1 /* 2 * Copyright (c) 2007, 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 sun.awt.util; 27 28 import java.util.AbstractList; 29 import java.util.Arrays; 30 import java.util.Collection; 31 import java.util.ConcurrentModificationException; 32 import java.util.List; 33 import java.util.RandomAccess; 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.)<p> 42 * 43 * 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.<p> 49 * 50 * Each {@code IdentityArrayList} 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 IdentityArrayList, 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.<p> 56 * 57 * An application can increase the capacity of an {@code IdentityArrayList} 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 IdentityArrayList} 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 java.util.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 IdentityArrayList(...));</pre> 75 * 76 * <p>The iterators returned by this class's {@code iterator} and 77 * {@code listIterator} methods are <i>fail-fast</i>: if the list is 78 * structurally modified at any time after the iterator is created, in any way 79 * except through the iterator's own {@code remove} or {@code add} methods, 80 * the iterator will throw a {@link ConcurrentModificationException}. Thus, in 81 * the face of concurrent modification, the iterator fails quickly and cleanly, 82 * rather than risking arbitrary, non-deterministic behavior at an undetermined 83 * time in the future.<p> 84 * 85 * 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><p> 92 * 93 */ 94 95 public class IdentityArrayList<E> extends AbstractList<E> 96 implements List<E>, RandomAccess 97 { 98 99 /** 100 * The array buffer into which the elements of the IdentityArrayList are stored. 101 * The capacity of the IdentityArrayList is the length of this array buffer. 102 */ 103 private transient Object[] elementData; 104 105 /** 106 * The size of the IdentityArrayList (the number of elements it contains). 107 * 108 * @serial 109 */ 110 private int size; 111 112 /** 113 * Constructs an empty list with the specified initial capacity. 114 * 115 * @param initialCapacity the initial capacity of the list 116 * @exception IllegalArgumentException if the specified initial capacity 117 * is negative 118 */ 119 public IdentityArrayList(int initialCapacity) { 120 super(); 121 if (initialCapacity < 0) 122 throw new IllegalArgumentException("Illegal Capacity: "+ 123 initialCapacity); 124 this.elementData = new Object[initialCapacity]; 125 } 126 127 /** 128 * Constructs an empty list with an initial capacity of ten. 129 */ 130 public IdentityArrayList() { 131 this(10); 132 } 133 134 /** 135 * Constructs a list containing the elements of the specified 136 * collection, in the order they are returned by the collection's 137 * iterator. 138 * 139 * @param c the collection whose elements are to be placed into this list 140 * @throws NullPointerException if the specified collection is null 141 */ 142 public IdentityArrayList(Collection<? extends E> c) { 143 elementData = c.toArray(); 144 size = elementData.length; 145 // defend against c.toArray (incorrectly) not returning Object[] 146 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) 147 if (elementData.getClass() != Object[].class) 148 elementData = Arrays.copyOf(elementData, size, Object[].class); 149 } 150 151 /** 152 * Trims the capacity of this {@code IdentityArrayList} instance to be the 153 * list's current size. An application can use this operation to minimize 154 * the storage of an {@code IdentityArrayList} instance. 155 */ 156 public void trimToSize() { 157 modCount++; 158 int oldCapacity = elementData.length; 159 if (size < oldCapacity) { 160 elementData = Arrays.copyOf(elementData, size); 161 } 162 } 163 164 /** 165 * Increases the capacity of this {@code IdentityArrayList} instance, if 166 * necessary, to ensure that it can hold at least the number of elements 167 * specified by the minimum capacity argument. 168 * 169 * @param minCapacity the desired minimum capacity 170 */ 171 public void ensureCapacity(int minCapacity) { 172 modCount++; 173 int oldCapacity = elementData.length; 174 if (minCapacity > oldCapacity) { 175 Object oldData[] = elementData; 176 int newCapacity = (oldCapacity * 3)/2 + 1; 177 if (newCapacity < minCapacity) 178 newCapacity = minCapacity; 179 // minCapacity is usually close to size, so this is a win: 180 elementData = Arrays.copyOf(elementData, newCapacity); 181 } 182 } 183 184 /** 185 * Returns the number of elements in this list. 186 * 187 * @return the number of elements in this list 188 */ 189 public int size() { 190 return size; 191 } 192 193 /** 194 * Returns {@code true} if this list contains no elements. 195 * 196 * @return {@code true} if this list contains no elements 197 */ 198 public boolean isEmpty() { 199 return size == 0; 200 } 201 202 /** 203 * Returns {@code true} if this list contains the specified element. 204 * More formally, returns {@code true} if and only if this list contains 205 * at least one element {@code e} such that 206 * {@code Objects.equals(o, e)}. 207 * 208 * @param o element whose presence in this list is to be tested 209 * @return {@code true} if this list contains the specified element 210 */ 211 public boolean contains(Object o) { 212 return indexOf(o) >= 0; 213 } 214 215 /** 216 * Returns the index of the first occurrence of the specified element 217 * in this list, or -1 if this list does not contain the element. 218 * More formally, returns the lowest index {@code i} such that 219 * {@code Objects.equals(o, get(i))}, 220 * or -1 if there is no such index. 221 */ 222 public int indexOf(Object o) { 223 for (int i = 0; i < size; i++) { 224 if (o == elementData[i]) { 225 return i; 226 } 227 } 228 return -1; 229 } 230 231 /** 232 * Returns the index of the last occurrence of the specified element 233 * in this list, or -1 if this list does not contain the element. 234 * More formally, returns the highest index {@code i} such that 235 * {@code Objects.equals(o, get(i))}, 236 * or -1 if there is no such index. 237 */ 238 public int lastIndexOf(Object o) { 239 for (int i = size-1; i >= 0; i--) { 240 if (o == elementData[i]) { 241 return i; 242 } 243 } 244 return -1; 245 } 246 247 /** 248 * Returns an array containing all of the elements in this list 249 * in proper sequence (from first to last element). 250 * 251 * <p>The returned array will be "safe" in that no references to it are 252 * maintained by this list. (In other words, this method must allocate 253 * a new array). The caller is thus free to modify the returned array. 254 * 255 * <p>This method acts as bridge between array-based and collection-based 256 * APIs. 257 * 258 * @return an array containing all of the elements in this list in 259 * proper sequence 260 */ 261 public Object[] toArray() { 262 return Arrays.copyOf(elementData, size); 263 } 264 265 /** 266 * Returns an array containing all of the elements in this list in proper 267 * sequence (from first to last element); the runtime type of the returned 268 * array is that of the specified array. If the list fits in the 269 * specified array, it is returned therein. Otherwise, a new array is 270 * allocated with the runtime type of the specified array and the size of 271 * this list. 272 * 273 * <p>If the list fits in the specified array with room to spare 274 * (i.e., the array has more elements than the list), the element in 275 * the array immediately following the end of the collection is set to 276 * {@code null}. (This is useful in determining the length of the 277 * list <i>only</i> if the caller knows that the list does not contain 278 * any null elements.) 279 * 280 * @param a the array into which the elements of the list are to 281 * be stored, if it is big enough; otherwise, a new array of the 282 * same runtime type is allocated for this purpose. 283 * @return an array containing the elements of the list 284 * @throws ArrayStoreException if the runtime type of the specified array 285 * is not a supertype of the runtime type of every element in 286 * this list 287 * @throws NullPointerException if the specified array is null 288 */ 289 @SuppressWarnings("unchecked") 290 public <T> T[] toArray(T[] a) { 291 if (a.length < size) 292 // Make a new array of a's runtime type, but my contents: 293 return (T[]) Arrays.copyOf(elementData, size, a.getClass()); 294 System.arraycopy(elementData, 0, a, 0, size); 295 if (a.length > size) 296 a[size] = null; 297 return a; 298 } 299 300 // Positional Access Operations 301 302 /** 303 * Returns the element at the specified position in this list. 304 * 305 * @param index index of the element to return 306 * @return the element at the specified position in this list 307 * @throws IndexOutOfBoundsException {@inheritDoc} 308 */ 309 public E get(int index) { 310 rangeCheck(index); 311 312 @SuppressWarnings("unchecked") 313 E rv = (E) elementData[index]; 314 return rv; 315 } 316 317 /** 318 * Replaces the element at the specified position in this list with 319 * the specified element. 320 * 321 * @param index index of the element to replace 322 * @param element element to be stored at the specified position 323 * @return the element previously at the specified position 324 * @throws IndexOutOfBoundsException {@inheritDoc} 325 */ 326 public E set(int index, E element) { 327 rangeCheck(index); 328 329 @SuppressWarnings("unchecked") 330 E oldValue = (E) elementData[index]; 331 elementData[index] = element; 332 return oldValue; 333 } 334 335 /** 336 * Appends the specified element to the end of this list. 337 * 338 * @param e element to be appended to this list 339 * @return {@code true} (as specified by {@link Collection#add}) 340 */ 341 public boolean add(E e) { 342 ensureCapacity(size + 1); // Increments modCount!! 343 elementData[size++] = e; 344 return true; 345 } 346 347 /** 348 * Inserts the specified element at the specified position in this 349 * list. Shifts the element currently at that position (if any) and 350 * any subsequent elements to the right (adds one to their indices). 351 * 352 * @param index index at which the specified element is to be inserted 353 * @param element element to be inserted 354 * @throws IndexOutOfBoundsException {@inheritDoc} 355 */ 356 public void add(int index, E element) { 357 rangeCheckForAdd(index); 358 359 ensureCapacity(size+1); // Increments modCount!! 360 System.arraycopy(elementData, index, elementData, index + 1, 361 size - index); 362 elementData[index] = element; 363 size++; 364 } 365 366 /** 367 * Removes the element at the specified position in this list. 368 * Shifts any subsequent elements to the left (subtracts one from their 369 * indices). 370 * 371 * @param index the index of the element to be removed 372 * @return the element that was removed from the list 373 * @throws IndexOutOfBoundsException {@inheritDoc} 374 */ 375 public E remove(int index) { 376 rangeCheck(index); 377 378 modCount++; 379 @SuppressWarnings("unchecked") 380 E oldValue = (E) elementData[index]; 381 382 int numMoved = size - index - 1; 383 if (numMoved > 0) 384 System.arraycopy(elementData, index+1, elementData, index, 385 numMoved); 386 elementData[--size] = null; // Let gc do its work 387 388 return oldValue; 389 } 390 391 /** 392 * Removes the first occurrence of the specified element from this list, 393 * if it is present. If the list does not contain the element, it is 394 * unchanged. More formally, removes the element with the lowest index 395 * {@code i} such that {@code Objects.equals(o, get(i))} 396 * (if such an element exists). Returns {@code true} if this list 397 * contained the specified element (or equivalently, if this list 398 * changed as a result of the call). 399 * 400 * @param o element to be removed from this list, if present 401 * @return {@code true} if this list contained the specified element 402 */ 403 public boolean remove(Object o) { 404 for (int index = 0; index < size; index++) { 405 if (o == elementData[index]) { 406 fastRemove(index); 407 return true; 408 } 409 } 410 return false; 411 } 412 413 /* 414 * Private remove method that skips bounds checking and does not 415 * return the value removed. 416 */ 417 private void fastRemove(int index) { 418 modCount++; 419 int numMoved = size - index - 1; 420 if (numMoved > 0) 421 System.arraycopy(elementData, index+1, elementData, index, 422 numMoved); 423 elementData[--size] = null; // Let gc do its work 424 } 425 426 /** 427 * Removes all of the elements from this list. The list will 428 * be empty after this call returns. 429 */ 430 public void clear() { 431 modCount++; 432 433 // Let gc do its work 434 for (int i = 0; i < size; i++) 435 elementData[i] = null; 436 437 size = 0; 438 } 439 440 /** 441 * Appends all of the elements in the specified collection to the end of 442 * this list, in the order that they are returned by the 443 * specified collection's Iterator. The behavior of this operation is 444 * undefined if the specified collection is modified while the operation 445 * is in progress. (This implies that the behavior of this call is 446 * undefined if the specified collection is this list, and this 447 * list is nonempty.) 448 * 449 * @param c collection containing elements to be added to this list 450 * @return {@code true} if this list changed as a result of the call 451 * @throws NullPointerException if the specified collection is null 452 */ 453 public boolean addAll(Collection<? extends E> c) { 454 Object[] a = c.toArray(); 455 int numNew = a.length; 456 ensureCapacity(size + numNew); // Increments modCount 457 System.arraycopy(a, 0, elementData, size, numNew); 458 size += numNew; 459 return numNew != 0; 460 } 461 462 /** 463 * Inserts all of the elements in the specified collection into this 464 * list, starting at the specified position. Shifts the element 465 * currently at that position (if any) and any subsequent elements to 466 * the right (increases their indices). The new elements will appear 467 * in the list in the order that they are returned by the 468 * specified collection's iterator. 469 * 470 * @param index index at which to insert the first element from the 471 * specified collection 472 * @param c collection containing elements to be added to this list 473 * @return {@code true} if this list changed as a result of the call 474 * @throws IndexOutOfBoundsException {@inheritDoc} 475 * @throws NullPointerException if the specified collection is null 476 */ 477 public boolean addAll(int index, Collection<? extends E> c) { 478 rangeCheckForAdd(index); 479 480 Object[] a = c.toArray(); 481 int numNew = a.length; 482 ensureCapacity(size + numNew); // Increments modCount 483 484 int numMoved = size - index; 485 if (numMoved > 0) { 486 System.arraycopy(elementData, index, elementData, index + numNew, numMoved); 487 } 488 489 System.arraycopy(a, 0, elementData, index, numNew); 490 size += numNew; 491 return numNew != 0; 492 } 493 494 /** 495 * Removes from this list all of the elements whose index is between 496 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. 497 * Shifts any succeeding elements to the left (reduces their index). 498 * This call shortens the list by {@code (toIndex - fromIndex)} elements. 499 * (If {@code toIndex==fromIndex}, this operation has no effect.) 500 * 501 * @param fromIndex index of first element to be removed 502 * @param toIndex index after last element to be removed 503 * @throws IndexOutOfBoundsException if fromIndex or toIndex out of 504 * range (fromIndex < 0 || fromIndex >= size() || toIndex 505 * > size() || toIndex < fromIndex) 506 */ 507 protected void removeRange(int fromIndex, int toIndex) { 508 modCount++; 509 int numMoved = size - toIndex; 510 System.arraycopy(elementData, toIndex, elementData, fromIndex, 511 numMoved); 512 513 // Let gc do its work 514 int newSize = size - (toIndex-fromIndex); 515 while (size != newSize) 516 elementData[--size] = null; 517 } 518 519 /** 520 * Checks if the given index is in range. If not, throws an appropriate 521 * runtime exception. This method does *not* check if the index is 522 * negative: It is always used immediately prior to an array access, 523 * which throws an ArrayIndexOutOfBoundsException if index is negative. 524 */ 525 private void rangeCheck(int index) { 526 if (index >= size) 527 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 528 } 529 530 /** 531 * A version of rangeCheck used by add and addAll. 532 */ 533 private void rangeCheckForAdd(int index) { 534 if (index > size || index < 0) 535 throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); 536 } 537 538 /** 539 * Constructs an IndexOutOfBoundsException detail message. 540 * Of the many possible refactorings of the error handling code, 541 * this "outlining" performs best with both server and client VMs. 542 */ 543 private String outOfBoundsMsg(int index) { 544 return "Index: "+index+", Size: "+size; 545 } 546 }