    rev 47953 : 8177290: add copy factory methods for unmodifiable List, Set, Map
    8184690: add Collectors for collecting into unmodifiable List, Set, and Map
    Reviewed-by: alanb, briangoetz, dholmes, jrose, rriggs, scolebourne

       1 /*
       2  * Copyright (c) 1997, 2017, 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.UnaryOperator;
      29
      30 /**
      31  * An ordered collection (also known as a <i>sequence</i>).  The user of this
      32  * interface has precise control over where in the list each element is
      33  * inserted.  The user can access elements by their integer index (position in
      34  * the list), and search for elements in the list.<p>
      35  *
      36  * Unlike sets, lists typically allow duplicate elements.  More formally,
      37  * lists typically allow pairs of elements {@code e1} and {@code e2}
      38  * such that {@code e1.equals(e2)}, and they typically allow multiple
      39  * null elements if they allow null elements at all.  It is not inconceivable
      40  * that someone might wish to implement a list that prohibits duplicates, by
      41  * throwing runtime exceptions when the user attempts to insert them, but we
      42  * expect this usage to be rare.<p>
      43  *
      44  * The {@code List} interface places additional stipulations, beyond those
      45  * specified in the {@code Collection} interface, on the contracts of the
      46  * {@code iterator}, {@code add}, {@code remove}, {@code equals}, and
      47  * {@code hashCode} methods.  Declarations for other inherited methods are
      48  * also included here for convenience.<p>
      49  *
      50  * The {@code List} interface provides four methods for positional (indexed)
      51  * access to list elements.  Lists (like Java arrays) are zero based.  Note
      52  * that these operations may execute in time proportional to the index value
      53  * for some implementations (the {@code LinkedList} class, for
      54  * example). Thus, iterating over the elements in a list is typically
      55  * preferable to indexing through it if the caller does not know the
      56  * implementation.<p>
      57  *
      58  * The {@code List} interface provides a special iterator, called a
      59  * {@code ListIterator}, that allows element insertion and replacement, and
      60  * bidirectional access in addition to the normal operations that the
      61  * {@code Iterator} interface provides.  A method is provided to obtain a
      62  * list iterator that starts at a specified position in the list.<p>
      63  *
      64  * The {@code List} interface provides two methods to search for a specified
      65  * object.  From a performance standpoint, these methods should be used with
      66  * caution.  In many implementations they will perform costly linear
      67  * searches.<p>
      68  *
      69  * The {@code List} interface provides two methods to efficiently insert and
      70  * remove multiple elements at an arbitrary point in the list.<p>
      71  *
      72  * Note: While it is permissible for lists to contain themselves as elements,
      73  * extreme caution is advised: the {@code equals} and {@code hashCode}
      74  * methods are no longer well defined on such a list.
      75  *
      76  * <p>Some list implementations have restrictions on the elements that
      77  * they may contain.  For example, some implementations prohibit null elements,
      78  * and some have restrictions on the types of their elements.  Attempting to
      79  * add an ineligible element throws an unchecked exception, typically
      80  * {@code NullPointerException} or {@code ClassCastException}.  Attempting
      81  * to query the presence of an ineligible element may throw an exception,
      82  * or it may simply return false; some implementations will exhibit the former
      83  * behavior and some will exhibit the latter.  More generally, attempting an
      84  * operation on an ineligible element whose completion would not result in
      85  * the insertion of an ineligible element into the list may throw an
      86  * exception or it may succeed, at the option of the implementation.
      87  * Such exceptions are marked as "optional" in the specification for this
      88  * interface.
      89  *
      90  * <h2><a id="immutable">Immutable List Static Factory Methods</a></h2>
      91  * <p>The {@link List#of(Object...) List.of()} static factory methods
      92  * provide a convenient way to create immutable lists. The {@code List}

      93  * instances created by these methods have the following characteristics:
      94  *
      95  * <ul>
      96  * <li>They are <em>structurally immutable</em>. Elements cannot be added, removed,
      97  * or replaced. Calling any mutator method will always cause
      98  * {@code UnsupportedOperationException} to be thrown.
      99  * However, if the contained elements are themselves mutable,
     100  * this may cause the List's contents to appear to change.
     101  * <li>They disallow {@code null} elements. Attempts to create them with
     102  * {@code null} elements result in {@code NullPointerException}.
     103  * <li>They are serializable if all elements are serializable.
     104  * <li>The order of elements in the list is the same as the order of the
     105  * provided arguments, or of the elements in the provided array.
     106  * <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
     107  * Callers should make no assumptions about the identity of the returned instances.
     108  * Factories are free to create new instances or reuse existing ones. Therefore,
     109  * identity-sensitive operations on these instances (reference equality ({@code ==}),
     110  * identity hash code, and synchronization) are unreliable and should be avoided.
     111  * <li>They are serialized as specified on the
     112  * <a href="{@docRoot}/serialized-form.html#java.util.CollSer">Serialized Form</a>
     113  * page.
     114  * </ul>
     115  *
     116  * <p>This interface is a member of the
     117  * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
     118  * Java Collections Framework</a>.
     119  *
     120  * @param <E> the type of elements in this list
     121  *
     122  * @author  Josh Bloch
     123  * @author  Neal Gafter
     124  * @see Collection
     125  * @see Set
     126  * @see ArrayList
     127  * @see LinkedList
     128  * @see Vector
     129  * @see Arrays#asList(Object[])
     130  * @see Collections#nCopies(int, Object)
     131  * @see Collections#EMPTY_LIST
     132  * @see AbstractList
     133  * @see AbstractSequentialList
     134  * @since 1.2
     135  */
     136
     137 public interface List<E> extends Collection<E> {
     138     // Query Operations
     139
     140     /**
     141      * Returns the number of elements in this list.  If this list contains
     142      * more than {@code Integer.MAX_VALUE} elements, returns
     143      * {@code Integer.MAX_VALUE}.
     144      *
     145      * @return the number of elements in this list
     146      */
     147     int size();
     148
     149     /**
     150      * Returns {@code true} if this list contains no elements.
     151      *
     152      * @return {@code true} if this list contains no elements
     153      */
     154     boolean isEmpty();
     155
     156     /**
     157      * Returns {@code true} if this list contains the specified element.
     158      * More formally, returns {@code true} if and only if this list contains
     159      * at least one element {@code e} such that
     160      * {@code Objects.equals(o, e)}.
     161      *
     162      * @param o element whose presence in this list is to be tested
     163      * @return {@code true} if this list contains the specified element
     164      * @throws ClassCastException if the type of the specified element
     165      *         is incompatible with this list
     166      * (<a href="Collection.html#optional-restrictions">optional</a>)
     167      * @throws NullPointerException if the specified element is null and this
     168      *         list does not permit null elements
     169      * (<a href="Collection.html#optional-restrictions">optional</a>)
     170      */
     171     boolean contains(Object o);
     172
     173     /**
     174      * Returns an iterator over the elements in this list in proper sequence.
     175      *
     176      * @return an iterator over the elements in this list in proper sequence
     177      */
     178     Iterator<E> iterator();
     179
     180     /**
     181      * Returns an array containing all of the elements in this list in proper
     182      * sequence (from first to last element).
     183      *
     184      * <p>The returned array will be "safe" in that no references to it are
     185      * maintained by this list.  (In other words, this method must
     186      * allocate a new array even if this list is backed by an array).
     187      * The caller is thus free to modify the returned array.
     188      *
     189      * <p>This method acts as bridge between array-based and collection-based
     190      * APIs.
     191      *
     192      * @return an array containing all of the elements in this list in proper
     193      *         sequence
     194      * @see Arrays#asList(Object[])
     195      */
     196     Object[] toArray();
     197
     198     /**
     199      * Returns an array containing all of the elements in this list in
     200      * proper sequence (from first to last element); the runtime type of
     201      * the returned array is that of the specified array.  If the list fits
     202      * in the specified array, it is returned therein.  Otherwise, a new
     203      * array is allocated with the runtime type of the specified array and
     204      * the size of this list.
     205      *
     206      * <p>If the list fits in the specified array with room to spare (i.e.,
     207      * the array has more elements than the list), the element in the array
     208      * immediately following the end of the list is set to {@code null}.
     209      * (This is useful in determining the length of the list <i>only</i> if
     210      * the caller knows that the list does not contain any null elements.)
     211      *
     212      * <p>Like the {@link #toArray()} method, this method acts as bridge between
     213      * array-based and collection-based APIs.  Further, this method allows
     214      * precise control over the runtime type of the output array, and may,
     215      * under certain circumstances, be used to save allocation costs.
     216      *
     217      * <p>Suppose {@code x} is a list known to contain only strings.
     218      * The following code can be used to dump the list into a newly
     219      * allocated array of {@code String}:
     220      *
     221      * <pre>{@code
     222      *     String[] y = x.toArray(new String[0]);
     223      * }</pre>
     224      *
     225      * Note that {@code toArray(new Object[0])} is identical in function to
     226      * {@code toArray()}.
     227      *
     228      * @param a the array into which the elements of this list are to
     229      *          be stored, if it is big enough; otherwise, a new array of the
     230      *          same runtime type is allocated for this purpose.
     231      * @return an array containing the elements of this list
     232      * @throws ArrayStoreException if the runtime type of the specified array
     233      *         is not a supertype of the runtime type of every element in
     234      *         this list
     235      * @throws NullPointerException if the specified array is null
     236      */
     237     <T> T[] toArray(T[] a);
     238
     239
     240     // Modification Operations
     241
     242     /**
     243      * Appends the specified element to the end of this list (optional
     244      * operation).
     245      *
     246      * <p>Lists that support this operation may place limitations on what
     247      * elements may be added to this list.  In particular, some
     248      * lists will refuse to add null elements, and others will impose
     249      * restrictions on the type of elements that may be added.  List
     250      * classes should clearly specify in their documentation any restrictions
     251      * on what elements may be added.
     252      *
     253      * @param e element to be appended to this list
     254      * @return {@code true} (as specified by {@link Collection#add})
     255      * @throws UnsupportedOperationException if the {@code add} operation
     256      *         is not supported by this list
     257      * @throws ClassCastException if the class of the specified element
     258      *         prevents it from being added to this list
     259      * @throws NullPointerException if the specified element is null and this
     260      *         list does not permit null elements
     261      * @throws IllegalArgumentException if some property of this element
     262      *         prevents it from being added to this list
     263      */
     264     boolean add(E e);
     265
     266     /**
     267      * Removes the first occurrence of the specified element from this list,
     268      * if it is present (optional operation).  If this list does not contain
     269      * the element, it is unchanged.  More formally, removes the element with
     270      * the lowest index {@code i} such that
     271      * {@code Objects.equals(o, get(i))}
     272      * (if such an element exists).  Returns {@code true} if this list
     273      * contained the specified element (or equivalently, if this list changed
     274      * as a result of the call).
     275      *
     276      * @param o element to be removed from this list, if present
     277      * @return {@code true} if this list contained the specified element
     278      * @throws ClassCastException if the type of the specified element
     279      *         is incompatible with this list
     280      * (<a href="Collection.html#optional-restrictions">optional</a>)
     281      * @throws NullPointerException if the specified element is null and this
     282      *         list does not permit null elements
     283      * (<a href="Collection.html#optional-restrictions">optional</a>)
     284      * @throws UnsupportedOperationException if the {@code remove} operation
     285      *         is not supported by this list
     286      */
     287     boolean remove(Object o);
     288
     289
     290     // Bulk Modification Operations
     291
     292     /**
     293      * Returns {@code true} if this list contains all of the elements of the
     294      * specified collection.
     295      *
     296      * @param  c collection to be checked for containment in this list
     297      * @return {@code true} if this list contains all of the elements of the
     298      *         specified collection
     299      * @throws ClassCastException if the types of one or more elements
     300      *         in the specified collection are incompatible with this
     301      *         list
     302      * (<a href="Collection.html#optional-restrictions">optional</a>)
     303      * @throws NullPointerException if the specified collection contains one
     304      *         or more null elements and this list does not permit null
     305      *         elements
     306      *         (<a href="Collection.html#optional-restrictions">optional</a>),
     307      *         or if the specified collection is null
     308      * @see #contains(Object)
     309      */
     310     boolean containsAll(Collection<?> c);
     311
     312     /**
     313      * Appends all of the elements in the specified collection to the end of
     314      * this list, in the order that they are returned by the specified
     315      * collection's iterator (optional operation).  The behavior of this
     316      * operation is undefined if the specified collection is modified while
     317      * the operation is in progress.  (Note that this will occur if the
     318      * specified collection is this list, and it's nonempty.)
     319      *
     320      * @param c collection containing elements to be added to this list
     321      * @return {@code true} if this list changed as a result of the call
     322      * @throws UnsupportedOperationException if the {@code addAll} operation
     323      *         is not supported by this list
     324      * @throws ClassCastException if the class of an element of the specified
     325      *         collection prevents it from being added to this list
     326      * @throws NullPointerException if the specified collection contains one
     327      *         or more null elements and this list does not permit null
     328      *         elements, or if the specified collection is null
     329      * @throws IllegalArgumentException if some property of an element of the
     330      *         specified collection prevents it from being added to this list
     331      * @see #add(Object)
     332      */
     333     boolean addAll(Collection<? extends E> c);
     334
     335     /**
     336      * Inserts all of the elements in the specified collection into this
     337      * list at the specified position (optional operation).  Shifts the
     338      * element currently at that position (if any) and any subsequent
     339      * elements to the right (increases their indices).  The new elements
     340      * will appear in this list in the order that they are returned by the
     341      * specified collection's iterator.  The behavior of this operation is
     342      * undefined if the specified collection is modified while the
     343      * operation is in progress.  (Note that this will occur if the specified
     344      * collection is this list, and it's nonempty.)
     345      *
     346      * @param index index at which to insert the first element from the
     347      *              specified collection
     348      * @param c collection containing elements to be added to this list
     349      * @return {@code true} if this list changed as a result of the call
     350      * @throws UnsupportedOperationException if the {@code addAll} operation
     351      *         is not supported by this list
     352      * @throws ClassCastException if the class of an element of the specified
     353      *         collection prevents it from being added to this list
     354      * @throws NullPointerException if the specified collection contains one
     355      *         or more null elements and this list does not permit null
     356      *         elements, or if the specified collection is null
     357      * @throws IllegalArgumentException if some property of an element of the
     358      *         specified collection prevents it from being added to this list
     359      * @throws IndexOutOfBoundsException if the index is out of range
     360      *         ({@code index < 0 || index > size()})
     361      */
     362     boolean addAll(int index, Collection<? extends E> c);
     363
     364     /**
     365      * Removes from this list all of its elements that are contained in the
     366      * specified collection (optional operation).
     367      *
     368      * @param c collection containing elements to be removed from this list
     369      * @return {@code true} if this list changed as a result of the call
     370      * @throws UnsupportedOperationException if the {@code removeAll} operation
     371      *         is not supported by this list
     372      * @throws ClassCastException if the class of an element of this list
     373      *         is incompatible with the specified collection
     374      * (<a href="Collection.html#optional-restrictions">optional</a>)
     375      * @throws NullPointerException if this list contains a null element and the
     376      *         specified collection does not permit null elements
     377      *         (<a href="Collection.html#optional-restrictions">optional</a>),
     378      *         or if the specified collection is null
     379      * @see #remove(Object)
     380      * @see #contains(Object)
     381      */
     382     boolean removeAll(Collection<?> c);
     383
     384     /**
     385      * Retains only the elements in this list that are contained in the
     386      * specified collection (optional operation).  In other words, removes
     387      * from this list all of its elements that are not contained in the
     388      * specified collection.
     389      *
     390      * @param c collection containing elements to be retained in this list
     391      * @return {@code true} if this list changed as a result of the call
     392      * @throws UnsupportedOperationException if the {@code retainAll} operation
     393      *         is not supported by this list
     394      * @throws ClassCastException if the class of an element of this list
     395      *         is incompatible with the specified collection
     396      * (<a href="Collection.html#optional-restrictions">optional</a>)
     397      * @throws NullPointerException if this list contains a null element and the
     398      *         specified collection does not permit null elements
     399      *         (<a href="Collection.html#optional-restrictions">optional</a>),
     400      *         or if the specified collection is null
     401      * @see #remove(Object)
     402      * @see #contains(Object)
     403      */
     404     boolean retainAll(Collection<?> c);
     405
     406     /**
     407      * Replaces each element of this list with the result of applying the
     408      * operator to that element.  Errors or runtime exceptions thrown by
     409      * the operator are relayed to the caller.
     410      *
     411      * @implSpec
     412      * The default implementation is equivalent to, for this {@code list}:
     413      * <pre>{@code
     414      *     final ListIterator<E> li = list.listIterator();
     415      *     while (li.hasNext()) {
     416      *         li.set(operator.apply(li.next()));
     417      *     }
     418      * }</pre>
     419      *
     420      * If the list's list-iterator does not support the {@code set} operation
     421      * then an {@code UnsupportedOperationException} will be thrown when
     422      * replacing the first element.
     423      *
     424      * @param operator the operator to apply to each element
     425      * @throws UnsupportedOperationException if this list is unmodifiable.
     426      *         Implementations may throw this exception if an element
     427      *         cannot be replaced or if, in general, modification is not
     428      *         supported
     429      * @throws NullPointerException if the specified operator is null or
     430      *         if the operator result is a null value and this list does
     431      *         not permit null elements
     432      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     433      * @since 1.8
     434      */
     435     default void replaceAll(UnaryOperator<E> operator) {
     436         Objects.requireNonNull(operator);
     437         final ListIterator<E> li = this.listIterator();
     438         while (li.hasNext()) {
     439             li.set(operator.apply(li.next()));
     440         }
     441     }
     442
     443     /**
     444      * Sorts this list according to the order induced by the specified
     445      * {@link Comparator}.  The sort is <i>stable</i>: this method must not
     446      * reorder equal elements.
     447      *
     448      * <p>All elements in this list must be <i>mutually comparable</i> using the
     449      * specified comparator (that is, {@code c.compare(e1, e2)} must not throw
     450      * a {@code ClassCastException} for any elements {@code e1} and {@code e2}
     451      * in the list).
     452      *
     453      * <p>If the specified comparator is {@code null} then all elements in this
     454      * list must implement the {@link Comparable} interface and the elements'
     455      * {@linkplain Comparable natural ordering} should be used.
     456      *
     457      * <p>This list must be modifiable, but need not be resizable.
     458      *
     459      * @implSpec
     460      * The default implementation obtains an array containing all elements in
     461      * this list, sorts the array, and iterates over this list resetting each
     462      * element from the corresponding position in the array. (This avoids the
     463      * n<sup>2</sup> log(n) performance that would result from attempting
     464      * to sort a linked list in place.)
     465      *
     466      * @implNote
     467      * This implementation is a stable, adaptive, iterative mergesort that
     468      * requires far fewer than n lg(n) comparisons when the input array is
     469      * partially sorted, while offering the performance of a traditional
     470      * mergesort when the input array is randomly ordered.  If the input array
     471      * is nearly sorted, the implementation requires approximately n
     472      * comparisons.  Temporary storage requirements vary from a small constant
     473      * for nearly sorted input arrays to n/2 object references for randomly
     474      * ordered input arrays.
     475      *
     476      * <p>The implementation takes equal advantage of ascending and
     477      * descending order in its input array, and can take advantage of
     478      * ascending and descending order in different parts of the same
     479      * input array.  It is well-suited to merging two or more sorted arrays:
     480      * simply concatenate the arrays and sort the resulting array.
     481      *
     482      * <p>The implementation was adapted from Tim Peters's list sort for Python
     483      * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
     484      * TimSort</a>).  It uses techniques from Peter McIlroy's "Optimistic
     485      * Sorting and Information Theoretic Complexity", in Proceedings of the
     486      * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
     487      * January 1993.
     488      *
     489      * @param c the {@code Comparator} used to compare list elements.
     490      *          A {@code null} value indicates that the elements'
     491      *          {@linkplain Comparable natural ordering} should be used
     492      * @throws ClassCastException if the list contains elements that are not
     493      *         <i>mutually comparable</i> using the specified comparator
     494      * @throws UnsupportedOperationException if the list's list-iterator does
     495      *         not support the {@code set} operation
     496      * @throws IllegalArgumentException
     497      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     498      *         if the comparator is found to violate the {@link Comparator}
     499      *         contract
     500      * @since 1.8
     501      */
     502     @SuppressWarnings({"unchecked", "rawtypes"})
     503     default void sort(Comparator<? super E> c) {
     504         Object[] a = this.toArray();
     505         Arrays.sort(a, (Comparator) c);
     506         ListIterator<E> i = this.listIterator();
     507         for (Object e : a) {
     508             i.next();
     509             i.set((E) e);
     510         }
     511     }
     512
     513     /**
     514      * Removes all of the elements from this list (optional operation).
     515      * The list will be empty after this call returns.
     516      *
     517      * @throws UnsupportedOperationException if the {@code clear} operation
     518      *         is not supported by this list
     519      */
     520     void clear();
     521
     522
     523     // Comparison and hashing
     524
     525     /**
     526      * Compares the specified object with this list for equality.  Returns
     527      * {@code true} if and only if the specified object is also a list, both
     528      * lists have the same size, and all corresponding pairs of elements in
     529      * the two lists are <i>equal</i>.  (Two elements {@code e1} and
     530      * {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
     531      * In other words, two lists are defined to be
     532      * equal if they contain the same elements in the same order.  This
     533      * definition ensures that the equals method works properly across
     534      * different implementations of the {@code List} interface.
     535      *
     536      * @param o the object to be compared for equality with this list
     537      * @return {@code true} if the specified object is equal to this list
     538      */
     539     boolean equals(Object o);
     540
     541     /**
     542      * Returns the hash code value for this list.  The hash code of a list
     543      * is defined to be the result of the following calculation:
     544      * <pre>{@code
     545      *     int hashCode = 1;
     546      *     for (E e : list)
     547      *         hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
     548      * }</pre>
     549      * This ensures that {@code list1.equals(list2)} implies that
     550      * {@code list1.hashCode()==list2.hashCode()} for any two lists,
     551      * {@code list1} and {@code list2}, as required by the general
     552      * contract of {@link Object#hashCode}.
     553      *
     554      * @return the hash code value for this list
     555      * @see Object#equals(Object)
     556      * @see #equals(Object)
     557      */
     558     int hashCode();
     559
     560
     561     // Positional Access Operations
     562
     563     /**
     564      * Returns the element at the specified position in this list.
     565      *
     566      * @param index index of the element to return
     567      * @return the element at the specified position in this list
     568      * @throws IndexOutOfBoundsException if the index is out of range
     569      *         ({@code index < 0 || index >= size()})
     570      */
     571     E get(int index);
     572
     573     /**
     574      * Replaces the element at the specified position in this list with the
     575      * specified element (optional operation).
     576      *
     577      * @param index index of the element to replace
     578      * @param element element to be stored at the specified position
     579      * @return the element previously at the specified position
     580      * @throws UnsupportedOperationException if the {@code set} operation
     581      *         is not supported by this list
     582      * @throws ClassCastException if the class of the specified element
     583      *         prevents it from being added to this list
     584      * @throws NullPointerException if the specified element is null and
     585      *         this list does not permit null elements
     586      * @throws IllegalArgumentException if some property of the specified
     587      *         element prevents it from being added to this list
     588      * @throws IndexOutOfBoundsException if the index is out of range
     589      *         ({@code index < 0 || index >= size()})
     590      */
     591     E set(int index, E element);
     592
     593     /**
     594      * Inserts the specified element at the specified position in this list
     595      * (optional operation).  Shifts the element currently at that position
     596      * (if any) and any subsequent elements to the right (adds one to their
     597      * indices).
     598      *
     599      * @param index index at which the specified element is to be inserted
     600      * @param element element to be inserted
     601      * @throws UnsupportedOperationException if the {@code add} operation
     602      *         is not supported by this list
     603      * @throws ClassCastException if the class of the specified element
     604      *         prevents it from being added to this list
     605      * @throws NullPointerException if the specified element is null and
     606      *         this list does not permit null elements
     607      * @throws IllegalArgumentException if some property of the specified
     608      *         element prevents it from being added to this list
     609      * @throws IndexOutOfBoundsException if the index is out of range
     610      *         ({@code index < 0 || index > size()})
     611      */
     612     void add(int index, E element);
     613
     614     /**
     615      * Removes the element at the specified position in this list (optional
     616      * operation).  Shifts any subsequent elements to the left (subtracts one
     617      * from their indices).  Returns the element that was removed from the
     618      * list.
     619      *
     620      * @param index the index of the element to be removed
     621      * @return the element previously at the specified position
     622      * @throws UnsupportedOperationException if the {@code remove} operation
     623      *         is not supported by this list
     624      * @throws IndexOutOfBoundsException if the index is out of range
     625      *         ({@code index < 0 || index >= size()})
     626      */
     627     E remove(int index);
     628
     629
     630     // Search Operations
     631
     632     /**
     633      * Returns the index of the first occurrence of the specified element
     634      * in this list, or -1 if this list does not contain the element.
     635      * More formally, returns the lowest index {@code i} such that
     636      * {@code Objects.equals(o, get(i))},
     637      * or -1 if there is no such index.
     638      *
     639      * @param o element to search for
     640      * @return the index of the first occurrence of the specified element in
     641      *         this list, or -1 if this list does not contain the element
     642      * @throws ClassCastException if the type of the specified element
     643      *         is incompatible with this list
     644      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     645      * @throws NullPointerException if the specified element is null and this
     646      *         list does not permit null elements
     647      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     648      */
     649     int indexOf(Object o);
     650
     651     /**
     652      * Returns the index of the last occurrence of the specified element
     653      * in this list, or -1 if this list does not contain the element.
     654      * More formally, returns the highest index {@code i} such that
     655      * {@code Objects.equals(o, get(i))},
     656      * or -1 if there is no such index.
     657      *
     658      * @param o element to search for
     659      * @return the index of the last occurrence of the specified element in
     660      *         this list, or -1 if this list does not contain the element
     661      * @throws ClassCastException if the type of the specified element
     662      *         is incompatible with this list
     663      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     664      * @throws NullPointerException if the specified element is null and this
     665      *         list does not permit null elements
     666      *         (<a href="Collection.html#optional-restrictions">optional</a>)
     667      */
     668     int lastIndexOf(Object o);
     669
     670
     671     // List Iterators
     672
     673     /**
     674      * Returns a list iterator over the elements in this list (in proper
     675      * sequence).
     676      *
     677      * @return a list iterator over the elements in this list (in proper
     678      *         sequence)
     679      */
     680     ListIterator<E> listIterator();
     681
     682     /**
     683      * Returns a list iterator over the elements in this list (in proper
     684      * sequence), starting at the specified position in the list.
     685      * The specified index indicates the first element that would be
     686      * returned by an initial call to {@link ListIterator#next next}.
     687      * An initial call to {@link ListIterator#previous previous} would
     688      * return the element with the specified index minus one.
     689      *
     690      * @param index index of the first element to be returned from the
     691      *        list iterator (by a call to {@link ListIterator#next next})
     692      * @return a list iterator over the elements in this list (in proper
     693      *         sequence), starting at the specified position in the list
     694      * @throws IndexOutOfBoundsException if the index is out of range
     695      *         ({@code index < 0 || index > size()})
     696      */
     697     ListIterator<E> listIterator(int index);
     698
     699     // View
     700
     701     /**
     702      * Returns a view of the portion of this list between the specified
     703      * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.  (If
     704      * {@code fromIndex} and {@code toIndex} are equal, the returned list is
     705      * empty.)  The returned list is backed by this list, so non-structural
     706      * changes in the returned list are reflected in this list, and vice-versa.
     707      * The returned list supports all of the optional list operations supported
     708      * by this list.<p>
     709      *
     710      * This method eliminates the need for explicit range operations (of
     711      * the sort that commonly exist for arrays).  Any operation that expects
     712      * a list can be used as a range operation by passing a subList view
     713      * instead of a whole list.  For example, the following idiom
     714      * removes a range of elements from a list:
     715      * <pre>{@code
     716      *      list.subList(from, to).clear();
     717      * }</pre>
     718      * Similar idioms may be constructed for {@code indexOf} and
     719      * {@code lastIndexOf}, and all of the algorithms in the
     720      * {@code Collections} class can be applied to a subList.<p>
     721      *
     722      * The semantics of the list returned by this method become undefined if
     723      * the backing list (i.e., this list) is <i>structurally modified</i> in
     724      * any way other than via the returned list.  (Structural modifications are
     725      * those that change the size of this list, or otherwise perturb it in such
     726      * a fashion that iterations in progress may yield incorrect results.)
     727      *
     728      * @param fromIndex low endpoint (inclusive) of the subList
     729      * @param toIndex high endpoint (exclusive) of the subList
     730      * @return a view of the specified range within this list
     731      * @throws IndexOutOfBoundsException for an illegal endpoint index value
     732      *         ({@code fromIndex < 0 || toIndex > size ||
     733      *         fromIndex > toIndex})
     734      */
     735     List<E> subList(int fromIndex, int toIndex);
     736
     737     /**
     738      * Creates a {@link Spliterator} over the elements in this list.
     739      *
     740      * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
     741      * {@link Spliterator#ORDERED}.  Implementations should document the
     742      * reporting of additional characteristic values.
     743      *
     744      * @implSpec
     745      * The default implementation creates a
     746      * <em><a href="Spliterator.html#binding">late-binding</a></em>
     747      * spliterator as follows:
     748      * <ul>
     749      * <li>If the list is an instance of {@link RandomAccess} then the default
     750      *     implementation creates a spliterator that traverses elements by
     751      *     invoking the method {@link List#get}.  If such invocation results or
     752      *     would result in an {@code IndexOutOfBoundsException} then the
     753      *     spliterator will <em>fail-fast</em> and throw a
     754      *     {@code ConcurrentModificationException}.
     755      *     If the list is also an instance of {@link AbstractList} then the
     756      *     spliterator will use the list's {@link AbstractList#modCount modCount}
     757      *     field to provide additional <em>fail-fast</em> behavior.
     758      * <li>Otherwise, the default implementation creates a spliterator from the
     759      *     list's {@code Iterator}.  The spliterator inherits the
     760      *     <em>fail-fast</em> of the list's iterator.
     761      * </ul>
     762      *
     763      * @implNote
     764      * The created {@code Spliterator} additionally reports
     765      * {@link Spliterator#SUBSIZED}.
     766      *
     767      * @return a {@code Spliterator} over the elements in this list
     768      * @since 1.8
     769      */
     770     @Override
     771     default Spliterator<E> spliterator() {
     772         if (this instanceof RandomAccess) {
     773             return new AbstractList.RandomAccessSpliterator<>(this);
     774         } else {
     775             return Spliterators.spliterator(this, Spliterator.ORDERED);
     776         }
     777     }
     778
     779     /**
     780      * Returns an immutable list containing zero elements.
     781      *
     782      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     783      *
     784      * @param <E> the {@code List}'s element type
     785      * @return an empty {@code List}
     786      *
     787      * @since 9
     788      */
     789     static <E> List<E> of() {
     790         return ImmutableCollections.List0.instance();
     791     }
     792
     793     /**
     794      * Returns an immutable list containing one element.
     795      *
     796      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     797      *
     798      * @param <E> the {@code List}'s element type
     799      * @param e1 the single element
     800      * @return a {@code List} containing the specified element
     801      * @throws NullPointerException if the element is {@code null}
     802      *
     803      * @since 9
     804      */
     805     static <E> List<E> of(E e1) {
     806         return new ImmutableCollections.List1<>(e1);
     807     }
     808
     809     /**
     810      * Returns an immutable list containing two elements.
     811      *
     812      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     813      *
     814      * @param <E> the {@code List}'s element type
     815      * @param e1 the first element
     816      * @param e2 the second element
     817      * @return a {@code List} containing the specified elements
     818      * @throws NullPointerException if an element is {@code null}
     819      *
     820      * @since 9
     821      */
     822     static <E> List<E> of(E e1, E e2) {
     823         return new ImmutableCollections.List2<>(e1, e2);
     824     }
     825
     826     /**
     827      * Returns an immutable list containing three elements.
     828      *
     829      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     830      *
     831      * @param <E> the {@code List}'s element type
     832      * @param e1 the first element
     833      * @param e2 the second element
     834      * @param e3 the third element
     835      * @return a {@code List} containing the specified elements
     836      * @throws NullPointerException if an element is {@code null}
     837      *
     838      * @since 9
     839      */
     840     static <E> List<E> of(E e1, E e2, E e3) {
     841         return new ImmutableCollections.ListN<>(e1, e2, e3);
     842     }
     843
     844     /**
     845      * Returns an immutable list containing four elements.
     846      *
     847      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     848      *
     849      * @param <E> the {@code List}'s element type
     850      * @param e1 the first element
     851      * @param e2 the second element
     852      * @param e3 the third element
     853      * @param e4 the fourth element
     854      * @return a {@code List} containing the specified elements
     855      * @throws NullPointerException if an element is {@code null}
     856      *
     857      * @since 9
     858      */
     859     static <E> List<E> of(E e1, E e2, E e3, E e4) {
     860         return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
     861     }
     862
     863     /**
     864      * Returns an immutable list containing five elements.
     865      *
     866      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     867      *
     868      * @param <E> the {@code List}'s element type
     869      * @param e1 the first element
     870      * @param e2 the second element
     871      * @param e3 the third element
     872      * @param e4 the fourth element
     873      * @param e5 the fifth element
     874      * @return a {@code List} containing the specified elements
     875      * @throws NullPointerException if an element is {@code null}
     876      *
     877      * @since 9
     878      */
     879     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
     880         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
     881     }
     882
     883     /**
     884      * Returns an immutable list containing six elements.
     885      *
     886      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     887      *
     888      * @param <E> the {@code List}'s element type
     889      * @param e1 the first element
     890      * @param e2 the second element
     891      * @param e3 the third element
     892      * @param e4 the fourth element
     893      * @param e5 the fifth element
     894      * @param e6 the sixth element
     895      * @return a {@code List} containing the specified elements
     896      * @throws NullPointerException if an element is {@code null}
     897      *
     898      * @since 9
     899      */
     900     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
     901         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
     902                                                 e6);
     903     }
     904
     905     /**
     906      * Returns an immutable list containing seven elements.
     907      *
     908      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     909      *
     910      * @param <E> the {@code List}'s element type
     911      * @param e1 the first element
     912      * @param e2 the second element
     913      * @param e3 the third element
     914      * @param e4 the fourth element
     915      * @param e5 the fifth element
     916      * @param e6 the sixth element
     917      * @param e7 the seventh element
     918      * @return a {@code List} containing the specified elements
     919      * @throws NullPointerException if an element is {@code null}
     920      *
     921      * @since 9
     922      */
     923     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
     924         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
     925                                                 e6, e7);
     926     }
     927
     928     /**
     929      * Returns an immutable list containing eight elements.
     930      *
     931      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     932      *
     933      * @param <E> the {@code List}'s element type
     934      * @param e1 the first element
     935      * @param e2 the second element
     936      * @param e3 the third element
     937      * @param e4 the fourth element
     938      * @param e5 the fifth element
     939      * @param e6 the sixth element
     940      * @param e7 the seventh element
     941      * @param e8 the eighth element
     942      * @return a {@code List} containing the specified elements
     943      * @throws NullPointerException if an element is {@code null}
     944      *
     945      * @since 9
     946      */
     947     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
     948         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
     949                                                 e6, e7, e8);
     950     }
     951
     952     /**
     953      * Returns an immutable list containing nine elements.
     954      *
     955      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     956      *
     957      * @param <E> the {@code List}'s element type
     958      * @param e1 the first element
     959      * @param e2 the second element
     960      * @param e3 the third element
     961      * @param e4 the fourth element
     962      * @param e5 the fifth element
     963      * @param e6 the sixth element
     964      * @param e7 the seventh element
     965      * @param e8 the eighth element
     966      * @param e9 the ninth element
     967      * @return a {@code List} containing the specified elements
     968      * @throws NullPointerException if an element is {@code null}
     969      *
     970      * @since 9
     971      */
     972     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
     973         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
     974                                                 e6, e7, e8, e9);
     975     }
     976
     977     /**
     978      * Returns an immutable list containing ten elements.
     979      *
     980      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
     981      *
     982      * @param <E> the {@code List}'s element type
     983      * @param e1 the first element
     984      * @param e2 the second element
     985      * @param e3 the third element
     986      * @param e4 the fourth element
     987      * @param e5 the fifth element
     988      * @param e6 the sixth element
     989      * @param e7 the seventh element
     990      * @param e8 the eighth element
     991      * @param e9 the ninth element
     992      * @param e10 the tenth element
     993      * @return a {@code List} containing the specified elements
     994      * @throws NullPointerException if an element is {@code null}
     995      *
     996      * @since 9
     997      */
     998     static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
     999         return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
    1000                                                 e6, e7, e8, e9, e10);
    1001     }
    1002
    1003     /**
    1004      * Returns an immutable list containing an arbitrary number of elements.
    1005      * See <a href="#immutable">Immutable List Static Factory Methods</a> for details.
    1006      *
    1007      * @apiNote
    1008      * This method also accepts a single array as an argument. The element type of
    1009      * the resulting list will be the component type of the array, and the size of
    1010      * the list will be equal to the length of the array. To create a list with
    1011      * a single element that is an array, do the following:
    1012      *
    1013      * <pre>{@code
    1014      *     String[] array = ... ;
    1015      *     List<String[]> list = List.<String[]>of(array);
    1016      * }</pre>
    1017      *
    1018      * This will cause the {@link List#of(Object) List.of(E)} method
    1019      * to be invoked instead.
    1020      *
    1021      * @param <E> the {@code List}'s element type
    1022      * @param elements the elements to be contained in the list
    1023      * @return a {@code List} containing the specified elements
    1024      * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
    1025      *
    1026      * @since 9
    1027      */
    1028     @SafeVarargs
    1029     @SuppressWarnings("varargs")
    1030     static <E> List<E> of(E... elements) {
    1031         switch (elements.length) { // implicit null check of elements
    1032             case 0:
    1033                 return ImmutableCollections.List0.instance();
    1034             case 1:
    1035                 return new ImmutableCollections.List1<>(elements[0]);
    1036             case 2:
    1037                 return new ImmutableCollections.List2<>(elements[0], elements[1]);
    1038             default:
    1039                 return new ImmutableCollections.ListN<>(elements);
    1040         }
    1041     }

    1042 }
    --- EOF ---