FluentIterable

java.lang.Object
- com.google.common.collect.FluentIterable<E>

All Implemented Interfaces:

Iterable<E>
```
@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:
- chained methods which return a new FluentIterable based in some way on the contents of the current one (for example transform(com.google.common.base.Function<? super E, T>))
- conversion methods which copy the FluentIterable's contents into a new collection or array (for example toList())
- element extraction methods which facilitate the retrieval of certain elements (for example last())
- query methods which answer questions about the 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.
Since:

12.0

Constructor Summary

Constructors

Modifier	Constructor and Description
`protected`	`FluentIterable()` Constructor for use by subclasses.

Method Summary

All Methods

Static Methods

Instance Methods

Concrete Methods

Deprecated Methods
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.
`FluentIterable<E>`	`append(E... elements)` Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, followed by `elements`.
`FluentIterable<E>`	`append(Iterable<? extends E> other)` Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, followed by those of `other`.
`boolean`	`contains(Object element)` Returns `true` if this fluent iterable contains any object for which `equals(element)` is true.
`<C extends Collection<? super E>> C`	`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.
`String`	`join(Joiner joiner)` Returns a `String` containing all of the elements of this fluent iterable joined with `joiner`.
`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.
`static <E> FluentIterable<E>`	`of(E[] elements)` Returns a fluent iterable containing `elements` in the specified order.
`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.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable
forEach, iterator, spliterator

- Constructor Detail
  - FluentIterable
```
protected FluentIterable()
```
    Constructor for use by subclasses.
- Method Detail
  - from
```
public static <E> FluentIterable<E> from(Iterable<E> iterable)
```
    Returns a fluent iterable that wraps iterable, or iterable itself if it is already a FluentIterable.
  - from
```
@Deprecated
public static <E> FluentIterable<E> from(FluentIterable<E> iterable)
```
    Deprecated. instances of FluentIterable don't need to be converted to FluentIterable
    
    Construct a fluent iterable from another fluent iterable. This is obviously never necessary, but is intended to help call out cases where one migration from Iterable to FluentIterable has obviated the need to explicitly convert to a FluentIterable.
  - of
```
@Beta
public static <E> FluentIterable<E> of(E[] elements)
```
    Returns a fluent iterable containing elements in the specified order.
    
    Since:
    
    18.0
  - toString
```
public String toString()
```
    Returns a string representation of this fluent iterable, with the format [e1, e2, ..., en].
  - size
```
public final int size()
```
    Returns the number of elements in this fluent iterable.
  - contains
```
public final boolean contains(Object element)
```
    Returns true if this fluent iterable contains any object for which equals(element) is true.
  - cycle
```
public final FluentIterable<E> cycle()
```
    Returns a fluent iterable whose 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.
  - append
```
@Beta
public final FluentIterable<E> append(Iterable<? extends E> other)
```
    Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, followed by those of other. The iterators are not polled until necessary.
    The returned iterable's Iterator supports remove() when the corresponding Iterator supports it.
    
    Since:
    
    18.0
  - append
```
@Beta
public final FluentIterable<E> append(E... elements)
```
    Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, followed by elements.
    
    Since:
    
    18.0
  - filter
```
public final FluentIterable<E> filter(Predicate<? super E> predicate)
```
    Returns the elements from this fluent iterable that satisfy a predicate. The resulting fluent iterable's iterator does not support remove().
  - filter
```
@GwtIncompatible(value="Class.isInstance")
public final <T> FluentIterable<T> filter(Class<T> type)
```
    Returns the elements from this fluent iterable that are instances of class type.
    
    Parameters:
    
    type - the type of elements desired
  - anyMatch
```
public final boolean anyMatch(Predicate<? super E> predicate)
```
    Returns true if any element in this fluent iterable satisfies the predicate.
  - allMatch
```
public final boolean allMatch(Predicate<? super E> predicate)
```
    Returns true if every element in this fluent iterable satisfies the predicate. If this fluent iterable is empty, true is returned.
  - firstMatch
```
public final 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.
    Warning: avoid using a predicate that matches null. If null is matched in this fluent iterable, a NullPointerException will be thrown.
  - transform
```
public final <T> FluentIterable<T> transform(Function<? super E,T> function)
```
    Returns a fluent iterable that applies 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.
  - transformAndConcat
```
public <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. 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.
    
    Since:
    
    13.0 (required Function<E, Iterable<T>> until 14.0)
  - first
```
public final Optional<E> first()
```
    Returns an Optional containing the first element in this fluent iterable. If the iterable is empty, Optional.absent() is returned.
    
    Throws:
    
    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.
  - last
```
public final Optional<E> last()
```
    Returns an Optional containing the last element in this fluent iterable. If the iterable is empty, Optional.absent() is returned.
    
    Throws:
    
    NullPointerException - if the last element is null; if this is a possibility, use Iterables.getLast(java.lang.Iterable<T>) instead.
  - skip
```
public final FluentIterable<E> skip(int numberToSkip)
```
    Returns a view of this fluent iterable that skips its first 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.
  - limit
```
public final FluentIterable<E> limit(int size)
```
    Creates a fluent iterable with the first 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.
    
    Parameters:
    
    size - the maximum number of elements in the returned fluent iterable
    
    Throws:
    
    IllegalArgumentException - if size is negative
  - isEmpty
```
public final boolean isEmpty()
```
    Determines whether this fluent iterable is empty.
  - toList
```
public final ImmutableList<E> toList()
```
    Returns an ImmutableList containing all of the elements from this fluent iterable in proper sequence.
    
    Since:
    
    14.0 (since 12.0 as toImmutableList()).
  - toSortedList
```
public final ImmutableList<E> toSortedList(Comparator<? super E> comparator)
```
    Returns an 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()).
    
    Parameters:
    
    comparator - the function by which to sort list elements
    
    Throws:
    
    NullPointerException - if any element is null
    
    Since:
    
    14.0 (since 13.0 as toSortedImmutableList()).
  - toSet
```
public final ImmutableSet<E> toSet()
```
    Returns an ImmutableSet containing all of the elements from this fluent iterable with duplicates removed.
    
    Since:
    
    14.0 (since 12.0 as toImmutableSet()).
  - toSortedSet
```
public final 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. To produce an ImmutableSortedSet sorted by its natural ordering, use toSortedSet(Ordering.natural()).
    
    Parameters:
    
    comparator - the function by which to sort set elements
    
    Throws:
    
    NullPointerException - if any element is null
    
    Since:
    
    14.0 (since 12.0 as toImmutableSortedSet()).
  - toMap
```
public final <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. If this iterable contains duplicate elements, the returned map will contain each distinct element once in the order it first appears.
    
    Throws:
    
    NullPointerException - if any element of this iterable is null, or if valueFunction produces null for any key
    
    Since:
    
    14.0
  - index
```
public final <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. 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.
    Parameters:
    
    keyFunction - the function used to produce the key for each value
    
    Throws:
    NullPointerException - if any of the following cases is true:
    
    keyFunction is null
    
    An element in this fluent iterable is null
    
    keyFunction returns null for any element of this iterable
    Since:
    
    14.0
  - uniqueIndex
```
public final <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.
    
    Parameters:
    
    keyFunction - the function used to produce the key for each value
    
    Throws:
    
    IllegalArgumentException - if keyFunction produces the same key for more than one value in this fluent iterable
    
    NullPointerException - if any element of this fluent iterable is null, or if keyFunction produces null for any value
    
    Since:
    
    14.0
  - toArray
```
@GwtIncompatible(value="Array.newArray(Class, int)")
public final E[] toArray(Class<E> type)
```
    Returns an array containing all of the elements from this fluent iterable in iteration order.
    
    Parameters:
    
    type - the type of the elements
    
    Returns:
    
    a newly-allocated array into which all the elements of this fluent iterable have been copied
  - copyInto
```
public final <C extends Collection<? super E>> C copyInto(C collection)
```
    Copies all the elements from this fluent iterable to collection. This is equivalent to calling Iterables.addAll(collection, this).
    
    Parameters:
    
    collection - the collection to copy elements to
    
    Returns:
    
    collection, for convenience
    
    Since:
    
    14.0
  - join
```
@Beta
public final String join(Joiner joiner)
```
    Returns a String containing all of the elements of this fluent iterable joined with joiner.
    
    Since:
    
    18.0
  - get
```
public final E get(int position)
```
    Returns the element at the specified position in this fluent iterable.
    
    Parameters:
    
    position - position of the element to return
    
    Returns:
    
    the element at the specified position in this fluent iterable
    
    Throws:
    
    IndexOutOfBoundsException - if position is negative or greater than or equal to the size of this fluent iterable

Class FluentIterable<E>

Constructor Summary

Constructors

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Constructor Detail

FluentIterable

Method Detail

from

from

of

toString

size

contains

cycle

append

append

filter

filter

anyMatch

allMatch

firstMatch

transform

transformAndConcat

first

last

skip

limit

isEmpty

toList

toSortedList

toSet

toSortedSet

toMap

index

uniqueIndex

toArray

copyInto

join

get