- 001
/* - 002
* @(#)List.java 1.49 06/04/21 - 003 *
- 004 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
- 005 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- 006
*/ - 007
- 008package java.util;
- 009
- 010/**
- 011 * An ordered collection (also known as a <i>sequence</i>). The user of this
- 012 * interface has precise control over where in the list each element is
- 013 * inserted. The user can access elements by their integer index (position in
- 014 * the list), and search for elements in the list.<p>
- 015 *
- 016 * Unlike sets, lists typically allow duplicate elements. More formally,
- 017 * lists typically allow pairs of elements <tt>e1</tt> and <tt>e2</tt>
- 018 * such that <tt>e1.equals(e2)</tt>, and they typically allow multiple
- 019 * null elements if they allow null elements at all. It is not inconceivable
- 020 * that someone might wish to implement a list that prohibits duplicates, by
- 021 * throwing runtime exceptions when the user attempts to insert them, but we
- 022 * expect this usage to be rare.<p>
- 023 *
- 024 * The <tt>List</tt> interface places additional stipulations, beyond those
- 025 * specified in the <tt>Collection</tt> interface, on the contracts of the
- 026 * <tt>iterator</tt>, <tt>add</tt>, <tt>remove</tt>, <tt>equals</tt>, and
- 027 * <tt>hashCode</tt> methods. Declarations for other inherited methods are
- 028 * also included here for convenience.<p>
- 029 *
- 030 * The <tt>List</tt> interface provides four methods for positional (indexed)
- 031 * access to list elements. Lists (like Java arrays) are zero based. Note
- 032 * that these operations may execute in time proportional to the index value
- 033 * for some implementations (the <tt>LinkedList</tt> class, for
- 034 * example). Thus, iterating over the elements in a list is typically
- 035 * preferable to indexing through it if the caller does not know the
- 036 * implementation.<p>
- 037 *
- 038 * The <tt>List</tt> interface provides a special iterator, called a
- 039 * <tt>ListIterator</tt>, that allows element insertion and replacement, and
- 040 * bidirectional access in addition to the normal operations that the
- 041 * <tt>Iterator</tt> interface provides. A method is provided to obtain a
- 042 * list iterator that starts at a specified position in the list.<p>
- 043 *
- 044 * The <tt>List</tt> interface provides two methods to search for a specified
- 045 * object. From a performance standpoint, these methods should be used with
- 046 * caution. In many implementations they will perform costly linear
- 047 * searches.<p>
- 048 *
- 049 * The <tt>List</tt> interface provides two methods to efficiently insert and
- 050 * remove multiple elements at an arbitrary point in the list.<p>
- 051 *
- 052 * Note: While it is permissible for lists to contain themselves as elements,
- 053 * extreme caution is advised: the <tt>equals</tt> and <tt>hashCode</tt>
- 054 * methods are no longer well defined on such a list.
- 055 *
- 056 * <p>Some list implementations have restrictions on the elements that
- 057 * they may contain. For example, some implementations prohibit null elements,
- 058 * and some have restrictions on the types of their elements. Attempting to
- 059 * add an ineligible element throws an unchecked exception, typically
- 060 * <tt>NullPointerException</tt> or <tt>ClassCastException</tt>. Attempting
- 061 * to query the presence of an ineligible element may throw an exception,
- 062 * or it may simply return false; some implementations will exhibit the former
- 063 * behavior and some will exhibit the latter. More generally, attempting an
- 064 * operation on an ineligible element whose completion would not result in
- 065 * the insertion of an ineligible element into the list may throw an
- 066 * exception or it may succeed, at the option of the implementation.
- 067 * Such exceptions are marked as "optional" in the specification for this
- 068 * interface.
- 069 *
- 070 * <p>This interface is a member of the
- 071 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
- 072 * Java Collections Framework</a>.
- 073 *
- 074 * @author Josh Bloch
- 075 * @author Neal Gafter
- 076 * @version 1.49, 04/21/06
- 077 * @see Collection
- 078 * @see Set
- 079 * @see ArrayList
- 080 * @see LinkedList
- 081 * @see Vector
- 082 * @see Arrays#asList(Object[])
- 083 * @see Collections#nCopies(int, Object)
- 084 * @see Collections#EMPTY_LIST
- 085 * @see AbstractList
- 086 * @see AbstractSequentialList
- 087 * @since 1.2
- 088 */
- 089
- 090public interface List<E> extends Collection<E> {
- 091 // Query Operations
- 092
- 093 /**
- 094 * Returns the number of elements in this list. If this list contains
- 095 * more than <tt>Integer.MAX_VALUE</tt> elements, returns
- 096 * <tt>Integer.MAX_VALUE</tt>.
- 097 *
- 098 * @return the number of elements in this list
- 099 */
- 100 int size();
- 101
- 102 /**
- 103 * Returns <tt>true</tt> if this list contains no elements.
- 104 *
- 105 * @return <tt>true</tt> if this list contains no elements
- 106 */
- 107 boolean isEmpty();
- 108
- 109 /**
- 110 * Returns <tt>true</tt> if this list contains the specified element.
- 111 * More formally, returns <tt>true</tt> if and only if this list contains
- 112 * at least one element <tt>e</tt> such that
- 113 * <tt>(o==null ? e==null : o.equals(e))</tt>.
- 114 *
- 115 * @param o element whose presence in this list is to be tested
- 116 * @return <tt>true</tt> if this list contains the specified element
- 117 * @throws ClassCastException if the type of the specified element
- 118 * is incompatible with this list (optional)
- 119 * @throws NullPointerException if the specified element is null and this
- 120 * list does not permit null elements (optional)
- 121 */
- 122 boolean contains(Object o);
- 123
- 124 /**
- 125 * Returns an iterator over the elements in this list in proper sequence.
- 126 *
- 127 * @return an iterator over the elements in this list in proper sequence
- 128 */
- 129 Iterator<E> iterator();
- 130
- 131 /**
- 132 * Returns an array containing all of the elements in this list in proper
- 133 * sequence (from first to last element).
- 134 *
- 135 * <p>The returned array will be "safe" in that no references to it are
- 136 * maintained by this list. (In other words, this method must
- 137 * allocate a new array even if this list is backed by an array).
- 138 * The caller is thus free to modify the returned array.
- 139 *
- 140 * <p>This method acts as bridge between array-based and collection-based
- 141 * APIs.
- 142 *
- 143 * @return an array containing all of the elements in this list in proper
- 144 * sequence
- 145 * @see Arrays#asList(Object[])
- 146 */
- 147 Object[] toArray();
- 148
- 149 /**
- 150 * Returns an array containing all of the elements in this list in
- 151 * proper sequence (from first to last element); the runtime type of
- 152 * the returned array is that of the specified array. If the list fits
- 153 * in the specified array, it is returned therein. Otherwise, a new
- 154 * array is allocated with the runtime type of the specified array and
- 155 * the size of this list.
- 156 *
- 157 * <p>If the list fits in the specified array with room to spare (i.e.,
- 158 * the array has more elements than the list), the element in the array
- 159 * immediately following the end of the list is set to <tt>null</tt>.
- 160 * (This is useful in determining the length of the list <i>only</i> if
- 161 * the caller knows that the list does not contain any null elements.)
- 162 *
- 163 * <p>Like the {@link #toArray()} method, this method acts as bridge between
- 164 * array-based and collection-based APIs. Further, this method allows
- 165 * precise control over the runtime type of the output array, and may,
- 166 * under certain circumstances, be used to save allocation costs.
- 167 *
- 168 * <p>Suppose <tt>x</tt> is a list known to contain only strings.
- 169 * The following code can be used to dump the list into a newly
- 170 * allocated array of <tt>String</tt>:
- 171 *
- 172 * <pre>
- 173 * String[] y = x.toArray(new String[0]);</pre>
- 174 *
- 175 * Note that <tt>toArray(new Object[0])</tt> is identical in function to
- 176 * <tt>toArray()</tt>.
- 177 *
- 178 * @param a the array into which the elements of this list are to
- 179 * be stored, if it is big enough; otherwise, a new array of the
- 180 * same runtime type is allocated for this purpose.
- 181 * @return an array containing the elements of this list
- 182 * @throws ArrayStoreException if the runtime type of the specified array
- 183 * is not a supertype of the runtime type of every element in
- 184 * this list
- 185 * @throws NullPointerException if the specified array is null
- 186 */
- 187 <T> T[] toArray(T[] a);
- 188
- 189
- 190 // Modification Operations
- 191
- 192 /**
- 193 * Appends the specified element to the end of this list (optional
- 194 * operation).
- 195 *
- 196 * <p>Lists that support this operation may place limitations on what
- 197 * elements may be added to this list. In particular, some
- 198 * lists will refuse to add null elements, and others will impose
- 199 * restrictions on the type of elements that may be added. List
- 200 * classes should clearly specify in their documentation any restrictions
- 201 * on what elements may be added.
- 202 *
- 203 * @param e element to be appended to this list
- 204 * @return <tt>true</tt> (as specified by {@link Collection#add})
- 205 * @throws UnsupportedOperationException if the <tt>add</tt> operation
- 206 * is not supported by this list
- 207 * @throws ClassCastException if the class of the specified element
- 208 * prevents it from being added to this list
- 209 * @throws NullPointerException if the specified element is null and this
- 210 * list does not permit null elements
- 211 * @throws IllegalArgumentException if some property of this element
- 212 * prevents it from being added to this list
- 213 */
- 214 boolean add(E e);
- 215
- 216 /**
- 217 * Removes the first occurrence of the specified element from this list,
- 218 * if it is present (optional operation). If this list does not contain
- 219 * the element, it is unchanged. More formally, removes the element with
- 220 * the lowest index <tt>i</tt> such that
- 221 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
- 222 * (if such an element exists). Returns <tt>true</tt> if this list
- 223 * contained the specified element (or equivalently, if this list changed
- 224 * as a result of the call).
- 225 *
- 226 * @param o element to be removed from this list, if present
- 227 * @return <tt>true</tt> if this list contained the specified element
- 228 * @throws ClassCastException if the type of the specified element
- 229 * is incompatible with this list (optional)
- 230 * @throws NullPointerException if the specified element is null and this
- 231 * list does not permit null elements (optional)
- 232 * @throws UnsupportedOperationException if the <tt>remove</tt> operation
- 233 * is not supported by this list
- 234 */
- 235 boolean remove(Object o);
- 236
- 237
- 238 // Bulk Modification Operations
- 239
- 240 /**
- 241 * Returns <tt>true</tt> if this list contains all of the elements of the
- 242 * specified collection.
- 243 *
- 244 * @param c collection to be checked for containment in this list
- 245 * @return <tt>true</tt> if this list contains all of the elements of the
- 246 * specified collection
- 247 * @throws ClassCastException if the types of one or more elements
- 248 * in the specified collection are incompatible with this
- 249 * list (optional)
- 250 * @throws NullPointerException if the specified collection contains one
- 251 * or more null elements and this list does not permit null
- 252 * elements (optional), or if the specified collection is null
- 253 * @see #contains(Object)
- 254 */
- 255 boolean containsAll(Collection<?> c);
- 256
- 257 /**
- 258 * Appends all of the elements in the specified collection to the end of
- 259 * this list, in the order that they are returned by the specified
- 260 * collection's iterator (optional operation). The behavior of this
- 261 * operation is undefined if the specified collection is modified while
- 262 * the operation is in progress. (Note that this will occur if the
- 263 * specified collection is this list, and it's nonempty.)
- 264 *
- 265 * @param c collection containing elements to be added to this list
- 266 * @return <tt>true</tt> if this list changed as a result of the call
- 267 * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
- 268 * is not supported by this list
- 269 * @throws ClassCastException if the class of an element of the specified
- 270 * collection prevents it from being added to this list
- 271 * @throws NullPointerException if the specified collection contains one
- 272 * or more null elements and this list does not permit null
- 273 * elements, or if the specified collection is null
- 274 * @throws IllegalArgumentException if some property of an element of the
- 275 * specified collection prevents it from being added to this list
- 276 * @see #add(Object)
- 277 */
- 278 boolean addAll(Collection<? extends E> c);
- 279
- 280 /**
- 281 * Inserts all of the elements in the specified collection into this
- 282 * list at the specified position (optional operation). Shifts the
- 283 * element currently at that position (if any) and any subsequent
- 284 * elements to the right (increases their indices). The new elements
- 285 * will appear in this list in the order that they are returned by the
- 286 * specified collection's iterator. The behavior of this operation is
- 287 * undefined if the specified collection is modified while the
- 288 * operation is in progress. (Note that this will occur if the specified
- 289 * collection is this list, and it's nonempty.)
- 290 *
- 291 * @param index index at which to insert the first element from the
- 292 * specified collection
- 293 * @param c collection containing elements to be added to this list
- 294 * @return <tt>true</tt> if this list changed as a result of the call
- 295 * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
- 296 * is not supported by this list
- 297 * @throws ClassCastException if the class of an element of the specified
- 298 * collection prevents it from being added to this list
- 299 * @throws NullPointerException if the specified collection contains one
- 300 * or more null elements and this list does not permit null
- 301 * elements, or if the specified collection is null
- 302 * @throws IllegalArgumentException if some property of an element of the
- 303 * specified collection prevents it from being added to this list
- 304 * @throws IndexOutOfBoundsException if the index is out of range
- 305 * (<tt>index < 0 || index > size()</tt>)
- 306 */
- 307 boolean addAll(int index, Collection<? extends E> c);
- 308
- 309 /**
- 310 * Removes from this list all of its elements that are contained in the
- 311 * specified collection (optional operation).
- 312 *
- 313 * @param c collection containing elements to be removed from this list
- 314 * @return <tt>true</tt> if this list changed as a result of the call
- 315 * @throws UnsupportedOperationException if the <tt>removeAll</tt> operation
- 316 * is not supported by this list
- 317 * @throws ClassCastException if the class of an element of this list
- 318 * is incompatible with the specified collection (optional)
- 319 * @throws NullPointerException if this list contains a null element and the
- 320 * specified collection does not permit null elements (optional),
- 321 * or if the specified collection is null
- 322 * @see #remove(Object)
- 323 * @see #contains(Object)
- 324 */
- 325 boolean removeAll(Collection<?> c);
- 326
- 327 /**
- 328 * Retains only the elements in this list that are contained in the
- 329 * specified collection (optional operation). In other words, removes
- 330 * from this list all the elements that are not contained in the specified
- 331 * collection.
- 332 *
- 333 * @param c collection containing elements to be retained in this list
- 334 * @return <tt>true</tt> if this list changed as a result of the call
- 335 * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
- 336 * is not supported by this list
- 337 * @throws ClassCastException if the class of an element of this list
- 338 * is incompatible with the specified collection (optional)
- 339 * @throws NullPointerException if this list contains a null element and the
- 340 * specified collection does not permit null elements (optional),
- 341 * or if the specified collection is null
- 342 * @see #remove(Object)
- 343 * @see #contains(Object)
- 344 */
- 345 boolean retainAll(Collection<?> c);
- 346
- 347 /**
- 348 * Removes all of the elements from this list (optional operation).
- 349 * The list will be empty after this call returns.
- 350 *
- 351 * @throws UnsupportedOperationException if the <tt>clear</tt> operation
- 352 * is not supported by this list
- 353 */
- 354 void clear();
- 355
- 356
- 357 // Comparison and hashing
- 358
- 359 /**
- 360 * Compares the specified object with this list for equality. Returns
- 361 * <tt>true</tt> if and only if the specified object is also a list, both
- 362 * lists have the same size, and all corresponding pairs of elements in
- 363 * the two lists are <i>equal</i>. (Two elements <tt>e1</tt> and
- 364 * <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null :
- 365 * e1.equals(e2))</tt>.) In other words, two lists are defined to be
- 366 * equal if they contain the same elements in the same order. This
- 367 * definition ensures that the equals method works properly across
- 368 * different implementations of the <tt>List</tt> interface.
- 369 *
- 370 * @param o the object to be compared for equality with this list
- 371 * @return <tt>true</tt> if the specified object is equal to this list
- 372 */
- 373 boolean equals(Object o);
- 374
- 375 /**
- 376 * Returns the hash code value for this list. The hash code of a list
- 377 * is defined to be the result of the following calculation:
- 378 * <pre>
- 379 * int hashCode = 1;
- 380 * Iterator<E> i = list.iterator();
- 381 * while (i.hasNext()) {
- 382 * E obj = i.next();
- 383 * hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
- 384 * }
- 385 * </pre>
- 386 * This ensures that <tt>list1.equals(list2)</tt> implies that
- 387 * <tt>list1.hashCode()==list2.hashCode()</tt> for any two lists,
- 388 * <tt>list1</tt> and <tt>list2</tt>, as required by the general
- 389 * contract of {@link Object#hashCode}.
- 390 *
- 391 * @return the hash code value for this list
- 392 * @see Object#equals(Object)
- 393 * @see #equals(Object)
- 394 */
- 395 int hashCode();
- 396
- 397
- 398 // Positional Access Operations
- 399
- 400 /**
- 401 * Returns the element at the specified position in this list.
- 402 *
- 403 * @param index index of the element to return
- 404 * @return the element at the specified position in this list
- 405 * @throws IndexOutOfBoundsException if the index is out of range
- 406 * (<tt>index < 0 || index >= size()</tt>)
- 407 */
- 408 E get(int index);
- 409
- 410 /**
- 411 * Replaces the element at the specified position in this list with the
- 412 * specified element (optional operation).
- 413 *
- 414 * @param index index of the element to replace
- 415 * @param element element to be stored at the specified position
- 416 * @return the element previously at the specified position
- 417 * @throws UnsupportedOperationException if the <tt>set</tt> operation
- 418 * is not supported by this list
- 419 * @throws ClassCastException if the class of the specified element
- 420 * prevents it from being added to this list
- 421 * @throws NullPointerException if the specified element is null and
- 422 * this list does not permit null elements
- 423 * @throws IllegalArgumentException if some property of the specified
- 424 * element prevents it from being added to this list
- 425 * @throws IndexOutOfBoundsException if the index is out of range
- 426 * (<tt>index < 0 || index >= size()</tt>)
- 427 */
- 428 E set(int index, E element);
- 429
- 430 /**
- 431 * Inserts the specified element at the specified position in this list
- 432 * (optional operation). Shifts the element currently at that position
- 433 * (if any) and any subsequent elements to the right (adds one to their
- 434 * indices).
- 435 *
- 436 * @param index index at which the specified element is to be inserted
- 437 * @param element element to be inserted
- 438 * @throws UnsupportedOperationException if the <tt>add</tt> operation
- 439 * is not supported by this list
- 440 * @throws ClassCastException if the class of the specified element
- 441 * prevents it from being added to this list
- 442 * @throws NullPointerException if the specified element is null and
- 443 * this list does not permit null elements
- 444 * @throws IllegalArgumentException if some property of the specified
- 445 * element prevents it from being added to this list
- 446 * @throws IndexOutOfBoundsException if the index is out of range
- 447 * (<tt>index < 0 || index > size()</tt>)
- 448 */
- 449 void add(int index, E element);
- 450
- 451 /**
- 452 * Removes the element at the specified position in this list (optional
- 453 * operation). Shifts any subsequent elements to the left (subtracts one
- 454 * from their indices). Returns the element that was removed from the
- 455 * list.
- 456 *
- 457 * @param index the index of the element to be removed
- 458 * @return the element previously at the specified position
- 459 * @throws UnsupportedOperationException if the <tt>remove</tt> operation
- 460 * is not supported by this list
- 461 * @throws IndexOutOfBoundsException if the index is out of range
- 462 * (<tt>index < 0 || index >= size()</tt>)
- 463 */
- 464 E remove(int index);
- 465
- 466
- 467 // Search Operations
- 468
- 469 /**
- 470 * Returns the index of the first occurrence of the specified element
- 471 * in this list, or -1 if this list does not contain the element.
- 472 * More formally, returns the lowest index <tt>i</tt> such that
- 473 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
- 474 * or -1 if there is no such index.
- 475 *
- 476 * @param o element to search for
- 477 * @return the index of the first occurrence of the specified element in
- 478 * this list, or -1 if this list does not contain the element
- 479 * @throws ClassCastException if the type of the specified element
- 480 * is incompatible with this list (optional)
- 481 * @throws NullPointerException if the specified element is null and this
- 482 * list does not permit null elements (optional)
- 483 */
- 484 int indexOf(Object o);
- 485
- 486 /**
- 487 * Returns the index of the last occurrence of the specified element
- 488 * in this list, or -1 if this list does not contain the element.
- 489 * More formally, returns the highest index <tt>i</tt> such that
- 490 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
- 491 * or -1 if there is no such index.
- 492 *
- 493 * @param o element to search for
- 494 * @return the index of the last occurrence of the specified element in
- 495 * this list, or -1 if this list does not contain the element
- 496 * @throws ClassCastException if the type of the specified element
- 497 * is incompatible with this list (optional)
- 498 * @throws NullPointerException if the specified element is null and this
- 499 * list does not permit null elements (optional)
- 500 */
- 501 int lastIndexOf(Object o);
- 502
- 503
- 504 // List Iterators
- 505
- 506 /**
- 507 * Returns a list iterator over the elements in this list (in proper
- 508 * sequence).
- 509 *
- 510 * @return a list iterator over the elements in this list (in proper
- 511 * sequence)
- 512 */
- 513 ListIterator<E> listIterator();
- 514
- 515 /**
- 516 * Returns a list iterator of the elements in this list (in proper
- 517 * sequence), starting at the specified position in this list.
- 518 * The specified index indicates the first element that would be
- 519 * returned by an initial call to {@link ListIterator#next next}.
- 520 * An initial call to {@link ListIterator#previous previous} would
- 521 * return the element with the specified index minus one.
- 522 *
- 523 * @param index index of first element to be returned from the
- 524 * list iterator (by a call to the <tt>next</tt> method)
- 525 * @return a list iterator of the elements in this list (in proper
- 526 * sequence), starting at the specified position in this list
- 527 * @throws IndexOutOfBoundsException if the index is out of range
- 528 * (<tt>index < 0 || index > size()</tt>)
- 529 */
- 530 ListIterator<E> listIterator(int index);
- 531
- 532 // View
- 533
- 534 /**
- 535 * Returns a view of the portion of this list between the specified
- 536 * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. (If
- 537 * <tt>fromIndex</tt> and <tt>toIndex</tt> are equal, the returned list is
- 538 * empty.) The returned list is backed by this list, so non-structural
- 539 * changes in the returned list are reflected in this list, and vice-versa.
- 540 * The returned list supports all of the optional list operations supported
- 541 * by this list.<p>
- 542 *
- 543 * This method eliminates the need for explicit range operations (of
- 544 * the sort that commonly exist for arrays). Any operation that expects
- 545 * a list can be used as a range operation by passing a subList view
- 546 * instead of a whole list. For example, the following idiom
- 547 * removes a range of elements from a list:
- 548 * <pre>
- 549 * list.subList(from, to).clear();
- 550 * </pre>
- 551 * Similar idioms may be constructed for <tt>indexOf</tt> and
- 552 * <tt>lastIndexOf</tt>, and all of the algorithms in the
- 553 * <tt>Collections</tt> class can be applied to a subList.<p>
- 554 *
- 555 * The semantics of the list returned by this method become undefined if
- 556 * the backing list (i.e., this list) is <i>structurally modified</i> in
- 557 * any way other than via the returned list. (Structural modifications are
- 558 * those that change the size of this list, or otherwise perturb it in such
- 559 * a fashion that iterations in progress may yield incorrect results.)
- 560 *
- 561 * @param fromIndex low endpoint (inclusive) of the subList
- 562 * @param toIndex high endpoint (exclusive) of the subList
- 563 * @return a view of the specified range within this list
- 564 * @throws IndexOutOfBoundsException for an illegal endpoint index value
- 565 * (<tt>fromIndex < 0 || toIndex > size ||
- 566 * fromIndex > toIndex</tt>)
- 567 */
- 568 List<E> subList(int fromIndex, int toIndex);
- 569}
