|
Java™ Platform Standard Ed. 6 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES All Classes | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Objectjava.util.AbstractCollection<E>
java.util.AbstractList<E>
public abstract class AbstractList<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. |
Constructor Summary | |
---|---|
protected |
AbstractList()
Sole constructor. |
Method Summary | |
---|---|
boolean |
add(E e)
Appends the specified element to the end of this list (optional operation). |
void |
add(int index,
E element)
Inserts the specified element at the specified position in 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 |
equals(Object o)
Compares the specified object with this list for equality. |
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 |
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. |
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()
Returns a list iterator over the elements in this list (in proper sequence). |
ListIterator<E> |
listIterator(int index)
Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list. |
E |
remove(int index)
Removes the element at the specified position in this list (optional operation). |
protected void |
removeRange(int fromIndex,
int toIndex)
Removes from this list all of the elements whose index is between fromIndex , inclusive, and toIndex , exclusive. |
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. |
Methods inherited from class java.util.AbstractCollection |
---|
addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, size, toArray, toArray, toString |
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Methods inherited from interface java.util.List |
---|
addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, size, toArray, toArray |
Field Detail |
---|
protected transient int modCount
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.
Constructor Detail |
---|
protected AbstractList()
Method Detail |
---|
public boolean add(E e)
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.
This implementation calls add(size(), e)
.
Note that this implementation throws an
UnsupportedOperationException
unless
add(int, E)
is overridden.
add
in interface Collection<E>
add
in interface List<E>
add
in class AbstractCollection<E>
e
- element to be appended to this list
true
(as specified by Collection.add(E)
)
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 listpublic abstract E get(int index)
get
in interface List<E>
index
- index of the element to return
IndexOutOfBoundsException
- if the index is out of range
(index < 0 || index >= size())public E set(int index, E element)
This implementation always throws an
UnsupportedOperationException
.
set
in interface List<E>
index
- index of the element to replaceelement
- element to be stored at the specified position
UnsupportedOperationException
- if the set 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 the specified
element prevents it from being added to this list
IndexOutOfBoundsException
- if the index is out of range
(index < 0 || index >= size())public void add(int index, E element)
This implementation always throws an
UnsupportedOperationException
.
add
in interface List<E>
index
- index at which the specified element is to be insertedelement
- element to be inserted
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 the specified
element prevents it from being added to this list
IndexOutOfBoundsException
- if the index is out of range
(index < 0 || index > size())public E remove(int index)
This implementation always throws an
UnsupportedOperationException
.
remove
in interface List<E>
index
- the index of the element to be removed
UnsupportedOperationException
- if the remove operation
is not supported by this list
IndexOutOfBoundsException
- if the index is out of range
(index < 0 || index >= size())public int indexOf(Object o)
This implementation first gets a list iterator (with
listIterator()
). Then, it iterates over the list until the
specified element is found or the end of the list is reached.
indexOf
in interface List<E>
o
- element to search for
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)public int lastIndexOf(Object o)
This implementation first gets a list iterator that points to the end
of the list (with listIterator(size())
). Then, it iterates
backwards over the list until the specified element is found, or the
beginning of the list is reached.
lastIndexOf
in interface List<E>
o
- element to search for
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)public void clear()
This implementation calls removeRange(0, size())
.
Note that this implementation throws an
UnsupportedOperationException
unless remove(int
index)
or removeRange(int fromIndex, int toIndex)
is
overridden.
clear
in interface Collection<E>
clear
in interface List<E>
clear
in class AbstractCollection<E>
UnsupportedOperationException
- if the clear
operation
is not supported by this listpublic boolean addAll(int index, Collection<? extends E> c)
This implementation gets an iterator over the specified collection
and iterates over it, inserting the elements obtained from the
iterator into this list at the appropriate position, one at a time,
using add(int, E)
.
Many implementations will override this method for efficiency.
Note that this implementation throws an
UnsupportedOperationException
unless
add(int, E)
is overridden.
addAll
in interface List<E>
index
- index at which to insert the first element from the
specified collectionc
- collection containing elements to be added to this list
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())public Iterator<E> iterator()
This implementation returns a straightforward implementation of the
iterator interface, relying on the backing list's size()
,
get(int)
, and remove(int)
methods.
Note that the iterator returned by this method will throw an
UnsupportedOperationException
in response to its
remove
method unless the list's remove(int)
method is
overridden.
This implementation can be made to throw runtime exceptions in the
face of concurrent modification, as described in the specification
for the (protected) modCount
field.
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in interface List<E>
iterator
in class AbstractCollection<E>
modCount
public ListIterator<E> listIterator()
This implementation returns listIterator(0)
.
listIterator
in interface List<E>
listIterator(int)
public ListIterator<E> listIterator(int index)
next
.
An initial call to previous
would
return the element with the specified index minus one.
This implementation returns a straightforward implementation of the
ListIterator
interface that extends the implementation of the
Iterator
interface returned by the iterator()
method.
The ListIterator
implementation relies on the backing list's
get(int)
, set(int, E)
, add(int, E)
and remove(int)
methods.
Note that the list iterator returned by this implementation will
throw an UnsupportedOperationException
in response to its
remove
, set
and add
methods unless the
list's remove(int)
, set(int, E)
, and
add(int, E)
methods are overridden.
This implementation can be made to throw runtime exceptions in the
face of concurrent modification, as described in the specification for
the (protected) modCount
field.
listIterator
in interface List<E>
index
- index of first element to be returned from the
list iterator (by a call to the next method)
IndexOutOfBoundsException
- if the index is out of range
(index < 0 || index > size())modCount
public List<E> subList(int fromIndex, int toIndex)
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.)
This implementation returns a list that subclasses
AbstractList
. The subclass stores, in private fields, the
offset of the subList within the backing list, the size of the subList
(which can change over its lifetime), and the expected
modCount
value of the backing list. There are two variants
of the subclass, one of which implements RandomAccess
.
If this list implements RandomAccess
the returned list will
be an instance of the subclass that implements RandomAccess
.
The subclass's set(int, E)
, get(int)
,
add(int, E)
, remove(int)
, addAll(int,
Collection)
and removeRange(int, int)
methods all
delegate to the corresponding methods on the backing abstract list,
after bounds-checking the index and adjusting for the offset. The
addAll(Collection c)
method merely returns addAll(size,
c)
.
The listIterator(int)
method returns a "wrapper object"
over a list iterator on the backing list, which is created with the
corresponding method on the backing list. The iterator
method
merely returns listIterator()
, and the size
method
merely returns the subclass's size
field.
All methods first check to see if the actual modCount
of
the backing list is equal to its expected value, and throw a
ConcurrentModificationException
if it is not.
subList
in interface List<E>
fromIndex
- low endpoint (inclusive) of the subListtoIndex
- high endpoint (exclusive) of the subList
IndexOutOfBoundsException
- endpoint index value out of range
(fromIndex < 0 || toIndex > size)
IllegalArgumentException
- if the endpoint indices are out of order
(fromIndex > toIndex)
public boolean equals(Object o)
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 implementation first checks if the specified object is this
list. If so, it returns true
; if not, it checks if the
specified object is a list. If not, it returns false
; if so,
it iterates over both lists, comparing corresponding pairs of elements.
If any comparison returns false
, this method returns
false
. If either iterator runs out of elements before the
other it returns false
(as the lists are of unequal length);
otherwise it returns true
when the iterations complete.
equals
in interface Collection<E>
equals
in interface List<E>
equals
in class Object
o
- the object to be compared for equality with this list
true
if the specified object is equal to this listObject.hashCode()
,
Hashtable
public int hashCode()
This implementation uses exactly the code that is used to define the
list hash function in the documentation for the List.hashCode()
method.
hashCode
in interface Collection<E>
hashCode
in interface List<E>
hashCode
in class Object
Object.equals(java.lang.Object)
,
Hashtable
protected void removeRange(int fromIndex, int toIndex)
fromIndex
, inclusive, and toIndex
, exclusive.
Shifts any succeeding elements to the left (reduces their index).
This call shortens the ArrayList 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.
This implementation gets a list iterator positioned before
fromIndex
, and repeatedly calls ListIterator.next
followed by ListIterator.remove
until the entire range has
been removed. Note: if ListIterator.remove
requires linear
time, this implementation requires quadratic time.
fromIndex
- index of first element to be removedtoIndex
- index after last element to be removed
|
Java™ Platform Standard Ed. 6 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES All Classes | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
Copyright © 1993, 2015, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
Scripting on this page tracks web page traffic, but does not change the content in any way.