J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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> e = iterator(); |
| 100 | if (o==null) { |
| 101 | while (e.hasNext()) |
| 102 | if (e.next()==null) |
| 103 | return true; |
| 104 | } else { |
| 105 | while (e.hasNext()) |
| 106 | if (o.equals(e.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 | * Reallocates the array being used within toArray when the iterator |
| 195 | * returned more elements than expected, and finishes filling it from |
| 196 | * the iterator. |
| 197 | * |
| 198 | * @param r the array, replete with previously stored elements |
| 199 | * @param it the in-progress iterator over this collection |
| 200 | * @return array containing the elements in the given array, plus any |
| 201 | * further elements returned by the iterator, trimmed to size |
| 202 | */ |
| 203 | private static <T> T[] finishToArray(T[] r, Iterator<?> it) { |
| 204 | int i = r.length; |
| 205 | while (it.hasNext()) { |
| 206 | int cap = r.length; |
| 207 | if (i == cap) { |
| 208 | int newCap = ((cap / 2) + 1) * 3; |
| 209 | if (newCap <= cap) { // integer overflow |
| 210 | if (cap == Integer.MAX_VALUE) |
| 211 | throw new OutOfMemoryError |
| 212 | ("Required array size too large"); |
| 213 | newCap = Integer.MAX_VALUE; |
| 214 | } |
| 215 | r = Arrays.copyOf(r, newCap); |
| 216 | } |
| 217 | r[i++] = (T)it.next(); |
| 218 | } |
| 219 | // trim if overallocated |
| 220 | return (i == r.length) ? r : Arrays.copyOf(r, i); |
| 221 | } |
| 222 | |
| 223 | // Modification Operations |
| 224 | |
| 225 | /** |
| 226 | * {@inheritDoc} |
| 227 | * |
| 228 | * <p>This implementation always throws an |
| 229 | * <tt>UnsupportedOperationException</tt>. |
| 230 | * |
| 231 | * @throws UnsupportedOperationException {@inheritDoc} |
| 232 | * @throws ClassCastException {@inheritDoc} |
| 233 | * @throws NullPointerException {@inheritDoc} |
| 234 | * @throws IllegalArgumentException {@inheritDoc} |
| 235 | * @throws IllegalStateException {@inheritDoc} |
| 236 | */ |
| 237 | public boolean add(E e) { |
| 238 | throw new UnsupportedOperationException(); |
| 239 | } |
| 240 | |
| 241 | /** |
| 242 | * {@inheritDoc} |
| 243 | * |
| 244 | * <p>This implementation iterates over the collection looking for the |
| 245 | * specified element. If it finds the element, it removes the element |
| 246 | * from the collection using the iterator's remove method. |
| 247 | * |
| 248 | * <p>Note that this implementation throws an |
| 249 | * <tt>UnsupportedOperationException</tt> if the iterator returned by this |
| 250 | * collection's iterator method does not implement the <tt>remove</tt> |
| 251 | * method and this collection contains the specified object. |
| 252 | * |
| 253 | * @throws UnsupportedOperationException {@inheritDoc} |
| 254 | * @throws ClassCastException {@inheritDoc} |
| 255 | * @throws NullPointerException {@inheritDoc} |
| 256 | */ |
| 257 | public boolean remove(Object o) { |
| 258 | Iterator<E> e = iterator(); |
| 259 | if (o==null) { |
| 260 | while (e.hasNext()) { |
| 261 | if (e.next()==null) { |
| 262 | e.remove(); |
| 263 | return true; |
| 264 | } |
| 265 | } |
| 266 | } else { |
| 267 | while (e.hasNext()) { |
| 268 | if (o.equals(e.next())) { |
| 269 | e.remove(); |
| 270 | return true; |
| 271 | } |
| 272 | } |
| 273 | } |
| 274 | return false; |
| 275 | } |
| 276 | |
| 277 | |
| 278 | // Bulk Operations |
| 279 | |
| 280 | /** |
| 281 | * {@inheritDoc} |
| 282 | * |
| 283 | * <p>This implementation iterates over the specified collection, |
| 284 | * checking each element returned by the iterator in turn to see |
| 285 | * if it's contained in this collection. If all elements are so |
| 286 | * contained <tt>true</tt> is returned, otherwise <tt>false</tt>. |
| 287 | * |
| 288 | * @throws ClassCastException {@inheritDoc} |
| 289 | * @throws NullPointerException {@inheritDoc} |
| 290 | * @see #contains(Object) |
| 291 | */ |
| 292 | public boolean containsAll(Collection<?> c) { |
| 293 | Iterator<?> e = c.iterator(); |
| 294 | while (e.hasNext()) |
| 295 | if (!contains(e.next())) |
| 296 | return false; |
| 297 | return true; |
| 298 | } |
| 299 | |
| 300 | /** |
| 301 | * {@inheritDoc} |
| 302 | * |
| 303 | * <p>This implementation iterates over the specified collection, and adds |
| 304 | * each object returned by the iterator to this collection, in turn. |
| 305 | * |
| 306 | * <p>Note that this implementation will throw an |
| 307 | * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is |
| 308 | * overridden (assuming the specified collection is non-empty). |
| 309 | * |
| 310 | * @throws UnsupportedOperationException {@inheritDoc} |
| 311 | * @throws ClassCastException {@inheritDoc} |
| 312 | * @throws NullPointerException {@inheritDoc} |
| 313 | * @throws IllegalArgumentException {@inheritDoc} |
| 314 | * @throws IllegalStateException {@inheritDoc} |
| 315 | * |
| 316 | * @see #add(Object) |
| 317 | */ |
| 318 | public boolean addAll(Collection<? extends E> c) { |
| 319 | boolean modified = false; |
| 320 | Iterator<? extends E> e = c.iterator(); |
| 321 | while (e.hasNext()) { |
| 322 | if (add(e.next())) |
| 323 | modified = true; |
| 324 | } |
| 325 | return modified; |
| 326 | } |
| 327 | |
| 328 | /** |
| 329 | * {@inheritDoc} |
| 330 | * |
| 331 | * <p>This implementation iterates over this collection, checking each |
| 332 | * element returned by the iterator in turn to see if it's contained |
| 333 | * in the specified collection. If it's so contained, it's removed from |
| 334 | * this collection with the iterator's <tt>remove</tt> method. |
| 335 | * |
| 336 | * <p>Note that this implementation will throw an |
| 337 | * <tt>UnsupportedOperationException</tt> if the iterator returned by the |
| 338 | * <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
| 339 | * and this collection contains one or more elements in common with the |
| 340 | * specified collection. |
| 341 | * |
| 342 | * @throws UnsupportedOperationException {@inheritDoc} |
| 343 | * @throws ClassCastException {@inheritDoc} |
| 344 | * @throws NullPointerException {@inheritDoc} |
| 345 | * |
| 346 | * @see #remove(Object) |
| 347 | * @see #contains(Object) |
| 348 | */ |
| 349 | public boolean removeAll(Collection<?> c) { |
| 350 | boolean modified = false; |
| 351 | Iterator<?> e = iterator(); |
| 352 | while (e.hasNext()) { |
| 353 | if (c.contains(e.next())) { |
| 354 | e.remove(); |
| 355 | modified = true; |
| 356 | } |
| 357 | } |
| 358 | return modified; |
| 359 | } |
| 360 | |
| 361 | /** |
| 362 | * {@inheritDoc} |
| 363 | * |
| 364 | * <p>This implementation iterates over this collection, checking each |
| 365 | * element returned by the iterator in turn to see if it's contained |
| 366 | * in the specified collection. If it's not so contained, it's removed |
| 367 | * from this collection with the iterator's <tt>remove</tt> method. |
| 368 | * |
| 369 | * <p>Note that this implementation will throw an |
| 370 | * <tt>UnsupportedOperationException</tt> if the iterator returned by the |
| 371 | * <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
| 372 | * and this collection contains one or more elements not present in the |
| 373 | * specified collection. |
| 374 | * |
| 375 | * @throws UnsupportedOperationException {@inheritDoc} |
| 376 | * @throws ClassCastException {@inheritDoc} |
| 377 | * @throws NullPointerException {@inheritDoc} |
| 378 | * |
| 379 | * @see #remove(Object) |
| 380 | * @see #contains(Object) |
| 381 | */ |
| 382 | public boolean retainAll(Collection<?> c) { |
| 383 | boolean modified = false; |
| 384 | Iterator<E> e = iterator(); |
| 385 | while (e.hasNext()) { |
| 386 | if (!c.contains(e.next())) { |
| 387 | e.remove(); |
| 388 | modified = true; |
| 389 | } |
| 390 | } |
| 391 | return modified; |
| 392 | } |
| 393 | |
| 394 | /** |
| 395 | * {@inheritDoc} |
| 396 | * |
| 397 | * <p>This implementation iterates over this collection, removing each |
| 398 | * element using the <tt>Iterator.remove</tt> operation. Most |
| 399 | * implementations will probably choose to override this method for |
| 400 | * efficiency. |
| 401 | * |
| 402 | * <p>Note that this implementation will throw an |
| 403 | * <tt>UnsupportedOperationException</tt> if the iterator returned by this |
| 404 | * collection's <tt>iterator</tt> method does not implement the |
| 405 | * <tt>remove</tt> method and this collection is non-empty. |
| 406 | * |
| 407 | * @throws UnsupportedOperationException {@inheritDoc} |
| 408 | */ |
| 409 | public void clear() { |
| 410 | Iterator<E> e = iterator(); |
| 411 | while (e.hasNext()) { |
| 412 | e.next(); |
| 413 | e.remove(); |
| 414 | } |
| 415 | } |
| 416 | |
| 417 | |
| 418 | // String conversion |
| 419 | |
| 420 | /** |
| 421 | * Returns a string representation of this collection. The string |
| 422 | * representation consists of a list of the collection's elements in the |
| 423 | * order they are returned by its iterator, enclosed in square brackets |
| 424 | * (<tt>"[]"</tt>). Adjacent elements are separated by the characters |
| 425 | * <tt>", "</tt> (comma and space). Elements are converted to strings as |
| 426 | * by {@link String#valueOf(Object)}. |
| 427 | * |
| 428 | * @return a string representation of this collection |
| 429 | */ |
| 430 | public String toString() { |
| 431 | Iterator<E> i = iterator(); |
| 432 | if (! i.hasNext()) |
| 433 | return "[]"; |
| 434 | |
| 435 | StringBuilder sb = new StringBuilder(); |
| 436 | sb.append('['); |
| 437 | for (;;) { |
| 438 | E e = i.next(); |
| 439 | sb.append(e == this ? "(this Collection)" : e); |
| 440 | if (! i.hasNext()) |
| 441 | return sb.append(']').toString(); |
| 442 | sb.append(", "); |
| 443 | } |
| 444 | } |
| 445 | |
| 446 | } |