java.util
class AbstractSequentialList

java.lang.Object java.util.AbstractCollection java.util.AbstractList java.util.AbstractSequentialList

All Implemented Interfaces:

Collection, List

Direct Known Subclasses:

LinkedList

public abstract class AbstractSequentialList
extends AbstractList

This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a "sequential access" data store (such as a linked list). For random access data (such as an array), AbstractList should be used in preference to this class.

This class is the opposite of the AbstractList class in the sense that it implements the "random access" methods (get(int index), set(int index, E element), add(int index, E element) and remove(int index)) on top of the list's list iterator, instead of the other way around.

To implement a list the programmer needs only to extend this class and provide implementations for the listIterator and size methods. For an unmodifiable list, the programmer need only implement the list iterator's hasNext, next, hasPrevious, previous and index methods.

For a modifiable list the programmer should additionally implement the list iterator's set method. For a variable-size list the programmer should additionally implement the list iterator's remove and add methods.

The programmer should generally provide a void (no argument) and collection constructor, as per the recommendation in the Collection interface specification.

This class is a member of the Java Collections Framework.

AbstractSequentialList

protected AbstractSequentialList()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

add

public void add(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).

This implementation first gets a list iterator pointing to the indexed element (with listIterator(index)). Then, it inserts the specified element with ListIterator.add.

Note that this implementation will throw an UnsupportedOperationException if the list iterator does not implement the add operation.

Overrides:

add in class AbstractList

Parameters:

index

element

addAll

public boolean addAll(int index,
                      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 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.)

This implementation gets an iterator over the specified collection and a list iterator over this list pointing to the indexed element (with listIterator(index)). Then, it iterates over the specified collection, inserting the elements obtained from the iterator into this list, one at a time, using ListIterator.add followed by ListIterator.next (to skip over the added element).

Note that this implementation will throw an UnsupportedOperationException if the list iterator returned by the listIterator method does not implement the add operation.

Overrides:

addAll in class AbstractList

Parameters:

index

c

get

public Object get(int index)

Returns the element at the specified position in this list.

This implementation first gets a list iterator pointing to the indexed element (with listIterator(index)). Then, it gets the element using ListIterator.next and returns it.

Overrides:

get in class AbstractList

Parameters:

index

iterator

public Iterator iterator()

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

This implementation merely returns a list iterator over the list.

Overrides:

iterator in class AbstractList

Returns:

an iterator over the elements in this list (in proper sequence)

listIterator

public abstract ListIterator listIterator(int index)

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

Overrides:

listIterator in class AbstractList

Parameters:

index - index of first element to be returned from the list iterator (by a call to the next method)

Returns:

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

remove

public Object 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.

This implementation first gets a list iterator pointing to the indexed element (with listIterator(index)). Then, it removes the element with ListIterator.remove.

Note that this implementation will throw an UnsupportedOperationException if the list iterator does not implement the remove operation.

Overrides:

remove in class AbstractList

Parameters:

index

set

public Object set(int index,
                  Object element)

Replaces the element at the specified position in this list with the specified element (optional operation).

This implementation first gets a list iterator pointing to the indexed element (with listIterator(index)). Then, it gets the current element using ListIterator.next and replaces it with ListIterator.set.

Note that this implementation will throw an UnsupportedOperationException if the list iterator does not implement the set operation.

Overrides:

set in class AbstractList

Parameters:

index

element