Modifier and Type | Method and Description |
---|---|
static <E> List<E> |
asList(E first,
E[] rest)
Returns an unmodifiable list containing the specified first element and backed by the specified
array of additional elements.
|
static <E> List<E> |
asList(E first,
E second,
E[] rest)
Returns an unmodifiable list containing the specified first and second element, and backed by
the specified array of additional elements.
|
static <B> List<List<B>> |
cartesianProduct(List<? extends B>... lists)
Returns every possible list that can be formed by choosing one element from each of the given
lists in order; the "n-ary Cartesian
product" of the lists.
|
static <B> List<List<B>> |
cartesianProduct(List<? extends List<? extends B>> lists)
Returns every possible list that can be formed by choosing one element from each of the given
lists in order; the "n-ary Cartesian
product" of the lists.
|
static List<Character> |
charactersOf(CharSequence sequence)
Returns a view of the specified
CharSequence as a List<Character> , viewing
sequence as a sequence of Unicode code units. |
static ImmutableList<Character> |
charactersOf(String string)
Returns a view of the specified string as an immutable list of
Character values. |
static <E> ArrayList<E> |
newArrayList()
Creates a mutable, empty
ArrayList instance (for Java 6 and earlier). |
static <E> ArrayList<E> |
newArrayList(E... elements)
Creates a mutable
ArrayList instance containing the given elements. |
static <E> ArrayList<E> |
newArrayList(Iterable<? extends E> elements)
Creates a mutable
ArrayList instance containing the given elements; a very thin
shortcut for creating an empty list then calling Iterables.addAll(java.util.Collection<T>, java.lang.Iterable<? extends T>) . |
static <E> ArrayList<E> |
newArrayList(Iterator<? extends E> elements)
Creates a mutable
ArrayList instance containing the given elements; a very thin
shortcut for creating an empty list and then calling Iterators.addAll(java.util.Collection<T>, java.util.Iterator<? extends T>) . |
static <E> ArrayList<E> |
newArrayListWithCapacity(int initialArraySize)
Creates an
ArrayList instance backed by an array with the specified initial size;
simply delegates to ArrayList.ArrayList(int) . |
static <E> ArrayList<E> |
newArrayListWithExpectedSize(int estimatedSize)
Creates an
ArrayList instance to hold estimatedSize elements, plus an
unspecified amount of padding; you almost certainly mean to call newArrayListWithCapacity(int) (see that method for further advice on usage). |
static <E> CopyOnWriteArrayList<E> |
newCopyOnWriteArrayList()
Creates an empty
CopyOnWriteArrayList instance. |
static <E> CopyOnWriteArrayList<E> |
newCopyOnWriteArrayList(Iterable<? extends E> elements)
Creates a
CopyOnWriteArrayList instance containing the given elements. |
static <E> LinkedList<E> |
newLinkedList()
Creates a mutable, empty
LinkedList instance (for Java 6 and earlier). |
static <E> LinkedList<E> |
newLinkedList(Iterable<? extends E> elements)
Creates a mutable
LinkedList instance containing the given elements; a very thin
shortcut for creating an empty list then calling Iterables.addAll(java.util.Collection<T>, java.lang.Iterable<? extends T>) . |
static <T> List<List<T>> |
partition(List<T> list,
int size)
Returns consecutive sublists of a list, each of the same
size (the final list may be smaller).
|
static <T> List<T> |
reverse(List<T> list)
Returns a reversed view of the specified list.
|
static <F,T> List<T> |
transform(List<F> fromList,
Function<? super F,? extends T> function)
Returns a list that applies
function to each element of fromList . |
@GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayList()
ArrayList
instance (for Java 6 and earlier).
Note: if mutability is not required, use ImmutableList.of()
instead.
Note for Java 7 and later: this method is now unnecessary and should be treated as
deprecated. Instead, use the ArrayList
constructor
directly, taking advantage of the new "diamond" syntax.
@SafeVarargs @GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayList(E... elements)
ArrayList
instance containing the given elements.
Note: essentially the only reason to use this method is when you will need to add or
remove elements later. Otherwise, for non-null elements use ImmutableList.of()
(for
varargs) or ImmutableList.copyOf(Object[])
(for an array) instead. If any elements
might be null, or you need support for List.set(int, Object)
, use Arrays.asList(T...)
.
Note that even when you do need the ability to add or remove, this method provides only a
tiny bit of syntactic sugar for newArrayList(
asList
(...))
, or for creating an empty list then calling Collections.addAll(java.util.Collection<? super T>, T...)
. This method is
not actually very useful and will likely be deprecated in the future.
@GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayList(Iterable<? extends E> elements)
ArrayList
instance containing the given elements; a very thin
shortcut for creating an empty list then calling Iterables.addAll(java.util.Collection<T>, java.lang.Iterable<? extends T>)
.
Note: if mutability is not required and the elements are non-null, use ImmutableList.copyOf(Iterable)
instead. (Or, change elements
to be a FluentIterable
and call elements.toList()
.)
Note for Java 7 and later: if elements
is a Collection
, you don't
need this method. Use the ArrayList
constructor directly, taking advantage of the new "diamond"
syntax.
@GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayList(Iterator<? extends E> elements)
ArrayList
instance containing the given elements; a very thin
shortcut for creating an empty list and then calling Iterators.addAll(java.util.Collection<T>, java.util.Iterator<? extends T>)
.
Note: if mutability is not required and the elements are non-null, use ImmutableList.copyOf(Iterator)
instead.
@GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayListWithCapacity(int initialArraySize)
ArrayList
instance backed by an array with the specified initial size;
simply delegates to ArrayList.ArrayList(int)
.
Note for Java 7 and later: this method is now unnecessary and should be treated as
deprecated. Instead, use new
ArrayList
<>(int)
directly, taking advantage of the new "diamond" syntax.
(Unlike here, there is no risk of overload ambiguity, since the ArrayList
constructors
very wisely did not accept varargs.)
initialArraySize
- the exact size of the initial backing array for the returned array list
(ArrayList
documentation calls this value the "capacity")ArrayList
which is guaranteed not to resize itself unless its size
reaches initialArraySize + 1
IllegalArgumentException
- if initialArraySize
is negative@GwtCompatible(serializable=true) public static <E> ArrayList<E> newArrayListWithExpectedSize(int estimatedSize)
ArrayList
instance to hold estimatedSize
elements, plus an
unspecified amount of padding; you almost certainly mean to call newArrayListWithCapacity(int)
(see that method for further advice on usage).
Note: This method will soon be deprecated. Even in the rare case that you do want some amount of padding, it's best if you choose your desired amount explicitly.
estimatedSize
- an estimate of the eventual List.size()
of the new listArrayList
, sized appropriately to hold the estimated number of
elementsIllegalArgumentException
- if estimatedSize
is negative@GwtCompatible(serializable=true) public static <E> LinkedList<E> newLinkedList()
LinkedList
instance (for Java 6 and earlier).
Note: if you won't be adding any elements to the list, use ImmutableList.of()
instead.
Performance note: ArrayList
and ArrayDeque
consistently
outperform LinkedList
except in certain rare and specific situations. Unless you have
spent a lot of time benchmarking your specific needs, use one of those instead.
Note for Java 7 and later: this method is now unnecessary and should be treated as
deprecated. Instead, use the LinkedList
constructor directly, taking advantage of the new "diamond"
syntax.
@GwtCompatible(serializable=true) public static <E> LinkedList<E> newLinkedList(Iterable<? extends E> elements)
LinkedList
instance containing the given elements; a very thin
shortcut for creating an empty list then calling Iterables.addAll(java.util.Collection<T>, java.lang.Iterable<? extends T>)
.
Note: if mutability is not required and the elements are non-null, use ImmutableList.copyOf(Iterable)
instead. (Or, change elements
to be a FluentIterable
and call elements.toList()
.)
Performance note: ArrayList
and ArrayDeque
consistently
outperform LinkedList
except in certain rare and specific situations. Unless you have
spent a lot of time benchmarking your specific needs, use one of those instead.
Note for Java 7 and later: if elements
is a Collection
, you don't
need this method. Use the LinkedList
constructor directly, taking advantage of the new "diamond"
syntax.
@GwtIncompatible public static <E> CopyOnWriteArrayList<E> newCopyOnWriteArrayList()
CopyOnWriteArrayList
instance.
Note: if you need an immutable empty List
, use Collections.emptyList()
instead.
CopyOnWriteArrayList
@GwtIncompatible public static <E> CopyOnWriteArrayList<E> newCopyOnWriteArrayList(Iterable<? extends E> elements)
CopyOnWriteArrayList
instance containing the given elements.elements
- the elements that the list should contain, in orderCopyOnWriteArrayList
containing those elementspublic static <E> List<E> asList(E first, E[] rest)
rest
array will be reflected in the
returned list. Unlike Arrays.asList(T...)
, the returned list is unmodifiable.
This is useful when a varargs method needs to use a signature such as (Foo firstFoo,
Foo... moreFoos)
, in order to avoid overload ambiguity or to enforce a minimum argument count.
The returned list is serializable and implements RandomAccess
.
first
- the first elementrest
- an array of additional elements, possibly emptypublic static <E> List<E> asList(E first, E second, E[] rest)
rest
array will be reflected
in the returned list. Unlike Arrays.asList(T...)
, the returned list is unmodifiable.
This is useful when a varargs method needs to use a signature such as (Foo firstFoo,
Foo secondFoo, Foo... moreFoos)
, in order to avoid overload ambiguity or to enforce a minimum
argument count.
The returned list is serializable and implements RandomAccess
.
first
- the first elementsecond
- the second elementrest
- an array of additional elements, possibly emptypublic static <B> List<List<B>> cartesianProduct(List<? extends List<? extends B>> lists)
Lists.cartesianProduct(ImmutableList.of(
ImmutableList.of(1, 2),
ImmutableList.of("A", "B", "C")))
returns a list containing six lists in the following order:
ImmutableList.of(1, "A")
ImmutableList.of(1, "B")
ImmutableList.of(1, "C")
ImmutableList.of(2, "A")
ImmutableList.of(2, "B")
ImmutableList.of(2, "C")
The result is guaranteed to be in the "traditional", lexicographical order for Cartesian products that you would get from nesting for loops:
for (B b0 : lists.get(0)) {
for (B b1 : lists.get(1)) {
...
ImmutableList<B> tuple = ImmutableList.of(b0, b1, ...);
// operate on tuple
}
}
Note that if any input list is empty, the Cartesian product will also be empty. If no lists at all are provided (an empty list), the resulting Cartesian product has one element, an empty list (counter-intuitive, but mathematically consistent).
Performance notes: while the cartesian product of lists of size m, n, p
is a
list of size m x n x p
, its actual memory consumption is much smaller. When the
cartesian product is constructed, the input lists are merely copied. Only as the resulting list
is iterated are the individual lists created, and these are not retained after iteration.
B
- any common base class shared by all axes (often just Object
)lists
- the lists to choose elements from, in the order that the elements chosen from
those lists should appear in the resulting listsIllegalArgumentException
- if the size of the cartesian product would be greater than
Integer.MAX_VALUE
NullPointerException
- if lists
, any one of the lists
, or any element of
a provided list is null@SafeVarargs public static <B> List<List<B>> cartesianProduct(List<? extends B>... lists)
Lists.cartesianProduct(ImmutableList.of(
ImmutableList.of(1, 2),
ImmutableList.of("A", "B", "C")))
returns a list containing six lists in the following order:
ImmutableList.of(1, "A")
ImmutableList.of(1, "B")
ImmutableList.of(1, "C")
ImmutableList.of(2, "A")
ImmutableList.of(2, "B")
ImmutableList.of(2, "C")
The result is guaranteed to be in the "traditional", lexicographical order for Cartesian products that you would get from nesting for loops:
for (B b0 : lists.get(0)) {
for (B b1 : lists.get(1)) {
...
ImmutableList<B> tuple = ImmutableList.of(b0, b1, ...);
// operate on tuple
}
}
Note that if any input list is empty, the Cartesian product will also be empty. If no lists at all are provided (an empty list), the resulting Cartesian product has one element, an empty list (counter-intuitive, but mathematically consistent).
Performance notes: while the cartesian product of lists of size m, n, p
is a
list of size m x n x p
, its actual memory consumption is much smaller. When the
cartesian product is constructed, the input lists are merely copied. Only as the resulting list
is iterated are the individual lists created, and these are not retained after iteration.
B
- any common base class shared by all axes (often just Object
)lists
- the lists to choose elements from, in the order that the elements chosen from
those lists should appear in the resulting listsIllegalArgumentException
- if the size of the cartesian product would be greater than
Integer.MAX_VALUE
NullPointerException
- if lists
, any one of the lists
, or any element of
a provided list is nullpublic static <F,T> List<T> transform(List<F> fromList, Function<? super F,? extends T> function)
function
to each element of fromList
. The returned
list is a transformed view of fromList
; changes to fromList
will be reflected
in the returned list and vice versa.
Since functions are not reversible, the transform is one-way and new items cannot be stored
in the returned list. The add
, addAll
and set
methods are unsupported
in the returned list.
The function is applied lazily, invoked when needed. This is necessary for the returned list
to be a view, but it means that the function will be applied many times for bulk operations
like List.contains(java.lang.Object)
and List.hashCode()
. For this to perform well, function
should be fast. To avoid lazy evaluation when the returned list doesn't need to be a
view, copy the returned list into a new list of your choosing.
If fromList
implements RandomAccess
, so will the returned list. The returned
list is threadsafe if the supplied list and function are.
If only a Collection
or Iterable
input is available, use Collections2.transform(java.util.Collection<F>, com.google.common.base.Function<? super F, T>)
or Iterables.transform(java.lang.Iterable<F>, com.google.common.base.Function<? super F, ? extends T>)
.
Note: serializing the returned list is implemented by serializing fromList
,
its contents, and function
-- not by serializing the transformed values. This
can lead to surprising behavior, so serializing the returned list is not recommended.
Instead, copy the list using ImmutableList.copyOf(Collection)
(for example), then
serialize the copy. Other methods similar to this do not implement serialization at all for
this reason.
Java 8 users: many use cases for this method are better addressed by Stream.map(java.util.function.Function<? super T, ? extends R>)
. This method is not being deprecated, but we gently encourage you
to migrate to streams.
public static <T> List<List<T>> partition(List<T> list, int size)
[a, b,
c, d, e]
with a partition size of 3 yields [[a, b, c], [d, e]]
-- an outer list
containing two inner lists of three and two elements, all in the original order.
The outer list is unmodifiable, but reflects the latest state of the source list. The inner
lists are sublist views of the original list, produced on demand using List.subList(int,
int)
, and are subject to all the usual caveats about modification as explained in that API.
list
- the list to return consecutive sublists ofsize
- the desired size of each sublist (the last may be smaller)IllegalArgumentException
- if partitionSize
is nonpositivepublic static ImmutableList<Character> charactersOf(String string)
Character
values.@Beta public static List<Character> charactersOf(CharSequence sequence)
CharSequence
as a List<Character>
, viewing
sequence
as a sequence of Unicode code units. The view does not support any
modification operations, but reflects any changes to the underlying character sequence.sequence
- the character sequence to view as a List
of charactersList<Character>
view of the character sequencepublic static <T> List<T> reverse(List<T> list)
Lists.reverse(Arrays.asList(1, 2, 3))
returns a list containing 3, 2, 1
. The returned
list is backed by this list, so changes in the returned list are reflected in this list, and
vice-versa. The returned list supports all of the optional list operations supported by this
list.
The returned list is random-access if the specified list is random access.
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