Known Direct Subclasses
|
Known Indirect Subclasses
LinkedList<E>,
Stack<E>
|
This class provides a skeletal implementation of the List
interface to minimize the effort required to implement this interface
backed by a "random access" data store (such as an array). For sequential
access data (such as a linked list), AbstractSequentialList
should
be used in preference to this class.
To implement an unmodifiable list, the programmer needs only to extend
this class and provide implementations for the get(int)
and
size()
methods.
To implement a modifiable list, the programmer must additionally
override the set(int, E)
method (which otherwise
throws an UnsupportedOperationException
). If the list is
variable-size the programmer must additionally override the
add(int, E)
and remove(int)
methods.
The programmer should generally provide a void (no argument) and collection
constructor, as per the recommendation in the Collection
interface
specification.
Unlike the other abstract collection implementations, the programmer does
not have to provide an iterator implementation; the iterator and
list iterator are implemented by this class, on top of the "random access"
methods:
get(int)
,
set(int, E)
,
add(int, E)
and
remove(int)
.
The documentation for each non-abstract method in this class describes its implementation in detail. Each of these methods may be overridden if the collection being implemented admits a more efficient implementation.
This class is a member of the Java Collections Framework.
Field Summary
protected int | modCount | The number of times this list has been structurally modified. |
Protected Constructor Summary
AbstractList()
Sole constructor.
|
Public Method Summary
void |
add(int index, E element)
Inserts the specified element at the specified position in this list
(optional operation).
|
boolean |
add(E e)
Appends the specified element to the end of this list (optional
operation).
|
boolean |
addAll(int index, Collection<? extends E> c)
Inserts all of the elements in the specified collection into this
list at the specified position (optional operation).
|
void |
clear()
Removes all of the elements from this list (optional operation).
|
boolean | |
abstract E |
get(int index)
Returns the element at the specified position in this list.
|
int |
hashCode()
Returns the hash code value for this list.
|
int | |
Iterator<E> |
iterator()
Returns an iterator over the elements in this list in proper sequence.
|
int |
lastIndexOf(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.
|
ListIterator<E> |
listIterator(int index)
Returns a list iterator over the elements in this list (in proper
sequence), starting at the specified position in the list.
|
ListIterator<E> |
listIterator()
Returns a list iterator over the elements in this list (in proper
sequence).
|
E |
remove(int index)
Removes the element at the specified position in this list (optional
operation).
|
E |
set(int index, E element)
Replaces the element at the specified position in this list with the
specified element (optional operation).
|
List<E> |
subList(int fromIndex, int toIndex)
Returns a view of the portion of this list between the specified
fromIndex , inclusive, and toIndex , exclusive. |
Protected Method Summary
void |
removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between
fromIndex , inclusive, and toIndex , exclusive. |
Inherited Method Summary
Fields
protected int modCount
The number of times this list has been structurally modified. Structural modifications are those that change the size of the list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.
This field is used by the iterator and list iterator implementation
returned by the iterator
and listIterator
methods.
If the value of this field changes unexpectedly, the iterator (or list
iterator) will throw a ConcurrentModificationException
in
response to the next
, remove
, previous
,
set
or add
operations. This provides
fail-fast behavior, rather than non-deterministic behavior in
the face of concurrent modification during iteration.
Use of this field by subclasses is optional. If a subclass
wishes to provide fail-fast iterators (and list iterators), then it
merely has to increment this field in its add(int, E)
and
remove(int)
methods (and any other methods that it overrides
that result in structural modifications to the list). A single call to
add(int, E)
or remove(int)
must add no more than
one to this field, or the iterators (and list iterators) will throw
bogus ConcurrentModificationExceptions
. If an implementation
does not wish to provide fail-fast iterators, this field may be
ignored.
Protected Constructors
protected AbstractList ()
Sole constructor. (For invocation by subclass constructors, typically implicit.)
Public Methods
public void add (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).
Parameters
index | index at which the specified element is to be inserted |
---|---|
element | element to be inserted |
public boolean add (E e)
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.
Parameters
e | element to be appended to this list |
---|
Returns
true
(as specified byCollection.add(E)
)
Throws
UnsupportedOperationException | if the add operation
is not supported by this list |
---|---|
ClassCastException | if the class of the specified element prevents it from being added to this list |
NullPointerException | if the specified element is null and this list does not permit null elements |
IllegalArgumentException | if some property of this element prevents it from being added to this list |
public boolean addAll (int index, 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.)
Parameters
index | index at which to insert the first element from the specified collection |
---|---|
c | collection containing elements to be added to this list |
Returns
true
if this list changed as a result of the call
public void clear ()
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
|
---|
public boolean equals (Object o)
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.
Parameters
o | the object to be compared for equality with this list |
---|
Returns
true
if the specified object is equal to this list
public abstract E get (int index)
Returns the element at the specified position in this list.
Parameters
index | index of the element to return |
---|
Returns
- the element at the specified position in this list
Throws
IndexOutOfBoundsException |
---|
public int hashCode ()
Returns the hash code value for this list.
Returns
- the hash code value for this list
public int indexOf (Object o)
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
Objects.equals(o, get(i))
,
or -1 if there is no such index.
Parameters
o | element to search for |
---|
Returns
- the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
public Iterator<E> iterator ()
Returns an iterator over the elements in this list in proper sequence.
Returns
- an iterator over the elements in this list in proper sequence
public int lastIndexOf (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
Objects.equals(o, get(i))
,
or -1 if there is no such index.
Parameters
o | element to search for |
---|
Returns
- the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
public ListIterator<E> listIterator (int index)
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.
Parameters
index | index of the first element to be returned from the
list iterator (by a call to next ) |
---|
Returns
- a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list
Throws
IndexOutOfBoundsException |
---|
public ListIterator<E> listIterator ()
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)
See Also
public E remove (int index)
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.
Parameters
index | the index of the element to be removed |
---|
Returns
- the element previously at the specified position
public E set (int index, E element)
Replaces the element at the specified position in this list with the specified element (optional operation).
Parameters
index | index of the element to replace |
---|---|
element | element to be stored at the specified position |
Returns
- the element previously at the specified position
public List<E> subList (int fromIndex, int toIndex)
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.)
Parameters
fromIndex | low endpoint (inclusive) of the subList |
---|---|
toIndex | high endpoint (exclusive) of the subList |
Returns
- a view of the specified range within this list
Throws
IndexOutOfBoundsException | if an endpoint index value is out of range
(fromIndex < 0 || toIndex > size) |
---|---|
IllegalArgumentException | if the endpoint indices are out of order
(fromIndex > toIndex)
|
Protected Methods
protected void removeRange (int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between
fromIndex
, inclusive, and toIndex
, exclusive.
Shifts any succeeding elements to the left (reduces their index).
This call shortens the list by (toIndex - fromIndex)
elements.
(If toIndex==fromIndex
, this operation has no effect.)
This method is called by the clear
operation on this list
and its subLists. Overriding this method to take advantage of
the internals of the list implementation can substantially
improve the performance of the clear
operation on this list
and its subLists.
Parameters
fromIndex | index of first element to be removed |
---|---|
toIndex | index after last element to be removed |