Package org.apache.commons.collections4.list

Class TreeList<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList<E>

org.apache.commons.collections4.list.TreeList<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>, List<E>

public class TreeList<E>
extends AbstractList<E>

A List implementation that is optimised for fast insertions and removals at any index in the list.

This list implementation utilises a tree structure internally to ensure that all insertions and removals are O(log n). This provides much faster performance than both an ArrayList and a LinkedList where elements are inserted and removed repeatedly from anywhere in the list.

The following relative performance statistics are indicative of this class:

              get  add  insert  iterate  remove
 TreeList       3    5       1       2       1
 ArrayList      1    1      40       1      40
 LinkedList  5800    1     350       2     325
 

ArrayList is a good general purpose list implementation. It is faster than TreeList for most operations except inserting and removing in the middle of the list. ArrayList also uses less memory as TreeList uses one object per entry.

LinkedList is rarely a good choice of implementation. TreeList is almost always a good replacement for it, although it does use slightly more memory.

Since:

3.1

Constructor Summary

Constructors

Constructor	Description
TreeList()	Constructs a new empty list.
TreeList(Collection<? extends E> coll)	Constructs a new empty list that copies the specified collection.

Method Summary

Modifier and Type	Method	Description
void	add(int index, E obj)	Adds a new element to the list.
boolean	addAll(Collection<? extends E> c)	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.
void	clear()	Clears the list, removing all entries.
boolean	contains(Object object)	Searches for the presence of an object in the list.
E	get(int index)	Gets the element at the specified index.
int	indexOf(Object object)	Searches for the index of an object in the list.
Iterator<E>	iterator()	Gets an iterator over the list.
ListIterator<E>	listIterator()	Gets a ListIterator over the list.
ListIterator<E>	listIterator(int fromIndex)	Gets a ListIterator over the list.
E	remove(int index)	Removes the element at the specified index.
E	set(int index, E obj)	Sets the element at the specified index.
int	size()	Gets the current size of the list.
Object[]	toArray()	Converts the list into an array.

Methods inherited from class java.util.AbstractList

add, addAll, equals, hashCode, lastIndexOf, subList

Methods inherited from class java.util.AbstractCollection

containsAll, isEmpty, remove, removeAll, retainAll, toArray, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface java.util.List

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

Constructor Detail

TreeList

public TreeList()

Constructs a new empty list.

TreeList

public TreeList(Collection<? extends E> coll)

Constructs a new empty list that copies the specified collection.

Parameters:

coll - the collection to copy

Throws:

NullPointerException - if the collection is null

Method Detail

get

public E get(int index)

Gets the element at the specified index.

Specified by:

get in interface List<E>

Specified by:

get in class AbstractList<E>

Parameters:

index - the index to retrieve

Returns:

the element at the specified index

size

public int size()

Gets the current size of the list.

Specified by:

size in interface Collection<E>

Specified by:

size in interface List<E>

Specified by:

size in class AbstractCollection<E>

Returns:

the current size

iterator

public Iterator<E> iterator()

Gets an iterator over the list.

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface List<E>

Overrides:

iterator in class AbstractList<E>

Returns:

an iterator over the list

listIterator

public ListIterator<E> listIterator()

Gets a ListIterator over the list.

Specified by:

listIterator in interface List<E>

Overrides:

listIterator in class AbstractList<E>

Returns:

the new iterator

listIterator

public ListIterator<E> listIterator(int fromIndex)

Gets a ListIterator over the list.

Specified by:

listIterator in interface List<E>

Overrides:

listIterator in class AbstractList<E>

Parameters:

fromIndex - the index to start from

Returns:

the new iterator

indexOf

public int indexOf(Object object)

Searches for the index of an object in the list.

Specified by:

indexOf in interface List<E>

Overrides:

indexOf in class AbstractList<E>

Parameters:

object - the object to search

Returns:

the index of the object, -1 if not found

contains

public boolean contains(Object object)

Searches for the presence of an object in the list.

Specified by:

contains in interface Collection<E>

Specified by:

contains in interface List<E>

Overrides:

contains in class AbstractCollection<E>

Parameters:

object - the object to check

Returns:

true if the object is found

toArray

public Object[] toArray()

Converts the list into an array.

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Overrides:

toArray in class AbstractCollection<E>

Returns:

the list as an array

add

public void add(int index,
                E obj)

Adds a new element to the list.

Specified by:

add in interface List<E>

Overrides:

add in class AbstractList<E>

Parameters:

index - the index to add before

obj - the element to add

addAll

public boolean addAll(Collection<? extends E> c)

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.

This method runs in O(n + log m) time, where m is the size of this list and n is the size of c.

Specified by:

addAll in interface Collection<E>

Specified by:

addAll in interface List<E>

Overrides:

addAll in class AbstractCollection<E>

Parameters:

c - the collection to be added to this list

Returns:

true if this list changed as a result of the call

Throws:

NullPointerException

set

public E set(int index,
             E obj)

Sets the element at the specified index.

Specified by:

set in interface List<E>

Overrides:

set in class AbstractList<E>

Parameters:

index - the index to set

obj - the object to store at the specified index

Returns:

the previous object at that index

Throws:

IndexOutOfBoundsException - if the index is invalid

remove

public E remove(int index)

Removes the element at the specified index.

Specified by:

remove in interface List<E>

Overrides:

remove in class AbstractList<E>

Parameters:

index - the index to remove

Returns:

the previous object at that index

clear

public void clear()

Clears the list, removing all entries.

Specified by:

clear in interface Collection<E>

Specified by:

clear in interface List<E>

Overrides:

clear in class AbstractList<E>