java.util
Class RandomAccessSubList

java.lang.Object
  |
  +--java.util.AbstractCollection
        |
        +--java.util.AbstractList
              |
              +--java.util.SubList
                    |
                    +--java.util.RandomAccessSubList

All Implemented Interfaces:

Collection, List, RandomAccess

class RandomAccessSubList

extends SubList

implements RandomAccess

Field Summary

Fields inherited from class java.util.AbstractList

modCount

Constructor Summary

(package private)

RandomAccessSubList(AbstractList list, int fromIndex, int toIndex)

Method Summary

void	add(int index, Object element) Enabled: Inserts the specified element at the specified position in this list (optional operation).
boolean	addAll(Collection c) Enabled: 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).
boolean	addAll(int index, Collection c) Enabled: Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
Object	get(int index) Enabled: Returns the element at the specified position in this list.
Iterator	iterator() Enabled: Returns an iterator over the elements in this list in proper sequence.
ListIterator	listIterator(int index) Enabled: Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in the list.
Object	remove(int index) Enabled: 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.
Object	set(int index, Object element) Enabled: Replaces the element at the specified position in this list with the specified element (optional operation).
int	size() Enabled: Returns the number of elements in this list.
List	subList(int fromIndex, int toIndex) Enabled: Returns a view of the portion of this list between fromIndex, inclusive, and toIndex, exclusive.

Methods inherited from class java.util.AbstractList

add, clear, equals, hashCode, indexOf, lastIndexOf, listIterator

Methods inherited from class java.util.AbstractCollection

contains, containsAll, isEmpty, remove, removeAll, retainAll, 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

contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray

Constructor Detail

RandomAccessSubList

RandomAccessSubList(AbstractList list,
                    int fromIndex,
                    int toIndex)

Method Detail

subList

public List subList(int fromIndex,
                    int toIndex)

Description copied from class: AbstractList

Enabled: Returns a view of the portion of this list between 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 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 operating on 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 the 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, Object), get(int), add(int, Object), 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.

Specified by:

subList in interface List

Overrides:

subList in class SubList

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.

set

public Object set(int index,
                  Object element)

Description copied from class: AbstractList

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

This implementation always throws an UnsupportedOperationException.

Specified by:

set in interface List

Overrides:

set in class AbstractList

Parameters:

index - index of element to replace.

element - element to be stored at the specified position.

Returns:

the element previously at the specified position.

get

public Object get(int index)

Description copied from class: AbstractList

Enabled: Returns the element at the specified position in this list.

Specified by:

get in interface List

Specified by:

get in class AbstractList

Parameters:

index - index of element to return.

Returns:

the element at the specified position in this list.

size

public int size()

Description copied from interface: List

Enabled: Returns the number of elements in this list. If this list contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Specified by:

size in interface List

Specified by:

size in class AbstractCollection

Returns:

the number of elements in this list.

add

public void add(int index,
                Object element)

Description copied from class: AbstractList

Enabled: 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 always throws an UnsupportedOperationException.

Specified by:

add in interface List

Overrides:

add in class AbstractList

Parameters:

index - index at which the specified element is to be inserted.

element - element to be inserted.

remove

public Object remove(int index)

Description copied from class: AbstractList

Enabled: 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 always throws an UnsupportedOperationException.

Specified by:

remove in interface List

Overrides:

remove in class AbstractList

Parameters:

index - the index of the element to remove.

Returns:

the element previously at the specified position.

removeRange

protected void removeRange(int fromIndex,
                           int toIndex)

Description copied from class: AbstractList

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 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.

Overrides:

removeRange in class AbstractList

Parameters:

fromIndex - index of first element to be removed.

toIndex - index after last element to be removed.

addAll

public boolean addAll(Collection c)

Description copied from interface: List

Enabled: 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.)

Specified by:

addAll in interface List

Overrides:

addAll in class AbstractCollection

Parameters:

c - collection whose elements are to be added to this list.

Returns:

true if this list changed as a result of the call.

See Also:

List.add(Object)

addAll

public boolean addAll(int index,
                      Collection c)

Description copied from class: AbstractList

Enabled: 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 the 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.)

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, Object). Many implementations will override this method for efficiency.

Note that this implementation throws an UnsupportedOperationException unless add(int, Object) is overridden.

Specified by:

addAll in interface List

Overrides:

addAll in class AbstractList

Parameters:

index - index at which to insert the first element from the specified collection.

c - elements to be inserted into this List.

Returns:

true if this list changed as a result of the call.

iterator

public Iterator iterator()

Description copied from class: AbstractList

Enabled: Returns an iterator over the elements in this list in proper sequence.

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.

Specified by:

iterator in interface List

Overrides:

iterator in class AbstractList

Returns:

an iterator over the elements in this list in proper sequence.

See Also:

AbstractList.modCount

listIterator

public ListIterator listIterator(int index)

Description copied from class: AbstractList

Enabled: Returns a list iterator of 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 the next method. An initial call to the previous method 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, Object), add(int, Object) 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, Object), and add(int, Object) 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.

Specified by:

listIterator in interface List

Overrides:

listIterator in class AbstractList

Parameters:

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

Returns:

a list iterator of the elements in this list (in proper sequence), starting at the specified position in the list.

See Also:

AbstractList.modCount