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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  *

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  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

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

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  * accompanied this code).

  *

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  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 package java.util;

 /**

  * 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 <tt>e1</tt> and <tt>e2</tt>

  * such that <tt>e1.equals(e2)</tt>, 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 <tt>List</tt> interface places additional stipulations, beyond those

  * specified in the <tt>Collection</tt> interface, on the contracts of the

  * <tt>iterator</tt>, <tt>add</tt>, <tt>remove</tt>, <tt>equals</tt>, and

  * <tt>hashCode</tt> methods.  Declarations for other inherited methods are

  * also included here for convenience.<p>

  *

  * The <tt>List</tt> 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 <tt>LinkedList</tt> 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 <tt>List</tt> interface provides a special iterator, called a

  * <tt>ListIterator</tt>, that allows element insertion and replacement, and

  * bidirectional access in addition to the normal operations that the

  * <tt>Iterator</tt> interface provides.  A method is provided to obtain a

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

  *

  * The <tt>List</tt> 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 <tt>List</tt> 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 <tt>equals</tt> and <tt>hashCode</tt>

  * 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

  * <tt>NullPointerException</tt> or <tt>ClassCastException</tt>.  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.

  *

  * <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 <tt>Integer.MAX_VALUE</tt> elements, returns

      * <tt>Integer.MAX_VALUE</tt>.

      *

      * @return the number of elements in this list

      */

     int size();

     /**

      * Returns <tt>true</tt> if this list contains no elements.

      *

      * @return <tt>true</tt> if this list contains no elements

      */

     boolean isEmpty();

     /**

      * Returns <tt>true</tt> if this list contains the specified element.

      * More formally, returns <tt>true</tt> if and only if this list contains

      * at least one element <tt>e</tt> such that

      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.

      *

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

      * @return <tt>true</tt> 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 <tt>null</tt>.

      * (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 <tt>x</tt> is a list known to contain only strings.

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

      * allocated array of <tt>String</tt>:

      *

      * <pre>

      *     String[] y = x.toArray(new String[0]);</pre>

      *

      * Note that <tt>toArray(new Object[0])</tt> is identical in function to

      * <tt>toArray()</tt>.

      *

      * @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 <tt>true</tt> (as specified by {@link Collection#add})

      * @throws UnsupportedOperationException if the <tt>add</tt> 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 <tt>i</tt> such that

      * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>

      * (if such an element exists).  Returns <tt>true</tt> 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 <tt>true</tt> 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 <tt>remove</tt> operation

      *         is not supported by this list

      */

     boolean remove(Object o);

     // Bulk Modification Operations

     /**

      * Returns <tt>true</tt> if this list contains all of the elements of the

      * specified collection.

      *

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

      * @return <tt>true</tt> 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 <tt>true</tt> if this list changed as a result of the call

      * @throws UnsupportedOperationException if the <tt>addAll</tt> 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 <tt>true</tt> if this list changed as a result of the call

      * @throws UnsupportedOperationException if the <tt>addAll</tt> 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

      *         (<tt>index &lt; 0 || index &gt; size()</tt>)

      */

     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 <tt>true</tt> if this list changed as a result of the call

      * @throws UnsupportedOperationException if the <tt>removeAll</tt> 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 <tt>true</tt> if this list changed as a result of the call

      * @throws UnsupportedOperationException if the <tt>retainAll</tt> 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);

     /**

      * Removes all of the elements from this list (optional operation).

      * The list will be empty after this call returns.

      *

      * @throws UnsupportedOperationException if the <tt>clear</tt> operation

      *         is not supported by this list

      */

     void clear();

     // Comparison and hashing

     /**

      * Compares the specified object with this list for equality.  Returns

      * <tt>true</tt> if and only if the specified object is also a list, both

      * lists have the same size, and all corresponding pairs of elements in

      * the two lists are <i>equal</i>.  (Two elements <tt>e1</tt> and

      * <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null :

      * e1.equals(e2))</tt>.)  In other words, two lists are defined to be

      * equal if they contain the same elements in the same order.  This

      * definition ensures that the equals method works properly across

      * different implementations of the <tt>List</tt> interface.

      *

      * @param o the object to be compared for equality with this list

      * @return <tt>true</tt> if the specified object is equal to this list

      */

     boolean equals(Object o);

     /**

      * Returns the hash code value for this list.  The hash code of a list

      * is defined to be the result of the following calculation:

      * <pre>

      *  int hashCode = 1;

      *  for (E e : list)

      *      hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());

      * </pre>

      * This ensures that <tt>list1.equals(list2)</tt> implies that

      * <tt>list1.hashCode()==list2.hashCode()</tt> for any two lists,

      * <tt>list1</tt> and <tt>list2</tt>, as required by the general

      * contract of {@link Object#hashCode}.

      *

      * @return the hash code value for this list

      * @see Object#equals(Object)

      * @see #equals(Object)

      */

     int hashCode();

     // Positional Access Operations

     /**

      * Returns the element at the specified position in this list.

      *

      * @param index index of the element to return

      * @return the element at the specified position in this list

      * @throws IndexOutOfBoundsException if the index is out of range

      *         (<tt>index &lt; 0 || index &gt;= size()</tt>)

      */

     E get(int index);

     /**

      * Replaces the element at the specified position in this list with the

      * specified element (optional operation).

      *

      * @param index index of the element to replace

      * @param element element to be stored at the specified position

      * @return the element previously at the specified position

      * @throws UnsupportedOperationException if the <tt>set</tt> 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 the specified

      *         element prevents it from being added to this list

      * @throws IndexOutOfBoundsException if the index is out of range

      *         (<tt>index &lt; 0 || index &gt;= size()</tt>)

      */

     E set(int index, E element);

     /**

      * Inserts the specified element at the specified position in this list

      * (optional operation).  Shifts the element currently at that position

      * (if any) and any subsequent elements to the right (adds one to their

      * indices).

      *

      * @param index index at which the specified element is to be inserted

      * @param element element to be inserted

      * @throws UnsupportedOperationException if the <tt>add</tt> 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 the specified

      *         element prevents it from being added to this list

      * @throws IndexOutOfBoundsException if the index is out of range

      *         (<tt>index &lt; 0 || index &gt; size()</tt>)

      */

     void add(int index, E element);

     /**

      * Removes the element at the specified position in this list (optional

      * operation).  Shifts any subsequent elements to the left (subtracts one

      * from their indices).  Returns the element that was removed from the

      * list.

      *

      * @param index the index of the element to be removed

      * @return the element previously at the specified position

      * @throws UnsupportedOperationException if the <tt>remove</tt> operation

      *         is not supported by this list

      * @throws IndexOutOfBoundsException if the index is out of range

      *         (<tt>index &lt; 0 || index &gt;= size()</tt>)

      */

     E remove(int index);

     // Search Operations

     /**

      * Returns the index of the first occurrence of the specified element

      * in this list, or -1 if this list does not contain the element.

      * More formally, returns the lowest index <tt>i</tt> such that

      * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

      * or -1 if there is no such index.

      *

      * @param o element to search for

      * @return the index of the first occurrence of the specified element in

      *         this list, or -1 if this list does not contain the 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>)

      */

     int indexOf(Object o);

     /**

      * Returns the index of the last occurrence of the specified element

      * in this list, or -1 if this list does not contain the element.

      * More formally, returns the highest index <tt>i</tt> such that

      * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

      * or -1 if there is no such index.

      *

      * @param o element to search for

      * @return the index of the last occurrence of the specified element in

      *         this list, or -1 if this list does not contain the 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>)

      */

     int lastIndexOf(Object o);

     // List Iterators

     /**

      * Returns a list iterator over the elements in this list (in proper

      * sequence).

      *

      * @return a list iterator over the elements in this list (in proper

      *         sequence)

      */

     ListIterator<E> listIterator();

     /**

      * Returns a list iterator over the elements in this list (in proper

      * sequence), starting at the specified position in the list.

      * The specified index indicates the first element that would be

      * returned by an initial call to {@link ListIterator#next next}.

      * An initial call to {@link ListIterator#previous previous} would

      * return the element with the specified index minus one.

      *

      * @param index index of the first element to be returned from the

      *        list iterator (by a call to {@link ListIterator#next next})

      * @return a list iterator over the elements in this list (in proper

      *         sequence), starting at the specified position in the list

      * @throws IndexOutOfBoundsException if the index is out of range

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

      */

     ListIterator<E> listIterator(int index);

     // View

     /**

      * Returns a view of the portion of this list between the specified

      * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive.  (If

      * <tt>fromIndex</tt> and <tt>toIndex</tt> are equal, the returned list is

      * empty.)  The returned list is backed by this list, so non-structural

      * changes in the returned list are reflected in this list, and vice-versa.

      * The returned list supports all of the optional list operations supported

      * by this list.<p>

      *

      * This method eliminates the need for explicit range operations (of

      * the sort that commonly exist for arrays).  Any operation that expects

      * a list can be used as a range operation by passing a subList view

      * instead of a whole list.  For example, the following idiom

      * removes a range of elements from a list:

      * <pre>

      *      list.subList(from, to).clear();

      * </pre>

      * Similar idioms may be constructed for <tt>indexOf</tt> and

      * <tt>lastIndexOf</tt>, and all of the algorithms in the

      * <tt>Collections</tt> class can be applied to a subList.<p>

      *

      * The semantics of the list returned by this method become undefined if

      * the backing list (i.e., this list) is <i>structurally modified</i> in

      * any way other than via the returned list.  (Structural modifications are

      * those that change the size of this list, or otherwise perturb it in such

      * a fashion that iterations in progress may yield incorrect results.)

      *

      * @param fromIndex low endpoint (inclusive) of the subList

      * @param toIndex high endpoint (exclusive) of the subList

      * @return a view of the specified range within this list

      * @throws IndexOutOfBoundsException for an illegal endpoint index value

      *         (<tt>fromIndex &lt; 0 || toIndex &gt; size ||

      *         fromIndex &gt; toIndex</tt>)

      */

     List<E> subList(int fromIndex, int toIndex);

 }