com.solacesystems.common.util

Class TLinkedList<T extends TLinkable<T>>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList<E>

java.util.AbstractSequentialList<T>

com.solacesystems.common.util.TLinkedList<T>

All Implemented Interfaces:

Externalizable, Serializable, Iterable<T>, Collection<T>, List<T>

public class TLinkedList<T extends TLinkable<T>>
extends AbstractSequentialList<T>
implements Externalizable

A LinkedList implementation which holds instances of type TLinkable.

Using this implementation allows you to get java.util.LinkedList behavior (a doubly linked list, with Iterators that support insert and delete operations) without incurring the overhead of creating Node wrapper objects for every element in your list.

The requirement to achieve this time/space gain is that the Objects stored in the List implement the TLinkable interface.

The limitations are:

• the same object cannot be put into more than one list at the same time.
• the same object cannot be put into the same list more than once at the same time.
• objects must only be removed from list they are in. That is, if you have an object A and lists l1 and l2, you must ensure that you invoke List.remove(A) on the correct list.
• It is also forbidden to invoke List.remove() with an unaffiliated TLinkable (one that belongs to no list): this will destroy the list you invoke it on.

Version:

$Id: TLinkedList.java,v 1.1.2.3 2010/09/27 17:23:07 robeden Exp $

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
TLinkedList() Creates a new TLinkedList instance.

Method Summary

Modifier and Type	Method and Description
void	add(int index, T linkable) Inserts linkable at index index in the list.
boolean	add(T linkable) Appends linkable to the end of the list.
void	addAfter(T current, T newElement) Inserts newElement into the list immediately after current.
void	addBefore(T current, T newElement) Inserts newElement into the list immediately before current.
void	addFirst(T linkable) Inserts linkable at the head of the list.
void	addLast(T linkable) Adds linkable to the end of the list.
void	clear() Empties the list.
boolean	contains(Object o) A linear search for o in the list.
T	get(int index)
T	getFirst() Returns the head of the list
T	getLast() Returns the tail of the list.
T	getNext(T current) Return the node following the given node.
T	getPrevious(T current) Return the node preceding the given node.
ListIterator<T>	listIterator(int index) Returns an iterator positioned at index.
void	readExternal(ObjectInput in)
boolean	remove(Object o) Removes the specified element from the list.
T	removeFirst() Remove and return the first element in the list.
T	removeLast() Remove and return the last element in the list.
int	size() Returns the number of elements in the list.
Object[]	toArray() Copies the list's contents into a native array.
Object[]	toUnlinkedArray() Copies the list to a native array, destroying the next/previous links as the copy is made.
T[]	toUnlinkedArray(T[] a) Returns a typed array of the objects in the set.
void	writeExternal(ObjectOutput out)

Methods inherited from class java.util.AbstractSequentialList

addAll, iterator, remove, set

Methods inherited from class java.util.AbstractList

equals, hashCode, indexOf, lastIndexOf, listIterator, subList

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, isEmpty, removeAll, retainAll, toArray, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.List

addAll, containsAll, isEmpty, removeAll, replaceAll, retainAll, sort, spliterator, toArray

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

TLinkedList

public TLinkedList()

Creates a new TLinkedList instance.

Method Detail

listIterator

public ListIterator<T> listIterator(int index)

Returns an iterator positioned at index. Assuming that the list has a value at that index, calling next() will retrieve and advance the iterator. Assuming that there is a value before index in the list, calling previous() will retrieve it (the value at index - 1) and move the iterator to that position. So, iterating from front to back starts at 0; iterating from back to front starts at size().

Specified by:

listIterator in interface List<T extends TLinkable<T>>

Specified by:

listIterator in class AbstractSequentialList<T extends TLinkable<T>>

Parameters:

index - an int value

Returns:

a ListIterator value

size

public int size()

Returns the number of elements in the list.

Specified by:

size in interface Collection<T extends TLinkable<T>>

Specified by:

size in interface List<T extends TLinkable<T>>

Specified by:

size in class AbstractCollection<T extends TLinkable<T>>

Returns:

an int value

add

public void add(int index,
                T linkable)

Inserts linkable at index index in the list. All values greater than index are shifted over one position to accommodate the new addition.

Specified by:

add in interface List<T extends TLinkable<T>>

Overrides:

add in class AbstractSequentialList<T extends TLinkable<T>>

Parameters:

index - an int value

linkable - an object of type TLinkable

add

public boolean add(T linkable)

Appends linkable to the end of the list.

Specified by:

add in interface Collection<T extends TLinkable<T>>

Specified by:

add in interface List<T extends TLinkable<T>>

Overrides:

add in class AbstractList<T extends TLinkable<T>>

Parameters:

linkable - an object of type TLinkable

Returns:

always true

addFirst

public void addFirst(T linkable)

Inserts linkable at the head of the list.

Parameters:

linkable - an object of type TLinkable

addLast

public void addLast(T linkable)

Adds linkable to the end of the list.

Parameters:

linkable - an object of type TLinkable

clear

public void clear()

Empties the list.

Specified by:

clear in interface Collection<T extends TLinkable<T>>

Specified by:

clear in interface List<T extends TLinkable<T>>

Overrides:

clear in class AbstractList<T extends TLinkable<T>>

toArray

public Object[] toArray()

Copies the list's contents into a native array. This will be a shallow copy: the Tlinkable instances in the Object[] array have links to one another: changing those will put this list into an unpredictable state. Holding a reference to one element in the list will prevent the others from being garbage collected unless you clear the next/previous links. Caveat programmer!

Specified by:

toArray in interface Collection<T extends TLinkable<T>>

Specified by:

toArray in interface List<T extends TLinkable<T>>

Overrides:

toArray in class AbstractCollection<T extends TLinkable<T>>

Returns:

an Object[] value

toUnlinkedArray

public Object[] toUnlinkedArray()

Copies the list to a native array, destroying the next/previous links as the copy is made. This list will be emptied after the copy (as if clear() had been invoked). The Object[] array returned will contain TLinkables that do not hold references to one another and so are less likely to be the cause of memory leaks.

Returns:

an Object[] value

toUnlinkedArray

public T[] toUnlinkedArray(T[] a)

Returns a typed array of the objects in the set.

Parameters:

a - an Object[] value

Returns:

an Object[] value

contains

public boolean contains(Object o)

A linear search for o in the list.

Specified by:

contains in interface Collection<T extends TLinkable<T>>

Specified by:

contains in interface List<T extends TLinkable<T>>

Overrides:

contains in class AbstractCollection<T extends TLinkable<T>>

Parameters:

o - an Object value

Returns:

a boolean value

get

public T get(int index)

Specified by:

get in interface List<T extends TLinkable<T>>

Overrides:

get in class AbstractSequentialList<T extends TLinkable<T>>

getFirst

public T getFirst()

Returns the head of the list

Returns:

an Object value

getLast

public T getLast()

Returns the tail of the list.

Returns:

an Object value

getNext

public T getNext(T current)

Return the node following the given node. This method exists for two reasons:

1. It's really not recommended that the methods implemented by TLinkable be called directly since they're used internally by this class.
2. This solves problems arising from generics when working with the linked objects directly.

NOTE: this should only be used with nodes contained in the list. The results are undefined with anything else.

Parameters:

current - The current node

Returns:

the node after the current node

getPrevious

public T getPrevious(T current)

Return the node preceding the given node. This method exists for two reasons:

1. It's really not recommended that the methods implemented by TLinkable be called directly since they're used internally by this class.
2. This solves problems arising from generics when working with the linked objects directly.

NOTE: this should only be used with nodes contained in the list. The results are undefined with anything else.

Parameters:

current - The current node

Returns:

the node after the current node

removeFirst

public T removeFirst()

Remove and return the first element in the list.

Returns:

an Object value

removeLast

public T removeLast()

Remove and return the last element in the list.

Returns:

an Object value

remove

public boolean remove(Object o)

Removes the specified element from the list. Note that it is the caller's responsibility to ensure that the element does, in fact, belong to this list and not another instance of TLinkedList.

Specified by:

remove in interface Collection<T extends TLinkable<T>>

Specified by:

remove in interface List<T extends TLinkable<T>>

Overrides:

remove in class AbstractCollection<T extends TLinkable<T>>

Parameters:

o - a TLinkable element already inserted in this list.

Returns:

true if the element was a TLinkable and removed

addBefore

public void addBefore(T current,
                      T newElement)

Inserts newElement into the list immediately before current. All elements to the right of and including current are shifted over.

Parameters:

current - a TLinkable value currently in the list.

newElement - a TLinkable value to be added to the list.

addAfter

public void addAfter(T current,
                     T newElement)

Inserts newElement into the list immediately after current. All elements to the left of and including current are shifted over.

Parameters:

current - a TLinkable value currently in the list.

newElement - a TLinkable value to be added to the list.

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

Specified by:

readExternal in interface Externalizable

Throws:

IOException

ClassNotFoundException