/*
* @(#)List.java 1.39 06/10/10
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 only, as published by the Free Software Foundation.
*
* This program 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 at /legal/license.txt).
*
* 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, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*
*/
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 a 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}/../guide/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @version 1.32, 02/02/00
* @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 extends Collection {
// 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 ? e==null : 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 support null elements (optional).
*/
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 iterator();
/**
* Returns an array containing all of the elements in this list in proper
* sequence. Obeys the general contract of the
* <tt>Collection.toArray</tt> method.
*
* @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; the runtime type of the returned array is that of the
* specified array. Obeys the general contract of the
* <tt>Collection.toArray(Object[])</tt> method.
*
* @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 <tt>null</tt>.
*/
Object[] toArray(Object 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 o element to be appended to this list.
* @return <tt>true</tt> (as per the general contract of the
* <tt>Collection.add</tt> method).
*
* @throws UnsupportedOperationException if the <tt>add</tt> method 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 support null elements.
* @throws IllegalArgumentException if some aspect of this element
* prevents it from being added to this list.
*/
boolean add(Object o);
/**
* Removes the first occurrence in this list of the specified element
* (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 <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> (if
* such an element exists).
*
* @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 support null elements (optional).
* @throws UnsupportedOperationException if the <tt>remove</tt> method 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 (optional).
* @throws NullPointerException if the specified collection contains one
* or more null elements and this list does not support null
* elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @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 unspecified 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 whose elements are 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> method is
* not supported by this list.
* @throws ClassCastException if the class of an element in 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 support null
* elements, or if the specified collection is <tt>null</tt>.
* @throws IllegalArgumentException if some aspect of an element in the
* specified collection prevents it from being added to this
* list.
* @see #add(Object)
*/
boolean addAll(Collection 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
* unspecified 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 first element from the specified
* collection.
* @param c elements to be inserted into this list.
* @return <tt>true</tt> if this list changed as a result of the call.
*
* @throws UnsupportedOperationException if the <tt>addAll</tt> method is
* not supported by this list.
* @throws ClassCastException if the class of one of elements 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 support null
* elements, or if the specified collection is <tt>null</tt>.
* @throws IllegalArgumentException if some aspect of one of elements of
* the specified collection prevents it from being added to
* this list.
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index > size()).
*/
boolean addAll(int index, Collection c);
/**
* Removes from this list all the elements that are contained in the
* specified collection (optional operation).
*
* @param c collection that defines which elements will 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> method
* is not supported by this list.
* @throws ClassCastException if the types of one or more elements
* in this list are incompatible with the specified
* collection (optional).
* @throws NullPointerException if this list contains one or more
* null elements and the specified collection does not support
* null elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @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 the elements that are not contained in the specified
* collection.
*
* @param c collection that defines which elements this set will retain.
*
* @return <tt>true</tt> if this list changed as a result of the call.
*
* @throws UnsupportedOperationException if the <tt>retainAll</tt> method
* is not supported by this list.
* @throws ClassCastException if the types of one or more elements
* in this list are incompatible with the specified
* collection (optional).
* @throws NullPointerException if this list contains one or more
* null elements and the specified collection does not support
* null elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @see #remove(Object)
* @see #contains(Object)
*/
boolean retainAll(Collection c);
/**
* Removes all of the elements from this list (optional operation). This
* list will be empty after this call returns (unless it throws an
* exception).
*
* @throws UnsupportedOperationException if the <tt>clear</tt> method 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>
* hashCode = 1;
* Iterator i = list.iterator();
* while (i.hasNext()) {
* Object obj = i.next();
* hashCode = 31*hashCode + (obj==null ? 0 : obj.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 <tt>Object.hashCode</tt>.
*
* @return the hash code value for this list.
* @see Object#hashCode()
* @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 element to return.
* @return the element at the specified position in this list.
*
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index >= size()).
*/
Object get(int index);
/**
* Replaces the element at the specified position in this list with the
* specified element (optional operation).
*
* @param index index of 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> method 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 support null elements.
* @throws IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list.
* @throws IndexOutOfBoundsException if the index is out of range
* (index < 0 || index >= size()).
*/
Object set(int index, Object 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> method 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 support null elements.
* @throws IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list.
* @throws IndexOutOfBoundsException if the index is out of range
* (index < 0 || index > size()).
*/
void add(int index, Object 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 removed.
* @return the element previously at the specified position.
*
* @throws UnsupportedOperationException if the <tt>remove</tt> method is
* not supported by this list.
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index >= size()).
*/
Object remove(int index);
// Search Operations
/**
* Returns the index in this list of the first occurrence of the specified
* element, or -1 if this list does not contain this element.
* More formally, returns the lowest index <tt>i</tt> such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
* or -1 if there is no such index.
*
* @param o element to search for.
* @return the index in this list of the first occurrence of the specified
* element, or -1 if this list does not contain this 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 support null elements (optional).
*/
int indexOf(Object o);
/**
* Returns the index in this list of the last occurrence of the specified
* element, or -1 if this list does not contain this element.
* More formally, returns the highest index <tt>i</tt> such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
* or -1 if there is no such index.
*
* @param o element to search for.
* @return the index in this list of the last occurrence of the specified
* element, or -1 if this list does not contain this 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 support null elements (optional).
*/
int lastIndexOf(Object o);
// List Iterators
/**
* Returns a list iterator of the elements in this list (in proper
* sequence).
*
* @return a list iterator of the elements in this list (in proper
* sequence).
*/
ListIterator listIterator();
/**
* Returns a list iterator of the elements in this list (in proper
* sequence), starting at the specified position in this list. The
* specified index indicates the first element that would be returned by
* an initial call to the <tt>next</tt> method. An initial call to
* the <tt>previous</tt> method would return the element with the
* specified index minus one.
*
* @param index index of first element to be returned from the
* list iterator (by a call to the <tt>next</tt> method).
* @return a list iterator of the elements in this list (in proper
* sequence), starting at the specified position in this list.
* @throws IndexOutOfBoundsException if the index is out of range (index
* < 0 || index > size()).
*/
ListIterator 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
* (fromIndex < 0 || toIndex > size || fromIndex > toIndex).
*/
List subList(int fromIndex, int toIndex);
}