org.apache.commons.collections.list

Class TreeList

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList

org.apache.commons.collections.list.TreeList

All Implemented Interfaces:

java.lang.Iterable, java.util.Collection, java.util.List

public class TreeList
extends java.util.AbstractList

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 sligtly more memory.

Since:

Commons Collections 3.1

Constructor Summary

Constructors

Constructor and Description
TreeList() Constructs a new empty list.
TreeList(java.util.Collection coll) Constructs a new empty list that copies the specified list.

Method Summary

Modifier and Type	Method and Description
void	add(int index, java.lang.Object obj) Adds a new element to the list.
void	clear() Clears the list, removing all entries.
boolean	contains(java.lang.Object object) Searches for the presence of an object in the list.
java.lang.Object	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	iterator() Gets an iterator over the list.
java.util.ListIterator	listIterator() Gets a ListIterator over the list.
java.util.ListIterator	listIterator(int fromIndex) Gets a ListIterator over the list.
java.lang.Object	remove(int index) Removes the element at the specified index.
java.lang.Object	set(int index, java.lang.Object 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

addAll, 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

addAll, 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 coll)

Constructs a new empty list that copies the specified list.

Parameters:

coll - the collection to copy

Throws:

java.lang.NullPointerException - if the collection is null

Method Detail

get

public java.lang.Object get(int index)

Gets the element at the specified index.

Specified by:

get in interface java.util.List

Specified by:

get in class java.util.AbstractList

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

Specified by:

size in interface java.util.List

Specified by:

size in class java.util.AbstractCollection

Returns:

the current size

iterator

public java.util.Iterator iterator()

Gets an iterator over the list.

Specified by:

iterator in interface java.lang.Iterable

Specified by:

iterator in interface java.util.Collection

Specified by:

iterator in interface java.util.List

Overrides:

iterator in class java.util.AbstractList

Returns:

an iterator over the list

listIterator

public java.util.ListIterator listIterator()

Gets a ListIterator over the list.

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class java.util.AbstractList

Returns:

the new iterator

listIterator

public java.util.ListIterator listIterator(int fromIndex)

Gets a ListIterator over the list.

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class java.util.AbstractList

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

Overrides:

indexOf in class java.util.AbstractList

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

Specified by:

contains in interface java.util.List

Overrides:

contains in class java.util.AbstractCollection

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

Specified by:

toArray in interface java.util.List

Overrides:

toArray in class java.util.AbstractCollection

Returns:

the list as an array

add

public void add(int index,
                java.lang.Object obj)

Adds a new element to the list.

Specified by:

add in interface java.util.List

Overrides:

add in class java.util.AbstractList

Parameters:

index - the index to add before

obj - the element to add

set

public java.lang.Object set(int index,
                            java.lang.Object obj)

Sets the element at the specified index.

Specified by:

set in interface java.util.List

Overrides:

set in class java.util.AbstractList

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 java.lang.Object remove(int index)

Removes the element at the specified index.

Specified by:

remove in interface java.util.List

Overrides:

remove in class java.util.AbstractList

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

Specified by:

clear in interface java.util.List

Overrides:

clear in class java.util.AbstractList