) 796 */ removeAll(Collection<?> c)797 public boolean removeAll(Collection<?> c) { 798 return batchRemove(c, false, 0, size); 799 } 800 801 /** 802 * Retains only the elements in this list that are contained in the 803 * specified collection. In other words, removes from this list all 804 * of its elements that are not contained in the specified collection. 805 * 806 * @param c collection containing elements to be retained in this list 807 * @return {@code true} if this list changed as a result of the call 808 * @throws ClassCastException if the class of an element of this list 809 * is incompatible with the specified collection 810 * (<a href="Collection.html#optional-restrictions">optional</a>) 811 * @throws NullPointerException if this list contains a null element and the 812 * specified collection does not permit null elements 813 * (<a href="Collection.html#optional-restrictions">optional</a>), 814 * or if the specified collection is null 815 * @see Collection#contains(Object) 816 */ retainAll(Collection<?> c)817 public boolean retainAll(Collection<?> c) { 818 return batchRemove(c, true, 0, size); 819 } 820 batchRemove(Collection<?> c, boolean complement, final int from, final int end)821 boolean batchRemove(Collection<?> c, boolean complement, 822 final int from, final int end) { 823 Objects.requireNonNull(c); 824 final Object[] es = elementData; 825 int r; 826 // Optimize for initial run of survivors 827 for (r = from;; r++) { 828 if (r == end) 829 return false; 830 if (c.contains(es[r]) != complement) 831 break; 832 } 833 int w = r++; 834 try { 835 for (Object e; r < end; r++) 836 if (c.contains(e = es[r]) == complement) 837 es[w++] = e; 838 } catch (Throwable ex) { 839 // Preserve behavioral compatibility with AbstractCollection, 840 // even if c.contains() throws. 841 System.arraycopy(es, r, es, w, end - r); 842 w += end - r; 843 throw ex; 844 } finally { 845 modCount += end - w; 846 shiftTailOverGap(es, w, end); 847 } 848 return true; 849 } 850 851 /** 852 * Saves the state of the {@code ArrayList} instance to a stream 853 * (that is, serializes it). 854 * 855 * @param s the stream 856 * @throws java.io.IOException if an I/O error occurs 857 * @serialData The length of the array backing the {@code ArrayList} 858 * instance is emitted (int), followed by all of its elements 859 * (each an {@code Object}) in the proper order. 860 */ 861 @java.io.Serial writeObject(java.io.ObjectOutputStream s)862 private void writeObject(java.io.ObjectOutputStream s) 863 throws java.io.IOException { 864 // Write out element count, and any hidden stuff 865 int expectedModCount = modCount; 866 s.defaultWriteObject(); 867 868 // Write out size as capacity for behavioral compatibility with clone() 869 s.writeInt(size); 870 871 // Write out all elements in the proper order. 872 for (int i=0; i<size; i++) { 873 s.writeObject(elementData[i]); 874 } 875 876 if (modCount != expectedModCount) { 877 throw new ConcurrentModificationException(); 878 } 879 } 880 881 /** 882 * Reconstitutes the {@code ArrayList} instance from a stream (that is, 883 * deserializes it). 884 * @param s the stream 885 * @throws ClassNotFoundException if the class of a serialized object 886 * could not be found 887 * @throws java.io.IOException if an I/O error occurs 888 */ 889 @java.io.Serial readObject(java.io.ObjectInputStream s)890 private void readObject(java.io.ObjectInputStream s) 891 throws java.io.IOException, ClassNotFoundException { 892 893 // Read in size, and any hidden stuff 894 s.defaultReadObject(); 895 896 // Read in capacity 897 s.readInt(); // ignored 898 899 if (size > 0) { 900 // like clone(), allocate array based upon size not capacity 901 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size); 902 Object[] elements = new Object[size]; 903 904 // Read in all elements in the proper order. 905 for (int i = 0; i < size; i++) { 906 elements[i] = s.readObject(); 907 } 908 909 elementData = elements; 910 } else if (size == 0) { 911 elementData = EMPTY_ELEMENTDATA; 912 } else { 913 throw new java.io.InvalidObjectException("Invalid size: " + size); 914 } 915 } 916 917 /** 918 * Returns a list iterator over the elements in this list (in proper 919 * sequence), starting at the specified position in the list. 920 * The specified index indicates the first element that would be 921 * returned by an initial call to {@link ListIterator#next next}. 922 * An initial call to {@link ListIterator#previous previous} would 923 * return the element with the specified index minus one. 924 * 925 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 926 * 927 * @throws IndexOutOfBoundsException {@inheritDoc} 928 */ listIterator(int index)929 public ListIterator<E> listIterator(int index) { 930 rangeCheckForAdd(index); 931 return new ListItr(index); 932 } 933 934 /** 935 * Returns a list iterator over the elements in this list (in proper 936 * sequence). 937 * 938 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 939 * 940 * @see #listIterator(int) 941 */ listIterator()942 public ListIterator<E> listIterator() { 943 return new ListItr(0); 944 } 945 946 /** 947 * Returns an iterator over the elements in this list in proper sequence. 948 * 949 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 950 * 951 * @return an iterator over the elements in this list in proper sequence 952 */ iterator()953 public Iterator<E> iterator() { 954 return new Itr(); 955 } 956 957 /** 958 * An optimized version of AbstractList.Itr 959 */ 960 private class Itr implements Iterator<E> { 961 // Android-changed: Add "limit" field to detect end of iteration. 962 // The "limit" of this iterator. This is the size of the list at the time the 963 // iterator was created. Adding & removing elements will invalidate the iteration 964 // anyway (and cause next() to throw) so saving this value will guarantee that the 965 // value of hasNext() remains stable and won't flap between true and false when elements 966 // are added and removed from the list. 967 protected int limit = ArrayList.this.size; 968 969 int cursor; // index of next element to return 970 int lastRet = -1; // index of last element returned; -1 if no such 971 int expectedModCount = modCount; 972 973 // prevent creating a synthetic constructor Itr()974 Itr() {} 975 hasNext()976 public boolean hasNext() { 977 return cursor < limit; 978 } 979 980 @SuppressWarnings("unchecked") next()981 public E next() { 982 checkForComodification(); 983 int i = cursor; 984 if (i >= limit) 985 throw new NoSuchElementException(); 986 Object[] elementData = ArrayList.this.elementData; 987 if (i >= elementData.length) 988 throw new ConcurrentModificationException(); 989 cursor = i + 1; 990 return (E) elementData[lastRet = i]; 991 } 992 remove()993 public void remove() { 994 if (lastRet < 0) 995 throw new IllegalStateException(); 996 checkForComodification(); 997 998 try { 999 ArrayList.this.remove(lastRet); 1000 cursor = lastRet; 1001 lastRet = -1; 1002 expectedModCount = modCount; 1003 limit--; 1004 } catch (IndexOutOfBoundsException ex) { 1005 throw new ConcurrentModificationException(); 1006 } 1007 } 1008 1009 @Override forEachRemaining(Consumer<? super E> action)1010 public void forEachRemaining(Consumer<? super E> action) { 1011 Objects.requireNonNull(action); 1012 final int size = ArrayList.this.size; 1013 int i = cursor; 1014 if (i < size) { 1015 final Object[] es = elementData; 1016 if (i >= es.length) 1017 throw new ConcurrentModificationException(); 1018 for (; i < size && modCount == expectedModCount; i++) 1019 action.accept(elementAt(es, i)); 1020 // update once at end to reduce heap write traffic 1021 cursor = i; 1022 lastRet = i - 1; 1023 checkForComodification(); 1024 } 1025 } 1026 checkForComodification()1027 final void checkForComodification() { 1028 if (modCount != expectedModCount) 1029 throw new ConcurrentModificationException(); 1030 } 1031 } 1032 1033 /** 1034 * An optimized version of AbstractList.ListItr 1035 */ 1036 private class ListItr extends Itr implements ListIterator<E> { ListItr(int index)1037 ListItr(int index) { 1038 super(); 1039 cursor = index; 1040 } 1041 hasPrevious()1042 public boolean hasPrevious() { 1043 return cursor != 0; 1044 } 1045 nextIndex()1046 public int nextIndex() { 1047 return cursor; 1048 } 1049 previousIndex()1050 public int previousIndex() { 1051 return cursor - 1; 1052 } 1053 1054 @SuppressWarnings("unchecked") previous()1055 public E previous() { 1056 checkForComodification(); 1057 int i = cursor - 1; 1058 if (i < 0) 1059 throw new NoSuchElementException(); 1060 Object[] elementData = ArrayList.this.elementData; 1061 if (i >= elementData.length) 1062 throw new ConcurrentModificationException(); 1063 cursor = i; 1064 return (E) elementData[lastRet = i]; 1065 } 1066 set(E e)1067 public void set(E e) { 1068 if (lastRet < 0) 1069 throw new IllegalStateException(); 1070 checkForComodification(); 1071 1072 try { 1073 ArrayList.this.set(lastRet, e); 1074 } catch (IndexOutOfBoundsException ex) { 1075 throw new ConcurrentModificationException(); 1076 } 1077 } 1078 add(E e)1079 public void add(E e) { 1080 checkForComodification(); 1081 1082 try { 1083 int i = cursor; 1084 ArrayList.this.add(i, e); 1085 cursor = i + 1; 1086 lastRet = -1; 1087 expectedModCount = modCount; 1088 limit++; 1089 } catch (IndexOutOfBoundsException ex) { 1090 throw new ConcurrentModificationException(); 1091 } 1092 } 1093 } 1094 1095 /** 1096 * Returns a view of the portion of this list between the specified 1097 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If 1098 * {@code fromIndex} and {@code toIndex} are equal, the returned list is 1099 * empty.) The returned list is backed by this list, so non-structural 1100 * changes in the returned list are reflected in this list, and vice-versa. 1101 * The returned list supports all of the optional list operations. 1102 * 1103 * <p>This method eliminates the need for explicit range operations (of 1104 * the sort that commonly exist for arrays). Any operation that expects 1105 * a list can be used as a range operation by passing a subList view 1106 * instead of a whole list. For example, the following idiom 1107 * removes a range of elements from a list: 1108 * <pre> 1109 * list.subList(from, to).clear(); 1110 * </pre> 1111 * Similar idioms may be constructed for {@link #indexOf(Object)} and 1112 * {@link #lastIndexOf(Object)}, and all of the algorithms in the 1113 * {@link Collections} class can be applied to a subList. 1114 * 1115 * <p>The semantics of the list returned by this method become undefined if 1116 * the backing list (i.e., this list) is <i>structurally modified</i> in 1117 * any way other than via the returned list. (Structural modifications are 1118 * those that change the size of this list, or otherwise perturb it in such 1119 * a fashion that iterations in progress may yield incorrect results.) 1120 * 1121 * @throws IndexOutOfBoundsException {@inheritDoc} 1122 * @throws IllegalArgumentException {@inheritDoc} 1123 */ subList(int fromIndex, int toIndex)1124 public List<E> subList(int fromIndex, int toIndex) { 1125 subListRangeCheck(fromIndex, toIndex, size); 1126 return new SubList<>(this, fromIndex, toIndex); 1127 } 1128 1129 private static class SubList<E> extends AbstractList<E> implements RandomAccess { 1130 private final ArrayList<E> root; 1131 private final SubList<E> parent; 1132 private final int offset; 1133 private int size; 1134 1135 /** 1136 * Constructs a sublist of an arbitrary ArrayList. 1137 */ SubList(ArrayList<E> root, int fromIndex, int toIndex)1138 public SubList(ArrayList<E> root, int fromIndex, int toIndex) { 1139 this.root = root; 1140 this.parent = null; 1141 this.offset = fromIndex; 1142 this.size = toIndex - fromIndex; 1143 this.modCount = root.modCount; 1144 } 1145 1146 /** 1147 * Constructs a sublist of another SubList. 1148 */ SubList(SubList<E> parent, int fromIndex, int toIndex)1149 private SubList(SubList<E> parent, int fromIndex, int toIndex) { 1150 this.root = parent.root; 1151 this.parent = parent; 1152 this.offset = parent.offset + fromIndex; 1153 this.size = toIndex - fromIndex; 1154 this.modCount = parent.modCount; 1155 } 1156 set(int index, E element)1157 public E set(int index, E element) { 1158 Objects.checkIndex(index, size); 1159 checkForComodification(); 1160 E oldValue = root.elementData(offset + index); 1161 root.elementData[offset + index] = element; 1162 return oldValue; 1163 } 1164 get(int index)1165 public E get(int index) { 1166 Objects.checkIndex(index, size); 1167 checkForComodification(); 1168 return root.elementData(offset + index); 1169 } 1170 size()1171 public int size() { 1172 checkForComodification(); 1173 return size; 1174 } 1175 add(int index, E element)1176 public void add(int index, E element) { 1177 rangeCheckForAdd(index); 1178 checkForComodification(); 1179 root.add(offset + index, element); 1180 updateSizeAndModCount(1); 1181 } 1182 remove(int index)1183 public E remove(int index) { 1184 Objects.checkIndex(index, size); 1185 checkForComodification(); 1186 E result = root.remove(offset + index); 1187 updateSizeAndModCount(-1); 1188 return result; 1189 } 1190 removeRange(int fromIndex, int toIndex)1191 protected void removeRange(int fromIndex, int toIndex) { 1192 checkForComodification(); 1193 root.removeRange(offset + fromIndex, offset + toIndex); 1194 updateSizeAndModCount(fromIndex - toIndex); 1195 } 1196 addAll(Collection<? extends E> c)1197 public boolean addAll(Collection<? extends E> c) { 1198 return addAll(this.size, c); 1199 } 1200 addAll(int index, Collection<? extends E> c)1201 public boolean addAll(int index, Collection<? extends E> c) { 1202 rangeCheckForAdd(index); 1203 int cSize = c.size(); 1204 if (cSize==0) 1205 return false; 1206 checkForComodification(); 1207 root.addAll(offset + index, c); 1208 updateSizeAndModCount(cSize); 1209 return true; 1210 } 1211 replaceAll(UnaryOperator<E> operator)1212 public void replaceAll(UnaryOperator<E> operator) { 1213 root.replaceAllRange(operator, offset, offset + size); 1214 } 1215 removeAll(Collection<?> c)1216 public boolean removeAll(Collection<?> c) { 1217 return batchRemove(c, false); 1218 } 1219 retainAll(Collection<?> c)1220 public boolean retainAll(Collection<?> c) { 1221 return batchRemove(c, true); 1222 } 1223 batchRemove(Collection<?> c, boolean complement)1224 private boolean batchRemove(Collection<?> c, boolean complement) { 1225 checkForComodification(); 1226 int oldSize = root.size; 1227 boolean modified = 1228 root.batchRemove(c, complement, offset, offset + size); 1229 if (modified) 1230 updateSizeAndModCount(root.size - oldSize); 1231 return modified; 1232 } 1233 removeIf(Predicate<? super E> filter)1234 public boolean removeIf(Predicate<? super E> filter) { 1235 checkForComodification(); 1236 int oldSize = root.size; 1237 boolean modified = root.removeIf(filter, offset, offset + size); 1238 if (modified) 1239 updateSizeAndModCount(root.size - oldSize); 1240 return modified; 1241 } 1242 toArray()1243 public Object[] toArray() { 1244 checkForComodification(); 1245 return Arrays.copyOfRange(root.elementData, offset, offset + size); 1246 } 1247 1248 @SuppressWarnings("unchecked") toArray(T[] a)1249 public <T> T[] toArray(T[] a) { 1250 checkForComodification(); 1251 if (a.length < size) 1252 return (T[]) Arrays.copyOfRange( 1253 root.elementData, offset, offset + size, a.getClass()); 1254 System.arraycopy(root.elementData, offset, a, 0, size); 1255 if (a.length > size) 1256 a[size] = null; 1257 return a; 1258 } 1259 equals(Object o)1260 public boolean equals(Object o) { 1261 if (o == this) { 1262 return true; 1263 } 1264 1265 if (!(o instanceof List)) { 1266 return false; 1267 } 1268 1269 boolean equal = root.equalsRange((List<?>)o, offset, offset + size); 1270 checkForComodification(); 1271 return equal; 1272 } 1273 hashCode()1274 public int hashCode() { 1275 int hash = root.hashCodeRange(offset, offset + size); 1276 checkForComodification(); 1277 return hash; 1278 } 1279 indexOf(Object o)1280 public int indexOf(Object o) { 1281 int index = root.indexOfRange(o, offset, offset + size); 1282 checkForComodification(); 1283 return index >= 0 ? index - offset : -1; 1284 } 1285 lastIndexOf(Object o)1286 public int lastIndexOf(Object o) { 1287 int index = root.lastIndexOfRange(o, offset, offset + size); 1288 checkForComodification(); 1289 return index >= 0 ? index - offset : -1; 1290 } 1291 contains(Object o)1292 public boolean contains(Object o) { 1293 return indexOf(o) >= 0; 1294 } 1295 iterator()1296 public Iterator<E> iterator() { 1297 return listIterator(); 1298 } 1299 listIterator(int index)1300 public ListIterator<E> listIterator(int index) { 1301 checkForComodification(); 1302 rangeCheckForAdd(index); 1303 1304 return new ListIterator<E>() { 1305 int cursor = index; 1306 int lastRet = -1; 1307 int expectedModCount = SubList.this.modCount; 1308 1309 public boolean hasNext() { 1310 return cursor != SubList.this.size; 1311 } 1312 1313 @SuppressWarnings("unchecked") 1314 public E next() { 1315 checkForComodification(); 1316 int i = cursor; 1317 if (i >= SubList.this.size) 1318 throw new NoSuchElementException(); 1319 Object[] elementData = root.elementData; 1320 if (offset + i >= elementData.length) 1321 throw new ConcurrentModificationException(); 1322 cursor = i + 1; 1323 return (E) elementData[offset + (lastRet = i)]; 1324 } 1325 1326 public boolean hasPrevious() { 1327 return cursor != 0; 1328 } 1329 1330 @SuppressWarnings("unchecked") 1331 public E previous() { 1332 checkForComodification(); 1333 int i = cursor - 1; 1334 if (i < 0) 1335 throw new NoSuchElementException(); 1336 Object[] elementData = root.elementData; 1337 if (offset + i >= elementData.length) 1338 throw new ConcurrentModificationException(); 1339 cursor = i; 1340 return (E) elementData[offset + (lastRet = i)]; 1341 } 1342 1343 public void forEachRemaining(Consumer<? super E> action) { 1344 Objects.requireNonNull(action); 1345 final int size = SubList.this.size; 1346 int i = cursor; 1347 if (i < size) { 1348 final Object[] es = root.elementData; 1349 if (offset + i >= es.length) 1350 throw new ConcurrentModificationException(); 1351 for (; i < size && root.modCount == expectedModCount; i++) 1352 action.accept(elementAt(es, offset + i)); 1353 // update once at end to reduce heap write traffic 1354 cursor = i; 1355 lastRet = i - 1; 1356 checkForComodification(); 1357 } 1358 } 1359 1360 public int nextIndex() { 1361 return cursor; 1362 } 1363 1364 public int previousIndex() { 1365 return cursor - 1; 1366 } 1367 1368 public void remove() { 1369 if (lastRet < 0) 1370 throw new IllegalStateException(); 1371 checkForComodification(); 1372 1373 try { 1374 SubList.this.remove(lastRet); 1375 cursor = lastRet; 1376 lastRet = -1; 1377 expectedModCount = SubList.this.modCount; 1378 } catch (IndexOutOfBoundsException ex) { 1379 throw new ConcurrentModificationException(); 1380 } 1381 } 1382 1383 public void set(E e) { 1384 if (lastRet < 0) 1385 throw new IllegalStateException(); 1386 checkForComodification(); 1387 1388 try { 1389 root.set(offset + lastRet, e); 1390 } catch (IndexOutOfBoundsException ex) { 1391 throw new ConcurrentModificationException(); 1392 } 1393 } 1394 1395 public void add(E e) { 1396 checkForComodification(); 1397 1398 try { 1399 int i = cursor; 1400 SubList.this.add(i, e); 1401 cursor = i + 1; 1402 lastRet = -1; 1403 expectedModCount = SubList.this.modCount; 1404 } catch (IndexOutOfBoundsException ex) { 1405 throw new ConcurrentModificationException(); 1406 } 1407 } 1408 1409 final void checkForComodification() { 1410 if (root.modCount != expectedModCount) 1411 throw new ConcurrentModificationException(); 1412 } 1413 }; 1414 } 1415 subList(int fromIndex, int toIndex)1416 public List<E> subList(int fromIndex, int toIndex) { 1417 subListRangeCheck(fromIndex, toIndex, size); 1418 return new SubList<>(this, fromIndex, toIndex); 1419 } 1420 rangeCheckForAdd(int index)1421 private void rangeCheckForAdd(int index) { 1422 if (index < 0 || index > this.size) 1423 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 1424 } 1425 outOfBoundsMsg(int index)1426 private String outOfBoundsMsg(int index) { 1427 return "Index: "+index+", Size: "+this.size; 1428 } 1429 checkForComodification()1430 private void checkForComodification() { 1431 if (root.modCount != modCount) 1432 throw new ConcurrentModificationException(); 1433 } 1434 updateSizeAndModCount(int sizeChange)1435 private void updateSizeAndModCount(int sizeChange) { 1436 SubList<E> slist = this; 1437 do { 1438 slist.size += sizeChange; 1439 slist.modCount = root.modCount; 1440 slist = slist.parent; 1441 } while (slist != null); 1442 } 1443 spliterator()1444 public Spliterator<E> spliterator() { 1445 checkForComodification(); 1446 1447 // ArrayListSpliterator not used here due to late-binding 1448 return new Spliterator<E>() { 1449 private int index = offset; // current index, modified on advance/split 1450 private int fence = -1; // -1 until used; then one past last index 1451 private int expectedModCount; // initialized when fence set 1452 1453 private int getFence() { // initialize fence to size on first use 1454 int hi; // (a specialized variant appears in method forEach) 1455 if ((hi = fence) < 0) { 1456 expectedModCount = modCount; 1457 hi = fence = offset + size; 1458 } 1459 return hi; 1460 } 1461 1462 public ArrayList<E>.ArrayListSpliterator trySplit() { 1463 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; 1464 // ArrayListSpliterator can be used here as the source is already bound 1465 return (lo >= mid) ? null : // divide range in half unless too small 1466 root.new ArrayListSpliterator(lo, index = mid, expectedModCount); 1467 } 1468 1469 public boolean tryAdvance(Consumer<? super E> action) { 1470 Objects.requireNonNull(action); 1471 int hi = getFence(), i = index; 1472 if (i < hi) { 1473 index = i + 1; 1474 @SuppressWarnings("unchecked") E e = (E)root.elementData[i]; 1475 action.accept(e); 1476 if (root.modCount != expectedModCount) 1477 throw new ConcurrentModificationException(); 1478 return true; 1479 } 1480 return false; 1481 } 1482 1483 public void forEachRemaining(Consumer<? super E> action) { 1484 Objects.requireNonNull(action); 1485 int i, hi, mc; // hoist accesses and checks from loop 1486 ArrayList<E> lst = root; 1487 Object[] a; 1488 if ((a = lst.elementData) != null) { 1489 if ((hi = fence) < 0) { 1490 mc = modCount; 1491 hi = offset + size; 1492 } 1493 else 1494 mc = expectedModCount; 1495 if ((i = index) >= 0 && (index = hi) <= a.length) { 1496 for (; i < hi; ++i) { 1497 @SuppressWarnings("unchecked") E e = (E) a[i]; 1498 action.accept(e); 1499 } 1500 if (lst.modCount == mc) 1501 return; 1502 } 1503 } 1504 throw new ConcurrentModificationException(); 1505 } 1506 1507 public long estimateSize() { 1508 return getFence() - index; 1509 } 1510 1511 public int characteristics() { 1512 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; 1513 } 1514 }; 1515 } 1516 } 1517 1518 /** 1519 * @throws NullPointerException {@inheritDoc} 1520 */ 1521 @Override 1522 public void forEach(Consumer<? super E> action) { 1523 Objects.requireNonNull(action); 1524 final int expectedModCount = modCount; 1525 final Object[] es = elementData; 1526 final int size = this.size; 1527 for (int i = 0; modCount == expectedModCount && i < size; i++) 1528 action.accept(elementAt(es, i)); 1529 if (modCount != expectedModCount) 1530 throw new ConcurrentModificationException(); 1531 } 1532 1533 /** 1534 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> 1535 * and <em>fail-fast</em> {@link Spliterator} over the elements in this 1536 * list. 1537 * 1538 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, 1539 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}. 1540 * Overriding implementations should document the reporting of additional 1541 * characteristic values. 1542 * 1543 * @return a {@code Spliterator} over the elements in this list 1544 * @since 1.8 1545 */ 1546 @Override 1547 public Spliterator<E> spliterator() { 1548 return new ArrayListSpliterator(0, -1, 0); 1549 } 1550 1551 /** Index-based split-by-two, lazily initialized Spliterator */ 1552 final class ArrayListSpliterator implements Spliterator<E> { 1553 1554 /* 1555 * If ArrayLists were immutable, or structurally immutable (no 1556 * adds, removes, etc), we could implement their spliterators 1557 * with Arrays.spliterator. Instead we detect as much 1558 * interference during traversal as practical without 1559 * sacrificing much performance. We rely primarily on 1560 * modCounts. These are not guaranteed to detect concurrency 1561 * violations, and are sometimes overly conservative about 1562 * within-thread interference, but detect enough problems to 1563 * be worthwhile in practice. To carry this out, we (1) lazily 1564 * initialize fence and expectedModCount until the latest 1565 * point that we need to commit to the state we are checking 1566 * against; thus improving precision. (This doesn't apply to 1567 * SubLists, that create spliterators with current non-lazy 1568 * values). (2) We perform only a single 1569 * ConcurrentModificationException check at the end of forEach 1570 * (the most performance-sensitive method). When using forEach 1571 * (as opposed to iterators), we can normally only detect 1572 * interference after actions, not before. Further 1573 * CME-triggering checks apply to all other possible 1574 * violations of assumptions for example null or too-small 1575 * elementData array given its size(), that could only have 1576 * occurred due to interference. This allows the inner loop 1577 * of forEach to run without any further checks, and 1578 * simplifies lambda-resolution. While this does entail a 1579 * number of checks, note that in the common case of 1580 * list.stream().forEach(a), no checks or other computation 1581 * occur anywhere other than inside forEach itself. The other 1582 * less-often-used methods cannot take advantage of most of 1583 * these streamlinings. 1584 */ 1585 1586 private int index; // current index, modified on advance/split 1587 private int fence; // -1 until used; then one past last index 1588 private int expectedModCount; // initialized when fence set 1589 1590 /** Creates new spliterator covering the given range. */ 1591 ArrayListSpliterator(int origin, int fence, int expectedModCount) { 1592 this.index = origin; 1593 this.fence = fence; 1594 this.expectedModCount = expectedModCount; 1595 } 1596 1597 private int getFence() { // initialize fence to size on first use 1598 int hi; // (a specialized variant appears in method forEach) 1599 if ((hi = fence) < 0) { 1600 expectedModCount = modCount; 1601 hi = fence = size; 1602 } 1603 return hi; 1604 } 1605 1606 public ArrayListSpliterator trySplit() { 1607 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; 1608 return (lo >= mid) ? null : // divide range in half unless too small 1609 new ArrayListSpliterator(lo, index = mid, expectedModCount); 1610 } 1611 1612 public boolean tryAdvance(Consumer<? super E> action) { 1613 if (action == null) 1614 throw new NullPointerException(); 1615 int hi = getFence(), i = index; 1616 if (i < hi) { 1617 index = i + 1; 1618 @SuppressWarnings("unchecked") E e = (E)elementData[i]; 1619 action.accept(e); 1620 if (modCount != expectedModCount) 1621 throw new ConcurrentModificationException(); 1622 return true; 1623 } 1624 return false; 1625 } 1626 1627 public void forEachRemaining(Consumer<? super E> action) { 1628 int i, hi, mc; // hoist accesses and checks from loop 1629 Object[] a; 1630 if (action == null) 1631 throw new NullPointerException(); 1632 if ((a = elementData) != null) { 1633 if ((hi = fence) < 0) { 1634 mc = modCount; 1635 hi = size; 1636 } 1637 else 1638 mc = expectedModCount; 1639 if ((i = index) >= 0 && (index = hi) <= a.length) { 1640 for (; i < hi; ++i) { 1641 @SuppressWarnings("unchecked") E e = (E) a[i]; 1642 action.accept(e); 1643 } 1644 if (modCount == mc) 1645 return; 1646 } 1647 } 1648 throw new ConcurrentModificationException(); 1649 } 1650 1651 public long estimateSize() { 1652 return getFence() - index; 1653 } 1654 1655 public int characteristics() { 1656 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; 1657 } 1658 } 1659 1660 // A tiny bit set implementation 1661 1662 private static long[] nBits(int n) { 1663 return new long[((n - 1) >> 6) + 1]; 1664 } 1665 private static void setBit(long[] bits, int i) { 1666 bits[i >> 6] |= 1L << i; 1667 } 1668 private static boolean isClear(long[] bits, int i) { 1669 return (bits[i >> 6] & (1L << i)) == 0; 1670 } 1671 1672 /** 1673 * @throws NullPointerException {@inheritDoc} 1674 */ 1675 @Override 1676 public boolean removeIf(Predicate<? super E> filter) { 1677 return removeIf(filter, 0, size); 1678 } 1679 1680 /** 1681 * Removes all elements satisfying the given predicate, from index 1682 * i (inclusive) to index end (exclusive). 1683 */ 1684 boolean removeIf(Predicate<? super E> filter, int i, final int end) { 1685 Objects.requireNonNull(filter); 1686 int expectedModCount = modCount; 1687 final Object[] es = elementData; 1688 // Optimize for initial run of survivors 1689 for (; i < end && !filter.test(elementAt(es, i)); i++) 1690 ; 1691 // Tolerate predicates that reentrantly access the collection for 1692 // read (but writers still get CME), so traverse once to find 1693 // elements to delete, a second pass to physically expunge. 1694 if (i < end) { 1695 final int beg = i; 1696 final long[] deathRow = nBits(end - beg); 1697 deathRow[0] = 1L; // set bit 0 1698 for (i = beg + 1; i < end; i++) 1699 if (filter.test(elementAt(es, i))) 1700 setBit(deathRow, i - beg); 1701 if (modCount != expectedModCount) 1702 throw new ConcurrentModificationException(); 1703 modCount++; 1704 int w = beg; 1705 for (i = beg; i < end; i++) 1706 if (isClear(deathRow, i - beg)) 1707 es[w++] = es[i]; 1708 shiftTailOverGap(es, w, end); 1709 return true; 1710 } else { 1711 if (modCount != expectedModCount) 1712 throw new ConcurrentModificationException(); 1713 return false; 1714 } 1715 } 1716 1717 @Override 1718 public void replaceAll(UnaryOperator<E> operator) { 1719 replaceAllRange(operator, 0, size); 1720 // TODO(8203662): remove increment of modCount from ... 1721 modCount++; 1722 } 1723 1724 private void replaceAllRange(UnaryOperator<E> operator, int i, int end) { 1725 Objects.requireNonNull(operator); 1726 final int expectedModCount = modCount; 1727 final Object[] es = elementData; 1728 for (; modCount == expectedModCount && i < end; i++) 1729 es[i] = operator.apply(elementAt(es, i)); 1730 if (modCount != expectedModCount) 1731 throw new ConcurrentModificationException(); 1732 } 1733 1734 @Override 1735 @SuppressWarnings("unchecked") 1736 public void sort(Comparator<? super E> c) { 1737 final int expectedModCount = modCount; 1738 Arrays.sort((E[]) elementData, 0, size, c); 1739 if (modCount != expectedModCount) 1740 throw new ConcurrentModificationException(); 1741 modCount++; 1742 } 1743 1744 void checkInvariants() { 1745 // assert size >= 0; 1746 // assert size == elementData.length || elementData[size] == null; 1747 } 1748 } 1749