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| 1 | /* | ||
| 2 | * Copyright (c) 1997, 2010, 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 | /** | ||
| 29 | * This class provides a skeletal implementation of the <tt>Collection</tt> | ||
| 30 | * interface, to minimize the effort required to implement this interface. <p> | ||
| 31 | * | ||
| 32 | * To implement an unmodifiable collection, the programmer needs only to | ||
| 33 | * extend this class and provide implementations for the <tt>iterator</tt> and | ||
| 34 | * <tt>size</tt> methods. (The iterator returned by the <tt>iterator</tt> | ||
| 35 | * method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p> | ||
| 36 | * | ||
| 37 | * To implement a modifiable collection, the programmer must additionally | ||
| 38 | * override this class's <tt>add</tt> method (which otherwise throws an | ||
| 39 | * <tt>UnsupportedOperationException</tt>), and the iterator returned by the | ||
| 40 | * <tt>iterator</tt> method must additionally implement its <tt>remove</tt> | ||
| 41 | * method.<p> | ||
| 42 | * | ||
| 43 | * The programmer should generally provide a void (no argument) and | ||
| 44 | * <tt>Collection</tt> constructor, as per the recommendation in the | ||
| 45 | * <tt>Collection</tt> interface specification.<p> | ||
| 46 | * | ||
| 47 | * The documentation for each non-abstract method in this class describes its | ||
| 48 | * implementation in detail. Each of these methods may be overridden if | ||
| 49 | * the collection being implemented admits a more efficient implementation.<p> | ||
| 50 | * | ||
| 51 | * This class is a member of the | ||
| 52 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> | ||
| 53 | * Java Collections Framework</a>. | ||
| 54 | * | ||
| 55 | * @author Josh Bloch | ||
| 56 | * @author Neal Gafter | ||
| 57 | * @see Collection | ||
| 58 | * @since 1.2 | ||
| 59 | */ | ||
| 60 | |||
| 61 | public abstract class AbstractCollection<E> implements Collection<E> { | ||
| 62 | /** | ||
| 63 | * Sole constructor. (For invocation by subclass constructors, typically | ||
| 64 | * implicit.) | ||
| 65 | */ | ||
| 66 | protected AbstractCollection() { | ||
| 67 | } | ||
| 68 | |||
| 69 | // Query Operations | ||
| 70 | |||
| 71 | /** | ||
| 72 | * Returns an iterator over the elements contained in this collection. | ||
| 73 | * | ||
| 74 | * @return an iterator over the elements contained in this collection | ||
| 75 | */ | ||
| 76 | public abstract Iterator<E> iterator(); | ||
| 77 | |||
| 78 | public abstract int size(); | ||
| 79 | |||
| 80 | /** | ||
| 81 | * {@inheritDoc} | ||
| 82 | * | ||
| 83 | * <p>This implementation returns <tt>size() == 0</tt>. | ||
| 84 | */ | ||
| 85 | public boolean isEmpty() { | ||
| 86 | return size() == 0; | ||
| 87 | } | ||
| 88 | |||
| 89 | /** | ||
| 90 | * {@inheritDoc} | ||
| 91 | * | ||
| 92 | * <p>This implementation iterates over the elements in the collection, | ||
| 93 | * checking each element in turn for equality with the specified element. | ||
| 94 | * | ||
| 95 | * @throws ClassCastException {@inheritDoc} | ||
| 96 | * @throws NullPointerException {@inheritDoc} | ||
| 97 | */ | ||
| 98 | public boolean contains(Object o) { | ||
| 99 | Iterator<E> it = iterator(); | ||
| 100 | if (o==null) { | ||
| 101 | while (it.hasNext()) | ||
| 102 | if (it.next()==null) | ||
| 103 | return true; | ||
| 104 | } else { | ||
| 105 | while (it.hasNext()) | ||
| 106 | if (o.equals(it.next())) | ||
| 107 | return true; | ||
| 108 | } | ||
| 109 | return false; | ||
| 110 | } | ||
| 111 | |||
| 112 | /** | ||
| 113 | * {@inheritDoc} | ||
| 114 | * | ||
| 115 | * <p>This implementation returns an array containing all the elements | ||
| 116 | * returned by this collection's iterator, in the same order, stored in | ||
| 117 | * consecutive elements of the array, starting with index {@code 0}. | ||
| 118 | * The length of the returned array is equal to the number of elements | ||
| 119 | * returned by the iterator, even if the size of this collection changes | ||
| 120 | * during iteration, as might happen if the collection permits | ||
| 121 | * concurrent modification during iteration. The {@code size} method is | ||
| 122 | * called only as an optimization hint; the correct result is returned | ||
| 123 | * even if the iterator returns a different number of elements. | ||
| 124 | * | ||
| 125 | * <p>This method is equivalent to: | ||
| 126 | * | ||
| 127 | * <pre> {@code | ||
| 128 | * List<E> list = new ArrayList<E>(size()); | ||
| 129 | * for (E e : this) | ||
| 130 | * list.add(e); | ||
| 131 | * return list.toArray(); | ||
| 132 | * }</pre> | ||
| 133 | */ | ||
| 134 | public Object[] toArray() { | ||
| 135 | // Estimate size of array; be prepared to see more or fewer elements | ||
| 136 | Object[] r = new Object[size()]; | ||
| 137 | Iterator<E> it = iterator(); | ||
| 138 | for (int i = 0; i < r.length; i++) { | ||
| 139 | if (! it.hasNext()) // fewer elements than expected | ||
| 140 | return Arrays.copyOf(r, i); | ||
| 141 | r[i] = it.next(); | ||
| 142 | } | ||
| 143 | return it.hasNext() ? finishToArray(r, it) : r; | ||
| 144 | } | ||
| 145 | |||
| 146 | /** | ||
| 147 | * {@inheritDoc} | ||
| 148 | * | ||
| 149 | * <p>This implementation returns an array containing all the elements | ||
| 150 | * returned by this collection's iterator in the same order, stored in | ||
| 151 | * consecutive elements of the array, starting with index {@code 0}. | ||
| 152 | * If the number of elements returned by the iterator is too large to | ||
| 153 | * fit into the specified array, then the elements are returned in a | ||
| 154 | * newly allocated array with length equal to the number of elements | ||
| 155 | * returned by the iterator, even if the size of this collection | ||
| 156 | * changes during iteration, as might happen if the collection permits | ||
| 157 | * concurrent modification during iteration. The {@code size} method is | ||
| 158 | * called only as an optimization hint; the correct result is returned | ||
| 159 | * even if the iterator returns a different number of elements. | ||
| 160 | * | ||
| 161 | * <p>This method is equivalent to: | ||
| 162 | * | ||
| 163 | * <pre> {@code | ||
| 164 | * List<E> list = new ArrayList<E>(size()); | ||
| 165 | * for (E e : this) | ||
| 166 | * list.add(e); | ||
| 167 | * return list.toArray(a); | ||
| 168 | * }</pre> | ||
| 169 | * | ||
| 170 | * @throws ArrayStoreException {@inheritDoc} | ||
| 171 | * @throws NullPointerException {@inheritDoc} | ||
| 172 | */ | ||
| 173 | public <T> T[] toArray(T[] a) { | ||
| 174 | // Estimate size of array; be prepared to see more or fewer elements | ||
| 175 | int size = size(); | ||
| 176 | T[] r = a.length >= size ? a : | ||
| 177 | (T[])java.lang.reflect.Array | ||
| 178 | .newInstance(a.getClass().getComponentType(), size); | ||
| 179 | Iterator<E> it = iterator(); | ||
| 180 | |||
| 181 | for (int i = 0; i < r.length; i++) { | ||
| 182 | if (! it.hasNext()) { // fewer elements than expected | ||
| 183 | if (a != r) | ||
| 184 | return Arrays.copyOf(r, i); | ||
| 185 | r[i] = null; // null-terminate | ||
| 186 | return r; | ||
| 187 | } | ||
| 188 | r[i] = (T)it.next(); | ||
| 189 | } | ||
| 190 | return it.hasNext() ? finishToArray(r, it) : r; | ||
| 191 | } | ||
| 192 | |||
| 193 | /** | ||
| 194 | * The maximum size of array to allocate. | ||
| 195 | * Some VMs reserve some header words in an array. | ||
| 196 | * Attempts to allocate larger arrays may result in | ||
| 197 | * OutOfMemoryError: Requested array size exceeds VM limit | ||
| 198 | */ | ||
| 199 | private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; | ||
| 200 | |||
| 201 | /** | ||
| 202 | * Reallocates the array being used within toArray when the iterator | ||
| 203 | * returned more elements than expected, and finishes filling it from | ||
| 204 | * the iterator. | ||
| 205 | * | ||
| 206 | * @param r the array, replete with previously stored elements | ||
| 207 | * @param it the in-progress iterator over this collection | ||
| 208 | * @return array containing the elements in the given array, plus any | ||
| 209 | * further elements returned by the iterator, trimmed to size | ||
| 210 | */ | ||
| 211 | private static <T> T[] finishToArray(T[] r, Iterator<?> it) { | ||
| 212 | int i = r.length; | ||
| 213 | while (it.hasNext()) { | ||
| 214 | int cap = r.length; | ||
| 215 | if (i == cap) { | ||
| 216 | int newCap = cap + (cap >> 1) + 1; | ||
| 217 | // overflow-conscious code | ||
| 218 | if (newCap - MAX_ARRAY_SIZE > 0) | ||
| 219 | newCap = hugeCapacity(cap + 1); | ||
| 220 | r = Arrays.copyOf(r, newCap); | ||
| 221 | } | ||
| 222 | r[i++] = (T)it.next(); | ||
| 223 | } | ||
| 224 | // trim if overallocated | ||
| 225 | return (i == r.length) ? r : Arrays.copyOf(r, i); | ||
| 226 | } | ||
| 227 | |||
| 228 | private static int hugeCapacity(int minCapacity) { | ||
| 229 | if (minCapacity < 0) // overflow | ||
| 230 | throw new OutOfMemoryError | ||
| 231 | ("Required array size too large"); | ||
| 232 | return (minCapacity > MAX_ARRAY_SIZE) ? | ||
| 233 | Integer.MAX_VALUE : | ||
| 234 | MAX_ARRAY_SIZE; | ||
| 235 | } | ||
| 236 | |||
| 237 | // Modification Operations | ||
| 238 | |||
| 239 | /** | ||
| 240 | * {@inheritDoc} | ||
| 241 | * | ||
| 242 | * <p>This implementation always throws an | ||
| 243 | * <tt>UnsupportedOperationException</tt>. | ||
| 244 | * | ||
| 245 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 246 | * @throws ClassCastException {@inheritDoc} | ||
| 247 | * @throws NullPointerException {@inheritDoc} | ||
| 248 | * @throws IllegalArgumentException {@inheritDoc} | ||
| 249 | * @throws IllegalStateException {@inheritDoc} | ||
| 250 | */ | ||
| 251 | public boolean add(E e) { | ||
| 252 | throw new UnsupportedOperationException(); | ||
| 253 | } | ||
| 254 | |||
| 255 | /** | ||
| 256 | * {@inheritDoc} | ||
| 257 | * | ||
| 258 | * <p>This implementation iterates over the collection looking for the | ||
| 259 | * specified element. If it finds the element, it removes the element | ||
| 260 | * from the collection using the iterator's remove method. | ||
| 261 | * | ||
| 262 | * <p>Note that this implementation throws an | ||
| 263 | * <tt>UnsupportedOperationException</tt> if the iterator returned by this | ||
| 264 | * collection's iterator method does not implement the <tt>remove</tt> | ||
| 265 | * method and this collection contains the specified object. | ||
| 266 | * | ||
| 267 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 268 | * @throws ClassCastException {@inheritDoc} | ||
| 269 | * @throws NullPointerException {@inheritDoc} | ||
| 270 | */ | ||
| 271 | public boolean remove(Object o) { | ||
| 272 | Iterator<E> it = iterator(); | ||
| 273 | if (o==null) { | ||
| 274 | while (it.hasNext()) { | ||
| 275 | if (it.next()==null) { | ||
| 276 | it.remove(); | ||
| 277 | return true; | ||
| 278 | } | ||
| 279 | } | ||
| 280 | } else { | ||
| 281 | while (it.hasNext()) { | ||
| 282 | if (o.equals(it.next())) { | ||
| 283 | it.remove(); | ||
| 284 | return true; | ||
| 285 | } | ||
| 286 | } | ||
| 287 | } | ||
| 288 | return false; | ||
| 289 | } | ||
| 290 | |||
| 291 | |||
| 292 | // Bulk Operations | ||
| 293 | |||
| 294 | /** | ||
| 295 | * {@inheritDoc} | ||
| 296 | * | ||
| 297 | * <p>This implementation iterates over the specified collection, | ||
| 298 | * checking each element returned by the iterator in turn to see | ||
| 299 | * if it's contained in this collection. If all elements are so | ||
| 300 | * contained <tt>true</tt> is returned, otherwise <tt>false</tt>. | ||
| 301 | * | ||
| 302 | * @throws ClassCastException {@inheritDoc} | ||
| 303 | * @throws NullPointerException {@inheritDoc} | ||
| 304 | * @see #contains(Object) | ||
| 305 | */ | ||
| 306 | public boolean containsAll(Collection<?> c) { | ||
| 307 | for (Object e : c) | ||
| 308 | if (!contains(e)) | ||
| 309 | return false; | ||
| 310 | return true; | ||
| 311 | } | ||
| 312 | |||
| 313 | /** | ||
| 314 | * {@inheritDoc} | ||
| 315 | * | ||
| 316 | * <p>This implementation iterates over the specified collection, and adds | ||
| 317 | * each object returned by the iterator to this collection, in turn. | ||
| 318 | * | ||
| 319 | * <p>Note that this implementation will throw an | ||
| 320 | * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is | ||
| 321 | * overridden (assuming the specified collection is non-empty). | ||
| 322 | * | ||
| 323 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 324 | * @throws ClassCastException {@inheritDoc} | ||
| 325 | * @throws NullPointerException {@inheritDoc} | ||
| 326 | * @throws IllegalArgumentException {@inheritDoc} | ||
| 327 | * @throws IllegalStateException {@inheritDoc} | ||
| 328 | * | ||
| 329 | * @see #add(Object) | ||
| 330 | */ | ||
| 331 | public boolean addAll(Collection<? extends E> c) { | ||
| 332 | boolean modified = false; | ||
| 333 | for (E e : c) | ||
| 334 | if (add(e)) | ||
| 335 | modified = true; | ||
| 336 | return modified; | ||
| 337 | } | ||
| 338 | |||
| 339 | /** | ||
| 340 | * {@inheritDoc} | ||
| 341 | * | ||
| 342 | * <p>This implementation iterates over this collection, checking each | ||
| 343 | * element returned by the iterator in turn to see if it's contained | ||
| 344 | * in the specified collection. If it's so contained, it's removed from | ||
| 345 | * this collection with the iterator's <tt>remove</tt> method. | ||
| 346 | * | ||
| 347 | * <p>Note that this implementation will throw an | ||
| 348 | * <tt>UnsupportedOperationException</tt> if the iterator returned by the | ||
| 349 | * <tt>iterator</tt> method does not implement the <tt>remove</tt> method | ||
| 350 | * and this collection contains one or more elements in common with the | ||
| 351 | * specified collection. | ||
| 352 | * | ||
| 353 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 354 | * @throws ClassCastException {@inheritDoc} | ||
| 355 | * @throws NullPointerException {@inheritDoc} | ||
| 356 | * | ||
| 357 | * @see #remove(Object) | ||
| 358 | * @see #contains(Object) | ||
| 359 | */ | ||
| 360 | public boolean removeAll(Collection<?> c) { | ||
| 361 | boolean modified = false; | ||
| 362 | Iterator<?> it = iterator(); | ||
| 363 | while (it.hasNext()) { | ||
| 364 | if (c.contains(it.next())) { | ||
| 365 | it.remove(); | ||
| 366 | modified = true; | ||
| 367 | } | ||
| 368 | } | ||
| 369 | return modified; | ||
| 370 | } | ||
| 371 | |||
| 372 | /** | ||
| 373 | * {@inheritDoc} | ||
| 374 | * | ||
| 375 | * <p>This implementation iterates over this collection, checking each | ||
| 376 | * element returned by the iterator in turn to see if it's contained | ||
| 377 | * in the specified collection. If it's not so contained, it's removed | ||
| 378 | * from this collection with the iterator's <tt>remove</tt> method. | ||
| 379 | * | ||
| 380 | * <p>Note that this implementation will throw an | ||
| 381 | * <tt>UnsupportedOperationException</tt> if the iterator returned by the | ||
| 382 | * <tt>iterator</tt> method does not implement the <tt>remove</tt> method | ||
| 383 | * and this collection contains one or more elements not present in the | ||
| 384 | * specified collection. | ||
| 385 | * | ||
| 386 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 387 | * @throws ClassCastException {@inheritDoc} | ||
| 388 | * @throws NullPointerException {@inheritDoc} | ||
| 389 | * | ||
| 390 | * @see #remove(Object) | ||
| 391 | * @see #contains(Object) | ||
| 392 | */ | ||
| 393 | public boolean retainAll(Collection<?> c) { | ||
| 394 | boolean modified = false; | ||
| 395 | Iterator<E> it = iterator(); | ||
| 396 | while (it.hasNext()) { | ||
| 397 | if (!c.contains(it.next())) { | ||
| 398 | it.remove(); | ||
| 399 | modified = true; | ||
| 400 | } | ||
| 401 | } | ||
| 402 | return modified; | ||
| 403 | } | ||
| 404 | |||
| 405 | /** | ||
| 406 | * {@inheritDoc} | ||
| 407 | * | ||
| 408 | * <p>This implementation iterates over this collection, removing each | ||
| 409 | * element using the <tt>Iterator.remove</tt> operation. Most | ||
| 410 | * implementations will probably choose to override this method for | ||
| 411 | * efficiency. | ||
| 412 | * | ||
| 413 | * <p>Note that this implementation will throw an | ||
| 414 | * <tt>UnsupportedOperationException</tt> if the iterator returned by this | ||
| 415 | * collection's <tt>iterator</tt> method does not implement the | ||
| 416 | * <tt>remove</tt> method and this collection is non-empty. | ||
| 417 | * | ||
| 418 | * @throws UnsupportedOperationException {@inheritDoc} | ||
| 419 | */ | ||
| 420 | public void clear() { | ||
| 421 | Iterator<E> it = iterator(); | ||
| 422 | while (it.hasNext()) { | ||
| 423 | it.next(); | ||
| 424 | it.remove(); | ||
| 425 | } | ||
| 426 | } | ||
| 427 | |||
| 428 | |||
| 429 | // String conversion | ||
| 430 | |||
| 431 | /** | ||
| 432 | * Returns a string representation of this collection. The string | ||
| 433 | * representation consists of a list of the collection's elements in the | ||
| 434 | * order they are returned by its iterator, enclosed in square brackets | ||
| 435 | * (<tt>"[]"</tt>). Adjacent elements are separated by the characters | ||
| 436 | * <tt>", "</tt> (comma and space). Elements are converted to strings as | ||
| 437 | * by {@link String#valueOf(Object)}. | ||
| 438 | * | ||
| 439 | * @return a string representation of this collection | ||
| 440 | */ | ||
| 441 | public String toString() { | ||
| 442 | Iterator<E> it = iterator(); | ||
| 443 | if (! it.hasNext()) | ||
| 444 | return "[]"; | ||
| 445 | |||
| 446 | StringBuilder sb = new StringBuilder(); | ||
| 447 | sb.append('['); | ||
| 448 | for (;;) { | ||
| 449 | E e = it.next(); | ||
| 450 | sb.append(e == this ? "(this Collection)" : e); | ||
| 451 | if (! it.hasNext()) | ||
| 452 | return sb.append(']').toString(); | ||
| 453 | sb.append(',').append(' '); | ||
| 454 | } | ||
| 455 | } | ||
| 456 | |||
| 457 | } | ||