org.apache.commons.collections

Class FastArrayList

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList<E>

java.util.ArrayList

org.apache.commons.collections.FastArrayList

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.lang.Iterable, java.util.Collection, java.util.List, java.util.RandomAccess

public class FastArrayList
extends java.util.ArrayList

A customized implementation of java.util.ArrayList designed to operate in a multithreaded environment where the large majority of method calls are read-only, instead of structural changes. When operating in "fast" mode, read calls are non-synchronized and write calls perform the following steps:

• Clone the existing collection
• Perform the modification on the clone
• Replace the existing collection with the (modified) clone

When first created, objects of this class default to "slow" mode, where all accesses of any type are synchronized but no cloning takes place. This is appropriate for initially populating the collection, followed by a switch to "fast" mode (by calling setFast(true)) after initialization is complete.

NOTE: If you are creating and accessing an ArrayList only within a single thread, you should use java.util.ArrayList directly (with no synchronization), for maximum performance.

NOTE: This class is not cross-platform. Using it may cause unexpected failures on some architectures. It suffers from the same problems as the double-checked locking idiom. In particular, the instruction that clones the internal collection and the instruction that sets the internal reference to the clone can be executed or perceived out-of-order. This means that any read operation might fail unexpectedly, as it may be reading the state of the internal collection before the internal collection is fully formed. For more information on the double-checked locking idiom, see the Double-Checked Locking Idiom Is Broken Declaration.

Since:

Commons Collections 1.0

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FastArrayList() Construct a an empty list.
FastArrayList(java.util.Collection collection) Construct a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.
FastArrayList(int capacity) Construct an empty list with the specified capacity.

Method Summary

Modifier and Type	Method and Description
void	add(int index, java.lang.Object element) Insert the specified element at the specified position in this list, and shift all remaining elements up one position.
boolean	add(java.lang.Object element) Appends the specified element to the end of this list.
boolean	addAll(java.util.Collection collection) Append 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.
boolean	addAll(int index, java.util.Collection collection) Insert all of the elements in the specified Collection at the specified position in this list, and shift any previous elements upwards as needed.
void	clear() Remove all of the elements from this list.
java.lang.Object	clone() Return a shallow copy of this FastArrayList instance.
boolean	contains(java.lang.Object element) Return true if this list contains the specified element.
boolean	containsAll(java.util.Collection collection) Return true if this list contains all of the elements in the specified Collection.
void	ensureCapacity(int capacity) Increase the capacity of this ArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.
boolean	equals(java.lang.Object o) Compare the specified object with this list for equality.
java.lang.Object	get(int index) Return the element at the specified position in the list.
boolean	getFast() Returns true if this list is operating in fast mode.
int	hashCode() Return the hash code value for this list.
int	indexOf(java.lang.Object element) Search for the first occurrence of the given argument, testing for equality using the equals() method, and return the corresponding index, or -1 if the object is not found.
boolean	isEmpty() Test if this list has no elements.
java.util.Iterator	iterator() Return an iterator over the elements in this list in proper sequence.
int	lastIndexOf(java.lang.Object element) Search for the last occurrence of the given argument, testing for equality using the equals() method, and return the corresponding index, or -1 if the object is not found.
java.util.ListIterator	listIterator() Return an iterator of the elements of this list, in proper sequence.
java.util.ListIterator	listIterator(int index) Return an iterator of the elements of this list, in proper sequence, starting at the specified position.
java.lang.Object	remove(int index) Remove the element at the specified position in the list, and shift any subsequent elements down one position.
boolean	remove(java.lang.Object element) Remove the first occurrence of the specified element from the list, and shift any subsequent elements down one position.
boolean	removeAll(java.util.Collection collection) Remove from this collection all of its elements that are contained in the specified collection.
boolean	retainAll(java.util.Collection collection) Remove from this collection all of its elements except those that are contained in the specified collection.
java.lang.Object	set(int index, java.lang.Object element) Replace the element at the specified position in this list with the specified element.
void	setFast(boolean fast) Sets whether this list will operate in fast mode.
int	size() Return the number of elements in this list.
java.util.List	subList(int fromIndex, int toIndex) Return a view of the portion of this list between fromIndex (inclusive) and toIndex (exclusive).
java.lang.Object[]	toArray() Return an array containing all of the elements in this list in the correct order.
java.lang.Object[]	toArray(java.lang.Object[] array) Return an array containing all of the elements in this list in the correct order.
java.lang.String	toString() Return a String representation of this object.
void	trimToSize() Trim the capacity of this ArrayList instance to be the list's current size.

Methods inherited from class java.util.ArrayList

forEach, removeIf, replaceAll, sort, spliterator

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, stream

Constructor Detail

FastArrayList

public FastArrayList()

Construct a an empty list.

FastArrayList

public FastArrayList(int capacity)

Construct an empty list with the specified capacity.

Parameters:

capacity - The initial capacity of the empty list

FastArrayList

public FastArrayList(java.util.Collection collection)

Construct a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Parameters:

collection - The collection whose elements initialize the contents of this list

Method Detail

getFast

public boolean getFast()

Returns true if this list is operating in fast mode.

Returns:

true if this list is operating in fast mode

setFast

public void setFast(boolean fast)

Sets whether this list will operate in fast mode.

Parameters:

fast - true if the list should operate in fast mode

add

public boolean add(java.lang.Object element)

Appends the specified element to the end of this list.

Specified by:

add in interface java.util.Collection

Specified by:

add in interface java.util.List

Overrides:

add in class java.util.ArrayList

Parameters:

element - The element to be appended

add

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

Insert the specified element at the specified position in this list, and shift all remaining elements up one position.

Specified by:

add in interface java.util.List

Overrides:

add in class java.util.ArrayList

Parameters:

index - Index at which to insert this element

element - The element to be inserted

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

addAll

public boolean addAll(java.util.Collection collection)

Append 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.

Specified by:

addAll in interface java.util.Collection

Specified by:

addAll in interface java.util.List

Overrides:

addAll in class java.util.ArrayList

Parameters:

collection - The collection to be appended

addAll

public boolean addAll(int index,
                      java.util.Collection collection)

Insert all of the elements in the specified Collection at the specified position in this list, and shift any previous elements upwards as needed.

Specified by:

addAll in interface java.util.List

Overrides:

addAll in class java.util.ArrayList

Parameters:

index - Index at which insertion takes place

collection - The collection to be added

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

clear

public void clear()

Remove all of the elements from this list. The list will be empty after this call returns.

Specified by:

clear in interface java.util.Collection

Specified by:

clear in interface java.util.List

Overrides:

clear in class java.util.ArrayList

Throws:

java.lang.UnsupportedOperationException - if clear() is not supported by this list

clone

public java.lang.Object clone()

Return a shallow copy of this FastArrayList instance. The elements themselves are not copied.

Overrides:

clone in class java.util.ArrayList

contains

public boolean contains(java.lang.Object element)

Return true if this list contains the specified element.

Specified by:

contains in interface java.util.Collection

Specified by:

contains in interface java.util.List

Overrides:

contains in class java.util.ArrayList

Parameters:

element - The element to test for

containsAll

public boolean containsAll(java.util.Collection collection)

Return true if this list contains all of the elements in the specified Collection.

Specified by:

containsAll in interface java.util.Collection

Specified by:

containsAll in interface java.util.List

Overrides:

containsAll in class java.util.AbstractCollection

Parameters:

collection - Collection whose elements are to be checked

ensureCapacity

public void ensureCapacity(int capacity)

Increase the capacity of this ArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.

Overrides:

ensureCapacity in class java.util.ArrayList

Parameters:

capacity - The new minimum capacity

equals

public boolean equals(java.lang.Object o)

Compare the specified object with this list for equality. This implementation uses exactly the code that is used to define the list equals function in the documentation for the List.equals method.

Specified by:

equals in interface java.util.Collection

Specified by:

equals in interface java.util.List

Overrides:

equals in class java.util.AbstractList

Parameters:

o - Object to be compared to this list

get

public java.lang.Object get(int index)

Return the element at the specified position in the list.

Specified by:

get in interface java.util.List

Overrides:

get in class java.util.ArrayList

Parameters:

index - The index of the element to return

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

hashCode

public int hashCode()

Return the hash code value for this list. This implementation uses exactly the code that is used to define the list hash function in the documentation for the List.hashCode method.

Specified by:

hashCode in interface java.util.Collection

Specified by:

hashCode in interface java.util.List

Overrides:

hashCode in class java.util.AbstractList

indexOf

public int indexOf(java.lang.Object element)

Search for the first occurrence of the given argument, testing for equality using the equals() method, and return the corresponding index, or -1 if the object is not found.

Specified by:

indexOf in interface java.util.List

Overrides:

indexOf in class java.util.ArrayList

Parameters:

element - The element to search for

isEmpty

public boolean isEmpty()

Test if this list has no elements.

Specified by:

isEmpty in interface java.util.Collection

Specified by:

isEmpty in interface java.util.List

Overrides:

isEmpty in class java.util.ArrayList

iterator

public java.util.Iterator iterator()

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

Thread safety
The iterator returned is thread-safe ONLY in FAST mode. In slow mode there is no way to synchronize, or make the iterator thread-safe.

In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).

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.ArrayList

Returns:

the iterator

lastIndexOf

public int lastIndexOf(java.lang.Object element)

Search for the last occurrence of the given argument, testing for equality using the equals() method, and return the corresponding index, or -1 if the object is not found.

Specified by:

lastIndexOf in interface java.util.List

Overrides:

lastIndexOf in class java.util.ArrayList

Parameters:

element - The element to search for

listIterator

public java.util.ListIterator listIterator()

Return an iterator of the elements of this list, in proper sequence.

Thread safety
The iterator returned is thread-safe ONLY in FAST mode. In slow mode there is no way to synchronize, or make the iterator thread-safe.

In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class java.util.ArrayList

Returns:

the list iterator

listIterator

public java.util.ListIterator listIterator(int index)

Return an iterator of the elements of this list, in proper sequence, starting at the specified position.

Thread safety
The iterator returned is thread-safe ONLY in FAST mode. In slow mode there is no way to synchronize, or make the iterator thread-safe.

In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class java.util.ArrayList

Parameters:

index - The starting position of the iterator to return

Returns:

the list iterator

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

remove

public java.lang.Object remove(int index)

Remove the element at the specified position in the list, and shift any subsequent elements down one position.

Specified by:

remove in interface java.util.List

Overrides:

remove in class java.util.ArrayList

Parameters:

index - Index of the element to be removed

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

remove

public boolean remove(java.lang.Object element)

Remove the first occurrence of the specified element from the list, and shift any subsequent elements down one position.

Specified by:

remove in interface java.util.Collection

Specified by:

remove in interface java.util.List

Overrides:

remove in class java.util.ArrayList

Parameters:

element - Element to be removed

removeAll

public boolean removeAll(java.util.Collection collection)

Remove from this collection all of its elements that are contained in the specified collection.

Specified by:

removeAll in interface java.util.Collection

Specified by:

removeAll in interface java.util.List

Overrides:

removeAll in class java.util.ArrayList

Parameters:

collection - Collection containing elements to be removed

Throws:

java.lang.UnsupportedOperationException - if this optional operation is not supported by this list

retainAll

public boolean retainAll(java.util.Collection collection)

Remove from this collection all of its elements except those that are contained in the specified collection.

Specified by:

retainAll in interface java.util.Collection

Specified by:

retainAll in interface java.util.List

Overrides:

retainAll in class java.util.ArrayList

Parameters:

collection - Collection containing elements to be retained

Throws:

java.lang.UnsupportedOperationException - if this optional operation is not supported by this list

set

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

Replace the element at the specified position in this list with the specified element. Returns the previous object at that position.

IMPLEMENTATION NOTE - This operation is specifically documented to not be a structural change, so it is safe to be performed without cloning.

Specified by:

set in interface java.util.List

Overrides:

set in class java.util.ArrayList

Parameters:

index - Index of the element to replace

element - The new element to be stored

Throws:

java.lang.IndexOutOfBoundsException - if the index is out of range

size

public int size()

Return the number of elements in this list.

Specified by:

size in interface java.util.Collection

Specified by:

size in interface java.util.List

Overrides:

size in class java.util.ArrayList

subList

public java.util.List subList(int fromIndex,
                              int toIndex)

Return a view of the portion of this list between fromIndex (inclusive) and toIndex (exclusive). The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list. The returned list supports all of the optional list operations supported by this list.

Specified by:

subList in interface java.util.List

Overrides:

subList in class java.util.ArrayList

Parameters:

fromIndex - The starting index of the sublist view

toIndex - The index after the end of the sublist view

Throws:

java.lang.IndexOutOfBoundsException - if an index is out of range

toArray

public java.lang.Object[] toArray()

Return an array containing all of the elements in this list in the correct order.

Specified by:

toArray in interface java.util.Collection

Specified by:

toArray in interface java.util.List

Overrides:

toArray in class java.util.ArrayList

toArray

public java.lang.Object[] toArray(java.lang.Object[] array)

Return an array containing all of the elements in this list in the correct order. The runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array, and the size of this list.

Specified by:

toArray in interface java.util.Collection

Specified by:

toArray in interface java.util.List

Overrides:

toArray in class java.util.ArrayList

Parameters:

array - Array defining the element type of the returned list

Throws:

java.lang.ArrayStoreException - if the runtime type of array is not a supertype of the runtime type of every element in this list

toString

public java.lang.String toString()

Return a String representation of this object.

Overrides:

toString in class java.util.AbstractCollection

trimToSize

public void trimToSize()

Trim the capacity of this ArrayList instance to be the list's current size. An application can use this operation to minimize the storage of an ArrayList instance.

Overrides:

trimToSize in class java.util.ArrayList