/* List.java -- An ordered collection which allows indexed access
Copyright (C) 1998, 2001 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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it under the terms of the GNU General Public License as published by
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Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
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package java.util;
/**
* An ordered collection (also known as a list). This collection allows
* access to elements by position, as well as control on where elements
* are inserted. Unlike sets, duplicate elements are permitted by this
* general contract (if a subclass forbids duplicates, this should be
* documented).
* <p>
*
* List places additional requirements on <code>iterator</code>,
* <code>add</code>, <code>remove</code>, <code>equals</code>, and
* <code>hashCode</code>, in addition to requiring more methods. List
* indexing is 0-based (like arrays), although some implementations may
* require time proportional to the index to obtain an arbitrary element.
* The List interface is incompatible with Set; you cannot implement both
* simultaneously.
* <p>
*
* Lists also provide a <code>ListIterator</code> which allows bidirectional
* traversal and other features atop regular iterators. Lists can be
* searched for arbitrary elements, and allow easy insertion and removal
* of multiple elements in one method call.
* <p>
*
* Note: While lists may contain themselves as elements, this leads to
* undefined (usually infinite recursive) behavior for some methods like
* hashCode or equals.
*
* @author Original author unknown
* @author Eric Blake <ebb9@email.byu.edu>
* @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
* @status updated to 1.4
*/
public interface List extends Collection
{
/**
* Insert an element into the list at a given position (optional operation).
* This shifts all existing elements from that position to the end one
* index to the right. This version of add has no return, since it is
* assumed to always succeed if there is no exception.
*
* @param index the location to insert the item
* @param o the object to insert
* @throws UnsupportedOperationException if this list does not support the
* add operation
* @throws IndexOutOfBoundsException if index < 0 || index > size()
* @throws ClassCastException if o cannot be added to this list due to its
* type
* @throws IllegalArgumentException if o cannot be added to this list for
* some other reason
* @throws NullPointerException if o is null and this list doesn't support
* the addition of null values.
*/
void add(int index, Object o);
/**
* Add an element to the end of the list (optional operation). If the list
* imposes restraints on what can be inserted, such as no null elements,
* this should be documented.
*
* @param o the object to add
* @return true, as defined by Collection for a modified list
* @throws UnsupportedOperationException if this list does not support the
* add operation
* @throws ClassCastException if o cannot be added to this list due to its
* type
* @throws IllegalArgumentException if o cannot be added to this list for
* some other reason
* @throws NullPointerException if o is null and this list doesn't support
* the addition of null values.
*/
boolean add(Object o);
/**
* Insert the contents of a collection into the list at a given position
* (optional operation). Shift all elements at that position to the right
* by the number of elements inserted. This operation is undefined if
* this list is modified during the operation (for example, if you try
* to insert a list into itself).
*
* @param index the location to insert the collection
* @param c the collection to insert
* @return true if the list was modified by this action, that is, if c is
* non-empty
* @throws UnsupportedOperationException if this list does not support the
* addAll operation
* @throws IndexOutOfBoundsException if index < 0 || index > size()
* @throws ClassCastException if some element of c cannot be added to this
* list due to its type
* @throws IllegalArgumentException if some element of c cannot be added
* to this list for some other reason
* @throws NullPointerException if some element of c is null and this list
* doesn't support the addition of null values.
* @throws NullPointerException if the specified collection is null
* @see #add(int, Object)
*/
boolean addAll(int index, Collection c);
/**
* Add the contents of a collection to the end of the list (optional
* operation). This operation is undefined if this list is modified
* during the operation (for example, if you try to insert a list into
* itself).
*
* @param c the collection to add
* @return true if the list was modified by this action, that is, if c is
* non-empty
* @throws UnsupportedOperationException if this list does not support the
* addAll operation
* @throws ClassCastException if some element of c cannot be added to this
* list due to its type
* @throws IllegalArgumentException if some element of c cannot be added
* to this list for some other reason
* @throws NullPointerException if the specified collection is null
* @throws NullPointerException if some element of c is null and this list
* doesn't support the addition of null values.
* @see #add(Object)
*/
boolean addAll(Collection c);
/**
* Clear the list, such that a subsequent call to isEmpty() would return
* true (optional operation).
*
* @throws UnsupportedOperationException if this list does not support the
* clear operation
*/
void clear();
/**
* Test whether this list contains a given object as one of its elements.
* This is defined as the existence of an element e such that
* <code>o == null ? e == null : o.equals(e)</code>.
*
* @param o the element to look for
* @return true if this list contains the element
* @throws ClassCastException if the type of o is not a valid type
* for this list.
* @throws NullPointerException if o is null and the list doesn't
* support null values.
*/
boolean contains(Object o);
/**
* Test whether this list contains every element in a given collection.
*
* @param c the collection to test for
* @return true if for every element o in c, contains(o) would return true
* @throws NullPointerException if the collection is null
* @throws ClassCastException if the type of any element in c is not a valid
* type for this list.
* @throws NullPointerException if some element of c is null and this
* list does not support null values.
* @see #contains(Object)
*/
boolean containsAll(Collection c);
/**
* Test whether this list is equal to another object. A List is defined to be
* equal to an object if and only if that object is also a List, and the two
* lists have the same sequence. Two lists l1 and l2 are equal if and only
* if <code>l1.size() == l2.size()</code>, and for every integer n between 0
* and <code>l1.size() - 1</code> inclusive, <code>l1.get(n) == null ?
* l2.get(n) == null : l1.get(n).equals(l2.get(n))</code>.
*
* @param o the object to test for equality with this list
* @return true if o is equal to this list
* @see Object#equals(Object)
* @see #hashCode()
*/
boolean equals(Object o);
/**
* Get the element at a given index in this list.
*
* @param index the index of the element to be returned
* @return the element at index index in this list
* @throws IndexOutOfBoundsException if index < 0 || index >= size()
*/
Object get(int index);
/**
* Obtains a hash code for this list. In order to obey the general
* contract of the hashCode method of class Object, this value is
* calculated as follows:
*
<p><pre>hashCode = 1;
Iterator i = list.iterator();
while (i.hasNext())
{
Object obj = i.next();
hashCode = 31 * hashCode + (obj == null ? 0 : obj.hashCode());
}</pre>
*
* <p>This ensures that the general contract of Object.hashCode()
* is adhered to.
*
* @return the hash code of this list
* @see Object#hashCode()
* @see #equals(Object)
*/
int hashCode();
/**
* Obtain the first index at which a given object is to be found in this
* list.
*
* @param o the object to search for
* @return the least integer n such that <code>o == null ? get(n) == null :
* o.equals(get(n))</code>, or -1 if there is no such index.
* @throws ClassCastException if the type of o is not a valid
* type for this list.
* @throws NullPointerException if o is null and this
* list does not support null values.
*/
int indexOf(Object o);
/**
* Test whether this list is empty, that is, if size() == 0.
*
* @return true if this list contains no elements
*/
boolean isEmpty();
/**
* Obtain an Iterator over this list, whose sequence is the list order.
*
* @return an Iterator over the elements of this list, in order
*/
Iterator iterator();
/**
* Obtain the last index at which a given object is to be found in this
* list.
*
* @return the greatest integer n such that <code>o == null ? get(n) == null
* : o.equals(get(n))</code>, or -1 if there is no such index.
* @throws ClassCastException if the type of o is not a valid
* type for this list.
* @throws NullPointerException if o is null and this
* list does not support null values.
*/
int lastIndexOf(Object o);
/**
* Obtain a ListIterator over this list, starting at the beginning.
*
* @return a ListIterator over the elements of this list, in order, starting
* at the beginning
*/
ListIterator listIterator();
/**
* Obtain a ListIterator over this list, starting at a given position.
* A first call to next() would return the same as get(index), and a
* first call to previous() would return the same as get(index - 1).
*
* @param index the position, between 0 and size() inclusive, to begin the
* iteration from
* @return a ListIterator over the elements of this list, in order, starting
* at index
* @throws IndexOutOfBoundsException if index < 0 || index > size()
*/
ListIterator listIterator(int index);
/**
* Remove the element at a given position in this list (optional operation).
* Shifts all remaining elements to the left to fill the gap.
*
* @param index the position within the list of the object to remove
* @return the object that was removed
* @throws UnsupportedOperationException if this list does not support the
* remove operation
* @throws IndexOutOfBoundsException if index < 0 || index >= size()
*/
Object remove(int index);
/**
* Remove the first occurence of an object from this list (optional
* operation). That is, remove the first element e such that
* <code>o == null ? e == null : o.equals(e)</code>.
*
* @param o the object to remove
* @return true if the list changed as a result of this call, that is, if
* the list contained at least one occurrence of o
* @throws UnsupportedOperationException if this list does not support the
* remove operation
* @throws ClassCastException if the type of o is not a valid
* type for this list.
* @throws NullPointerException if o is null and this
* list does not support removing null values.
*/
boolean remove(Object o);
/**
* Remove all elements of a given collection from this list (optional
* operation). That is, remove every element e such that c.contains(e).
*
* @param c the collection to filter out
* @return true if this list was modified as a result of this call
* @throws UnsupportedOperationException if this list does not support the
* removeAll operation
* @throws NullPointerException if the collection is null
* @throws ClassCastException if the type of any element in c is not a valid
* type for this list.
* @throws NullPointerException if some element of c is null and this
* list does not support removing null values.
* @see #remove(Object)
* @see #contains(Object)
*/
boolean removeAll(Collection c);
/**
* Remove all elements of this list that are not contained in a given
* collection (optional operation). That is, remove every element e such
* that !c.contains(e).
*
* @param c the collection to retain
* @return true if this list was modified as a result of this call
* @throws UnsupportedOperationException if this list does not support the
* retainAll operation
* @throws NullPointerException if the collection is null
* @throws ClassCastException if the type of any element in c is not a valid
* type for this list.
* @throws NullPointerException if some element of c is null and this
* list does not support retaining null values.
* @see #remove(Object)
* @see #contains(Object)
*/
boolean retainAll(Collection c);
/**
* Replace an element of this list with another object (optional operation).
*
* @param index the position within this list of the element to be replaced
* @param o the object to replace it with
* @return the object that was replaced
* @throws UnsupportedOperationException if this list does not support the
* set operation
* @throws IndexOutOfBoundsException if index < 0 || index >= size()
* @throws ClassCastException if o cannot be added to this list due to its
* type
* @throws IllegalArgumentException if o cannot be added to this list for
* some other reason
* @throws NullPointerException if o is null and this
* list does not support null values.
*/
Object set(int index, Object o);
/**
* Get the number of elements in this list. If the list contains more
* than Integer.MAX_VALUE elements, return Integer.MAX_VALUE.
*
* @return the number of elements in the list
*/
int size();
/**
* Obtain a List view of a subsection of this list, from fromIndex
* (inclusive) to toIndex (exclusive). If the two indices are equal, the
* sublist is empty. The returned list should be modifiable if and only
* if this list is modifiable. Changes to the returned list should be
* reflected in this list. If this list is structurally modified in
* any way other than through the returned list, the result of any subsequent
* operations on the returned list is undefined.
*
* @param fromIndex the index that the returned list should start from
* (inclusive)
* @param toIndex the index that the returned list should go to (exclusive)
* @return a List backed by a subsection of this list
* @throws IndexOutOfBoundsException if fromIndex < 0
* || toIndex > size() || fromIndex > toIndex
*/
List subList(int fromIndex, int toIndex);
/**
* Copy the current contents of this list into an array.
*
* @return an array of type Object[] and length equal to the length of this
* list, containing the elements currently in this list, in order
*/
Object[] toArray();
/**
* Copy the current contents of this list into an array. If the array passed
* as an argument has length less than that of this list, an array of the
* same run-time type as a, and length equal to the length of this list, is
* allocated using Reflection. Otherwise, a itself is used. The elements of
* this list are copied into it, and if there is space in the array, the
* following element is set to null. The resultant array is returned.
* Note: The fact that the following element is set to null is only useful
* if it is known that this list does not contain any null elements.
*
* @param a the array to copy this list into
* @return an array containing the elements currently in this list, in
* order
* @throws ArrayStoreException if the type of any element of the
* collection is not a subtype of the element type of a
* @throws NullPointerException if the specified array is null
*/
Object[] toArray(Object[] a);
}