Package it.unimi.dsi.fastutil.ints

Class IntArrayList

java.lang.Object

java.util.AbstractCollection<Integer>

it.unimi.dsi.fastutil.ints.AbstractIntCollection

it.unimi.dsi.fastutil.ints.AbstractIntList

it.unimi.dsi.fastutil.ints.IntArrayList

All Implemented Interfaces:

IntCollection, IntIterable, IntList, IntStack, Stack<Integer>, Serializable, Cloneable, Comparable<List<? extends Integer>>, Iterable<Integer>, Collection<Integer>, List<Integer>, RandomAccess, SequencedCollection<Integer>

public class IntArrayList
extends AbstractIntList
implements RandomAccess, Cloneable, Serializable

A type-specific array-based list; provides some additional methods that use polymorphism to avoid (un)boxing.

This class implements a lightweight, fast, open, optimized, reuse-oriented version of array-based lists. Instances of this class represent a list with an array that is enlarged as needed when new entries are created (by increasing its current length by 50%), but is never made smaller (even on a clear()). A family of trimming methods lets you control the size of the backing array; this is particularly useful if you reuse instances of this class. Range checks are equivalent to those of java.util's classes, but they are delayed as much as possible. The backing array is exposed by the elements() method.

This class implements the bulk methods removeElements(), addElements() and getElements() using high-performance system calls (e.g., System.arraycopy()) instead of expensive loops.

See Also:

• ArrayList
• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.ints.AbstractIntList

AbstractIntList.IntRandomAccessSubList, AbstractIntList.IntSubList

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_INITIAL_CAPACITY	The initial default capacity of an array list.

Constructor Summary

Constructors

Constructor	Description
IntArrayList()	Creates a new array list with DEFAULT_INITIAL_CAPACITY capacity.
IntArrayList(int capacity)	Creates a new array list with given capacity.
IntArrayList(int[] a)	Creates a new array list and fills it with the elements of a given array.
IntArrayList(int[] a, int offset, int length)	Creates a new array list and fills it with the elements of a given array.
IntArrayList(IntCollection c)	Creates a new array list and fills it with a given type-specific collection.
IntArrayList(IntIterator i)	Creates a new array list and fills it with the elements returned by a type-specific iterator..
IntArrayList(IntList l)	Creates a new array list and fills it with a given type-specific list.
IntArrayList(Collection<? extends Integer> c)	Creates a new array list and fills it with a given collection.
IntArrayList(Iterator<? extends Integer> i)	Creates a new array list and fills it with the elements returned by an iterator..

Method Summary

Modifier and Type	Method	Description
boolean	add(int k)	Ensures that this collection contains the specified element (optional operation).
void	add(int index, int k)	Inserts the specified element at the specified position in this list (optional operation).
boolean	addAll(int index, IntCollection c)	Inserts all of the elements in the specified type-specific collection into this type-specific list at the specified position (optional operation).
boolean	addAll(int index, IntList l)	Inserts all of the elements in the specified type-specific list into this type-specific list at the specified position (optional operation).
void	addElements(int index, int[] a, int offset, int length)	Adds elements to this type-specific list using optimized system calls.
void	clear()
IntArrayList	clone()
int	compareTo(IntArrayList l)	Compares this array list to another array list.
int	compareTo(List<? extends Integer> l)	Compares this list to another object.
int[]	elements()	Returns the backing array of this list.
void	ensureCapacity(int capacity)	Ensures that this array list can contain the given number of entries without resizing.
boolean	equals(IntArrayList l)	Compares this type-specific array list to another one.
boolean	equals(Object o)
void	forEach(IntConsumer action)	Performs the given action for each element of this type-specific Iterable until all elements have been processed or the action throws an exception.
void	getElements(int from, int[] a, int offset, int length)	Copies element of this type-specific list into the given array using optimized system calls.
int	getInt(int index)	Returns the element at the specified position in this list.
int	indexOf(int k)	Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
boolean	isEmpty()	Checks whether the stack is empty.
int	lastIndexOf(int k)	Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
IntListIterator	listIterator(int index)	Returns a type-specific list iterator on the list starting at a given index.
static IntArrayList	of()	Creates a new empty array list.
static IntArrayList	of(int... init)	Creates an array list using an array of elements.
boolean	rem(int k)	Removes a single instance of the specified element from this collection, if it is present (optional operation).
boolean	removeAll(IntCollection c)	Remove from this collection all elements in the given type-specific collection.
void	removeElements(int from, int to)	Removes elements of this type-specific list using optimized system calls.
boolean	removeIf(IntPredicate filter)	Remove from this collection all elements which satisfy the given predicate.
int	removeInt(int index)	Removes the element at the specified position in this list (optional operation).
int	set(int index, int k)	Replaces the element at the specified position in this list with the specified element (optional operation).
void	setElements(int index, int[] a, int offset, int length)	Sets elements to this type-specific list using optimized system calls.
int	size()
void	size(int size)	Sets the size of this list.
void	sort(IntComparator comp)	Sort a list using a type-specific comparator.
IntSpliterator	spliterator()	Returns a type-specific spliterator on the elements of this list.
IntList	subList(int from, int to)	Returns a type-specific view of the portion of this list from the index from, inclusive, to the index to, exclusive.
int[]	toArray(int[] a)	Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
static IntArrayList	toList(IntStream stream)	Collects the result of a primitive Stream into a new ArrayList.
static IntArrayList	toListWithExpectedSize(IntStream stream, int expectedSize)	Collects the result of a primitive Stream into a new ArrayList, potentially pre-allocated to handle the given size.
void	trim()	Trims this array list so that the capacity is equal to the size.
void	trim(int n)	Trims the backing array if it is too large.
void	unstableSort(IntComparator comp)	Sorts this list using a sort not assured to be stable.
static IntArrayList	wrap(int[] a)	Wraps a given array into an array list.
static IntArrayList	wrap(int[] a, int length)	Wraps a given array into an array list of given size.

Methods inherited from class it.unimi.dsi.fastutil.ints.AbstractIntList

addAll, addAll, addAll, addElements, contains, hashCode, iterator, listIterator, peekInt, popInt, push, replaceAll, toIntArray, topInt, toString

Methods inherited from class it.unimi.dsi.fastutil.ints.AbstractIntCollection

add, contains, containsAll, containsAll, forEach, remove, removeAll, removeIf, retainAll, retainAll, toIntArray

Methods inherited from class java.util.AbstractCollection

toArray, toArray

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

toArray

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntCollection

containsAll, intIterator, intParallelStream, intSpliterator, intStream, parallelStream, removeIf, removeIf, retainAll, stream, toIntArray

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntIterable

forEach, forEach

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntList

add, add, addAll, contains, get, indexOf, lastIndexOf, remove, remove, replaceAll, replaceAll, set, setElements, setElements, sort, unstableSort

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntStack

peek, pop, push, top

Methods inherited from interface java.util.List

addFirst, addLast, containsAll, getFirst, getLast, removeAll, removeFirst, removeLast, retainAll, reversed, toArray, toArray

Field Details

DEFAULT_INITIAL_CAPACITY

public static final int DEFAULT_INITIAL_CAPACITY

The initial default capacity of an array list.

See Also:

• Constant Field Values

Constructor Details

IntArrayList

public IntArrayList(int capacity)

Creates a new array list with given capacity.

Parameters:

capacity - the initial capacity of the array list (may be 0).

IntArrayList

public IntArrayList()

Creates a new array list with DEFAULT_INITIAL_CAPACITY capacity.

IntArrayList

public IntArrayList(Collection<? extends Integer> c)

Creates a new array list and fills it with a given collection.

Parameters:

c - a collection that will be used to fill the array list.

IntArrayList

public IntArrayList(IntCollection c)

Creates a new array list and fills it with a given type-specific collection.

Parameters:

c - a type-specific collection that will be used to fill the array list.

IntArrayList

public IntArrayList(IntList l)

Creates a new array list and fills it with a given type-specific list.

Parameters:

l - a type-specific list that will be used to fill the array list.

IntArrayList

public IntArrayList(int[] a)

Creates a new array list and fills it with the elements of a given array.

Parameters:

a - an array whose elements will be used to fill the array list.

IntArrayList

public IntArrayList(int[] a,
 int offset,
 int length)

Creates a new array list and fills it with the elements of a given array.

Parameters:

a - an array whose elements will be used to fill the array list.

offset - the first element to use.

length - the number of elements to use.

IntArrayList

public IntArrayList(Iterator<? extends Integer> i)

Creates a new array list and fills it with the elements returned by an iterator..

Parameters:

i - an iterator whose returned elements will fill the array list.

IntArrayList

public IntArrayList(IntIterator i)

Creates a new array list and fills it with the elements returned by a type-specific iterator..

Parameters:

i - a type-specific iterator whose returned elements will fill the array list.

Method Details

elements

public int[] elements()

Returns the backing array of this list.

Returns:

the backing array.

wrap

public static IntArrayList wrap(int[] a,
 int length)

Wraps a given array into an array list of given size.

Note it is guaranteed that the type of the array returned by elements() will be the same (see the comments in the class documentation).

Parameters:

a - an array to wrap.

length - the length of the resulting array list.

Returns:

a new array list of the given size, wrapping the given array.

wrap

public static IntArrayList wrap(int[] a)

Wraps a given array into an array list.

Note it is guaranteed that the type of the array returned by elements() will be the same (see the comments in the class documentation).

Parameters:

a - an array to wrap.

Returns:

a new array list wrapping the given array.

of

public static IntArrayList of()

Creates a new empty array list.

Returns:

a new empty array list.

of

public static IntArrayList of(int... init)

Creates an array list using an array of elements.

Parameters:

init - a the array the will become the new backing array of the array list.

Returns:

a new array list backed by the given array.

See Also:

• wrap(int[], int)

toList

public static IntArrayList toList(IntStream stream)

Collects the result of a primitive Stream into a new ArrayList.

This method performs a terminal operation on the given Stream

API Notes:

Taking a primitive stream instead of returning something like a Collector is necessary because there is no primitive Collector equivalent in the Java API.

toListWithExpectedSize

public static IntArrayList toListWithExpectedSize(IntStream stream,
 int expectedSize)

Collects the result of a primitive Stream into a new ArrayList, potentially pre-allocated to handle the given size.

This method performs a terminal operation on the given Stream

API Notes:

Taking a primitive stream instead returning something like a Collector is necessary because there is no primitive Collector equivalent in the Java API.

ensureCapacity

public void ensureCapacity(int capacity)

Ensures that this array list can contain the given number of entries without resizing.

Parameters:

capacity - the new minimum capacity for this array list.

add

public void add(int index,
 int k)

Description copied from class: AbstractIntList

Inserts the specified element at the specified position in this list (optional operation).

Specified by:

add in interface IntList

Overrides:

add in class AbstractIntList

See Also:

• List.add(int,Object)

add

public boolean add(int k)

Description copied from class: AbstractIntList

Ensures that this collection contains the specified element (optional operation).

Specified by:

add in interface IntCollection

Specified by:

add in interface IntList

Overrides:

add in class AbstractIntList

See Also:

• Collection.add(Object)

getInt

public int getInt(int index)

Description copied from interface: IntList

Returns the element at the specified position in this list.

Specified by:

getInt in interface IntList

See Also:

• List.get(int)

indexOf

public int indexOf(int k)

Description copied from interface: IntList

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

Specified by:

indexOf in interface IntList

Overrides:

indexOf in class AbstractIntList

See Also:

• List.indexOf(Object)

lastIndexOf

public int lastIndexOf(int k)

Description copied from interface: IntList

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.

Specified by:

lastIndexOf in interface IntList

Overrides:

lastIndexOf in class AbstractIntList

See Also:

• List.lastIndexOf(Object)

removeInt

public int removeInt(int index)

Description copied from class: AbstractIntList

Removes the element at the specified position in this list (optional operation).

Specified by:

removeInt in interface IntList

Overrides:

removeInt in class AbstractIntList

See Also:

• List.remove(int)

rem

public boolean rem(int k)

Description copied from class: AbstractIntList

Removes a single instance of the specified element from this collection, if it is present (optional operation).

Specified by:

rem in interface IntCollection

Overrides:

rem in class AbstractIntList

See Also:

• List.remove(Object)

set

public int set(int index,
 int k)

Description copied from class: AbstractIntList

Replaces the element at the specified position in this list with the specified element (optional operation).

Specified by:

set in interface IntList

Overrides:

set in class AbstractIntList

See Also:

• List.set(int,Object)

clear

public void clear()

Description copied from class: AbstractIntList

Specified by:

clear in interface Collection<Integer>

Specified by:

clear in interface List<Integer>

Overrides:

clear in class AbstractIntList

size

public int size()

Specified by:

size in interface Collection<Integer>

Specified by:

size in interface List<Integer>

Specified by:

size in class AbstractCollection<Integer>

size

public void size(int size)

Description copied from interface: IntList

Sets the size of this list.

If the specified size is smaller than the current size, the last elements are discarded. Otherwise, they are filled with 0/null/false.

Specified by:

size in interface IntList

Overrides:

size in class AbstractIntList

Parameters:

size - the new size.

isEmpty

public boolean isEmpty()

Description copied from interface: Stack

Checks whether the stack is empty.

Specified by:

isEmpty in interface Collection<Integer>

Specified by:

isEmpty in interface List<Integer>

Specified by:

isEmpty in interface Stack<Integer>

Overrides:

isEmpty in class AbstractCollection<Integer>

Returns:

true if the stack is empty.

trim

public void trim()

Trims this array list so that the capacity is equal to the size.

See Also:

• ArrayList.trimToSize()

trim

public void trim(int n)

Trims the backing array if it is too large. If the current array length is smaller than or equal to n, this method does nothing. Otherwise, it trims the array length to the maximum between n and size().

This method is useful when reusing lists. Clearing a list leaves the array length untouched. If you are reusing a list many times, you can call this method with a typical size to avoid keeping around a very large array just because of a few large transient lists.

Parameters:

n - the threshold for the trimming.

subList

public IntList subList(int from,
 int to)

Description copied from interface: IntList

Returns a type-specific view of the portion of this list from the index from, inclusive, to the index to, exclusive.

Specified by:

subList in interface IntList

Specified by:

subList in interface List<Integer>

Overrides:

subList in class AbstractIntList

See Also:

• List.subList(int,int)

getElements

public void getElements(int from,
 int[] a,
 int offset,
 int length)

Copies element of this type-specific list into the given array using optimized system calls.

Specified by:

getElements in interface IntList

Overrides:

getElements in class AbstractIntList

Parameters:

from - the start index (inclusive).

a - the destination array.

offset - the offset into the destination array where to store the first element copied.

length - the number of elements to be copied.

removeElements

public void removeElements(int from,
 int to)

Removes elements of this type-specific list using optimized system calls.

Specified by:

removeElements in interface IntList

Overrides:

removeElements in class AbstractIntList

Parameters:

from - the start index (inclusive).

to - the end index (exclusive).

addElements

public void addElements(int index,
 int[] a,
 int offset,
 int length)

Adds elements to this type-specific list using optimized system calls.

Specified by:

addElements in interface IntList

Overrides:

addElements in class AbstractIntList

Parameters:

index - the index at which to add elements.

a - the array containing the elements.

offset - the offset of the first element to add.

length - the number of elements to add.

setElements

public void setElements(int index,
 int[] a,
 int offset,
 int length)

Sets elements to this type-specific list using optimized system calls.

Specified by:

setElements in interface IntList

Overrides:

setElements in class AbstractIntList

Parameters:

index - the index at which to start setting elements.

a - the array containing the elements.

offset - the offset of the first element to add.

length - the number of elements to add.

forEach

public void forEach(IntConsumer action)

Description copied from class: AbstractIntList

Performs the given action for each element of this type-specific Iterable until all elements have been processed or the action throws an exception.

Specified by:

forEach in interface IntIterable

Overrides:

forEach in class AbstractIntList

Parameters:

action - the action to be performed for each element.

See Also:

• Iterable.forEach(java.util.function.Consumer)

addAll

public boolean addAll(int index,
 IntCollection c)

Description copied from interface: IntList

Inserts all of the elements in the specified type-specific collection into this type-specific list at the specified position (optional operation).

Specified by:

addAll in interface IntList

Overrides:

addAll in class AbstractIntList

See Also:

• List.addAll(int,java.util.Collection)

addAll

public boolean addAll(int index,
 IntList l)

Description copied from interface: IntList

Inserts all of the elements in the specified type-specific list into this type-specific list at the specified position (optional operation).

Specified by:

addAll in interface IntList

See Also:

• List.addAll(int,Collection)

removeAll

public boolean removeAll(IntCollection c)

Description copied from interface: IntCollection

Remove from this collection all elements in the given type-specific collection.

Specified by:

removeAll in interface IntCollection

Overrides:

removeAll in class AbstractIntCollection

Parameters:

c - a type-specific collection.

Returns:

true if this collection changed as a result of the call.

See Also:

• Collection.removeAll(Collection)

removeIf

public boolean removeIf(IntPredicate filter)

Description copied from interface: IntCollection

Remove from this collection all elements which satisfy the given predicate.

Specified by:

removeIf in interface IntCollection

Parameters:

filter - a predicate which returns true for elements to be removed.

Returns:

true if any elements were removed.

See Also:

• Collection.removeIf(java.util.function.Predicate)

toArray

public int[] toArray(int[] a)

Description copied from interface: IntCollection

Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.

Note that, contrarily to Collection.toArray(Object[]), this methods just writes all elements of this collection: no special value will be added after the last one.

Specified by:

toArray in interface IntCollection

Overrides:

toArray in class AbstractIntList

Parameters:

a - if this array is big enough, it will be used to store this collection.

Returns:

a primitive type array containing the items of this collection.

See Also:

• Collection.toArray(Object[])

listIterator

public IntListIterator listIterator(int index)

Description copied from class: AbstractIntList

Returns a type-specific list iterator on the list starting at a given index.

Specified by:

listIterator in interface IntList

Specified by:

listIterator in interface List<Integer>

Overrides:

listIterator in class AbstractIntList

See Also:

• List.listIterator(int)

spliterator

public IntSpliterator spliterator()

Returns a type-specific spliterator on the elements of this list.

List spliterators must report at least Spliterator.SIZED and Spliterator.ORDERED.

See List.spliterator() for more documentation on the requirements of the returned spliterator.

The returned spliterator is late-binding; it will track structural changes after the current index, up until the first trySplit(), at which point the maximum index will be fixed.
Structural changes before the current index or after the first trySplit() will result in unspecified behavior.

Specified by:

spliterator in interface Collection<Integer>

Specified by:

spliterator in interface IntCollection

Specified by:

spliterator in interface IntIterable

Specified by:

spliterator in interface IntList

Specified by:

spliterator in interface Iterable<Integer>

Specified by:

spliterator in interface List<Integer>

Returns:

a type-specific spliterator on the elements of this collection.

sort

public void sort(IntComparator comp)

Description copied from interface: IntList

Sort a list using a type-specific comparator.

Pass null to sort using natural ordering.

Specified by:

sort in interface IntList

See Also:

• List.sort(java.util.Comparator)

unstableSort

public void unstableSort(IntComparator comp)

Description copied from interface: IntList

Sorts this list using a sort not assured to be stable.

Pass null to sort using natural ordering.

This differs from List.sort(java.util.Comparator) in that the results are not assured to be stable, but may be a bit faster.

Unless a subclass specifies otherwise, the results of the method if the list is concurrently modified during the sort are unspecified.

Specified by:

unstableSort in interface IntList

clone

public IntArrayList clone()

equals

public boolean equals(IntArrayList l)

Compares this type-specific array list to another one.

Parameters:

l - a type-specific array list.

Returns:

true if the argument contains the same elements of this type-specific array list.

API Notes:

This method exists only for sake of efficiency. The implementation inherited from the abstract implementation would already work.

equals

public boolean equals(Object o)

Specified by:

equals in interface Collection<Integer>

Specified by:

equals in interface List<Integer>

Overrides:

equals in class AbstractIntList

compareTo

public int compareTo(IntArrayList l)

Compares this array list to another array list.

Parameters:

l - an array list.

Returns:

a negative integer, zero, or a positive integer as this list is lexicographically less than, equal to, or greater than the argument.

API Notes:

This method exists only for sake of efficiency. The implementation inherited from the abstract implementation would already work.

compareTo

public int compareTo(List<? extends Integer> l)

Description copied from class: AbstractIntList

Compares this list to another object. If the argument is a List, this method performs a lexicographical comparison; otherwise, it throws a ClassCastException.

Specified by:

compareTo in interface Comparable<List<? extends Integer>>

Overrides:

compareTo in class AbstractIntList

Parameters:

l - a list.

Returns:

if the argument is a List, a negative integer, zero, or a positive integer as this list is lexicographically less than, equal to, or greater than the argument.