Traversable (vavr 1.0.0-alpha-4 API)

Type Parameters:

T - Component type

All Superinterfaces:

Foldable<T>, java.lang.Iterable<T>, Value<T>

All Known Subinterfaces:

IndexedSeq<T>, Iterator<T>, LinearSeq<T>, Map<K,V>, Multimap<K,V>, Seq<T>, Set<T>, SortedMap<K,V>, SortedMultimap<K,V>, SortedSet<T>

All Known Implementing Classes:

Array, BitSet, CharSeq, HashMap, HashMultimap, HashSet, LinkedHashMap, LinkedHashMultimap, LinkedHashSet, List, List.Cons, List.Nil, PriorityQueue, Queue, Stream, Stream.Cons, Stream.Empty, Tree, Tree.Empty, Tree.Node, TreeMap, TreeMultimap, TreeSet, Vector
```
public interface Traversable<T>
extends java.lang.Iterable<T>, Foldable<T>, Value<T>
```
An interface for inherently recursive, multi-valued data structures. The order of elements is determined by Iterable.iterator(), which may vary each time it is called.
Basic operations:
Iteration:
Numeric operations:
Reduction/Folding:
Selection:
Tests:
Transformation:

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`default <K> Option<Map<K,T>>`	`arrangeBy(java.util.function.Function<? super T,? extends K> getKey)` Matches each element with a unique key that you extract from it.
`default Option<java.lang.Double>`	`average()` Calculates the average of this elements, assuming that the element type is `Number`.
`<R> Traversable<R>`	`collect(PartialFunction<? super T,? extends R> partialFunction)` Collects all elements that are in the domain of the given `partialFunction` by mapping the elements to type `R`.
`default boolean`	`containsAll(java.lang.Iterable<? extends T> elements)` Tests if this Traversable contains all given elements.
`default int`	`count(java.util.function.Predicate<? super T> predicate)` Counts the elements which satisfy the given predicate.
`Traversable<T>`	`distinct()` Returns a new version of this which contains no duplicates.
`Traversable<T>`	`distinctBy(java.util.Comparator<? super T> comparator)` Returns a new version of this which contains no duplicates.
`<U> Traversable<T>`	`distinctBy(java.util.function.Function<? super T,? extends U> keyExtractor)` Returns a new version of this which contains no duplicates.
`Traversable<T>`	`drop(int n)` Drops the first n elements of this or all elements, if this length < n.
`Traversable<T>`	`dropRight(int n)` Drops the last n elements of this or all elements, if this length < n.
`Traversable<T>`	`dropUntil(java.util.function.Predicate<? super T> predicate)` Drops elements until the predicate holds for the current element.
`Traversable<T>`	`dropWhile(java.util.function.Predicate<? super T> predicate)` Drops elements while the predicate holds for the current element.
`boolean`	`equals(java.lang.Object obj)` In Vavr there are four basic classes of collections: Seq (sequential elements) Set (distinct elements) Map (indexed elements) Multimap (indexed collections) Two collection instances of these classes are equal if and only if both collections belong to the same basic collection class (Seq, Set, Map or Multimap) contain the same elements have the same element order, if the collections are of type Seq Two Map/Multimap elements, resp.
`default boolean`	`existsUnique(java.util.function.Predicate<? super T> predicate)` Checks, if a unique elements exists such that the predicate holds.
`Traversable<T>`	`filter(java.util.function.Predicate<? super T> predicate)` Returns a new traversable consisting of all elements which satisfy the given predicate.
`default Traversable<T>`	`filterNot(java.util.function.Predicate<? super T> predicate)` Returns a new traversable consisting of all elements which do not satisfy the given predicate.
`default Option<T>`	`find(java.util.function.Predicate<? super T> predicate)` Returns the first element of this which satisfies the given predicate.
`default Option<T>`	`findLast(java.util.function.Predicate<? super T> predicate)` Returns the last element of this which satisfies the given predicate.
`<U> Traversable<U>`	`flatMap(java.util.function.Function<? super T,? extends java.lang.Iterable<? extends U>> mapper)` FlatMaps this Traversable.
`default T`	`fold(T zero, java.util.function.BiFunction<? super T,? super T,? extends T> combine)` Folds this elements using the given associative binary operator, starting with `zero` and successively calling `combine`.
`default <U> U`	`foldLeft(U zero, java.util.function.BiFunction<? super U,? super T,? extends U> combine)` Folds this elements from the left, starting with `zero` and successively calling `combine`.
`<U> U`	`foldRight(U zero, java.util.function.BiFunction<? super T,? super U,? extends U> combine)` Folds this elements from the right, starting with `zero` and successively calling `combine`.
`default void`	`forEachWithIndex(java.util.function.ObjIntConsumer<? super T> action)` Performs an action on each element.
`default T`	`get()` Gets the first value in iteration order if this `Traversable` is not empty, otherwise throws.
`<C> Map<C,? extends Traversable<T>>`	`groupBy(java.util.function.Function<? super T,? extends C> classifier)` Groups this elements by classifying the elements.
`Iterator<? extends Traversable<T>>`	`grouped(int size)` Groups this `Traversable` into fixed size blocks.
`boolean`	`hasDefiniteSize()` Checks if this Traversable is known to have a finite size.
`int`	`hashCode()` Returns the hash code of this collection.
`T`	`head()` Returns the first element of a non-empty Traversable.
`default Option<T>`	`headOption()` Returns the first element of a non-empty Traversable as `Option`.
`Traversable<T>`	`init()` Dual of tail(), returning all elements except the last.
`default Option<? extends Traversable<T>>`	`initOption()` Dual of tailOption(), returning all elements except the last as `Option`.
`default boolean`	`isDistinct()` Checks if this Traversable may consist of distinct elements only.
`default boolean`	`isEmpty()` Checks if this Traversable is empty.
`default boolean`	`isOrdered()` Checks if this Traversable is ordered
`default boolean`	`isSequential()` Checks if the elements of this Traversable appear in encounter order.
`default boolean`	`isSingleValued()` Each of Vavr's collections may contain more than one element.
`boolean`	`isTraversableAgain()` Checks if this Traversable can be repeatedly traversed.
`default Iterator<T>`	`iterator()` An iterator by means of head() and tail().
`T`	`last()` Dual of head(), returning the last element.
`default Option<T>`	`lastOption()` Dual of headOption(), returning the last element as `Option`.
`int`	`length()` Computes the number of elements of this Traversable.
`<U> Traversable<U>`	`map(java.util.function.Function<? super T,? extends U> mapper)` Maps the elements of this `Traversable` to elements of a new type preserving their order, if any.
`default Option<T>`	`max()` Calculates the maximum of this elements according to their natural order.
`default Option<T>`	`maxBy(java.util.Comparator<? super T> comparator)` Calculates the maximum of this elements using a specific comparator.
`default <U extends java.lang.Comparable<? super U>> Option<T>`	`maxBy(java.util.function.Function<? super T,? extends U> f)` Calculates the maximum of this elements within the co-domain of a specific function.
`default Option<T>`	`min()` Calculates the minimum of this elements according to their natural order in O(n).
`default Option<T>`	`minBy(java.util.Comparator<? super T> comparator)` Calculates the minimum of this elements using a specific comparator.
`default <U extends java.lang.Comparable<? super U>> Option<T>`	`minBy(java.util.function.Function<? super T,? extends U> f)` Calculates the minimum of this elements within the co-domain of a specific function.
`default CharSeq`	`mkCharSeq()` Joins the elements of this by concatenating their string representations.
`default CharSeq`	`mkCharSeq(java.lang.CharSequence delimiter)` Joins the string representations of this elements using a specific delimiter.
`default CharSeq`	`mkCharSeq(java.lang.CharSequence prefix, java.lang.CharSequence delimiter, java.lang.CharSequence suffix)` Joins the string representations of this elements using a specific delimiter, prefix and suffix.
`default java.lang.String`	`mkString()` Joins the elements of this by concatenating their string representations.
`default java.lang.String`	`mkString(java.lang.CharSequence delimiter)` Joins the string representations of this elements using a specific delimiter.
`default java.lang.String`	`mkString(java.lang.CharSequence prefix, java.lang.CharSequence delimiter, java.lang.CharSequence suffix)` Joins the string representations of this elements using a specific delimiter, prefix and suffix.
`static <T> Traversable<T>`	`narrow(Traversable<? extends T> traversable)` Narrows a widened `Traversable<? extends T>` to `Traversable<T>` by performing a type-safe cast.
`default boolean`	`nonEmpty()` Checks, this `Traversable` is not empty.
`Traversable<T>`	`orElse(java.lang.Iterable<? extends T> other)` Returns this `Traversable` if it is nonempty, otherwise return the alternative.
`Traversable<T>`	`orElse(java.util.function.Supplier<? extends java.lang.Iterable<? extends T>> supplier)` Returns this `Traversable` if it is nonempty, otherwise return the result of evaluating supplier.
`Tuple2<? extends Traversable<T>,? extends Traversable<T>>`	`partition(java.util.function.Predicate<? super T> predicate)` Creates a partition of this `Traversable` by splitting this elements in two in distinct traversables according to a predicate.
`Traversable<T>`	`peek(java.util.function.Consumer<? super T> action)` Performs the given `action` on the first element if this is an eager implementation.
`default java.lang.Number`	`product()` Calculates the product of this elements.
`default T`	`reduce(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op`.
`default T`	`reduceLeft(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op` from the left.
`default Option<T>`	`reduceLeftOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op` from the left.
`default Option<T>`	`reduceOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op`.
`default T`	`reduceRight(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op` from the right.
`default Option<T>`	`reduceRightOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)` Accumulates the elements of this Traversable by successively calling the given operation `op` from the right.
`Traversable<T>`	`replace(T currentElement, T newElement)` Replaces the first occurrence (if exists) of the given currentElement with newElement.
`Traversable<T>`	`replaceAll(T currentElement, T newElement)` Replaces all occurrences of the given currentElement with newElement.
`Traversable<T>`	`retainAll(java.lang.Iterable<? extends T> elements)` Keeps all occurrences of the given elements from this.
`Traversable<T>`	`scan(T zero, java.util.function.BiFunction<? super T,? super T,? extends T> operation)` Computes a prefix scan of the elements of the collection.
`<U> Traversable<U>`	`scanLeft(U zero, java.util.function.BiFunction<? super U,? super T,? extends U> operation)` Produces a collection containing cumulative results of applying the operator going left to right.
`<U> Traversable<U>`	`scanRight(U zero, java.util.function.BiFunction<? super T,? super U,? extends U> operation)` Produces a collection containing cumulative results of applying the operator going right to left.
`default T`	`single()` Returns the single element of this Traversable or throws, if this is empty or contains more than one element.
`default Option<T>`	`singleOption()` Returns the only element of a Traversable as `Option`.
`default int`	`size()` Computes the number of elements of this Traversable.
`Iterator<? extends Traversable<T>>`	`slideBy(java.util.function.Function<? super T,?> classifier)` Slides a non-overlapping window of a variable size over this `Traversable`.
`Iterator<? extends Traversable<T>>`	`sliding(int size)` Slides a window of a specific `size` and step size 1 over this `Traversable` by calling `sliding(int, int)`.
`Iterator<? extends Traversable<T>>`	`sliding(int size, int step)` Slides a window of a specific `size` and `step` size over this `Traversable`.
`Tuple2<? extends Traversable<T>,? extends Traversable<T>>`	`span(java.util.function.Predicate<? super T> predicate)` Returns a tuple where the first element is the longest prefix of elements that satisfy the given `predicate` and the second element is the remainder.
`default java.util.Spliterator<T>`	`spliterator()`
`default java.lang.Number`	`sum()` Calculates the sum of this elements.
`Traversable<T>`	`tail()` Drops the first element of a non-empty Traversable.
`Option<? extends Traversable<T>>`	`tailOption()` Drops the first element of a non-empty Traversable and returns an `Option`.
`Traversable<T>`	`take(int n)` Takes the first n elements of this or all elements, if this length < n.
`Traversable<T>`	`takeRight(int n)` Takes the last n elements of this or all elements, if this length < n.
`Traversable<T>`	`takeUntil(java.util.function.Predicate<? super T> predicate)` Takes elements until the predicate holds for the current element.
`Traversable<T>`	`takeWhile(java.util.function.Predicate<? super T> predicate)` Takes elements while the predicate holds for the current element.
`default <K extends java.lang.Comparable<? super K>,V> Map<K,V>`	`toLinkedMap(java.util.function.Function<? super T,? extends K> keyMapper, java.util.function.Function<? super T,? extends V> valueMapper, java.util.function.BiFunction<? super V,? super V,? extends V> merge)` Converts this collection to a `Map`.
`default <K,V> Map<K,V>`	`toMap(java.util.function.Function<? super T,? extends K> keyMapper, java.util.function.Function<? super T,? extends V> valueMapper, java.util.function.BiFunction<? super V,? super V,? extends V> merge)` Converts this collection to a `Map`.
`default <K,V> SortedMap<K,V>`	`toSortedMap(java.util.Comparator<? super K> keyComparator, java.util.function.Function<? super T,? extends K> keyMapper, java.util.function.Function<? super T,? extends V> valueMapper, java.util.function.BiFunction<? super V,? super V,? extends V> merge)` Converts this collection to a `SortedMap`.
`default <K extends java.lang.Comparable<? super K>,V> SortedMap<K,V>`	`toSortedMap(java.util.function.Function<? super T,? extends K> keyMapper, java.util.function.Function<? super T,? extends V> valueMapper, java.util.function.BiFunction<? super V,? super V,? extends V> merge)` Converts this collection to a `SortedMap`.
`default <T1,T2> Tuple2<Iterator<T1>,Iterator<T2>>`	`unzip(java.util.function.Function<? super T,? extends T1> unzipper1, java.util.function.Function<? super T,? extends T2> unzipper2)` Unzips this elements by mapping this elements to a pair of distinct sets.
`default <T1,T2,T3> Tuple3<Iterator<T1>,Iterator<T2>,Iterator<T3>>`	`unzip3(java.util.function.Function<? super T,? extends T1> unzipper1, java.util.function.Function<? super T,? extends T2> unzipper2, java.util.function.Function<? super T,? extends T3> unzipper3)` Unzips this elements by mapping this elements to three distinct sets.
`<U> Traversable<Tuple2<T,U>>`	`zip(java.lang.Iterable<? extends U> that)` Returns a traversable formed from this traversable and another Iterable collection by combining corresponding elements in pairs.
`<U> Traversable<Tuple2<T,U>>`	`zipAll(java.lang.Iterable<? extends U> that, T thisElem, U thatElem)` Returns a traversable formed from this traversable and another Iterable by combining corresponding elements in pairs.
`<U,R> Traversable<R>`	`zipWith(java.lang.Iterable<? extends U> that, java.util.function.BiFunction<? super T,? super U,? extends R> mapper)` Returns a traversable formed from this traversable and another Iterable collection by mapping elements.
`Traversable<Tuple2<T,java.lang.Integer>>`	`zipWithIndex()` Zips this traversable with its indices.
`<U> Traversable<U>`	`zipWithIndex(java.util.function.BiFunction<? super T,? super java.lang.Integer,? extends U> mapper)` Returns a traversable formed from this traversable and another Iterable collection by mapping elements.

Methods inherited from interface io.vavr.Value
collect, collect, contains, corresponds, eq, exists, forAll, forEach, getOrElse, getOrElse, getOrElseThrow, getOrElseTry, getOrNull, isAsync, isLazy, narrow, out, out, stderr, stdout, stringPrefix, toArray, toCharSeq, toCompletableFuture, toEither, toEither, toInvalid, toInvalid, toJavaArray, toJavaArray, toJavaArray, toJavaCollection, toJavaList, toJavaList, toJavaMap, toJavaMap, toJavaMap, toJavaOptional, toJavaParallelStream, toJavaSet, toJavaSet, toJavaStream, toLeft, toLeft, toLinkedMap, toLinkedMap, toLinkedSet, toList, toMap, toMap, toOption, toPriorityQueue, toPriorityQueue, toQueue, toRight, toRight, toSet, toSortedMap, toSortedMap, toSortedMap, toSortedMap, toSortedSet, toSortedSet, toStream, toString, toTree, toTree, toTry, toTry, toValid, toValid, toValidation, toValidation, toVector

- Method Detail
 - narrow
```
static <T> Traversable<T> narrow(Traversable<? extends T> traversable)
```
 Narrows a widened Traversable<? extends T> to Traversable<T> by performing a type-safe cast. This is eligible because immutable/read-only collections are covariant.
 
 Type Parameters:
 
 T - Component type of the Traversable.
 
 Parameters:
 
 traversable - An Traversable.
 
 Returns:
 
 the given traversable instance as narrowed type Traversable<T>.
 - arrangeBy
```
default <K> Option<Map<K,T>> arrangeBy(java.util.function.Function<? super T,? extends K> getKey)
```
 Matches each element with a unique key that you extract from it. If the same key is present twice, the function will return None.
 
 Type Parameters:
 
 K - key class type
 
 Parameters:
 
 getKey - A function which extracts a key from elements
 
 Returns:
 
 A Map containing the elements arranged by their keys.
 
 Throws:
 
 java.lang.NullPointerException - if getKey is null.
 
 See Also:
 
 groupBy(Function)
 - average
```
default Option<java.lang.Double> average()
```
 Calculates the average of this elements, assuming that the element type is Number. Since we do not know if the component type T is of type Number, the average() call might throw at runtime (see examples below).
 Examples:
```
 List.empty().average() // = None
 List.of(1, 2, 3).average() // = Some(2.0)
 List.of(1.0, 10e100, 2.0, -10e100).average() // = Some(0.75)
 List.of(1.0, Double.NaN).average() // = NaN
 List.of("apple", "pear").average() // throws
 
```
 Please note that Java's DoubleStream.average() uses the Kahan summation algorithm (also known as compensated summation), which has known limitations.
 Vavr uses Neumaier's modification of the Kahan algorithm, which yields better results.
```
 // = OptionalDouble(0.0) (wrong)
 j.u.s.DoubleStream.of(1.0, 10e100, 2.0, -10e100).average()

 // = Some(0.75) (correct)
 List.of(1.0, 10e100, 2.0, -10e100).average()
 
```
 Returns:
 
 Some(average) or None, if there are no elements
 
 Throws:
 
 java.lang.UnsupportedOperationException - if this elements are not numeric
 - collect
```
<R> Traversable<R> collect(PartialFunction<? super T,? extends R> partialFunction)
```
 Collects all elements that are in the domain of the given partialFunction by mapping the elements to type R.
 More specifically, for each of this elements in iteration order first it is checked
```
 partialFunction.isDefinedAt(element)
 
```
 If the elements makes it through that filter, the mapped instance is added to the result collection
```
 R newElement = partialFunction.apply(element)
 
```
 Note:If this Traversable is ordered (i.e. extends Ordered, the caller of collect has to ensure that the elements are comparable (i.e. extend Comparable).
 Type Parameters:
 
 R - The new element type
 
 Parameters:
 
 partialFunction - A function that is not necessarily defined of all elements of this traversable.
 
 Returns:
 
 A new Traversable instance containing elements of type R
 
 Throws:
 
 java.lang.NullPointerException - if partialFunction is null
 - containsAll
```
default boolean containsAll(java.lang.Iterable<? extends T> elements)
```
 Tests if this Traversable contains all given elements.
 The result is equivalent to elements.isEmpty() ? true : contains(elements.head()) && containsAll(elements.tail()) but implemented without recursion.
 
 Parameters:
 
 elements - A List of values of type T.
 
 Returns:
 
 true, if this List contains all given elements, false otherwise.
 
 Throws:
 
 java.lang.NullPointerException - if elements is null
 - count
```
default int count(java.util.function.Predicate<? super T> predicate)
```
 Counts the elements which satisfy the given predicate.
 
 Parameters:
 
 predicate - A predicate
 
 Returns:
 
 A number >= 0
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null.
 - distinct
```
Traversable<T> distinct()
```
 Returns a new version of this which contains no duplicates. Elements are compared using equals.
 
 Returns:
 
 a new Traversable containing this elements without duplicates
 - distinctBy
```
Traversable<T> distinctBy(java.util.Comparator<? super T> comparator)
```
 Returns a new version of this which contains no duplicates. Elements are compared using the given comparator.
 
 Parameters:
 
 comparator - A comparator
 
 Returns:
 
 a new Traversable containing this elements without duplicates
 
 Throws:
 
 java.lang.NullPointerException - if comparator is null.
 - distinctBy
```
 Traversable<T> distinctBy(java.util.function.Function<? super T,? extends U> keyExtractor)
```
 Returns a new version of this which contains no duplicates. Elements mapped to keys which are compared using equals.
 The elements of the result are determined in the order of their occurrence - first match wins.
 
 Type Parameters:
 
 U - key type
 
 Parameters:
 
 keyExtractor - A key extractor
 
 Returns:
 
 a new Traversable containing this elements without duplicates
 
 Throws:
 
 java.lang.NullPointerException - if keyExtractor is null
 - drop
```
Traversable<T> drop(int n)
```
 Drops the first n elements of this or all elements, if this length < n.
 
 Parameters:
 
 n - The number of elements to drop.
 
 Returns:
 
 a new instance consisting of all elements of this except the first n ones, or else the empty instance, if this has less than n elements.
 - dropRight
```
Traversable<T> dropRight(int n)
```
 Drops the last n elements of this or all elements, if this length < n.
 
 Parameters:
 
 n - The number of elements to drop.
 
 Returns:
 
 a new instance consisting of all elements of this except the last n ones, or else the empty instance, if this has less than n elements.
 - dropUntil
```
Traversable<T> dropUntil(java.util.function.Predicate<? super T> predicate)
```
 Drops elements until the predicate holds for the current element.
 
 Parameters:
 
 predicate - A condition tested subsequently for this elements.
 
 Returns:
 
 a new instance consisting of all elements starting from the first one which does satisfy the given predicate.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - dropWhile
```
Traversable<T> dropWhile(java.util.function.Predicate<? super T> predicate)
```
 Drops elements while the predicate holds for the current element.
 Note: This is essentially the same as dropUntil(predicate.negate()). It is intended to be used with method references, which cannot be negated directly.
 
 Parameters:
 
 predicate - A condition tested subsequently for this elements.
 
 Returns:
 
 a new instance consisting of all elements starting from the first one which does not satisfy the given predicate.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - equals
```
boolean equals(java.lang.Object obj)
```
 In Vavr there are four basic classes of collections:
 - Seq (sequential elements)
 - Set (distinct elements)
 - Map (indexed elements)
 - Multimap (indexed collections)
 Two collection instances of these classes are equal if and only if both collections
 - belong to the same basic collection class (Seq, Set, Map or Multimap)
 - contain the same elements
 - have the same element order, if the collections are of type Seq
 Two Map/Multimap elements, resp. entries, (key1, value1) and (key2, value2) are equal, if the keys are equal and the values are equal.
 Notes:
 - No collection instance equals null, e.g. Queue(1) not equals null.
 - Nulls are allowed and handled as expected, e.g. List(null, 1) equals Stream(null, 1) and HashMap((null, 1)) equals LinkedHashMap((null, 1)).
 - The element order is taken into account for Seq only. E.g. List(null, 1) not equals Stream(1, null) and HashMap((null, 1), ("a", null)) equals LinkedHashMap(("a", null), (null, 1)). The reason is, that we do not know which implementations we compare when having two instances of type Map, Multimap or Set (see Liskov Substitution Principle).
 - Other collection classes are equal if their types are equal and their elements are equal (in iteration order).
 - Iterator equality is defined to be object reference equality.
 Specified by:
 
 equals in interface Value<T>
 
 Overrides:
 
 equals in class java.lang.Object
 
 Parameters:
 
 obj - an object, may be null
 
 Returns:
 
 true, if this collection equals the given object according to the rules described above, false otherwise.
 - existsUnique
```
default boolean existsUnique(java.util.function.Predicate<? super T> predicate)
```
 Checks, if a unique elements exists such that the predicate holds.
 
 Parameters:
 
 predicate - A Predicate
 
 Returns:
 
 true, if predicate holds for a unique element, false otherwise
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - filter
```
Traversable<T> filter(java.util.function.Predicate<? super T> predicate)
```
 Returns a new traversable consisting of all elements which satisfy the given predicate.
 
 Parameters:
 
 predicate - A predicate
 
 Returns:
 
 a new traversable
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - filterNot
```
default Traversable<T> filterNot(java.util.function.Predicate<? super T> predicate)
```
 Returns a new traversable consisting of all elements which do not satisfy the given predicate.
 The default implementation is equivalent to
```
 filter(predicate.negate()
```
 Parameters:
 
 predicate - A predicate
 
 Returns:
 
 a new traversable
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - find
```
default Option<T> find(java.util.function.Predicate<? super T> predicate)
```
 Returns the first element of this which satisfies the given predicate.
 
 Parameters:
 
 predicate - A predicate.
 
 Returns:
 
 Some(element) or None, where element may be null (i.e. List.of(null).find(e -> e == null)).
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - findLast
```
default Option<T> findLast(java.util.function.Predicate<? super T> predicate)
```
 Returns the last element of this which satisfies the given predicate.
 Same as reverse().find(predicate).
 
 Parameters:
 
 predicate - A predicate.
 
 Returns:
 
 Some(element) or None, where element may be null (i.e. List.of(null).find(e -> e == null)).
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - flatMap
```
 Traversable flatMap(java.util.function.Function<? super T,? extends java.lang.Iterable<? extends U>> mapper)
```
 FlatMaps this Traversable.
 
 Type Parameters:
 
 U - The resulting component type.
 
 Parameters:
 
 mapper - A mapper
 
 Returns:
 
 A new Traversable instance.
 - fold
```
default T fold(T zero,
 java.util.function.BiFunction<? super T,? super T,? extends T> combine)
```
 Folds this elements using the given associative binary operator, starting with zero and successively calling combine. The order in which the elements are combined is non-deterministic.
 The methods fold, foldLeft and foldRight differ in how the elements are combined:
 - foldLeft(Object, BiFunction) associates to the left
 - foldRight(Object, BiFunction) associates to the right
 - fold takes an associative combine operation because the traversal of elements is unordered/non-deterministic. The associativity guarantees that in each case the result will be the same, it does not matter in which order the elements are combined. Generally binary operators aren't associative, i.e. the result may differ if elements are combined in a different order.
 We say that this Traversable and the associative combine operation form a Monoid.
 Example:
```
 
 // = 6
 Set(1, 2, 3).fold(0, (a, b) -> a + b);
 
```
 Specified by:
 
 fold in interface Foldable<T>
 
 Parameters:
 
 zero - A zero element to start with.
 
 combine - A function which combines elements.
 
 Returns:
 
 a folded value
 
 Throws:
 
 java.lang.NullPointerException - if combine is null
 - foldLeft
```
default  U foldLeft(U zero,
 java.util.function.BiFunction<? super U,? super T,? extends U> combine)
```
 Folds this elements from the left, starting with zero and successively calling combine.
 Example:
```
 
 // = "cba!"
 List("a", "b", "c").foldLeft("!", (xs, x) -> x + xs)
 
```
 Specified by:
 
 foldLeft in interface Foldable<T>
 
 Type Parameters:
 
 U - the type to fold over
 
 Parameters:
 
 zero - A zero element to start with.
 
 combine - A function which combines elements.
 
 Returns:
 
 a folded value
 
 Throws:
 
 java.lang.NullPointerException - if combine is null
 - foldRight
```
 U foldRight(U zero,
 java.util.function.BiFunction<? super T,? super U,? extends U> combine)
```
 Folds this elements from the right, starting with zero and successively calling combine.
 Example:
```
 
 // = "!cba"
 List("a", "b", "c").foldRight("!", (x, xs) -> xs + x)
 
```
 Specified by:
 
 foldRight in interface Foldable<T>
 
 Type Parameters:
 
 U - the type of the folded value
 
 Parameters:
 
 zero - A zero element to start with.
 
 combine - A function which combines elements.
 
 Returns:
 
 a folded value
 
 Throws:
 
 java.lang.NullPointerException - if combine is null
 - forEachWithIndex
```
default void forEachWithIndex(java.util.function.ObjIntConsumer<? super T> action)
```
 Performs an action on each element. In contrast to Iterable.forEach(Consumer), additionally the element's index is passed to the given action.
 This is essentially the same as iterator().zipWithIndex().forEach() but performs better because no intermediate Tuple2 instances are created and no boxing of int values takes place.
 Please note that subsequent calls to forEachWithIndex might lead to different iteration orders, depending on the underlying Traversable implementation.
 Please also note that forEachWithIndex might loop infinitely if the Traversable is lazily evaluated, like Stream.
 
 Parameters:
 
 action - A ObjIntConsumer
 
 Throws:
 
 java.lang.NullPointerException - if action is null
 - get
```
default T get()
```
 Gets the first value in iteration order if this Traversable is not empty, otherwise throws.
 
 Specified by:
 
 get in interface Value<T>
 
 Returns:
 
 the first value
 
 Throws:
 
 java.util.NoSuchElementException - if this Traversable is empty.
 - groupBy
```
<C> Map<C,? extends Traversable<T>> groupBy(java.util.function.Function<? super T,? extends C> classifier)
```
 Groups this elements by classifying the elements.
 
 Type Parameters:
 
 C - classified class type
 
 Parameters:
 
 classifier - A function which classifies elements into classes
 
 Returns:
 
 A Map containing the grouped elements
 
 Throws:
 
 java.lang.NullPointerException - if classifier is null.
 
 See Also:
 
 arrangeBy(Function)
 - grouped
```
Iterator<? extends Traversable<T>> grouped(int size)
```
 Groups this Traversable into fixed size blocks.
 Let length be the length of this Iterable. Then grouped is defined as follows:
 - If this.isEmpty(), the resulting Iterator is empty.
 - If size <= length, the resulting Iterator will contain length / size blocks of size size and maybe a non-empty block of size length % size, if there are remaining elements.
 - If size > length, the resulting Iterator will contain one block of size length.
 Examples:
```
 
 [].grouped(1) = []
 [].grouped(0) throws
 [].grouped(-1) throws
 [1,2,3,4].grouped(2) = [[1,2],[3,4]]
 [1,2,3,4,5].grouped(2) = [[1,2],[3,4],[5]]
 [1,2,3,4].grouped(5) = [[1,2,3,4]]
 
 
```
 Please note that grouped(int) is a special case of sliding(int, int), i.e. grouped(size) is the same as sliding(size, size).
 Parameters:
 
 size - a positive block size
 
 Returns:
 
 A new Iterator of grouped blocks of the given size
 
 Throws:
 
 java.lang.IllegalArgumentException - if size is negative or zero
 - hasDefiniteSize
```
boolean hasDefiniteSize()
```
 Checks if this Traversable is known to have a finite size.
 This method should be implemented by classes only, i.e. not by interfaces.
 
 Returns:
 
 true, if this Traversable is known to have a finite size, false otherwise.
 - head
```
T head()
```
 Returns the first element of a non-empty Traversable.
 
 Returns:
 
 The first element of this Traversable.
 
 Throws:
 
 java.util.NoSuchElementException - if this is empty
 - headOption
```
default Option<T> headOption()
```
 Returns the first element of a non-empty Traversable as Option.
 
 Returns:
 
 Some(element) or None if this is empty.
 - hashCode
```
int hashCode()
```
 Returns the hash code of this collection.
 We distinguish between two types of hashes, those for collections with predictable iteration order (like Seq) and those with arbitrary iteration order (like Set, Map and Multimap).
 In all cases the hash of an empty collection is defined to be 1.
 Collections with predictable iteration order are hashed as follows:
```
 int hash = 1;
 for (T t : this) { hash = hash * 31 + Objects.hashCode(t); }
 
```
 Collections with arbitrary iteration order are hashed in a way such that the hash of a fixed number of elements is independent of their iteration order.
```
 int hash = 1;
 for (T t : this) { hash += Objects.hashCode(t); }
 
```
 Please note that the particular hashing algorithms may change in a future version of Vavr.
 Generally, hash codes of collections aren't cached in Vavr (opposed to the size/length). Storing hash codes in order to reduce the time complexity would increase the memory footprint. Persistent collections are built upon tree structures, it allows us to implement efficient memory sharing. A drawback of tree structures is that they make it necessary to store collection attributes at each tree node (read: element).
 The computation of the hash code is linear in time, i.e. O(n). If the hash code of a collection is re-calculated often, e.g. when using a List as HashMap key, we might want to cache the hash code. This can be achieved by simply using a wrapper class, which is not included in Vavr but could be implemented like this:
```
 public final class Hashed<K> {

 private final K key;
 private final Lazy<Integer> hashCode;

 public Hashed(K key) {
 this.key = key;
 this.hashCode = Lazy.of(() -> Objects.hashCode(key));
 }

 public K key() {
 return key;
 }

 &#64;Override
 public boolean equals(Object o) {
 if (o == key) {
 return true;
 } else if (key != null && o instanceof Hashed) {
 final Hashed that = (Hashed) o;
 return key.equals(that.key);
 } else {
 return false;
 }
 }

 &#64;Override
 public int hashCode() {
 return hashCode.get();
 }

 &#64;Override
 public String toString() {
 return "Hashed(" + (key == null ? "null" : key.toString()) + ")";
 }
 }
 
```
 Specified by:
 
 hashCode in interface Value<T>
 
 Overrides:
 
 hashCode in class java.lang.Object
 
 Returns:
 
 The hash code of this collection
 - init
```
Traversable<T> init()
```
 Dual of tail(), returning all elements except the last.
 
 Returns:
 
 a new instance containing all elements except the last.
 
 Throws:
 
 java.lang.UnsupportedOperationException - if this is empty
 - initOption
```
default Option<? extends Traversable<T>> initOption()
```
 Dual of tailOption(), returning all elements except the last as Option.
 
 Returns:
 
 Some(traversable) or None if this is empty.
 - isDistinct
```
default boolean isDistinct()
```
 Checks if this Traversable may consist of distinct elements only.
 
 Returns:
 
 true if this Traversable may consist of distinct elements only, false otherwise.
 - isEmpty
```
default boolean isEmpty()
```
 Checks if this Traversable is empty.
 
 Specified by:
 
 isEmpty in interface Value<T>
 
 Returns:
 
 true, if this Traversable contains no elements, false otherwise.
 - isOrdered
```
default boolean isOrdered()
```
 Checks if this Traversable is ordered
 
 Returns:
 
 true, if this Traversable is ordered, false otherwise.
 - isSequential
```
default boolean isSequential()
```
 Checks if the elements of this Traversable appear in encounter order.
 
 Returns:
 
 true, if the insertion order of elements is preserved, false otherwise.
 - isSingleValued
```
default boolean isSingleValued()
```
 Each of Vavr's collections may contain more than one element.
 
 Specified by:
 
 isSingleValued in interface Value<T>
 
 Returns:
 
 false
 - isTraversableAgain
```
boolean isTraversableAgain()
```
 Checks if this Traversable can be repeatedly traversed.
 This method should be implemented by classes only, i.e. not by interfaces.
 
 Returns:
 
 true, if this Traversable is known to be traversable repeatedly, false otherwise.
 - iterator
```
default Iterator<T> iterator()
```
 An iterator by means of head() and tail(). Subclasses may want to override this method.
 
 Specified by:
 
 iterator in interface java.lang.Iterable<T>
 
 Specified by:
 
 iterator in interface Value<T>
 
 Returns:
 
 A new Iterator of this Traversable elements.
 - last
```
T last()
```
 Dual of head(), returning the last element.
 
 Returns:
 
 the last element.
 
 Throws:
 
 java.util.NoSuchElementException - if this is empty
 - lastOption
```
default Option<T> lastOption()
```
 Dual of headOption(), returning the last element as Option.
 
 Returns:
 
 Some(element) or None if this is empty.
 - length
```
int length()
```
 Computes the number of elements of this Traversable.
 Same as size().
 
 Returns:
 
 the number of elements
 - map
```
 Traversable map(java.util.function.Function<? super T,? extends U> mapper)
```
 Maps the elements of this Traversable to elements of a new type preserving their order, if any.
 
 Specified by:
 
 map in interface Value<T>
 
 Type Parameters:
 
 U - Component type of the target Traversable
 
 Parameters:
 
 mapper - A mapper.
 
 Returns:
 
 a mapped Traversable
 
 Throws:
 
 java.lang.NullPointerException - if mapper is null
 - max
```
default Option<T> max()
```
 Calculates the maximum of this elements according to their natural order. Especially the underlying order of sorted collections is not taken into account.
 Examples:
```
 
 List.empty().max() // = None
 List.of(1, 2, 3).max() // = Some(3)
 List.of("a", "b", "c").max() // = Some("c")
 List.of(1.0, Double.NaN).max() // = NaN
 List.of(1, "a").max() // throws
 
 
```
 Returns:
 
 Some(maximum) of this elements or None if this is empty
 
 Throws:
 
 java.lang.NullPointerException - if an element is null
 
 java.lang.ClassCastException - if the elements do not have a natural order, i.e. they do not implement Comparable
 - maxBy
```
default Option<T> maxBy(java.util.Comparator<? super T> comparator)
```
 Calculates the maximum of this elements using a specific comparator.
 
 Parameters:
 
 comparator - A non-null element comparator
 
 Returns:
 
 Some(maximum) of this elements or None if this is empty
 
 Throws:
 
 java.lang.NullPointerException - if comparator is null
 - maxBy
```
default > Option<T> maxBy(java.util.function.Function<? super T,? extends U> f)
```
 Calculates the maximum of this elements within the co-domain of a specific function.
 
 Type Parameters:
 
 U - The type where elements are compared
 
 Parameters:
 
 f - A function that maps this elements to comparable elements
 
 Returns:
 
 The element of type T which is the maximum within U
 
 Throws:
 
 java.lang.NullPointerException - if f is null.
 - min
```
default Option<T> min()
```
 Calculates the minimum of this elements according to their natural order in O(n). Especially the underlying order of sorted collections is not taken into account.
 Examples:
```
 
 List.empty().min() // = None
 List.of(1, 2, 3).min() // = Some(1)
 List.of("a", "b", "c").min() // = Some("a")
 List.of(1.0, Double.NaN).min() // = NaN
 List.of(1, "a").min() // throws
 
 
```
 There is an exception for Double and Float: The minimum is defined to be NaN if this contains NaN. According to the natural order NaN would be the maximum element instead.
 Returns:
 
 Some(minimum) of this elements or None if this is empty
 
 Throws:
 
 java.lang.NullPointerException - if an element is null
 
 java.lang.ClassCastException - if the elements do not have a natural order, i.e. they do not implement Comparable
 - minBy
```
default Option<T> minBy(java.util.Comparator<? super T> comparator)
```
 Calculates the minimum of this elements using a specific comparator.
 
 Parameters:
 
 comparator - A non-null element comparator
 
 Returns:
 
 Some(minimum) of this elements or None if this is empty
 
 Throws:
 
 java.lang.NullPointerException - if comparator is null
 - minBy
```
default > Option<T> minBy(java.util.function.Function<? super T,? extends U> f)
```
 Calculates the minimum of this elements within the co-domain of a specific function.
 
 Type Parameters:
 
 U - The type where elements are compared
 
 Parameters:
 
 f - A function that maps this elements to comparable elements
 
 Returns:
 
 The element of type T which is the minimum within U
 
 Throws:
 
 java.lang.NullPointerException - if f is null.
 - mkCharSeq
```
default CharSeq mkCharSeq()
```
 Joins the elements of this by concatenating their string representations.
 This has the same effect as calling mkCharSeq("", "", "").
 
 Returns:
 
 a new CharSeq
 - mkCharSeq
```
default CharSeq mkCharSeq(java.lang.CharSequence delimiter)
```
 Joins the string representations of this elements using a specific delimiter.
 This has the same effect as calling mkCharSeq("", delimiter, "").
 
 Parameters:
 
 delimiter - A delimiter string put between string representations of elements of this
 
 Returns:
 
 A new CharSeq
 - mkCharSeq
```
default CharSeq mkCharSeq(java.lang.CharSequence prefix,
 java.lang.CharSequence delimiter,
 java.lang.CharSequence suffix)
```
 Joins the string representations of this elements using a specific delimiter, prefix and suffix.
 Example: List.of("a", "b", "c").mkCharSeq("Chars(", ", ", ")") = CharSeq.of("Chars(a, b, c))"
 
 Parameters:
 
 prefix - prefix of the resulting CharSeq
 
 delimiter - A delimiter string put between string representations of elements of this
 
 suffix - suffix of the resulting CharSeq
 
 Returns:
 
 a new CharSeq
 - mkString
```
default java.lang.String mkString()
```
 Joins the elements of this by concatenating their string representations.
 This has the same effect as calling mkString("", "", "").
 
 Returns:
 
 a new String
 - mkString
```
default java.lang.String mkString(java.lang.CharSequence delimiter)
```
 Joins the string representations of this elements using a specific delimiter.
 This has the same effect as calling mkString("", delimiter, "").
 
 Parameters:
 
 delimiter - A delimiter string put between string representations of elements of this
 
 Returns:
 
 A new String
 - mkString
```
default java.lang.String mkString(java.lang.CharSequence prefix,
 java.lang.CharSequence delimiter,
 java.lang.CharSequence suffix)
```
 Joins the string representations of this elements using a specific delimiter, prefix and suffix.
 Example: List.of("a", "b", "c").mkString("Chars(", ", ", ")") = "Chars(a, b, c)"
 
 Parameters:
 
 prefix - prefix of the resulting string
 
 delimiter - A delimiter string put between string representations of elements of this
 
 suffix - suffix of the resulting string
 
 Returns:
 
 a new String
 - nonEmpty
```
default boolean nonEmpty()
```
 Checks, this Traversable is not empty.
 The call is equivalent to !isEmpty().
 
 Returns:
 
 true, if an underlying value is present, false otherwise.
 - orElse
```
Traversable<T> orElse(java.lang.Iterable<? extends T> other)
```
 Returns this Traversable if it is nonempty, otherwise return the alternative.
 
 Parameters:
 
 other - An alternative Traversable
 
 Returns:
 
 this Traversable if it is nonempty, otherwise return the alternative.
 - orElse
```
Traversable<T> orElse(java.util.function.Supplier<? extends java.lang.Iterable<? extends T>> supplier)
```
 Returns this Traversable if it is nonempty, otherwise return the result of evaluating supplier.
 
 Parameters:
 
 supplier - An alternative Traversable supplier
 
 Returns:
 
 this Traversable if it is nonempty, otherwise return the result of evaluating supplier.
 - partition
```
Tuple2<? extends Traversable<T>,? extends Traversable<T>> partition(java.util.function.Predicate<? super T> predicate)
```
 Creates a partition of this Traversable by splitting this elements in two in distinct traversables according to a predicate.
 
 Parameters:
 
 predicate - A predicate which classifies an element if it is in the first or the second traversable.
 
 Returns:
 
 A disjoint union of two traversables. The first Traversable contains all elements that satisfy the given predicate, the second Traversable contains all elements that don't. The original order of elements is preserved.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - peek
```
Traversable<T> peek(java.util.function.Consumer<? super T> action)
```
 Description copied from interface: Value
 
 Performs the given action on the first element if this is an eager implementation. Performs the given action on all elements (the first immediately, successive deferred), if this is a lazy implementation.
 
 Specified by:
 
 peek in interface Value<T>
 
 Parameters:
 
 action - The action that will be performed on the element(s).
 
 Returns:
 
 this instance
 - product
```
default java.lang.Number product()
```
 Calculates the product of this elements. Supported component types are Byte, Double, Float, Integer, Long, Short, BigInteger and BigDecimal.
 Examples:
```
 
 List.empty().product() // = 1
 List.of(1, 2, 3).product() // = 6L
 List.of(0.1, 0.2, 0.3).product() // = 0.006
 List.of("apple", "pear").product() // throws
 
 
```
 Please also see fold(Object, BiFunction), a way to do a type-safe multiplication of elements.
 Returns:
 
 a Number representing the sum of this elements
 
 Throws:
 
 java.lang.UnsupportedOperationException - if this elements are not numeric
 - reduce
```
default T reduce(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op. The order of element iteration is undetermined.
 
 Specified by:
 
 reduce in interface Foldable<T>
 
 Parameters:
 
 op - A BiFunction of type T
 
 Returns:
 
 the reduced value.
 
 Throws:
 
 java.util.NoSuchElementException - if this is empty
 
 java.lang.NullPointerException - if op is null
 - reduceOption
```
default Option<T> reduceOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op. The order of element iteration is undetermined.
 
 Specified by:
 
 reduceOption in interface Foldable<T>
 
 Parameters:
 
 op - A BiFunction of type T
 
 Returns:
 
 Some of reduced value or None if the Foldable is empty.
 
 Throws:
 
 java.lang.NullPointerException - if op is null
 - reduceLeft
```
default T reduceLeft(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op from the left.
 
 Specified by:
 
 reduceLeft in interface Foldable<T>
 
 Parameters:
 
 op - A BiFunction of type T
 
 Returns:
 
 the reduced value.
 
 Throws:
 
 java.util.NoSuchElementException - if this is empty
 
 java.lang.NullPointerException - if op is null
 - reduceLeftOption
```
default Option<T> reduceLeftOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op from the left.
 Shortcut for isEmpty() ? Option.none() : Option.some(reduceLeft(op)).
 
 Specified by:
 
 reduceLeftOption in interface Foldable<T>
 
 Parameters:
 
 op - A BiFunction of type T
 
 Returns:
 
 Some of reduced value or None if the Traversable is empty.
 
 Throws:
 
 java.lang.NullPointerException - if op is null
 - reduceRight
```
default T reduceRight(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op from the right.
 
 Specified by:
 
 reduceRight in interface Foldable<T>
 
 Parameters:
 
 op - An operation of type T
 
 Returns:
 
 the reduced value.
 
 Throws:
 
 java.util.NoSuchElementException - if this is empty
 
 java.lang.NullPointerException - if op is null
 - reduceRightOption
```
default Option<T> reduceRightOption(java.util.function.BiFunction<? super T,? super T,? extends T> op)
```
 Accumulates the elements of this Traversable by successively calling the given operation op from the right.
 Shortcut for isEmpty() ? Option.none() : Option.some(reduceRight(op)).
 
 Specified by:
 
 reduceRightOption in interface Foldable<T>
 
 Parameters:
 
 op - An operation of type T
 
 Returns:
 
 Some of reduced value or None.
 
 Throws:
 
 java.lang.NullPointerException - if op is null
 - replace
```
Traversable<T> replace(T currentElement,
 T newElement)
```
 Replaces the first occurrence (if exists) of the given currentElement with newElement.
 
 Parameters:
 
 currentElement - An element to be substituted.
 
 newElement - A replacement for currentElement.
 
 Returns:
 
 a Traversable containing all elements of this where the first occurrence of currentElement is replaced with newElement.
 - replaceAll
```
Traversable<T> replaceAll(T currentElement,
 T newElement)
```
 Replaces all occurrences of the given currentElement with newElement.
 
 Parameters:
 
 currentElement - An element to be substituted.
 
 newElement - A replacement for currentElement.
 
 Returns:
 
 a Traversable containing all elements of this where all occurrences of currentElement are replaced with newElement.
 - retainAll
```
Traversable<T> retainAll(java.lang.Iterable<? extends T> elements)
```
 Keeps all occurrences of the given elements from this.
 
 Parameters:
 
 elements - Elements to be kept.
 
 Returns:
 
 a Traversable containing all occurrences of the given elements.
 
 Throws:
 
 java.lang.NullPointerException - if elements is null
 - scan
```
Traversable<T> scan(T zero,
 java.util.function.BiFunction<? super T,? super T,? extends T> operation)
```
 Computes a prefix scan of the elements of the collection. Note: The neutral element z may be applied more than once.
 
 Parameters:
 
 zero - neutral element for the operator op
 
 operation - the associative operator for the scan
 
 Returns:
 
 a new traversable collection containing the prefix scan of the elements in this traversable collection
 
 Throws:
 
 java.lang.NullPointerException - if operation is null.
 - scanLeft
```
 Traversable scanLeft(U zero,
 java.util.function.BiFunction<? super U,? super T,? extends U> operation)
```
 Produces a collection containing cumulative results of applying the operator going left to right. Note: will not terminate for infinite-sized collections. Note: might return different results for different runs, unless the underlying collection type is ordered.
 
 Type Parameters:
 
 U - the type of the elements in the resulting collection
 
 Parameters:
 
 zero - the initial value
 
 operation - the binary operator applied to the intermediate result and the element
 
 Returns:
 
 collection with intermediate results
 
 Throws:
 
 java.lang.NullPointerException - if operation is null.
 - scanRight
```
 Traversable scanRight(U zero,
 java.util.function.BiFunction<? super T,? super U,? extends U> operation)
```
 Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result. Note: will not terminate for infinite-sized collections. Note: might return different results for different runs, unless the underlying collection type is ordered.
 
 Type Parameters:
 
 U - the type of the elements in the resulting collection
 
 Parameters:
 
 zero - the initial value
 
 operation - the binary operator applied to the intermediate result and the element
 
 Returns:
 
 collection with intermediate results
 
 Throws:
 
 java.lang.NullPointerException - if operation is null.
 - single
```
default T single()
```
 Returns the single element of this Traversable or throws, if this is empty or contains more than one element.
 
 Returns:
 
 the single element from the Traversable
 
 Throws:
 
 java.util.NoSuchElementException - if the Traversable does not contain a single element.
 - singleOption
```
default Option<T> singleOption()
```
 Returns the only element of a Traversable as Option.
 
 Returns:
 
 Some(element) or None if the Traversable does not contain a single element.
 - size
```
default int size()
```
 Computes the number of elements of this Traversable.
 Same as length().
 
 Returns:
 
 the number of elements
 - slideBy
```
Iterator<? extends Traversable<T>> slideBy(java.util.function.Function<? super T,?> classifier)
```
 Slides a non-overlapping window of a variable size over this Traversable.
 Each window contains elements with the same class, as determined by classifier. Two consecutive values in this Traversable will be in the same window only if classifier returns equal values for them. Otherwise, the values will constitute the last element of the previous window and the first element of the next window.
 Examples:
```
 [].slideBy(Function.identity()) = []
 [1,2,3,4,4,5].slideBy(Function.identity()) = [[1],[2],[3],[4,4],[5]]
 [1,2,3,10,12,5,7,20,29].slideBy(x -> x/10) = [[1,2,3],[10,12],[5,7],[20,29]]
 
```
 Parameters:
 
 classifier - A function which classifies elements into classes
 
 Returns:
 
 A new Iterator of windows of the grouped elements
 
 Throws:
 
 java.lang.NullPointerException - if classifier is null.
 - sliding
```
Iterator<? extends Traversable<T>> sliding(int size)
```
 Slides a window of a specific size and step size 1 over this Traversable by calling sliding(int, int).
 
 Parameters:
 
 size - a positive window size
 
 Returns:
 
 a new Iterator of windows of a specific size using step size 1
 
 Throws:
 
 java.lang.IllegalArgumentException - if size is negative or zero
 - sliding
```
Iterator<? extends Traversable<T>> sliding(int size,
 int step)
```
 Slides a window of a specific size and step size over this Traversable.
 Examples:
```
 
 [].sliding(1,1) = []
 [1,2,3,4,5].sliding(2,3) = [[1,2],[4,5]]
 [1,2,3,4,5].sliding(2,4) = [[1,2],[5]]
 [1,2,3,4,5].sliding(2,5) = [[1,2]]
 [1,2,3,4].sliding(5,3) = [[1,2,3,4]]
 
 
```
 Parameters:
 
 size - a positive window size
 
 step - a positive step size
 
 Returns:
 
 a new Iterator of windows of a specific size using a specific step size
 
 Throws:
 
 java.lang.IllegalArgumentException - if size or step are negative or zero
 - span
```
Tuple2<? extends Traversable<T>,? extends Traversable<T>> span(java.util.function.Predicate<? super T> predicate)
```
 Returns a tuple where the first element is the longest prefix of elements that satisfy the given predicate and the second element is the remainder.
 
 Parameters:
 
 predicate - A predicate.
 
 Returns:
 
 a Tuple containing the longest prefix of elements that satisfy p and the remainder.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - spliterator
```
default java.util.Spliterator<T> spliterator()
```
 Specified by:
 
 spliterator in interface java.lang.Iterable<T>
 
 Specified by:
 
 spliterator in interface Value<T>
 - sum
```
default java.lang.Number sum()
```
 Calculates the sum of this elements. Supported component types are Byte, Double, Float, Integer, Long, Short, BigInteger and BigDecimal.
 Examples:
```
 
 List.empty().sum() // = 0
 List.of(1, 2, 3).sum() // = 6L
 List.of(0.1, 0.2, 0.3).sum() // = 0.6
 List.of("apple", "pear").sum() // throws
 
 
```
 Please also see fold(Object, BiFunction), a way to do a type-safe summation of elements.
 Returns:
 
 a Number representing the sum of this elements
 
 Throws:
 
 java.lang.UnsupportedOperationException - if this elements are not numeric
 - tail
```
Traversable<T> tail()
```
 Drops the first element of a non-empty Traversable.
 
 Returns:
 
 A new instance of Traversable containing all elements except the first.
 
 Throws:
 
 java.lang.UnsupportedOperationException - if this is empty
 - tailOption
```
Option<? extends Traversable<T>> tailOption()
```
 Drops the first element of a non-empty Traversable and returns an Option.
 
 Returns:
 
 Some(traversable) or None if this is empty.
 - take
```
Traversable<T> take(int n)
```
 Takes the first n elements of this or all elements, if this length < n.
 The result is equivalent to sublist(0, max(0, min(length(), n))) but does not throw if n < 0 or n > length().
 In the case of n < 0 the empty instance is returned, in the case of n > length() this is returned.
 
 Parameters:
 
 n - The number of elements to take.
 
 Returns:
 
 A new instance consisting of the first n elements of this or all elements, if this has less than n elements.
 - takeRight
```
Traversable<T> takeRight(int n)
```
 Takes the last n elements of this or all elements, if this length < n.
 The result is equivalent to sublist(max(0, min(length(), length() - n)), n), i.e. takeRight will not throw if n < 0 or n > length().
 In the case of n < 0 the empty instance is returned, in the case of n > length() this is returned.
 
 Parameters:
 
 n - The number of elements to take.
 
 Returns:
 
 A new instance consisting of the last n elements of this or all elements, if this has less than n elements.
 - takeUntil
```
Traversable<T> takeUntil(java.util.function.Predicate<? super T> predicate)
```
 Takes elements until the predicate holds for the current element.
 Note: This is essentially the same as takeWhile(predicate.negate()). It is intended to be used with method references, which cannot be negated directly.
 
 Parameters:
 
 predicate - A condition tested subsequently for this elements.
 
 Returns:
 
 a new instance consisting of all elements before the first one which does satisfy the given predicate.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - takeWhile
```
Traversable<T> takeWhile(java.util.function.Predicate<? super T> predicate)
```
 Takes elements while the predicate holds for the current element.
 
 Parameters:
 
 predicate - A condition tested subsequently for the contained elements.
 
 Returns:
 
 a new instance consisting of all elements before the first one which does not satisfy the given predicate.
 
 Throws:
 
 java.lang.NullPointerException - if predicate is null
 - unzip
```
default <T1,T2> Tuple2<Iterator<T1>,Iterator<T2>> unzip(java.util.function.Function<? super T,? extends T1> unzipper1,
 java.util.function.Function<? super T,? extends T2> unzipper2)
```
 Unzips this elements by mapping this elements to a pair of distinct sets.
 
 Type Parameters:
 
 T1 - element type returned by unzipper1
 
 T2 - element type returned by unzipper2
 
 Parameters:
 
 unzipper1 - a function which converts elements of this to elements of first set
 
 unzipper2 - a function which converts elements of this to elements of second set
 
 Returns:
 
 A pair of set containing elements split by unzipper1, unzipper2
 
 Throws:
 
 java.lang.NullPointerException - if any of unzipper1, unzipper2 are null
 - unzip3
```
default <T1,T2,T3> Tuple3<Iterator<T1>,Iterator<T2>,Iterator<T3>> unzip3(java.util.function.Function<? super T,? extends T1> unzipper1,
 java.util.function.Function<? super T,? extends T2> unzipper2,
 java.util.function.Function<? super T,? extends T3> unzipper3)
```
 Unzips this elements by mapping this elements to three distinct sets.
 
 Type Parameters:
 
 T1 - element type returned by unzipper1
 
 T2 - element type returned by unzipper2
 
 T3 - element type returned by unzipper3
 
 Parameters:
 
 unzipper1 - a function which converts elements of this to first set
 
 unzipper2 - a function which converts elements of this to second set
 
 unzipper3 - a function which converts elements of this to third set
 
 Returns:
 
 A triplet of Iterator to iterate over elements of sets split by unzipper1, unzipper2, unzipper3
 
 Throws:
 
 java.lang.NullPointerException - if any of unzipper1, unzipper2, unzipper3 is null
 - zip
```
 Traversable<Tuple2<T,U>> zip(java.lang.Iterable<? extends U> that)
```
 Returns a traversable formed from this traversable and another Iterable collection by combining corresponding elements in pairs. If one of the two iterables is longer than the other, its remaining elements are ignored.
 The length of the returned traversable is the minimum of the lengths of this traversable and that iterable.
 
 Type Parameters:
 
 U - The type of the second half of the returned pairs.
 
 Parameters:
 
 that - The Iterable providing the second half of each result pair.
 
 Returns:
 
 a new traversable containing pairs consisting of corresponding elements of this traversable and that iterable.
 
 Throws:
 
 java.lang.NullPointerException - if that is null
 - zipAll
```
 Traversable<Tuple2<T,U>> zipAll(java.lang.Iterable<? extends U> that,
 T thisElem,
 U thatElem)
```
 Returns a traversable formed from this traversable and another Iterable by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
 The length of the returned traversable is the maximum of the lengths of this traversable and that iterable.
 Special case: if this traversable is shorter than that elements, and that elements contains duplicates, the resulting traversable may be shorter than the maximum of the lengths of this and that because a traversable contains an element at most once.
 If this Traversable is shorter than that, thisElem values are used to fill the result. If that is shorter than this Traversable, thatElem values are used to fill the result.
 
 Type Parameters:
 
 U - The type of the second half of the returned pairs.
 
 Parameters:
 
 that - The Iterable providing the second half of each result pair.
 
 thisElem - The element to be used to fill up the result if this traversable is shorter than that.
 
 thatElem - The element to be used to fill up the result if that is shorter than this traversable.
 
 Returns:
 
 A new traversable containing pairs consisting of corresponding elements of this traversable and that.
 
 Throws:
 
 java.lang.NullPointerException - if that is null
 - zipWith
```
<U,R> Traversable<R> zipWith(java.lang.Iterable<? extends U> that,
 java.util.function.BiFunction<? super T,? super U,? extends R> mapper)
```
 Returns a traversable formed from this traversable and another Iterable collection by mapping elements. If one of the two iterables is longer than the other, its remaining elements are ignored.
 The length of the returned traversable is the minimum of the lengths of this traversable and that iterable.
 
 Type Parameters:
 
 U - The type of the second parameter of the mapper.
 
 R - The type of the mapped elements.
 
 Parameters:
 
 that - The Iterable providing the second parameter of the mapper.
 
 mapper - a mapper.
 
 Returns:
 
 a new traversable containing mapped elements of this traversable and that iterable.
 
 Throws:
 
 java.lang.NullPointerException - if that or mapper is null
 - zipWithIndex
```
Traversable<Tuple2<T,java.lang.Integer>> zipWithIndex()
```
 Zips this traversable with its indices.
 
 Returns:
 
 A new traversable containing all elements of this traversable paired with their index, starting with 0.
 - zipWithIndex
```
 Traversable zipWithIndex(java.util.function.BiFunction<? super T,? super java.lang.Integer,? extends U> mapper)
```
 Returns a traversable formed from this traversable and another Iterable collection by mapping elements. If one of the two iterables is longer than the other, its remaining elements are ignored.
 The length of the returned traversable is the minimum of the lengths of this traversable and that iterable.
 
 Type Parameters:
 
 U - The type of the mapped elements.
 
 Parameters:
 
 mapper - a mapper.
 
 Returns:
 
 a new traversable containing mapped elements of this traversable and that iterable.
 
 Throws:
 
 java.lang.NullPointerException - if mapper is null
 - toSortedMap
```
default <K,V> SortedMap<K,V> toSortedMap(java.util.Comparator<? super K> keyComparator,
 java.util.function.Function<? super T,? extends K> keyMapper,
 java.util.function.Function<? super T,? extends V> valueMapper,
 java.util.function.BiFunction<? super V,? super V,? extends V> merge)
```
 Converts this collection to a SortedMap.
 
 Type Parameters:
 
 K - The key type
 
 V - The value type
 
 Parameters:
 
 keyComparator - A comparator that induces an order of the Map keys.
 
 keyMapper - A function that maps an element to a key
 
 valueMapper - A function that maps an element to a value
 
 merge - A function that merges values that are associated with the same key
 
 Returns:
 
 A new TreeMap.
 - toSortedMap
```
default <K extends java.lang.Comparable<? super K>,V> SortedMap<K,V> toSortedMap(java.util.function.Function<? super T,? extends K> keyMapper,
 java.util.function.Function<? super T,? extends V> valueMapper,
 java.util.function.BiFunction<? super V,? super V,? extends V> merge)
```
 Converts this collection to a SortedMap.
 
 Type Parameters:
 
 K - The key type
 
 V - The value type
 
 Parameters:
 
 keyMapper - A function that maps an element to a key
 
 valueMapper - A function that maps an element to a value
 
 merge - A function that merges values that are associated with the same key
 
 Returns:
 
 A new TreeMap.
 - toLinkedMap
```
default <K extends java.lang.Comparable<? super K>,V> Map<K,V> toLinkedMap(java.util.function.Function<? super T,? extends K> keyMapper,
 java.util.function.Function<? super T,? extends V> valueMapper,
 java.util.function.BiFunction<? super V,? super V,? extends V> merge)
```
 Converts this collection to a Map.
 
 Type Parameters:
 
 K - The key type
 
 V - The value type
 
 Parameters:
 
 keyMapper - A function that maps an element to a key
 
 valueMapper - A function that maps an element to a value
 
 merge - A function that merges values that are associated with the same key
 
 Returns:
 
 A new LinkedHashMap.
 - toMap
```
default <K,V> Map<K,V> toMap(java.util.function.Function<? super T,? extends K> keyMapper,
 java.util.function.Function<? super T,? extends V> valueMapper,
 java.util.function.BiFunction<? super V,? super V,? extends V> merge)
```
 Converts this collection to a Map.
 
 Type Parameters:
 
 K - The key type
 
 V - The value type
 
 Parameters:
 
 keyMapper - A function that maps an element to a key
 
 valueMapper - A function that maps an element to a value
 
 merge - A function that merges values that are associated with the same key
 
 Returns:
 
 A new HashMap.

Interface Traversable<T>

Method Summary

Methods inherited from interface io.vavr.Value

Method Detail

narrow

arrangeBy

average

collect

containsAll

count

distinct

distinctBy

distinctBy

drop

dropRight

dropUntil

dropWhile

equals

existsUnique

filter

filterNot

find

findLast

flatMap

fold

foldLeft

foldRight

forEachWithIndex

get

groupBy

grouped

hasDefiniteSize

head

headOption

hashCode

init

initOption

isDistinct

isEmpty

isOrdered

isSequential

isSingleValued

isTraversableAgain

iterator

last

lastOption

length

map

max

maxBy

maxBy

min

minBy

minBy

mkCharSeq

mkCharSeq

mkCharSeq

mkString

mkString

mkString

nonEmpty

orElse

orElse

partition

peek

product

reduce

reduceOption

reduceLeft

reduceLeftOption

reduceRight

reduceRightOption

replace

replaceAll

retainAll

scan

scanLeft

scanRight

single

singleOption