@GwtCompatible(emulated=true) public abstract class FluentIterable<E> extends Object implements Iterable<E>
FluentIterable
provides a rich interface for manipulating Iterable
instances in a
chained fashion. A FluentIterable
can be created from an Iterable
, or from a set
of elements. The following types of methods are provided on FluentIterable
:
FluentIterable
based in some way on the contents
of the current one (for example transform(com.google.common.base.Function<? super E, T>)
)
FluentIterable
's contents into a new collection or
array (for example toList()
)
last()
)
FluentIterable
's contents (for example
anyMatch(com.google.common.base.Predicate<? super E>)
)
Here is an example that merges the lists returned by two separate database calls, transforms
it by invoking toString()
on each element, and returns the first 10 elements as an
ImmutableList
:
FluentIterable
.from(database.getClientList())
.filter(activeInLastMonth())
.transform(Functions.toStringFunction())
.limit(10)
.toList();
Anything which can be done using FluentIterable
could be done in a different fashion
(often with Iterables
), however the use of FluentIterable
makes many sets of
operations significantly more concise.
Modifier | Constructor and Description |
---|---|
protected |
FluentIterable()
Constructor for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
boolean |
allMatch(Predicate<? super E> predicate)
Returns
true if every element in this fluent iterable satisfies the predicate. |
boolean |
anyMatch(Predicate<? super E> predicate)
Returns
true if any element in this fluent iterable satisfies the predicate. |
boolean |
contains(Object element)
Returns
true if this fluent iterable contains any object for which
equals(element) is true. |
<C extends Collection<? super E>> |
copyInto(C collection)
Copies all the elements from this fluent iterable to
collection . |
FluentIterable<E> |
cycle()
Returns a fluent iterable whose
Iterator cycles indefinitely over the elements of
this fluent iterable. |
<T> FluentIterable<T> |
filter(Class<T> type)
Returns the elements from this fluent iterable that are instances of class
type . |
FluentIterable<E> |
filter(Predicate<? super E> predicate)
Returns the elements from this fluent iterable that satisfy a predicate.
|
Optional<E> |
first()
Returns an
Optional containing the first element in this fluent iterable. |
Optional<E> |
firstMatch(Predicate<? super E> predicate)
Returns an
Optional containing the first element in this fluent iterable that
satisfies the given predicate, if such an element exists. |
static <E> FluentIterable<E> |
from(FluentIterable<E> iterable)
Deprecated.
instances of
FluentIterable don't need to be converted to
FluentIterable |
static <E> FluentIterable<E> |
from(Iterable<E> iterable)
Returns a fluent iterable that wraps
iterable , or iterable itself if it
is already a FluentIterable . |
E |
get(int position)
Returns the element at the specified position in this fluent iterable.
|
<K> ImmutableListMultimap<K,E> |
index(Function<? super E,K> keyFunction)
Creates an index
ImmutableListMultimap that contains the results of applying a
specified function to each item in this FluentIterable of values. |
boolean |
isEmpty()
Determines whether this fluent iterable is empty.
|
Optional<E> |
last()
Returns an
Optional containing the last element in this fluent iterable. |
FluentIterable<E> |
limit(int size)
Creates a fluent iterable with the first
size elements of this
fluent iterable. |
int |
size()
Returns the number of elements in this fluent iterable.
|
FluentIterable<E> |
skip(int numberToSkip)
Returns a view of this fluent iterable that skips its first
numberToSkip
elements. |
E[] |
toArray(Class<E> type)
Returns an array containing all of the elements from this fluent iterable in iteration order.
|
ImmutableList<E> |
toList()
Returns an
ImmutableList containing all of the elements from this fluent iterable in
proper sequence. |
<V> ImmutableMap<E,V> |
toMap(Function<? super E,V> valueFunction)
Returns an immutable map for which the elements of this
FluentIterable are the keys in
the same order, mapped to values by the given function. |
ImmutableSet<E> |
toSet()
Returns an
ImmutableSet containing all of the elements from this fluent iterable with
duplicates removed. |
ImmutableList<E> |
toSortedList(Comparator<? super E> comparator)
Returns an
ImmutableList containing all of the elements from this FluentIterable in the order specified by comparator . |
ImmutableSortedSet<E> |
toSortedSet(Comparator<? super E> comparator)
Returns an
ImmutableSortedSet containing all of the elements from this FluentIterable in the order specified by comparator , with duplicates (determined by
comparator.compare(x, y) == 0 ) removed. |
String |
toString()
Returns a string representation of this fluent iterable, with the format
[e1, e2, ..., en] . |
<T> FluentIterable<T> |
transform(Function<? super E,T> function)
Returns a fluent iterable that applies
function to each element of this
fluent iterable. |
<T> FluentIterable<T> |
transformAndConcat(Function<? super E,? extends Iterable<? extends T>> function)
Applies
function to each element of this fluent iterable and returns
a fluent iterable with the concatenated combination of results. |
<K> ImmutableMap<K,E> |
uniqueIndex(Function<? super E,K> keyFunction)
Returns an immutable map for which the
Map.values() are the elements of this
FluentIterable in the given order, and each key is the product of invoking a supplied
function on its corresponding value. |
protected FluentIterable()
public static <E> FluentIterable<E> from(Iterable<E> iterable)
iterable
, or iterable
itself if it
is already a FluentIterable
.@Deprecated public static <E> FluentIterable<E> from(FluentIterable<E> iterable)
FluentIterable
don't need to be converted to
FluentIterable
Iterable
to
FluentIterable
has obviated the need to explicitly convert to a FluentIterable
.public String toString()
[e1, e2, ..., en]
.public final int size()
public final boolean contains(@Nullable Object element)
true
if this fluent iterable contains any object for which
equals(element)
is true.@CheckReturnValue public final FluentIterable<E> cycle()
Iterator
cycles indefinitely over the elements of
this fluent iterable.
That iterator supports remove()
if iterable.iterator()
does. After
remove()
is called, subsequent cycles omit the removed element, which is no longer in
this fluent iterable. The iterator's hasNext()
method returns true
until
this fluent iterable is empty.
Warning: Typical uses of the resulting iterator may produce an infinite loop. You
should use an explicit break
or be certain that you will eventually remove all the
elements.
@CheckReturnValue public final FluentIterable<E> filter(Predicate<? super E> predicate)
remove()
.@GwtIncompatible(value="Class.isInstance") @CheckReturnValue public final <T> FluentIterable<T> filter(Class<T> type)
type
.type
- the type of elements desiredpublic final boolean anyMatch(Predicate<? super E> predicate)
true
if any element in this fluent iterable satisfies the predicate.public final boolean allMatch(Predicate<? super E> predicate)
true
if every element in this fluent iterable satisfies the predicate.
If this fluent iterable is empty, true
is returned.public final Optional<E> firstMatch(Predicate<? super E> predicate)
Optional
containing the first element in this fluent iterable that
satisfies the given predicate, if such an element exists.
Warning: avoid using a predicate
that matches null
. If null
is matched in this fluent iterable, a NullPointerException
will be thrown.
public final <T> FluentIterable<T> transform(Function<? super E,T> function)
function
to each element of this
fluent iterable.
The returned fluent iterable's iterator supports remove()
if this iterable's
iterator does. After a successful remove()
call, this fluent iterable no longer
contains the corresponding element.
public <T> FluentIterable<T> transformAndConcat(Function<? super E,? extends Iterable<? extends T>> function)
function
to each element of this fluent iterable and returns
a fluent iterable with the concatenated combination of results. function
returns an Iterable of results.
The returned fluent iterable's iterator supports remove()
if this
function-returned iterables' iterator does. After a successful remove()
call,
the returned fluent iterable no longer contains the corresponding element.
Function<E, Iterable<T>>
until 14.0)public final Optional<E> first()
Optional
containing the first element in this fluent iterable.
If the iterable is empty, Optional.absent()
is returned.NullPointerException
- if the first element is null; if this is a possibility, use
iterator().next()
or Iterables.getFirst(java.lang.Iterable<? extends T>, T)
instead.public final Optional<E> last()
Optional
containing the last element in this fluent iterable.
If the iterable is empty, Optional.absent()
is returned.NullPointerException
- if the last element is null; if this is a possibility, use
Iterables.getLast(java.lang.Iterable<T>)
instead.@CheckReturnValue public final FluentIterable<E> skip(int numberToSkip)
numberToSkip
elements. If this fluent iterable contains fewer than numberToSkip
elements,
the returned fluent iterable skips all of its elements.
Modifications to this fluent iterable before a call to iterator()
are
reflected in the returned fluent iterable. That is, the its iterator skips the first
numberToSkip
elements that exist when the iterator is created, not when skip()
is called.
The returned fluent iterable's iterator supports remove()
if the
Iterator
of this fluent iterable supports it. Note that it is not
possible to delete the last skipped element by immediately calling remove()
on the
returned fluent iterable's iterator, as the Iterator
contract states that a call
to * remove()
before a call to next()
will throw an
IllegalStateException
.
@CheckReturnValue public final FluentIterable<E> limit(int size)
size
elements of this
fluent iterable. If this fluent iterable does not contain that many elements,
the returned fluent iterable will have the same behavior as this fluent iterable.
The returned fluent iterable's iterator supports remove()
if this
fluent iterable's iterator does.size
- the maximum number of elements in the returned fluent iterableIllegalArgumentException
- if size
is negativepublic final boolean isEmpty()
public final ImmutableList<E> toList()
ImmutableList
containing all of the elements from this fluent iterable in
proper sequence.toImmutableList()
).@Beta public final ImmutableList<E> toSortedList(Comparator<? super E> comparator)
ImmutableList
containing all of the elements from this FluentIterable
in the order specified by comparator
. To produce an ImmutableList
sorted by its natural ordering, use toSortedList(Ordering.natural())
.comparator
- the function by which to sort list elementsNullPointerException
- if any element is nulltoSortedImmutableList()
).public final ImmutableSet<E> toSet()
ImmutableSet
containing all of the elements from this fluent iterable with
duplicates removed.toImmutableSet()
).public final ImmutableSortedSet<E> toSortedSet(Comparator<? super E> comparator)
ImmutableSortedSet
containing all of the elements from this FluentIterable
in the order specified by comparator
, with duplicates (determined by
comparator.compare(x, y) == 0
) removed. To produce an ImmutableSortedSet
sorted
by its natural ordering, use toSortedSet(Ordering.natural())
.comparator
- the function by which to sort set elementsNullPointerException
- if any element is nulltoImmutableSortedSet()
).public final <V> ImmutableMap<E,V> toMap(Function<? super E,V> valueFunction)
FluentIterable
are the keys in
the same order, mapped to values by the given function. If this iterable contains duplicate
elements, the returned map will contain each distinct element once in the order it first
appears.NullPointerException
- if any element of this iterable is null
, or if valueFunction
produces null
for any keypublic final <K> ImmutableListMultimap<K,E> index(Function<? super E,K> keyFunction)
ImmutableListMultimap
that contains the results of applying a
specified function to each item in this FluentIterable
of values. Each element of this
iterable will be stored as a value in the resulting multimap, yielding a multimap with the same
size as this iterable. The key used to store that value in the multimap will be the result of
calling the function on that value. The resulting multimap is created as an immutable snapshot.
In the returned multimap, keys appear in the order they are first encountered, and the values
corresponding to each key appear in the same order as they are encountered.keyFunction
- the function used to produce the key for each valueNullPointerException
- if any of the following cases is true:
keyFunction
is null
keyFunction
returns null
for any element of this iterable
public final <K> ImmutableMap<K,E> uniqueIndex(Function<? super E,K> keyFunction)
Map.values()
are the elements of this
FluentIterable
in the given order, and each key is the product of invoking a supplied
function on its corresponding value.keyFunction
- the function used to produce the key for each valueIllegalArgumentException
- if keyFunction
produces the same key for more than one
value in this fluent iterableNullPointerException
- if any element of this fluent iterable is null, or if
keyFunction
produces null
for any value@GwtIncompatible(value="Array.newArray(Class, int)") public final E[] toArray(Class<E> type)
type
- the type of the elementspublic final <C extends Collection<? super E>> C copyInto(C collection)
collection
. This is equivalent to
calling Iterables.addAll(collection, this)
.collection
- the collection to copy elements tocollection
, for conveniencepublic final E get(int position)
position
- position of the element to returnIndexOutOfBoundsException
- if position
is negative or greater than or equal to
the size of this fluent iterableCopyright © 2010-2013. All Rights Reserved.