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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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package java.util;

import java.util.function.UnaryOperator;

/**

 * An ordered collection (also known as a <i>sequence</i>).  The user of this

 * interface has precise control over where in the list each element is

 * inserted.  The user can access elements by their integer index (position in

 * the list), and search for elements in the list.<p>

 *

 * Unlike sets, lists typically allow duplicate elements.  More formally,

 * lists typically allow pairs of elements {@code e1} and {@code e2}

 * such that {@code e1.equals(e2)}, and they typically allow multiple

 * null elements if they allow null elements at all.  It is not inconceivable

 * that someone might wish to implement a list that prohibits duplicates, by

 * throwing runtime exceptions when the user attempts to insert them, but we

 * expect this usage to be rare.<p>

 *

 * The {@code List} interface places additional stipulations, beyond those

 * specified in the {@code Collection} interface, on the contracts of the

 * {@code iterator}, {@code add}, {@code remove}, {@code equals}, and

 * {@code hashCode} methods.  Declarations for other inherited methods are

 * also included here for convenience.<p>

 *

 * The {@code List} interface provides four methods for positional (indexed)

 * access to list elements.  Lists (like Java arrays) are zero based.  Note

 * that these operations may execute in time proportional to the index value

 * for some implementations (the {@code LinkedList} class, for

 * example). Thus, iterating over the elements in a list is typically

 * preferable to indexing through it if the caller does not know the

 * implementation.<p>

 *

 * The {@code List} interface provides a special iterator, called a

 * {@code ListIterator}, that allows element insertion and replacement, and

 * bidirectional access in addition to the normal operations that the

 * {@code Iterator} interface provides.  A method is provided to obtain a

 * list iterator that starts at a specified position in the list.<p>

 *

 * The {@code List} interface provides two methods to search for a specified

 * object.  From a performance standpoint, these methods should be used with

 * caution.  In many implementations they will perform costly linear

 * searches.<p>

 *

 * The {@code List} interface provides two methods to efficiently insert and

 * remove multiple elements at an arbitrary point in the list.<p>

 *

 * Note: While it is permissible for lists to contain themselves as elements,

 * extreme caution is advised: the {@code equals} and {@code hashCode}

 * methods are no longer well defined on such a list.

 *

 * <p>Some list implementations have restrictions on the elements that

 * they may contain.  For example, some implementations prohibit null elements,

 * and some have restrictions on the types of their elements.  Attempting to

 * add an ineligible element throws an unchecked exception, typically

 * {@code NullPointerException} or {@code ClassCastException}.  Attempting

 * to query the presence of an ineligible element may throw an exception,

 * or it may simply return false; some implementations will exhibit the former

 * behavior and some will exhibit the latter.  More generally, attempting an

 * operation on an ineligible element whose completion would not result in

 * the insertion of an ineligible element into the list may throw an

 * exception or it may succeed, at the option of the implementation.

 * Such exceptions are marked as "optional" in the specification for this

 * interface.

 *

 * <h2><a name="immutable">Immutable List Static Factory Methods</a></h2>

 * <p>The {@link List#of(Object...) List.of()} static factory methods

 * provide a convenient way to create immutable lists. The {@code List}

 * instances created by these methods have the following characteristics:

 *

 * <ul>

 * <li>They are <em>structurally immutable</em>. Elements cannot be added, removed,

 * or replaced. Attempts to do so result in {@code UnsupportedOperationException}.

 * However, if the contained elements are themselves mutable,

 * this may cause the List's contents to appear to change.

 * <li>They disallow {@code null} elements. Attempts to create them with

 * {@code null} elements result in {@code NullPointerException}.

 * <li>They are serializable if all elements are serializable.

 * <li>The order of elements in the list is the same as the order of the

 * provided arguments, or of the elements in the provided array.

 * <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.

 * Callers should make no assumptions about the identity of the returned instances.

 * Factories are free to create new instances or reuse existing ones. Therefore,

 * identity-sensitive operations on these instances (reference equality ({@code ==}),

 * identity hash code, and synchronization) are unreliable and should be avoided.

 * </ul>

 *

 * <p>This interface is a member of the

 * <a href="{@docRoot}/../technotes/guides/collections/index.html">

 * Java Collections Framework</a>.

 *

 * @param <E> the type of elements in this list

 *

 * @author  Josh Bloch

 * @author  Neal Gafter

 * @see Collection

 * @see Set

 * @see ArrayList

 * @see LinkedList

 * @see Vector

 * @see Arrays#asList(Object[])

 * @see Collections#nCopies(int, Object)

 * @see Collections#EMPTY_LIST

 * @see AbstractList

 * @see AbstractSequentialList

 * @since 1.2

 */

public interface List<E> extends Collection<E> {

    // Query Operations

    /**

     * Returns the number of elements in this list.  If this list contains

     * more than {@code Integer.MAX_VALUE} elements, returns

     * {@code Integer.MAX_VALUE}.

     *

     * @return the number of elements in this list

     */

    int size();

    /**

     * Returns {@code true} if this list contains no elements.

     *

     * @return {@code true} if this list contains no elements

     */

    boolean isEmpty();

    /**

     * Returns {@code true} if this list contains the specified element.

     * More formally, returns {@code true} if and only if this list contains

     * at least one element {@code e} such that

     * {@code Objects.equals(o, e)}.

     *

     * @param o element whose presence in this list is to be tested

     * @return {@code true} if this list contains the specified element

     * @throws ClassCastException if the type of the specified element

     *         is incompatible with this list

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws NullPointerException if the specified element is null and this

     *         list does not permit null elements

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     */

    boolean contains(Object o);

    /**

     * Returns an iterator over the elements in this list in proper sequence.

     *

     * @return an iterator over the elements in this list in proper sequence

     */

    Iterator<E> iterator();

    /**

     * Returns an array containing all of the elements in this list in proper

     * sequence (from first to last element).

     *

     * <p>The returned array will be "safe" in that no references to it are

     * maintained by this list.  (In other words, this method must

     * allocate a new array even if this list is backed by an array).

     * The caller is thus free to modify the returned array.

     *

     * <p>This method acts as bridge between array-based and collection-based

     * APIs.

     *

     * @return an array containing all of the elements in this list in proper

     *         sequence

     * @see Arrays#asList(Object[])

     */

    Object[] toArray();

    /**

     * Returns an array containing all of the elements in this list in

     * proper sequence (from first to last element); the runtime type of

     * the returned array is that of the specified array.  If the list fits

     * in the specified array, it is returned therein.  Otherwise, a new

     * array is allocated with the runtime type of the specified array and

     * the size of this list.

     *

     * <p>If the list fits in the specified array with room to spare (i.e.,

     * the array has more elements than the list), the element in the array

     * immediately following the end of the list is set to {@code null}.

     * (This is useful in determining the length of the list <i>only</i> if

     * the caller knows that the list does not contain any null elements.)

     *

     * <p>Like the {@link #toArray()} method, this method acts as bridge between

     * array-based and collection-based APIs.  Further, this method allows

     * precise control over the runtime type of the output array, and may,

     * under certain circumstances, be used to save allocation costs.

     *

     * <p>Suppose {@code x} is a list known to contain only strings.

     * The following code can be used to dump the list into a newly

     * allocated array of {@code String}:

     *

     * <pre>{@code

     *     String[] y = x.toArray(new String[0]);

     * }</pre>

     *

     * Note that {@code toArray(new Object[0])} is identical in function to

     * {@code toArray()}.

     *

     * @param a the array into which the elements of this list are to

     *          be stored, if it is big enough; otherwise, a new array of the

     *          same runtime type is allocated for this purpose.

     * @return an array containing the elements of this list

     * @throws ArrayStoreException if the runtime type of the specified array

     *         is not a supertype of the runtime type of every element in

     *         this list

     * @throws NullPointerException if the specified array is null

     */

    <T> T[] toArray(T[] a);

    // Modification Operations

    /**

     * Appends the specified element to the end of this list (optional

     * operation).

     *

     * <p>Lists that support this operation may place limitations on what

     * elements may be added to this list.  In particular, some

     * lists will refuse to add null elements, and others will impose

     * restrictions on the type of elements that may be added.  List

     * classes should clearly specify in their documentation any restrictions

     * on what elements may be added.

     *

     * @param e element to be appended to this list

     * @return {@code true} (as specified by {@link Collection#add})

     * @throws UnsupportedOperationException if the {@code add} operation

     *         is not supported by this list

     * @throws ClassCastException if the class of the specified element

     *         prevents it from being added to this list

     * @throws NullPointerException if the specified element is null and this

     *         list does not permit null elements

     * @throws IllegalArgumentException if some property of this element

     *         prevents it from being added to this list

     */

    boolean add(E e);

    /**

     * Removes the first occurrence of the specified element from this list,

     * if it is present (optional operation).  If this list does not contain

     * the element, it is unchanged.  More formally, removes the element with

     * the lowest index {@code i} such that

     * {@code Objects.equals(o, get(i))}

     * (if such an element exists).  Returns {@code true} if this list

     * contained the specified element (or equivalently, if this list changed

     * as a result of the call).

     *

     * @param o element to be removed from this list, if present

     * @return {@code true} if this list contained the specified element

     * @throws ClassCastException if the type of the specified element

     *         is incompatible with this list

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws NullPointerException if the specified element is null and this

     *         list does not permit null elements

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws UnsupportedOperationException if the {@code remove} operation

     *         is not supported by this list

     */

    boolean remove(Object o);

    // Bulk Modification Operations

    /**

     * Returns {@code true} if this list contains all of the elements of the

     * specified collection.

     *

     * @param  c collection to be checked for containment in this list

     * @return {@code true} if this list contains all of the elements of the

     *         specified collection

     * @throws ClassCastException if the types of one or more elements

     *         in the specified collection are incompatible with this

     *         list

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws NullPointerException if the specified collection contains one

     *         or more null elements and this list does not permit null

     *         elements

     *         (<a href="Collection.html#optional-restrictions">optional</a>),

     *         or if the specified collection is null

     * @see #contains(Object)

     */

    boolean containsAll(Collection<?> c);

    /**

     * Appends all of the elements in the specified collection to the end of

     * this list, in the order that they are returned by the specified

     * collection's iterator (optional operation).  The behavior of this

     * operation is undefined if the specified collection is modified while

     * the operation is in progress.  (Note that this will occur if the

     * specified collection is this list, and it's nonempty.)

     *

     * @param c collection containing elements to be added to this list

     * @return {@code true} if this list changed as a result of the call

     * @throws UnsupportedOperationException if the {@code addAll} operation

     *         is not supported by this list

     * @throws ClassCastException if the class of an element of the specified

     *         collection prevents it from being added to this list

     * @throws NullPointerException if the specified collection contains one

     *         or more null elements and this list does not permit null

     *         elements, or if the specified collection is null

     * @throws IllegalArgumentException if some property of an element of the

     *         specified collection prevents it from being added to this list

     * @see #add(Object)

     */

    boolean addAll(Collection<? extends E> c);

    /**

     * Inserts all of the elements in the specified collection into this

     * list at the specified position (optional operation).  Shifts the

     * element currently at that position (if any) and any subsequent

     * elements to the right (increases their indices).  The new elements

     * will appear in this list in the order that they are returned by the

     * specified collection's iterator.  The behavior of this operation is

     * undefined if the specified collection is modified while the

     * operation is in progress.  (Note that this will occur if the specified

     * collection is this list, and it's nonempty.)

     *

     * @param index index at which to insert the first element from the

     *              specified collection

     * @param c collection containing elements to be added to this list

     * @return {@code true} if this list changed as a result of the call

     * @throws UnsupportedOperationException if the {@code addAll} operation

     *         is not supported by this list

     * @throws ClassCastException if the class of an element of the specified

     *         collection prevents it from being added to this list

     * @throws NullPointerException if the specified collection contains one

     *         or more null elements and this list does not permit null

     *         elements, or if the specified collection is null

     * @throws IllegalArgumentException if some property of an element of the

     *         specified collection prevents it from being added to this list

     * @throws IndexOutOfBoundsException if the index is out of range

     *         ({@code index < 0 || index > size()})

     */

    boolean addAll(int index, Collection<? extends E> c);

    /**

     * Removes from this list all of its elements that are contained in the

     * specified collection (optional operation).

     *

     * @param c collection containing elements to be removed from this list

     * @return {@code true} if this list changed as a result of the call

     * @throws UnsupportedOperationException if the {@code removeAll} operation

     *         is not supported by this list

     * @throws ClassCastException if the class of an element of this list

     *         is incompatible with the specified collection

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws NullPointerException if this list contains a null element and the

     *         specified collection does not permit null elements

     *         (<a href="Collection.html#optional-restrictions">optional</a>),

     *         or if the specified collection is null

     * @see #remove(Object)

     * @see #contains(Object)

     */

    boolean removeAll(Collection<?> c);

    /**

     * Retains only the elements in this list that are contained in the

     * specified collection (optional operation).  In other words, removes

     * from this list all of its elements that are not contained in the

     * specified collection.

     *

     * @param c collection containing elements to be retained in this list

     * @return {@code true} if this list changed as a result of the call

     * @throws UnsupportedOperationException if the {@code retainAll} operation

     *         is not supported by this list

     * @throws ClassCastException if the class of an element of this list

     *         is incompatible with the specified collection

     * (<a href="Collection.html#optional-restrictions">optional</a>)

     * @throws NullPointerException if this list contains a null element and the

     *         specified collection does not permit null elements

     *         (<a href="Collection.html#optional-restrictions">optional</a>),

     *         or if the specified collection is null

     * @see #remove(Object)

     * @see #contains(Object)

     */

    boolean retainAll(Collection<?> c);

    /**

     * Replaces each element of this list with the result of applying the

     * operator to that element.  Errors or runtime exceptions thrown by

     * the operator are relayed to the caller.

     *

     * @implSpec

     * The default implementation is equivalent to, for this {@code list}:

     * <pre>{@code

     *     final ListIterator<E> li = list.listIterator();

     *     while (li.hasNext()) {

     *         li.set(operator.apply(li.next()));

     *     }

     * }</pre>

     *

     * If the list's list-iterator does not support the {@code set} operation

     * then an {@code UnsupportedOperationException} will be thrown when

     * replacing the first element.

     *

     * @param operator the operator to apply to each element

     * @throws UnsupportedOperationException if this list is unmodifiable.

     *         Implementations may throw this exception if an element

     *         cannot be replaced or if, in general, modification is not

     *         supported

     * @throws NullPointerException if the specified operator is null or

     *         if the operator result is a null value and this list does

     *         not permit null elements

     *         (<a href="Collection.html#optional-restrictions">optional</a>)

     * @since 1.8

     */

    default void replaceAll(UnaryOperator<E> operator) {

        Objects.requireNonNull(operator);

        final ListIterator<E> li = this.listIterator();

        while (li.hasNext()) {

            li.set(operator.apply(li.next()));

        }

    }

    /**

     * Sorts this list according to the order induced by the specified

     * {@link Comparator}.

     *

     * <p>All elements in this list must be <i>mutually comparable</i> using the

     * specified comparator (that is, {@code c.compare(e1, e2)} must not throw

     * a {@code ClassCastException} for any elements {@code e1} and {@code e2}

     * in the list).

     *

     * <p>If the specified comparator is {@code null} then all elements in this

     * list must implement the {@link Comparable} interface and the elements'

     * {@linkplain Comparable natural ordering} should be used.

     *

     * <p>This list must be modifiable, but need not be resizable.

     *

     * @implSpec

     * The default implementation obtains an array containing all elements in

     * this list, sorts the array, and iterates over this list resetting each

     * element from the corresponding position in the array. (This avoids the

     * n<sup>2</sup> log(n) performance that would result from attempting

     * to sort a linked list in place.)

     *

     * @implNote

     * This implementation is a stable, adaptive, iterative mergesort that

     * requires far fewer than n lg(n) comparisons when the input array is

     * partially sorted, while offering the performance of a traditional

     * mergesort when the input array is randomly ordered.  If the input array

     * is nearly sorted, the implementation requires approximately n

     * comparisons.  Temporary storage requirements vary from a small constant

     * for nearly sorted input arrays to n/2 object references for randomly

     * ordered input arrays.

     *

     * <p>The implementation takes equal advantage of ascending and

     * descending order in its input array, and can take advantage of

     * ascending and descending order in different parts of the same

     * input array.  It is well-suited to merging two or more sorted arrays:

     * simply concatenate the arrays and sort the resulting array.

     *

     * <p>The implementation was adapted from Tim Peters's list sort for Python

     * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">

     * TimSort</a>).  It uses techniques from Peter McIlroy's "Optimistic

     * Sorting and Information Theoretic Complexity", in Proceedings of the

     * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,

     * January 1993.

     *

     * @param c the {@code Comparator} used to compare list elements.

     *          A {@code null} value indicates that the elements'

     *          {@linkplain Comparable natural ordering} should be used

     * @throws ClassCastException if the list contains elements that are not

     *         <i>mutually comparable</i> using the specified comparator

     * @throws UnsupportedOperationException if the list's list-iterator does

     *         not support the {@code set} operation

     * @throws IllegalArgumentException

     *         (<a href="Collection.html#optional-restrictions">optional</a>)

     *         if the comparator is found to violate the {@link Comparator}

     *         contract

     * @since 1.8

     */

    @SuppressWarnings({"unchecked", "rawtypes"})

    default void sort(Comparator<? super E> c) {

        Object[] a = this.toArray();

        Arrays.sort(a, (Comparator) c);

        ListIterator<E> i = this.listIterator();

        for (Object e : a) {

            i.next();

            i.set((E) e);