1 /* 2 * Copyright (c) 1997, 2012, 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.Block; 29 import java.util.function.Predicate; 30 import java.util.function.UnaryOperator; 31 32 /** 33 * Resizable-array implementation of the <tt>List</tt> interface. Implements 34 * all optional list operations, and permits all elements, including 35 * <tt>null</tt>. In addition to implementing the <tt>List</tt> interface, 36 * this class provides methods to manipulate the size of the array that is 37 * used internally to store the list. (This class is roughly equivalent to 38 * <tt>Vector</tt>, except that it is unsynchronized.) 39 * 40 * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>, 41 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant 42 * time. The <tt>add</tt> operation runs in <i>amortized constant time</i>, 43 * that is, adding n elements requires O(n) time. All of the other operations 44 * run in linear time (roughly speaking). The constant factor is low compared 45 * to that for the <tt>LinkedList</tt> implementation. 46 * 47 * <p>Each <tt>ArrayList</tt> instance has a <i>capacity</i>. The capacity is 48 * the size of the array used to store the elements in the list. It is always 49 * at least as large as the list size. As elements are added to an ArrayList, 50 * its capacity grows automatically. The details of the growth policy are not 51 * specified beyond the fact that adding an element has constant amortized 52 * time cost. 53 * 54 * <p>An application can increase the capacity of an <tt>ArrayList</tt> instance 55 * before adding a large number of elements using the <tt>ensureCapacity</tt> 56 * operation. This may reduce the amount of incremental reallocation. 57 * 58 * <p><strong>Note that this implementation is not synchronized.</strong> 59 * If multiple threads access an <tt>ArrayList</tt> instance concurrently, 60 * and at least one of the threads modifies the list structurally, it 61 * <i>must</i> be synchronized externally. (A structural modification is 62 * any operation that adds or deletes one or more elements, or explicitly 63 * resizes the backing array; merely setting the value of an element is not 64 * a structural modification.) This is typically accomplished by 65 * synchronizing on some object that naturally encapsulates the list. 66 * 67 * If no such object exists, the list should be "wrapped" using the 68 * {@link Collections#synchronizedList Collections.synchronizedList} 69 * method. This is best done at creation time, to prevent accidental 70 * unsynchronized access to the list:<pre> 71 * List list = Collections.synchronizedList(new ArrayList(...));</pre> 72 * 73 * <p><a name="fail-fast"/> 74 * The iterators returned by this class's {@link #iterator() iterator} and 75 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>: 76 * if the list is structurally modified at any time after the iterator is 77 * created, in any way except through the iterator's own 78 * {@link ListIterator#remove() remove} or 79 * {@link ListIterator#add(Object) add} methods, the iterator will throw a 80 * {@link ConcurrentModificationException}. Thus, in the face of 81 * concurrent modification, the iterator fails quickly and cleanly, rather 82 * than risking arbitrary, non-deterministic behavior at an undetermined 83 * time in the future. 84 * 85 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed 86 * as it is, generally speaking, impossible to make any hard guarantees in the 87 * presence of unsynchronized concurrent modification. Fail-fast iterators 88 * throw {@code ConcurrentModificationException} on a best-effort basis. 89 * Therefore, it would be wrong to write a program that depended on this 90 * exception for its correctness: <i>the fail-fast behavior of iterators 91 * should be used only to detect bugs.</i> 92 * 93 * <p>This class is a member of the 94 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 95 * Java Collections Framework</a>. 96 * 97 * @author Josh Bloch 98 * @author Neal Gafter 99 * @see Collection 100 * @see List 101 * @see LinkedList 102 * @see Vector 103 * @since 1.2 104 */ 105 106 public class ArrayList<E> extends AbstractList<E> 107 implements List<E>, RandomAccess, Cloneable, java.io.Serializable 108 { 109 private static final long serialVersionUID = 8683452581122892189L; 110 111 /** 112 * The array buffer into which the elements of the ArrayList are stored. 113 * The capacity of the ArrayList is the length of this array buffer. 114 */ 115 private transient Object[] elementData; 116 117 /** 118 * The size of the ArrayList (the number of elements it contains). 119 * 120 * @serial 121 */ 122 private int size; 123 124 /** 125 * Constructs an empty list with the specified initial capacity. 126 * 127 * @param initialCapacity the initial capacity of the list 128 * @throws IllegalArgumentException if the specified initial capacity 129 * is negative 130 */ 131 public ArrayList(int initialCapacity) { 132 super(); 133 if (initialCapacity < 0) 134 throw new IllegalArgumentException("Illegal Capacity: "+ 135 initialCapacity); 136 this.elementData = new Object[initialCapacity]; 137 } 138 139 /** 140 * Constructs an empty list with an initial capacity of ten. 141 */ 142 public ArrayList() { 143 this(10); 144 } 145 146 /** 147 * Constructs a list containing the elements of the specified 148 * collection, in the order they are returned by the collection's 149 * iterator. 150 * 151 * @param c the collection whose elements are to be placed into this list 152 * @throws NullPointerException if the specified collection is null 153 */ 154 public ArrayList(Collection<? extends E> c) { 155 elementData = c.toArray(); 156 size = elementData.length; 157 // c.toArray might (incorrectly) not return Object[] (see 6260652) 158 if (elementData.getClass() != Object[].class) 159 elementData = Arrays.copyOf(elementData, size, Object[].class); 160 } 161 162 /** 163 * Trims the capacity of this <tt>ArrayList</tt> instance to be the 164 * list's current size. An application can use this operation to minimize 165 * the storage of an <tt>ArrayList</tt> instance. 166 */ 167 public void trimToSize() { 168 modCount++; 169 int oldCapacity = elementData.length; 170 if (size < oldCapacity) { 171 elementData = Arrays.copyOf(elementData, size); 172 } 173 } 174 175 /** 176 * Increases the capacity of this <tt>ArrayList</tt> instance, if 177 * necessary, to ensure that it can hold at least the number of elements 178 * specified by the minimum capacity argument. 179 * 180 * @param minCapacity the desired minimum capacity 181 */ 182 public void ensureCapacity(int minCapacity) { 183 if (minCapacity > 0) 184 ensureCapacityInternal(minCapacity); 185 } 186 187 private void ensureCapacityInternal(int minCapacity) { 188 modCount++; 189 // overflow-conscious code 190 if (minCapacity - elementData.length > 0) 191 grow(minCapacity); 192 } 193 194 /** 195 * The maximum size of array to allocate. 196 * Some VMs reserve some header words in an array. 197 * Attempts to allocate larger arrays may result in 198 * OutOfMemoryError: Requested array size exceeds VM limit 199 */ 200 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; 201 202 /** 203 * Increases the capacity to ensure that it can hold at least the 204 * number of elements specified by the minimum capacity argument. 205 * 206 * @param minCapacity the desired minimum capacity 207 */ 208 private void grow(int minCapacity) { 209 // overflow-conscious code 210 int oldCapacity = elementData.length; 211 int newCapacity = oldCapacity + (oldCapacity >> 1); 212 if (newCapacity - minCapacity < 0) 213 newCapacity = minCapacity; 214 if (newCapacity - MAX_ARRAY_SIZE > 0) 215 newCapacity = hugeCapacity(minCapacity); 216 // minCapacity is usually close to size, so this is a win: 217 elementData = Arrays.copyOf(elementData, newCapacity); 218 } 219 220 private static int hugeCapacity(int minCapacity) { 221 if (minCapacity < 0) // overflow 222 throw new OutOfMemoryError(); 223 return (minCapacity > MAX_ARRAY_SIZE) ? 224 Integer.MAX_VALUE : 225 MAX_ARRAY_SIZE; 226 } 227 228 /** 229 * Returns the number of elements in this list. 230 * 231 * @return the number of elements in this list 232 */ 233 public int size() { 234 return size; 235 } 236 237 /** 238 * Returns <tt>true</tt> if this list contains no elements. 239 * 240 * @return <tt>true</tt> if this list contains no elements 241 */ 242 public boolean isEmpty() { 243 return size == 0; 244 } 245 246 /** 247 * Returns <tt>true</tt> if this list contains the specified element. 248 * More formally, returns <tt>true</tt> if and only if this list contains 249 * at least one element <tt>e</tt> such that 250 * <tt>(o==null ? e==null : o.equals(e))</tt>. 251 * 252 * @param o element whose presence in this list is to be tested 253 * @return <tt>true</tt> if this list contains the specified element 254 */ 255 public boolean contains(Object o) { 256 return indexOf(o) >= 0; 257 } 258 259 /** 260 * Returns the index of the first occurrence of the specified element 261 * in this list, or -1 if this list does not contain the element. 262 * More formally, returns the lowest index <tt>i</tt> such that 263 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, 264 * or -1 if there is no such index. 265 */ 266 public int indexOf(Object o) { 267 if (o == null) { 268 for (int i = 0; i < size; i++) 269 if (elementData[i]==null) 270 return i; 271 } else { 272 for (int i = 0; i < size; i++) 273 if (o.equals(elementData[i])) 274 return i; 275 } 276 return -1; 277 } 278 279 /** 280 * Returns the index of the last occurrence of the specified element 281 * in this list, or -1 if this list does not contain the element. 282 * More formally, returns the highest index <tt>i</tt> such that 283 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, 284 * or -1 if there is no such index. 285 */ 286 public int lastIndexOf(Object o) { 287 if (o == null) { 288 for (int i = size-1; i >= 0; i--) 289 if (elementData[i]==null) 290 return i; 291 } else { 292 for (int i = size-1; i >= 0; i--) 293 if (o.equals(elementData[i])) 294 return i; 295 } 296 return -1; 297 } 298 299 /** 300 * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The 301 * elements themselves are not copied.) 302 * 303 * @return a clone of this <tt>ArrayList</tt> instance 304 */ 305 public Object clone() { 306 try { 307 ArrayList<?> v = (ArrayList<?>) super.clone(); 308 v.elementData = Arrays.copyOf(elementData, size); 309 v.modCount = 0; 310 return v; 311 } catch (CloneNotSupportedException e) { 312 // this shouldn't happen, since we are Cloneable 313 throw new InternalError(e); 314 } 315 } 316 317 /** 318 * Returns an array containing all of the elements in this list 319 * in proper sequence (from first to last element). 320 * 321 * <p>The returned array will be "safe" in that no references to it are 322 * maintained by this list. (In other words, this method must allocate 323 * a new array). The caller is thus free to modify the returned array. 324 * 325 * <p>This method acts as bridge between array-based and collection-based 326 * APIs. 327 * 328 * @return an array containing all of the elements in this list in 329 * proper sequence 330 */ 331 public Object[] toArray() { 332 return Arrays.copyOf(elementData, size); 333 } 334 335 /** 336 * Returns an array containing all of the elements in this list in proper 337 * sequence (from first to last element); the runtime type of the returned 338 * array is that of the specified array. If the list fits in the 339 * specified array, it is returned therein. Otherwise, a new array is 340 * allocated with the runtime type of the specified array and the size of 341 * this list. 342 * 343 * <p>If the list fits in the specified array with room to spare 344 * (i.e., the array has more elements than the list), the element in 345 * the array immediately following the end of the collection is set to 346 * <tt>null</tt>. (This is useful in determining the length of the 347 * list <i>only</i> if the caller knows that the list does not contain 348 * any null elements.) 349 * 350 * @param a the array into which the elements of the list are to 351 * be stored, if it is big enough; otherwise, a new array of the 352 * same runtime type is allocated for this purpose. 353 * @return an array containing the elements of the list 354 * @throws ArrayStoreException if the runtime type of the specified array 355 * is not a supertype of the runtime type of every element in 356 * this list 357 * @throws NullPointerException if the specified array is null 358 */ 359 @SuppressWarnings("unchecked") 360 public <T> T[] toArray(T[] a) { 361 if (a.length < size) 362 // Make a new array of a's runtime type, but my contents: 363 return (T[]) Arrays.copyOf(elementData, size, a.getClass()); 364 System.arraycopy(elementData, 0, a, 0, size); 365 if (a.length > size) 366 a[size] = null; 367 return a; 368 } 369 370 // Positional Access Operations 371 372 @SuppressWarnings("unchecked") 373 E elementData(int index) { 374 return (E) elementData[index]; 375 } 376 377 /** 378 * Returns the element at the specified position in this list. 379 * 380 * @param index index of the element to return 381 * @return the element at the specified position in this list 382 * @throws IndexOutOfBoundsException {@inheritDoc} 383 */ 384 public E get(int index) { 385 rangeCheck(index); 386 387 return elementData(index); 388 } 389 390 /** 391 * Replaces the element at the specified position in this list with 392 * the specified element. 393 * 394 * @param index index of the element to replace 395 * @param element element to be stored at the specified position 396 * @return the element previously at the specified position 397 * @throws IndexOutOfBoundsException {@inheritDoc} 398 */ 399 public E set(int index, E element) { 400 rangeCheck(index); 401 402 E oldValue = elementData(index); 403 elementData[index] = element; 404 return oldValue; 405 } 406 407 /** 408 * Appends the specified element to the end of this list. 409 * 410 * @param e element to be appended to this list 411 * @return <tt>true</tt> (as specified by {@link Collection#add}) 412 */ 413 public boolean add(E e) { 414 ensureCapacityInternal(size + 1); // Increments modCount!! 415 elementData[size++] = e; 416 return true; 417 } 418 419 /** 420 * Inserts the specified element at the specified position in this 421 * list. Shifts the element currently at that position (if any) and 422 * any subsequent elements to the right (adds one to their indices). 423 * 424 * @param index index at which the specified element is to be inserted 425 * @param element element to be inserted 426 * @throws IndexOutOfBoundsException {@inheritDoc} 427 */ 428 public void add(int index, E element) { 429 rangeCheckForAdd(index); 430 431 ensureCapacityInternal(size + 1); // Increments modCount!! 432 System.arraycopy(elementData, index, elementData, index + 1, 433 size - index); 434 elementData[index] = element; 435 size++; 436 } 437 438 /** 439 * Removes the element at the specified position in this list. 440 * Shifts any subsequent elements to the left (subtracts one from their 441 * indices). 442 * 443 * @param index the index of the element to be removed 444 * @return the element that was removed from the list 445 * @throws IndexOutOfBoundsException {@inheritDoc} 446 */ 447 public E remove(int index) { 448 rangeCheck(index); 449 450 modCount++; 451 E oldValue = elementData(index); 452 453 int numMoved = size - index - 1; 454 if (numMoved > 0) 455 System.arraycopy(elementData, index+1, elementData, index, 456 numMoved); 457 elementData[--size] = null; // Let gc do its work 458 459 return oldValue; 460 } 461 462 /** 463 * Removes the first occurrence of the specified element from this list, 464 * if it is present. If the list does not contain the element, it is 465 * unchanged. More formally, removes the element with the lowest index 466 * <tt>i</tt> such that 467 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> 468 * (if such an element exists). Returns <tt>true</tt> if this list 469 * contained the specified element (or equivalently, if this list 470 * changed as a result of the call). 471 * 472 * @param o element to be removed from this list, if present 473 * @return <tt>true</tt> if this list contained the specified element 474 */ 475 public boolean remove(Object o) { 476 if (o == null) { 477 for (int index = 0; index < size; index++) 478 if (elementData[index] == null) { 479 fastRemove(index); 480 return true; 481 } 482 } else { 483 for (int index = 0; index < size; index++) 484 if (o.equals(elementData[index])) { 485 fastRemove(index); 486 return true; 487 } 488 } 489 return false; 490 } 491 492 /* 493 * Private remove method that skips bounds checking and does not 494 * return the value removed. 495 */ 496 private void fastRemove(int index) { 497 modCount++; 498 int numMoved = size - index - 1; 499 if (numMoved > 0) 500 System.arraycopy(elementData, index+1, elementData, index, 501 numMoved); 502 elementData[--size] = null; // Let gc do its work 503 } 504 505 /** 506 * Removes all of the elements from this list. The list will 507 * be empty after this call returns. 508 */ 509 public void clear() { 510 modCount++; 511 512 // Let gc do its work 513 for (int i = 0; i < size; i++) 514 elementData[i] = null; 515 516 size = 0; 517 } 518 519 /** 520 * Appends all of the elements in the specified collection to the end of 521 * this list, in the order that they are returned by the 522 * specified collection's Iterator. The behavior of this operation is 523 * undefined if the specified collection is modified while the operation 524 * is in progress. (This implies that the behavior of this call is 525 * undefined if the specified collection is this list, and this 526 * list is nonempty.) 527 * 528 * @param c collection containing elements to be added to this list 529 * @return <tt>true</tt> if this list changed as a result of the call 530 * @throws NullPointerException if the specified collection is null 531 */ 532 public boolean addAll(Collection<? extends E> c) { 533 Object[] a = c.toArray(); 534 int numNew = a.length; 535 ensureCapacityInternal(size + numNew); // Increments modCount 536 System.arraycopy(a, 0, elementData, size, numNew); 537 size += numNew; 538 return numNew != 0; 539 } 540 541 /** 542 * Inserts all of the elements in the specified collection into this 543 * list, starting at the specified position. Shifts the element 544 * currently at that position (if any) and any subsequent elements to 545 * the right (increases their indices). The new elements will appear 546 * in the list in the order that they are returned by the 547 * specified collection's iterator. 548 * 549 * @param index index at which to insert the first element from the 550 * specified collection 551 * @param c collection containing elements to be added to this list 552 * @return <tt>true</tt> if this list changed as a result of the call 553 * @throws IndexOutOfBoundsException {@inheritDoc} 554 * @throws NullPointerException if the specified collection is null 555 */ 556 public boolean addAll(int index, Collection<? extends E> c) { 557 rangeCheckForAdd(index); 558 559 Object[] a = c.toArray(); 560 int numNew = a.length; 561 ensureCapacityInternal(size + numNew); // Increments modCount 562 563 int numMoved = size - index; 564 if (numMoved > 0) 565 System.arraycopy(elementData, index, elementData, index + numNew, 566 numMoved); 567 568 System.arraycopy(a, 0, elementData, index, numNew); 569 size += numNew; 570 return numNew != 0; 571 } 572 573 /** 574 * Removes from this list all of the elements whose index is between 575 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. 576 * Shifts any succeeding elements to the left (reduces their index). 577 * This call shortens the list by {@code (toIndex - fromIndex)} elements. 578 * (If {@code toIndex==fromIndex}, this operation has no effect.) 579 * 580 * @throws IndexOutOfBoundsException if {@code fromIndex} or 581 * {@code toIndex} is out of range 582 * ({@code fromIndex < 0 || 583 * fromIndex >= size() || 584 * toIndex > size() || 585 * toIndex < fromIndex}) 586 */ 587 protected void removeRange(int fromIndex, int toIndex) { 588 modCount++; 589 int numMoved = size - toIndex; 590 System.arraycopy(elementData, toIndex, elementData, fromIndex, 591 numMoved); 592 593 // Let gc do its work 594 int newSize = size - (toIndex-fromIndex); 595 while (size != newSize) 596 elementData[--size] = null; 597 } 598 599 /** 600 * Checks if the given index is in range. If not, throws an appropriate 601 * runtime exception. This method does *not* check if the index is 602 * negative: It is always used immediately prior to an array access, 603 * which throws an ArrayIndexOutOfBoundsException if index is negative. 604 */ 605 private void rangeCheck(int index) { 606 if (index >= size) 607 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 608 } 609 610 /** 611 * A version of rangeCheck used by add and addAll. 612 */ 613 private void rangeCheckForAdd(int index) { 614 if (index > size || index < 0) 615 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 616 } 617 618 /** 619 * Constructs an IndexOutOfBoundsException detail message. 620 * Of the many possible refactorings of the error handling code, 621 * this "outlining" performs best with both server and client VMs. 622 */ 623 private String outOfBoundsMsg(int index) { 624 return "Index: "+index+", Size: "+size; 625 } 626 627 /** 628 * Removes from this list all of its elements that are contained in the 629 * specified collection. 630 * 631 * @param c collection containing elements to be removed from this list 632 * @return {@code true} if this list changed as a result of the call 633 * @throws ClassCastException if the class of an element of this list 634 * is incompatible with the specified collection 635 * (<a href="Collection.html#optional-restrictions">optional</a>) 636 * @throws NullPointerException if this list contains a null element and the 637 * specified collection does not permit null elements 638 * (<a href="Collection.html#optional-restrictions">optional</a>), 639 * or if the specified collection is null 640 * @see Collection#contains(Object) 641 */ 642 public boolean removeAll(Collection<?> c) { 643 return batchRemove(c, false); 644 } 645 646 /** 647 * Retains only the elements in this list that are contained in the 648 * specified collection. In other words, removes from this list all 649 * of its elements that are not contained in the specified collection. 650 * 651 * @param c collection containing elements to be retained in this list 652 * @return {@code true} if this list changed as a result of the call 653 * @throws ClassCastException if the class of an element of this list 654 * is incompatible with the specified collection 655 * (<a href="Collection.html#optional-restrictions">optional</a>) 656 * @throws NullPointerException if this list contains a null element and the 657 * specified collection does not permit null elements 658 * (<a href="Collection.html#optional-restrictions">optional</a>), 659 * or if the specified collection is null 660 * @see Collection#contains(Object) 661 */ 662 public boolean retainAll(Collection<?> c) { 663 return batchRemove(c, true); 664 } 665 666 private boolean batchRemove(Collection<?> c, boolean complement) { 667 final Object[] elementData = this.elementData; 668 int r = 0, w = 0; 669 boolean modified = false; 670 try { 671 for (; r < size; r++) 672 if (c.contains(elementData[r]) == complement) 673 elementData[w++] = elementData[r]; 674 } finally { 675 // Preserve behavioral compatibility with AbstractCollection, 676 // even if c.contains() throws. 677 if (r != size) { 678 System.arraycopy(elementData, r, 679 elementData, w, 680 size - r); 681 w += size - r; 682 } 683 if (w != size) { 684 for (int i = w; i < size; i++) 685 elementData[i] = null; 686 modCount += size - w; 687 size = w; 688 modified = true; 689 } 690 } 691 return modified; 692 } 693 694 /** 695 * Save the state of the <tt>ArrayList</tt> instance to a stream (that 696 * is, serialize it). 697 * 698 * @serialData The length of the array backing the <tt>ArrayList</tt> 699 * instance is emitted (int), followed by all of its elements 700 * (each an <tt>Object</tt>) in the proper order. 701 */ 702 private void writeObject(java.io.ObjectOutputStream s) 703 throws java.io.IOException{ 704 // Write out element count, and any hidden stuff 705 int expectedModCount = modCount; 706 s.defaultWriteObject(); 707 708 // Write out array length 709 s.writeInt(elementData.length); 710 711 // Write out all elements in the proper order. 712 for (int i=0; i<size; i++) 713 s.writeObject(elementData[i]); 714 715 if (modCount != expectedModCount) { 716 throw new ConcurrentModificationException(); 717 } 718 719 } 720 721 /** 722 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, 723 * deserialize it). 724 */ 725 private void readObject(java.io.ObjectInputStream s) 726 throws java.io.IOException, ClassNotFoundException { 727 // Read in size, and any hidden stuff 728 s.defaultReadObject(); 729 730 // Read in array length and allocate array 731 int arrayLength = s.readInt(); 732 Object[] a = elementData = new Object[arrayLength]; 733 734 // Read in all elements in the proper order. 735 for (int i=0; i<size; i++) 736 a[i] = s.readObject(); 737 } 738 739 /** 740 * Returns a list iterator over the elements in this list (in proper 741 * sequence), starting at the specified position in the list. 742 * The specified index indicates the first element that would be 743 * returned by an initial call to {@link ListIterator#next next}. 744 * An initial call to {@link ListIterator#previous previous} would 745 * return the element with the specified index minus one. 746 * 747 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 748 * 749 * @throws IndexOutOfBoundsException {@inheritDoc} 750 */ 751 public ListIterator<E> listIterator(int index) { 752 if (index < 0 || index > size) 753 throw new IndexOutOfBoundsException("Index: "+index); 754 return new ListItr(index); 755 } 756 757 /** 758 * Returns a list iterator over the elements in this list (in proper 759 * sequence). 760 * 761 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 762 * 763 * @see #listIterator(int) 764 */ 765 public ListIterator<E> listIterator() { 766 return new ListItr(0); 767 } 768 769 /** 770 * Returns an iterator over the elements in this list in proper sequence. 771 * 772 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>. 773 * 774 * @return an iterator over the elements in this list in proper sequence 775 */ 776 public Iterator<E> iterator() { 777 return new Itr(); 778 } 779 780 /** 781 * An optimized version of AbstractList.Itr 782 */ 783 private class Itr implements Iterator<E> { 784 int cursor; // index of next element to return 785 int lastRet = -1; // index of last element returned; -1 if no such 786 int expectedModCount = modCount; 787 788 public boolean hasNext() { 789 return cursor != size; 790 } 791 792 @SuppressWarnings("unchecked") 793 public E next() { 794 checkForComodification(); 795 int i = cursor; 796 if (i >= size) 797 throw new NoSuchElementException(); 798 Object[] elementData = ArrayList.this.elementData; 799 if (i >= elementData.length) 800 throw new ConcurrentModificationException(); 801 cursor = i + 1; 802 return (E) elementData[lastRet = i]; 803 } 804 805 public void remove() { 806 if (lastRet < 0) 807 throw new IllegalStateException(); 808 checkForComodification(); 809 810 try { 811 ArrayList.this.remove(lastRet); 812 cursor = lastRet; 813 lastRet = -1; 814 expectedModCount = modCount; 815 } catch (IndexOutOfBoundsException ex) { 816 throw new ConcurrentModificationException(); 817 } 818 } 819 820 final void checkForComodification() { 821 if (modCount != expectedModCount) 822 throw new ConcurrentModificationException(); 823 } 824 } 825 826 /** 827 * An optimized version of AbstractList.ListItr 828 */ 829 private class ListItr extends Itr implements ListIterator<E> { 830 ListItr(int index) { 831 super(); 832 cursor = index; 833 } 834 835 public boolean hasPrevious() { 836 return cursor != 0; 837 } 838 839 public int nextIndex() { 840 return cursor; 841 } 842 843 public int previousIndex() { 844 return cursor - 1; 845 } 846 847 @SuppressWarnings("unchecked") 848 public E previous() { 849 checkForComodification(); 850 int i = cursor - 1; 851 if (i < 0) 852 throw new NoSuchElementException(); 853 Object[] elementData = ArrayList.this.elementData; 854 if (i >= elementData.length) 855 throw new ConcurrentModificationException(); 856 cursor = i; 857 return (E) elementData[lastRet = i]; 858 } 859 860 public void set(E e) { 861 if (lastRet < 0) 862 throw new IllegalStateException(); 863 checkForComodification(); 864 865 try { 866 ArrayList.this.set(lastRet, e); 867 } catch (IndexOutOfBoundsException ex) { 868 throw new ConcurrentModificationException(); 869 } 870 } 871 872 public void add(E e) { 873 checkForComodification(); 874 875 try { 876 int i = cursor; 877 ArrayList.this.add(i, e); 878 cursor = i + 1; 879 lastRet = -1; 880 expectedModCount = modCount; 881 } catch (IndexOutOfBoundsException ex) { 882 throw new ConcurrentModificationException(); 883 } 884 } 885 } 886 887 /** 888 * Returns a view of the portion of this list between the specified 889 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If 890 * {@code fromIndex} and {@code toIndex} are equal, the returned list is 891 * empty.) The returned list is backed by this list, so non-structural 892 * changes in the returned list are reflected in this list, and vice-versa. 893 * The returned list supports all of the optional list operations. 894 * 895 * <p>This method eliminates the need for explicit range operations (of 896 * the sort that commonly exist for arrays). Any operation that expects 897 * a list can be used as a range operation by passing a subList view 898 * instead of a whole list. For example, the following idiom 899 * removes a range of elements from a list: 900 * <pre> 901 * list.subList(from, to).clear(); 902 * </pre> 903 * Similar idioms may be constructed for {@link #indexOf(Object)} and 904 * {@link #lastIndexOf(Object)}, and all of the algorithms in the 905 * {@link Collections} class can be applied to a subList. 906 * 907 * <p>The semantics of the list returned by this method become undefined if 908 * the backing list (i.e., this list) is <i>structurally modified</i> in 909 * any way other than via the returned list. (Structural modifications are 910 * those that change the size of this list, or otherwise perturb it in such 911 * a fashion that iterations in progress may yield incorrect results.) 912 * 913 * @throws IndexOutOfBoundsException {@inheritDoc} 914 * @throws IllegalArgumentException {@inheritDoc} 915 */ 916 public List<E> subList(int fromIndex, int toIndex) { 917 subListRangeCheck(fromIndex, toIndex, size); 918 return new SubList(this, 0, fromIndex, toIndex); 919 } 920 921 static void subListRangeCheck(int fromIndex, int toIndex, int size) { 922 if (fromIndex < 0) 923 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); 924 if (toIndex > size) 925 throw new IndexOutOfBoundsException("toIndex = " + toIndex); 926 if (fromIndex > toIndex) 927 throw new IllegalArgumentException("fromIndex(" + fromIndex + 928 ") > toIndex(" + toIndex + ")"); 929 } 930 931 private class SubList extends AbstractList<E> implements RandomAccess { 932 private final AbstractList<E> parent; 933 private final int parentOffset; 934 private final int offset; 935 int size; 936 937 SubList(AbstractList<E> parent, 938 int offset, int fromIndex, int toIndex) { 939 this.parent = parent; 940 this.parentOffset = fromIndex; 941 this.offset = offset + fromIndex; 942 this.size = toIndex - fromIndex; 943 this.modCount = ArrayList.this.modCount; 944 } 945 946 public E set(int index, E e) { 947 rangeCheck(index); 948 checkForComodification(); 949 E oldValue = ArrayList.this.elementData(offset + index); 950 ArrayList.this.elementData[offset + index] = e; 951 return oldValue; 952 } 953 954 public E get(int index) { 955 rangeCheck(index); 956 checkForComodification(); 957 return ArrayList.this.elementData(offset + index); 958 } 959 960 public int size() { 961 checkForComodification(); 962 return this.size; 963 } 964 965 public void add(int index, E e) { 966 rangeCheckForAdd(index); 967 checkForComodification(); 968 parent.add(parentOffset + index, e); 969 this.modCount = parent.modCount; 970 this.size++; 971 } 972 973 public E remove(int index) { 974 rangeCheck(index); 975 checkForComodification(); 976 E result = parent.remove(parentOffset + index); 977 this.modCount = parent.modCount; 978 this.size--; 979 return result; 980 } 981 982 protected void removeRange(int fromIndex, int toIndex) { 983 checkForComodification(); 984 parent.removeRange(parentOffset + fromIndex, 985 parentOffset + toIndex); 986 this.modCount = parent.modCount; 987 this.size -= toIndex - fromIndex; 988 } 989 990 public boolean addAll(Collection<? extends E> c) { 991 return addAll(this.size, c); 992 } 993 994 public boolean addAll(int index, Collection<? extends E> c) { 995 rangeCheckForAdd(index); 996 int cSize = c.size(); 997 if (cSize==0) 998 return false; 999 1000 checkForComodification(); 1001 parent.addAll(parentOffset + index, c); 1002 this.modCount = parent.modCount; 1003 this.size += cSize; 1004 return true; 1005 } 1006 1007 public Iterator<E> iterator() { 1008 return listIterator(); 1009 } 1010 1011 public ListIterator<E> listIterator(final int index) { 1012 checkForComodification(); 1013 rangeCheckForAdd(index); 1014 final int offset = this.offset; 1015 1016 return new ListIterator<E>() { 1017 int cursor = index; 1018 int lastRet = -1; 1019 int expectedModCount = ArrayList.this.modCount; 1020 1021 public boolean hasNext() { 1022 return cursor != SubList.this.size; 1023 } 1024 1025 @SuppressWarnings("unchecked") 1026 public E next() { 1027 checkForComodification(); 1028 int i = cursor; 1029 if (i >= SubList.this.size) 1030 throw new NoSuchElementException(); 1031 Object[] elementData = ArrayList.this.elementData; 1032 if (offset + i >= elementData.length) 1033 throw new ConcurrentModificationException(); 1034 cursor = i + 1; 1035 return (E) elementData[offset + (lastRet = i)]; 1036 } 1037 1038 public boolean hasPrevious() { 1039 return cursor != 0; 1040 } 1041 1042 @SuppressWarnings("unchecked") 1043 public E previous() { 1044 checkForComodification(); 1045 int i = cursor - 1; 1046 if (i < 0) 1047 throw new NoSuchElementException(); 1048 Object[] elementData = ArrayList.this.elementData; 1049 if (offset + i >= elementData.length) 1050 throw new ConcurrentModificationException(); 1051 cursor = i; 1052 return (E) elementData[offset + (lastRet = i)]; 1053 } 1054 1055 public int nextIndex() { 1056 return cursor; 1057 } 1058 1059 public int previousIndex() { 1060 return cursor - 1; 1061 } 1062 1063 public void remove() { 1064 if (lastRet < 0) 1065 throw new IllegalStateException(); 1066 checkForComodification(); 1067 1068 try { 1069 SubList.this.remove(lastRet); 1070 cursor = lastRet; 1071 lastRet = -1; 1072 expectedModCount = ArrayList.this.modCount; 1073 } catch (IndexOutOfBoundsException ex) { 1074 throw new ConcurrentModificationException(); 1075 } 1076 } 1077 1078 public void set(E e) { 1079 if (lastRet < 0) 1080 throw new IllegalStateException(); 1081 checkForComodification(); 1082 1083 try { 1084 ArrayList.this.set(offset + lastRet, e); 1085 } catch (IndexOutOfBoundsException ex) { 1086 throw new ConcurrentModificationException(); 1087 } 1088 } 1089 1090 public void add(E e) { 1091 checkForComodification(); 1092 1093 try { 1094 int i = cursor; 1095 SubList.this.add(i, e); 1096 cursor = i + 1; 1097 lastRet = -1; 1098 expectedModCount = ArrayList.this.modCount; 1099 } catch (IndexOutOfBoundsException ex) { 1100 throw new ConcurrentModificationException(); 1101 } 1102 } 1103 1104 final void checkForComodification() { 1105 if (expectedModCount != ArrayList.this.modCount) 1106 throw new ConcurrentModificationException(); 1107 } 1108 }; 1109 } 1110 1111 public List<E> subList(int fromIndex, int toIndex) { 1112 subListRangeCheck(fromIndex, toIndex, size); 1113 return new SubList(this, offset, fromIndex, toIndex); 1114 } 1115 1116 private void rangeCheck(int index) { 1117 if (index < 0 || index >= this.size) 1118 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 1119 } 1120 1121 private void rangeCheckForAdd(int index) { 1122 if (index < 0 || index > this.size) 1123 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 1124 } 1125 1126 private String outOfBoundsMsg(int index) { 1127 return "Index: "+index+", Size: "+this.size; 1128 } 1129 1130 private void checkForComodification() { 1131 if (ArrayList.this.modCount != this.modCount) 1132 throw new ConcurrentModificationException(); 1133 } 1134 } 1135 1136 @Override 1137 public void forEach(Block<? super E> block) { 1138 Objects.requireNonNull(block); 1139 final int expectedModCount = modCount; 1140 final E[] elementData = (E[]) this.elementData; 1141 final int size = this.size; 1142 for (int i=0; modCount == expectedModCount && i < size; i++) { 1143 block.accept(elementData[i]); 1144 } 1145 if (modCount != expectedModCount) { 1146 throw new ConcurrentModificationException(); 1147 } 1148 } 1149 1150 @Override 1151 public boolean removeAll(Predicate<? super E> filter) { 1152 Objects.requireNonNull(filter); 1153 // figure out which elements are to be removed 1154 // any exception thrown from the filter predicate at this stage 1155 // will leave the collection unmodified 1156 int removeCount = 0; 1157 final BitSet removeSet = new BitSet(size); 1158 final int expectedModCount = modCount; 1159 final int size = this.size; 1160 for (int i=0; modCount == expectedModCount && i < size; i++) { 1161 @SuppressWarnings("unchecked") 1162 final E element = (E) elementData[i]; 1163 if (filter.test(element)) { 1164 removeSet.set(i); 1165 removeCount++; 1166 } 1167 } 1168 1169 if (modCount != expectedModCount) { 1170 throw new ConcurrentModificationException(); 1171 } 1172 1173 // shift surviving elements left over the spaces left by removed elements 1174 final boolean anyToRemove = removeCount > 0; 1175 if (anyToRemove) { 1176 final int newSize = size - removeCount; 1177 for (int i=0, j=0; modCount == expectedModCount && 1178 (i < size) && (j < newSize); i++, j++) { 1179 i = removeSet.nextClearBit(i); 1180 elementData[j] = elementData[i]; 1181 } 1182 for (int k=newSize; modCount == expectedModCount && k < size; k++) { 1183 elementData[k] = null; // Let gc do its work 1184 } 1185 this.size = newSize; 1186 if (modCount != expectedModCount) { 1187 throw new ConcurrentModificationException(); 1188 } 1189 modCount++; 1190 } 1191 1192 return anyToRemove; 1193 } 1194 1195 @Override 1196 @SuppressWarnings("unchecked") 1197 public void replaceAll(UnaryOperator<E> operator) { 1198 Objects.requireNonNull(operator); 1199 final int expectedModCount = modCount; 1200 final int size = this.size; 1201 for (int i=0; modCount == expectedModCount && i < size; i++) { 1202 elementData[i] = operator.operate((E) elementData[i]); 1203 } 1204 if (modCount != expectedModCount) { 1205 throw new ConcurrentModificationException(); 1206 } 1207 modCount++; 1208 } 1209 1210 @Override 1211 @SuppressWarnings("unchecked") 1212 public void sort(Comparator<? super E> c) { 1213 Objects.requireNonNull(c); 1214 final int expectedModCount = modCount; 1215 Arrays.sort((E[]) elementData, 0, size, c); 1216 if (modCount != expectedModCount) { 1217 throw new ConcurrentModificationException(); 1218 } 1219 modCount++; 1220 } 1221 }