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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
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 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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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 sequence).  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.

Unlike sets, lists typically allow duplicate elements.  More formally,
lists typically allow pairs of elements e1 and e2
such that 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.

The List interface places additional stipulations, beyond those
specified in the Collection interface, on the contracts of the
iterator, add, remove, equals, and
hashCode methods.  Declarations for other inherited methods are
also included here for convenience.

The 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 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.

The List interface provides a special iterator, called a
ListIterator, that allows element insertion and replacement, and
bidirectional access in addition to the normal operations that the
Iterator interface provides.  A method is provided to obtain a
list iterator that starts at a specified position in the list.

The 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.

The List interface provides two methods to efficiently insert and
remove multiple elements at an arbitrary point in the list.

Note: While it is permissible for lists to contain themselves as elements,
extreme caution is advised: the equals and hashCode
methods are no longer well defined on such a list.

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
NullPointerException or 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.

This interface is a member of the

Java Collections Framework.

Author: Josh Bloch,  Neal Gafter
See Also:
Since:1.2
/**
 * 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>.
 *
 * @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 Integer.MAX_VALUE elements, returns
Integer.MAX_VALUE.

Returns:the number of elements in this list
/**
     * 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 true if this list contains no elements.

Returns:true if this list contains no elements
/**
     * Returns <tt>true</tt> if this list contains no elements.
     *
     * @return <tt>true</tt> if this list contains no elements
     */
    boolean isEmpty();

    
Returns true if this list contains the specified element.
More formally, returns true if and only if this list contains
at least one element e such that
(o==null ? e==null : o.equals(e)).

Params:
  • o – element whose presence in this list is to be tested
Throws:
  • ClassCastException – if the type of the specified element
        is incompatible with this list (optional)
  • NullPointerException – if the specified element is null and this
        list does not permit null elements (optional)
Returns:true if this list contains the specified element
/**
     * 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 (optional)
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements (optional)
     */
    boolean contains(Object o);

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

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

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.

This method acts as bridge between array-based and collection-based
APIs.

See Also:
Returns:an array containing all of the elements in this list in proper
        sequence
/**
     * 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.

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 null.
(This is useful in determining the length of the list only if
the caller knows that the list does not contain any null elements.)

Like the 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. 
Suppose 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 String:

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

Note that toArray(new Object[0]) is identical in function to
toArray().

Params:
  • 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.
Throws:
Returns:an array containing the elements of this list
/**
     * 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).

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.

Params:
  • e – element to be appended to this list
Throws:
Returns:true (as specified by Collection.add)
/**
     * 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 i such that
(o==null ? get(i)==null : o.equals(get(i)))
(if such an element exists).  Returns true if this list
contained the specified element (or equivalently, if this list changed
as a result of the call).

Params:
  • o – element to be removed from this list, if present
Throws:
Returns:true if this list contained the specified element
/**
     * 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 (optional)
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements (optional)
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *         is not supported by this list
     */
    boolean remove(Object o);


    // Bulk Modification Operations

    
Returns true if this list contains all of the elements of the
specified collection.

Params:
  • c – collection to be checked for containment in this list
Throws:
  • ClassCastException – if the types of one or more elements
        in the specified collection are incompatible with this
        list (optional)
  • NullPointerException – if the specified collection contains one
        or more null elements and this list does not permit null
        elements (optional), or if the specified collection is null
See Also:
Returns:true if this list contains all of the elements of the
        specified collection
/**
     * 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 (optional)
     * @throws NullPointerException if the specified collection contains one
     *         or more null elements and this list does not permit null
     *         elements (optional), 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.)

Params:
  • c – collection containing elements to be added to this list
Throws:
  • UnsupportedOperationException – if the addAll operation
        is not supported by this list
  • ClassCastException – if the class of an element of the specified
        collection prevents it from being added to this list
  • 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
  • IllegalArgumentException – if some property of an element of the
        specified collection prevents it from being added to this list
See Also:
Returns:true if this list changed as a result of the call
/**
     * 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.)

Params:
  • index – index at which to insert the first element from the
             specified collection
  • c – collection containing elements to be added to this list
Throws:
  • UnsupportedOperationException – if the addAll operation
        is not supported by this list
  • ClassCastException – if the class of an element of the specified
        collection prevents it from being added to this list
  • 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
  • IllegalArgumentException – if some property of an element of the
        specified collection prevents it from being added to this list
  • IndexOutOfBoundsException – if the index is out of range
        (index < 0 || index > size())
Returns:true if this list changed as a result of the call
/**
     * 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).

Params:
  • c – collection containing elements to be removed from this list
Throws:
  • UnsupportedOperationException – if the removeAll operation
        is not supported by this list
  • ClassCastException – if the class of an element of this list
        is incompatible with the specified collection (optional)
  • NullPointerException – if this list contains a null element and the
        specified collection does not permit null elements (optional),
        or if the specified collection is null
See Also:
Returns:true if this list changed as a result of the call
/**
     * 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 (optional)
     * @throws NullPointerException if this list contains a null element and the
     *         specified collection does not permit null elements (optional),
     *         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.

Params:
  • c – collection containing elements to be retained in this list
Throws:
  • UnsupportedOperationException – if the retainAll operation
        is not supported by this list
  • ClassCastException – if the class of an element of this list
        is incompatible with the specified collection (optional)
  • NullPointerException – if this list contains a null element and the
        specified collection does not permit null elements (optional),
        or if the specified collection is null
See Also:
Returns:true if this list changed as a result of the call
/**
     * 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 (optional)
     * @throws NullPointerException if this list contains a null element and the
     *         specified collection does not permit null elements (optional),
     *         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 clear operation
        is not supported by this list
/**
     * 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
true 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 equal.  (Two elements e1 and
e2 are equal if (e1==null ? e2==null :
e1.equals(e2)).)  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 List interface.

Params:
  • o – the object to be compared for equality with this list
Returns:true if the specified object is equal to this list
/**
     * 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:

 int hashCode = 1;
 for (E e : list)
     hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());


This ensures that list1.equals(list2) implies that
list1.hashCode()==list2.hashCode() for any two lists,
list1 and list2, as required by the general contract of Object.hashCode. 
See Also:
Returns:the hash code value for this list
/**
     * 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.

Params:
  • index – index of the element to return
Throws:
Returns:the element at the specified position in this list
/**
     * 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).

Params:
  • index – index of the element to replace
  • element – element to be stored at the specified position
Throws:
Returns:the element previously at the specified position
/**
     * 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).

Params:
  • index – index at which the specified element is to be inserted
  • element – element to be inserted
Throws:
/**
     * 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.

Params:
  • index – the index of the element to be removed
Throws:
Returns:the element previously at the specified position
/**
     * 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 i such that
(o==null ? get(i)==null : o.equals(get(i))),
or -1 if there is no such index.

Params:
  • o – element to search for
Throws:
  • ClassCastException – if the type of the specified element
        is incompatible with this list (optional)
  • NullPointerException – if the specified element is null and this
        list does not permit null elements (optional)
Returns:the index of the first occurrence of the specified element in
        this list, or -1 if this list does not contain the element
/**
     * 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 (optional)
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements (optional)
     */
    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 i such that
(o==null ? get(i)==null : o.equals(get(i))),
or -1 if there is no such index.

Params:
  • o – element to search for
Throws:
  • ClassCastException – if the type of the specified element
        is incompatible with this list (optional)
  • NullPointerException – if the specified element is null and this
        list does not permit null elements (optional)
Returns:the index of the last occurrence of the specified element in
        this list, or -1 if this list does not contain the element
/**
     * 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 (optional)
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements (optional)
     */
    int lastIndexOf(Object o);


    // List Iterators

    
Returns a list iterator over the elements in this list (in proper
sequence).

Returns:a list iterator over the elements in this list (in proper
        sequence)
/**
     * 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 next. An initial call to previous would return the element with the specified index minus one. 
Params:
  • index – index of the first element to be returned from the list iterator (by a call to next)
Throws:
Returns:a list iterator over the elements in this list (in proper
        sequence), starting at the specified position in the list
/**
     * 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
fromIndex, inclusive, and toIndex, exclusive.  (If
fromIndex and toIndex 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.

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:

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


Similar idioms may be constructed for indexOf and
lastIndexOf, and all of the algorithms in the
Collections class can be applied to a subList.

The semantics of the list returned by this method become undefined if
the backing list (i.e., this list) is structurally modified 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.)

Params:
  • fromIndex – low endpoint (inclusive) of the subList
  • toIndex – high endpoint (exclusive) of the subList
Throws:
Returns:a view of the specified range within this list
/**
     * 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);
}