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:

java.lang.Iterable<E>, java.util.Collection<E>, java.util.List<E>

public class TreeList<E>
extends java.util.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 and Description
TreeList() Constructs a new empty list.
TreeList(java.util.Collection<? extends E> coll) Constructs a new empty list that copies the specified collection.

Method Summary

Modifier and Type	Method and Description
void	add(int index, E obj) Adds a new element to the list.
boolean	addAll(java.util.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(java.lang.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(java.lang.Object object) Searches for the index of an object in the list.
java.util.Iterator<E>	iterator() Gets an iterator over the list.
java.util.ListIterator<E>	listIterator() Gets a ListIterator over the list.
java.util.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.
java.lang.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.List

containsAll, isEmpty, remove, 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

TreeList

public TreeList()

Constructs a new empty list.

TreeList

public TreeList(java.util.Collection<? extends E> coll)

Constructs a new empty list that copies the specified collection.

Parameters:

coll - the collection to copy

Throws:

java.lang.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 java.util.List<E>

Specified by:

get in class java.util.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 java.util.Collection<E>

Specified by:

size in interface java.util.List<E>

Specified by:

size in class java.util.AbstractCollection<E>

Returns:

the current size

iterator

public java.util.Iterator<E> iterator()

Gets an iterator over the list.

Specified by:

iterator in interface java.lang.Iterable<E>

Specified by:

iterator in interface java.util.Collection<E>

Specified by:

iterator in interface java.util.List<E>

Overrides:

iterator in class java.util.AbstractList<E>

Returns:

an iterator over the list

listIterator

public java.util.ListIterator<E> listIterator()

Gets a ListIterator over the list.

Specified by:

listIterator in interface java.util.List<E>

Overrides:

listIterator in class java.util.AbstractList<E>

Returns:

the new iterator

listIterator

public java.util.ListIterator<E> listIterator(int fromIndex)

Gets a ListIterator over the list.

Specified by:

listIterator in interface java.util.List<E>

Overrides:

listIterator in class java.util.AbstractList<E>

Parameters:

fromIndex - the index to start from

Returns:

the new iterator

indexOf

public int indexOf(java.lang.Object object)

Searches for the index of an object in the list.

Specified by:

indexOf in interface java.util.List<E>

Overrides:

indexOf in class java.util.AbstractList<E>

Parameters:

object - the object to search

Returns:

the index of the object, -1 if not found

contains

public boolean contains(java.lang.Object object)

Searches for the presence of an object in the list.

Specified by:

contains in interface java.util.Collection<E>

Specified by:

contains in interface java.util.List<E>

Overrides:

contains in class java.util.AbstractCollection<E>

Parameters:

object - the object to check

Returns:

true if the object is found

toArray

public java.lang.Object[] toArray()

Converts the list into an array.

Specified by:

toArray in interface java.util.Collection<E>

Specified by:

toArray in interface java.util.List<E>

Overrides:

toArray in class java.util.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 java.util.List<E>

Overrides:

add in class java.util.AbstractList<E>

Parameters:

index - the index to add before

obj - the element to add

addAll

public boolean addAll(java.util.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 java.util.Collection<E>

Specified by:

addAll in interface java.util.List<E>

Overrides:

addAll in class java.util.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:

java.lang.NullPointerException

set

public E set(int index,
             E obj)

Sets the element at the specified index.

Specified by:

set in interface java.util.List<E>

Overrides:

set in class java.util.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:

java.lang.IndexOutOfBoundsException - if the index is invalid

remove

public E remove(int index)

Removes the element at the specified index.

Specified by:

remove in interface java.util.List<E>

Overrides:

remove in class java.util.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 java.util.Collection<E>

Specified by:

clear in interface java.util.List<E>

Overrides:

clear in class java.util.AbstractList<E>