Interface Tree<T>

Type Parameters:

T - component type of this Tree

All Superinterfaces:

Foldable<T>, Iterable<T>, Serializable, Traversable<T>, Value<T>

All Known Implementing Classes:

Tree.Empty, Tree.Node

public interface Tree<T>
extends Traversable<T>, Serializable

A general Tree interface.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static final class	Tree.Empty<T>	The empty tree.
static final class	Tree.Node<T>	Represents a tree node.
static enum	Tree.Order	Tree traversal order.

Field Summary

Fields

Modifier and Type	Field	Description
static final long	serialVersionUID	The serial version UID for serialization.

Method Summary

Modifier and Type	Method	Description
default int	branchCount()	Counts the number of branches of this tree.
static <T,ID> List<Tree.Node<T>>	build(@NonNull Iterable<? extends T> source, @NonNull Function<? super T, ? extends ID> idMapper, @NonNull Function<? super T, ? extends ID> parentMapper)	Build a List with roots of Tree from flat source.
default <R> Tree<R>	collect(@NonNull PartialFunction<? super T, ? extends R> partialFunction)	Applies a PartialFunction to all elements that are defined for it and collects the results.
static <T> Collector<T, ArrayList<T>, Tree<T>>	collector()	Returns a Collector which may be used in conjunction with Stream.collect(java.util.stream.Collector) to obtain a Tree.
default Seq<T>	distinct()	Returns a new Traversable containing the elements of this instance with all duplicates removed.
default Seq<T>	distinctBy(@NonNull Comparator<? super T> comparator)	Returns a new Traversable containing the elements of this instance without duplicates, as determined by the given comparator.
default <U> Seq<T>	distinctBy(@NonNull Function<? super T, ? extends U> keyExtractor)	Returns a new Traversable containing the elements of this instance without duplicates, based on keys extracted from elements using keyExtractor.
String	draw()	Creates a neat 2-dimensional drawing of a tree.
default Seq<T>	drop(int n)	Returns a new Traversable without the first n elements, or an empty instance if this contains fewer than n elements.
default Seq<T>	dropRight(int n)	Returns a new Traversable without the last n elements, or an empty instance if this contains fewer than n elements.
default Seq<T>	dropUntil(@NonNull Predicate<? super T> predicate)	Returns a new Traversable starting from the first element that satisfies the given predicate, dropping all preceding elements.
default Seq<T>	dropWhile(@NonNull Predicate<? super T> predicate)	Returns a new Traversable starting from the first element that does not satisfy the given predicate, dropping all preceding elements.
static <T> Tree.Empty<T>	empty()	Returns the singleton empty tree.
boolean	equals(Object o)	Determines whether this collection is equal to the given object.
static <T> Tree<T>	fill(int n, @NonNull Supplier<? extends T> s)	Returns a Tree containing n values supplied by a given Supplier s.
static <T> Tree<T>	fill(int n, T element)	Returns a Tree containing n times the given element
default Seq<T>	filter(@NonNull Predicate<? super T> predicate)	Returns a new traversable containing only the elements that satisfy the given predicate.
default <U> Tree<U>	flatMap(@NonNull Function<? super T, ? extends Iterable<? extends U>> mapper)	Transforms each element of this Traversable into an Iterable of elements and flattens the resulting iterables into a single Traversable.
default <U> U	foldRight(U zero, @NonNull BiFunction<? super T, ? super U, ? extends U> f)	Folds the elements of this structure from the right, starting with the given zero value and successively applying the combine function to each element.
List<Tree.Node<T>>	getChildren()	Returns the children of this tree.
T	getValue()	Gets the value of this tree.
default <C> Map<C,Seq<T>>	groupBy(@NonNull Function<? super T, ? extends C> classifier)	Groups elements of this Traversable based on a classifier function.
default Iterator<Seq<T>>	grouped(int size)	Splits this Traversable into consecutive blocks of the given size.
default boolean	hasDefiniteSize()	Indicates whether this Traversable has a known finite size.
int	hashCode()	Returns the hash code of this collection.
default T	head()	Returns the first element of this non-empty Traversable.
default Seq<T>	init()	Returns all elements of this Traversable except the last one.
default Option<Seq<T>>	initOption()	Returns all elements of this Traversable except the last one, wrapped in an Option.
default boolean	isAsync()	A Tree is computed synchronously.
default boolean	isBranch()	Checks if this Tree is a branch.
default boolean	isDistinct()	Indicates whether this Traversable may contain only distinct elements.
default boolean	isLazy()	A Tree is computed eagerly.
boolean	isLeaf()	Checks if this Tree is a leaf.
default boolean	isSequential()	Indicates whether the elements of this Traversable appear in encounter (insertion) order.
default boolean	isTraversableAgain()	Checks if this Traversable can be traversed multiple times without side effects.
default @NonNull Iterator<T>	iterator()	Returns an iterator over the elements of this Traversable, implemented via Traversable.head() and Traversable.tail().
default Iterator<T>	iterator(Tree.Order order)	Traverses this tree values in a specific Tree.Order.
default int	leafCount()	Counts the number of leaves of this tree.
default <U> Tree<U>	map(@NonNull Function<? super T, ? extends U> mapper)	Transforms the elements of this Traversable to a new type, preserving order if defined.
default <U> Tree<U>	mapTo(U value)	Maps the underlying value to another fixed value.
default Tree<Void>	mapToVoid()	Maps the underlying value to Void
static <T> Tree<T>	narrow(Tree<? extends T> tree)	Narrows a widened Tree<? extends T> to Tree<T> by performing a type-safe cast.
default int	nodeCount()	Counts the number of nodes (i.e.
static <T> Tree.Node<T>	of(T value)	Returns a new Node containing the given value and having no children.
static <T> Tree<T>	of(T @NonNull ... values)	Creates a Tree of the given elements.
static <T> Tree.Node<T>	of(T value, @NonNull Tree.Node<T> @NonNull ... children)	Returns a new Node containing the given value and having the given children.
static <T> Tree.Node<T>	of(T value, @NonNull Iterable<Tree.Node<T>> children)	Returns a new Node containing the given value and having the given children.
static <T> Tree<T>	ofAll(@NonNull Iterable<? extends T> iterable)	Creates a Tree of the given elements.
static <T> Tree<T>	ofAll(@NonNull Stream<? extends T> javaStream)	Creates a Tree that contains the elements of the given Stream.
default Tree<T>	orElse(@NonNull Iterable<? extends T> other)	Returns this Traversable if it is non-empty; otherwise, returns the given alternative.
default Tree<T>	orElse(@NonNull Supplier<? extends Iterable<? extends T>> supplier)	Returns this Traversable if it is non-empty; otherwise, returns the result of evaluating the given supplier.
default Tuple2<Seq<T>,Seq<T>>	partition(@NonNull Predicate<? super T> predicate)	Splits this Traversable into two partitions according to a predicate.
default Tree<T>	peek(@NonNull Consumer<? super T> action)	Performs the given action on the first element if this is an eager implementation.
static <T> Tree.Node<T>	recurse(T seed, @NonNull Function<? super T, ? extends Iterable<? extends T>> descend)	Recursively builds a non-empty Tree, starting with the given seed value and proceeding in depth-first order.
default Seq<T>	reject(@NonNull Predicate<? super T> predicate)	Returns a new traversable containing only the elements that do not satisfy the given predicate.
default Tree<T>	replace(T currentElement, T newElement)	Replaces the first occurrence of currentElement with newElement, if it exists.
default Tree<T>	replaceAll(T currentElement, T newElement)	Replaces all occurrences of currentElement with newElement.
default Seq<T>	retainAll(@NonNull Iterable<? extends T> elements)	Retains only the elements from this Traversable that are contained in the given elements.
default Seq<T>	scan(T zero, @NonNull BiFunction<? super T, ? super T, ? extends T> operation)	Computes a prefix scan of the elements of this Traversable.
default <U> Seq<U>	scanLeft(U zero, @NonNull BiFunction<? super U, ? super T, ? extends U> operation)	Produces a collection containing cumulative results of applying the operator from left to right.
default <U> Seq<U>	scanRight(U zero, @NonNull BiFunction<? super T, ? super U, ? extends U> operation)	Produces a collection containing cumulative results of applying the operator from right to left.
default Iterator<Seq<T>>	slideBy(@NonNull Function<? super T, ?> classifier)	Partitions this Traversable into consecutive non-overlapping windows according to a classification function.
default Iterator<Seq<T>>	sliding(int size)	Slides a window of a given size over this Traversable with a step size of 1.
default Iterator<Seq<T>>	sliding(int size, int step)	Slides a window of a specific size with a given step over this Traversable.
default Tuple2<Seq<T>,Seq<T>>	span(@NonNull Predicate<? super T> predicate)	Splits this Traversable into a prefix and remainder according to the given predicate.
default String	stringPrefix()	Returns the name of this Value type, which is used by toString().
static <T> Tree<T>	tabulate(int n, @NonNull Function<? super Integer, ? extends T> f)	Returns a Tree containing n values of a given Function f over a range of integer values from 0 to n - 1.
default Seq<T>	tail()	Returns a new Traversable without its first element.
default Option<Seq<T>>	tailOption()	Returns a new Traversable without its first element as an Option.
default Seq<T>	take(int n)	Returns the first n elements of this Traversable, or all elements if n exceeds the length.
default Seq<T>	takeRight(int n)	Returns the last n elements of this Traversable, or all elements if n exceeds the length.
default Seq<T>	takeUntil(@NonNull Predicate<? super T> predicate)	Takes elements from this Traversable until the given predicate holds for an element.
default Seq<T>	takeWhile(@NonNull Predicate<? super T> predicate)	Takes elements from this Traversable while the given predicate holds.
String	toLispString()	Creates a Lisp-like representation of this Tree.
String	toString()	Clarifies that values have a proper toString() method implemented.
default <U> U	transform(@NonNull Function<? super Tree<T>, ? extends U> f)	Transforms this Tree.
default Seq<Tree.Node<T>>	traverse()	Traverses this tree in Tree.Order.PRE_ORDER.
default Seq<Tree.Node<T>>	traverse(@NonNull Tree.Order order)	Traverses this tree in a specific order.
default <T1,T2> Tuple2<Tree<T1>,Tree<T2>>	unzip(@NonNull Function<? super T, Tuple2<? extends T1, ? extends T2>> unzipper)	Unzips the elements of this Traversable by mapping each element to a pair and splitting them into two separate Traversable collections.
default <T1,T2,T3> Tuple3<Tree<T1>,Tree<T2>,Tree<T3>>	unzip3(@NonNull Function<? super T, Tuple3<? extends T1, ? extends T2, ? extends T3>> unzipper)	Unzips the elements of this Traversable by mapping each element to a triple and splitting them into three separate Traversable collections.
default Seq<T>	values()	Traverses this tree values in Tree.Order.PRE_ORDER.
default Seq<T>	values(@NonNull Tree.Order order)	Traverses this tree values in a specific order.
default <U> Tree<Tuple2<T,U>>	zip(@NonNull Iterable<? extends U> that)	Returns a Traversable formed by pairing elements of this Traversable with elements of another Iterable.
default <U> Tree<Tuple2<T,U>>	zipAll(@NonNull Iterable<? extends U> that, T thisElem, U thatElem)	Returns a Traversable formed by pairing elements of this Traversable with elements of another Iterable, filling in placeholder elements when one collection is shorter than the other.
default <U,R> Tree<R>	zipWith(@NonNull Iterable<? extends U> that, BiFunction<? super T, ? super U, ? extends R> mapper)	Returns a Traversable by combining elements of this Traversable with elements of another Iterable using a mapping function.
default Tree<Tuple2<T,Integer>>	zipWithIndex()	Zips this Traversable with its indices, starting at 0.
default <U> Tree<U>	zipWithIndex(@NonNull BiFunction<? super T, ? super Integer, ? extends U> mapper)	Zips this Traversable with its indices and maps the resulting pairs using the provided mapper.

Methods inherited from interface Foldable

fold, reduce, reduceOption

Methods inherited from interface Traversable

arrangeBy, average, containsAll, count, existsUnique, find, findLast, foldLeft, forEachWithIndex, get, headOption, isEmpty, isOrdered, isSingleValued, last, lastOption, length, max, maxBy, maxBy, min, minBy, minBy, mkCharSeq, mkCharSeq, mkCharSeq, mkString, mkString, mkString, nonEmpty, product, reduceLeft, reduceLeftOption, reduceRight, reduceRightOption, single, singleOption, size, spliterator, sum

Methods inherited from interface Value

collect, collect, contains, corresponds, eq, exists, forAll, forEach, getOrElse, getOrElse, getOrElseThrow, getOrElseTry, getOrNull, out, out, stderr, stdout, 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, toTree, toTree, toTry, toTry, toValid, toValid, toValidation, toValidation, toVector

Field Details

serialVersionUID

static final long serialVersionUID

The serial version UID for serialization.

See Also:

• Constant Field Values

Method Details

collector

static <T> Collector<T, ArrayList<T>, Tree<T>> collector()

Returns a Collector which may be used in conjunction with Stream.collect(java.util.stream.Collector) to obtain a Tree.

Type Parameters:

T - Component type of the Tree.

Returns:

A io.vavr.collection.Tree Collector.

empty

static <T> Tree.Empty<T> empty()

Returns the singleton empty tree.

Type Parameters:

T - Type of tree values.

Returns:

The empty tree.

narrow

static <T> Tree<T> narrow(Tree<? extends T> tree)

Narrows a widened Tree<? extends T> to Tree<T> by performing a type-safe cast. This is eligible because immutable/read-only collections are covariant.

Type Parameters:

T - Component type of the Tree.

Parameters:

tree - An Tree.

Returns:

the given tree instance as narrowed type Tree<T>.

of

static <T> Tree.Node<T> of(T value)

Returns a new Node containing the given value and having no children.

Type Parameters:

T - Value type

Parameters:

value - A value

Returns:

A new Node instance.

of

@SafeVarargs
static <T> Tree.Node<T> of(T value,
 @NonNull Tree.Node<T> @NonNull ... children)

Returns a new Node containing the given value and having the given children.

Type Parameters:

T - Value type

Parameters:

value - A value

children - The child nodes, possibly empty

Returns:

A new Node instance.

of

static <T> Tree.Node<T> of(T value,
 @NonNull Iterable<Tree.Node<T>> children)

Returns a new Node containing the given value and having the given children.

Type Parameters:

T - Value type

Parameters:

value - A value

children - The child nodes, possibly empty

Returns:

A new Node instance.

of

@SafeVarargs
static <T> Tree<T> of(T @NonNull ... values)

Creates a Tree of the given elements.

Type Parameters:

T - Component type of the List.

Parameters:

values - Zero or more values.

Returns:

A Tree containing the given values.

Throws:

NullPointerException - if values is null

ofAll

static <T> Tree<T> ofAll(@NonNull Iterable<? extends T> iterable)

Creates a Tree of the given elements.

If the given iterable is a tree, it is returned as result. if the iteration order of the elements is stable.

Type Parameters:

T - Component type of the List.

Parameters:

iterable - An Iterable of elements.

Returns:

A list containing the given elements in the same order.

Throws:

NullPointerException - if elements is null

ofAll

static <T> Tree<T> ofAll(@NonNull Stream<? extends T> javaStream)

Creates a Tree that contains the elements of the given Stream.

Type Parameters:

T - Component type of the Stream.

Parameters:

javaStream - A Stream

Returns:

A Tree containing the given elements in the same order.

tabulate

static <T> Tree<T> tabulate(int n,
 @NonNull Function<? super Integer, ? extends T> f)

Returns a Tree containing n values of a given Function f over a range of integer values from 0 to n - 1.

Type Parameters:

T - Component type of the Tree

Parameters:

n - The number of elements in the Tree

f - The Function computing element values

Returns:

A Tree consisting of elements f(0),f(1), ..., f(n - 1)

Throws:

NullPointerException - if f is null

fill

static <T> Tree<T> fill(int n,
 @NonNull Supplier<? extends T> s)

Returns a Tree containing n values supplied by a given Supplier s.

Type Parameters:

T - Component type of the Tree

Parameters:

n - The number of elements in the Tree

s - The Supplier computing element values

Returns:

A Tree of size n, where each element contains the result supplied by s.

Throws:

NullPointerException - if s is null

fill

static <T> Tree<T> fill(int n,
 T element)

Returns a Tree containing n times the given element

Type Parameters:

T - Component type of the Tree

Parameters:

n - The number of elements in the Tree

element - The element

Returns:

A Tree of size n, where each element is the given element.

recurse

static <T> Tree.Node<T> recurse(T seed,
 @NonNull Function<? super T, ? extends Iterable<? extends T>> descend)

Recursively builds a non-empty Tree, starting with the given seed value and proceeding in depth-first order.

The children of a node are created by

1. applying the descend function to the node value
2. calling this method recursively by using each derived child value as new seed (in iteration order).

Example:

// = (1 (2 4 5) 3)
Tree.recurse(1, i ->
  (i == 1) ? List.of(2, 3) :
  (i == 2) ? List.(4, 5) :
  List.empty()
).toLispString();

Type Parameters:

T - Value type

Parameters:

seed - The start value for the Tree

descend - A function to calculate the child values

Returns:

a new, non-empty Tree instance

Throws:

NullPointerException - if descend is null

build

static <T,ID> List<Tree.Node<T>> build(@NonNull Iterable<? extends T> source,
 @NonNull Function<? super T, ? extends ID> idMapper,
 @NonNull Function<? super T, ? extends ID> parentMapper)

Build a List with roots of Tree from flat source.

parentMapper must return null for root element.

 // = [(1, null, "I"), (2, 1, "II"), (3, 1, "III"), (4, 2, "IV"), (5, 2, "V")]
 List<MenuItem> items = ...; // MenuItem(id, parentId, label)

 //      I
 //     / \
 //   II  III
 //   /\
 //  IV V
 Tree<MenuItem> menu = Tree.build(items, MenuItem::getId, MenuItem::getParentId);

Type Parameters:

T - Value type

ID - Id type

Parameters:

source - Flat source

idMapper - A mapper from source item to unique identifier of that item

parentMapper - A mapper from source item to unique identifier of parent item. Need return null for root items

Returns:

a new, maybe empty List instance with non-empty Tree instances

Throws:

NullPointerException - if source, idMapper or parentMapper is null

collect

default <R> Tree<R> collect(@NonNull PartialFunction<? super T, ? extends R> partialFunction)

Description copied from interface: Traversable

Applies a PartialFunction to all elements that are defined for it and collects the results.

For each element in iteration order, the function is first tested:

partialFunction.isDefinedAt(element)

If true, the element is mapped to type R:

R newElement = partialFunction.apply(element)

Note: If this Traversable is ordered (i.e., extends Ordered), the caller must ensure that the resulting elements are comparable (i.e., implement Comparable).

Specified by:

collect in interface Traversable<T>

Type Parameters:

R - the type of elements in the resulting Traversable

Parameters:

partialFunction - a function that may not be defined for all elements of this traversable

Returns:

a new Traversable containing the results of applying the partial function

getValue

T getValue()

Gets the value of this tree.

Returns:

The value of this tree.

Throws:

UnsupportedOperationException - if this tree is empty

getChildren

List<Tree.Node<T>> getChildren()

Returns the children of this tree.

Returns:

the tree's children

isLeaf

boolean isLeaf()

Checks if this Tree is a leaf. A tree is a leaf if it is a Node with no children. Because the empty tree is no Node, it is not a leaf by definition.

Returns:

true if this tree is a leaf, false otherwise.

isBranch

default boolean isBranch()

Checks if this Tree is a branch. A Tree is a branch if it is a Node which has children. Because the empty tree is not a Node, it is not a branch by definition.

Returns:

true if this tree is a branch, false otherwise.

isAsync

default boolean isAsync()

A Tree is computed synchronously.

Specified by:

isAsync in interface Value<T>

Returns:

false

isDistinct

default boolean isDistinct()

Description copied from interface: Traversable

Indicates whether this Traversable may contain only distinct elements.

Specified by:

isDistinct in interface Traversable<T>

Returns:

true if this Traversable may contain only distinct elements, false otherwise

isLazy

default boolean isLazy()

A Tree is computed eagerly.

Specified by:

isLazy in interface Value<T>

Returns:

false

isSequential

default boolean isSequential()

Description copied from interface: Traversable

Indicates whether the elements of this Traversable appear in encounter (insertion) order.

Specified by:

isSequential in interface Traversable<T>

Returns:

true if insertion order is preserved, false otherwise

iterator

default Iterator<T> iterator(Tree.Order order)

Traverses this tree values in a specific Tree.Order.

Parameters:

order - A traversal order

Returns:

A new Iterator

toLispString

String toLispString()

Creates a Lisp-like representation of this Tree.

Returns:

This Tree as Lisp-string, i.e. represented as list of lists.

transform

default <U> U transform(@NonNull Function<? super Tree<T>, ? extends U> f)

Transforms this Tree.

Type Parameters:

U - Type of transformation result

Parameters:

f - A transformation

Returns:

An instance of type U

Throws:

NullPointerException - if f is null

traverse

default Seq<Tree.Node<T>> traverse()

Traverses this tree in Tree.Order.PRE_ORDER.

Returns:

A sequence of nodes.

traverse

default Seq<Tree.Node<T>> traverse(@NonNull Tree.Order order)

Traverses this tree in a specific order.

Parameters:

order - the tree traversal order

Returns:

A sequence of nodes.

Throws:

NullPointerException - if order is null

values

default Seq<T> values()

Traverses this tree values in Tree.Order.PRE_ORDER. Syntactic sugar for traverse().map(Node::getValue).

Returns:

A sequence of the tree values.

values

default Seq<T> values(@NonNull Tree.Order order)

Traverses this tree values in a specific order. Syntactic sugar for traverse(order).map(Node::getValue).

Parameters:

order - the tree traversal order

Returns:

A sequence of the tree values.

Throws:

NullPointerException - if order is null

branchCount

default int branchCount()

Counts the number of branches of this tree. The empty tree and a leaf have no branches.

Returns:

The number of branches of this tree.

leafCount

default int leafCount()

Counts the number of leaves of this tree. The empty tree has no leaves.

Returns:

The number of leaves of this tree.

nodeCount

default int nodeCount()

Counts the number of nodes (i.e. branches and leaves) of this tree. The empty tree has no nodes.

Returns:

The number of nodes of this tree.

distinct

default Seq<T> distinct()

Description copied from interface: Traversable

Returns a new Traversable containing the elements of this instance with all duplicates removed. Element equality is determined using equals.

Specified by:

distinct in interface Traversable<T>

Returns:

a new Traversable without duplicate elements

distinctBy

default Seq<T> distinctBy(@NonNull Comparator<? super T> comparator)

Description copied from interface: Traversable

Returns a new Traversable containing the elements of this instance without duplicates, as determined by the given comparator.

Specified by:

distinctBy in interface Traversable<T>

Parameters:

comparator - a comparator used to determine equality of elements

Returns:

a new Traversable with duplicates removed

distinctBy

default <U> Seq<T> distinctBy(@NonNull Function<? super T, ? extends U> keyExtractor)

Description copied from interface: Traversable

Returns a new Traversable containing the elements of this instance without duplicates, based on keys extracted from elements using keyExtractor.

The first occurrence of each key is retained in the resulting sequence.

Specified by:

distinctBy in interface Traversable<T>

Type Parameters:

U - the type of key

Parameters:

keyExtractor - a function to extract keys for determining uniqueness

Returns:

a new Traversable with duplicates removed based on keys

drop

default Seq<T> drop(int n)

Description copied from interface: Traversable

Returns a new Traversable without the first n elements, or an empty instance if this contains fewer than n elements.

Specified by:

drop in interface Traversable<T>

Parameters:

n - the number of elements to drop

Returns:

a new instance excluding the first n elements

dropRight

default Seq<T> dropRight(int n)

Description copied from interface: Traversable

Returns a new Traversable without the last n elements, or an empty instance if this contains fewer than n elements.

Specified by:

dropRight in interface Traversable<T>

Parameters:

n - the number of elements to drop from the end

Returns:

a new instance excluding the last n elements

dropUntil

default Seq<T> dropUntil(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Returns a new Traversable starting from the first element that satisfies the given predicate, dropping all preceding elements.

Specified by:

dropUntil in interface Traversable<T>

Parameters:

predicate - a condition tested on each element

Returns:

a new instance starting from the first element matching the predicate

dropWhile

default Seq<T> dropWhile(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Returns a new Traversable starting from the first element that does not satisfy the given predicate, dropping all preceding elements.

This is equivalent to dropUntil(predicate.negate()), which is useful for method references that cannot be negated directly.

Specified by:

dropWhile in interface Traversable<T>

Parameters:

predicate - a condition tested on each element

Returns:

a new instance starting from the first element not matching the predicate

filter

default Seq<T> filter(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Returns a new traversable containing only the elements that satisfy the given predicate.

Specified by:

filter in interface Traversable<T>

Parameters:

predicate - the condition to test elements

Returns:

a traversable with elements matching the predicate

reject

default Seq<T> reject(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Returns a new traversable containing only the elements that do not satisfy the given predicate.

This is equivalent to filter(predicate.negate()).

Specified by:

reject in interface Traversable<T>

Parameters:

predicate - the condition to test elements

Returns:

a traversable with elements not matching the predicate

flatMap

default <U> Tree<U> flatMap(@NonNull Function<? super T, ? extends Iterable<? extends U>> mapper)

Description copied from interface: Traversable

Transforms each element of this Traversable into an Iterable of elements and flattens the resulting iterables into a single Traversable.

Specified by:

flatMap in interface Traversable<T>

Type Parameters:

U - the type of elements in the resulting Traversable

Parameters:

mapper - a function mapping elements to iterables

Returns:

a new Traversable containing all elements produced by applying mapper and flattening

foldRight

default <U> U foldRight(U zero,
 @NonNull BiFunction<? super T, ? super U, ? extends U> f)

Description copied from interface: Foldable

Folds the elements of this structure from the right, starting with the given zero value and successively applying the combine function to each element.

Folding from the right means that elements are combined starting from the last element and associating each step with the accumulated result so far.

Example:

// Result: "!cba"
List.of("a", "b", "c").foldRight("!", (x, acc) -> acc + x);

Specified by:

foldRight in interface Foldable<T>

Specified by:

foldRight in interface Traversable<T>

Type Parameters:

U - the type of the accumulated result

Parameters:

zero - the initial value to start folding with

f - a function that combines the next element and the accumulated value

Returns:

the folded result

groupBy

default <C> Map<C,Seq<T>> groupBy(@NonNull Function<? super T, ? extends C> classifier)

Description copied from interface: Traversable

Groups elements of this Traversable based on a classifier function.

Specified by:

groupBy in interface Traversable<T>

Type Parameters:

C - The type of the group keys

Parameters:

classifier - A function that assigns each element to a group

Returns:

A map where each key corresponds to a group of elements

See Also:

• Traversable.arrangeBy(Function)

grouped

default Iterator<Seq<T>> grouped(int size)

Description copied from interface: Traversable

Splits this Traversable into consecutive blocks of the given size.

Let length be the number of elements in this Traversable:

• If empty, the resulting Iterator is empty.
• If size <= length, the resulting Iterator contains length / size blocks of size size and possibly a final smaller block of size length % size.
• If size > length, the resulting Iterator contains a single 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]]

Note: grouped(size) is equivalent to sliding(size, size).

Specified by:

grouped in interface Traversable<T>

Parameters:

size - the block size; must be positive

Returns:

an Iterator over blocks of elements

hasDefiniteSize

default boolean hasDefiniteSize()

Description copied from interface: Traversable

Indicates whether this Traversable has a known finite size.

This should typically be implemented by concrete classes, not interfaces.

Specified by:

hasDefiniteSize in interface Traversable<T>

Returns:

true if the number of elements is finite and known, false otherwise.

head

default T head()

Description copied from interface: Traversable

Returns the first element of this non-empty Traversable.

Specified by:

head in interface Traversable<T>

Returns:

the first element

init

default Seq<T> init()

Description copied from interface: Traversable

Returns all elements of this Traversable except the last one.

This is the dual of Traversable.tail().

Specified by:

init in interface Traversable<T>

Returns:

a new instance containing all elements except the last

initOption

default Option<Seq<T>> initOption()

Description copied from interface: Traversable

Returns all elements of this Traversable except the last one, wrapped in an Option.

This is the dual of Traversable.tailOption().

Specified by:

initOption in interface Traversable<T>

Returns:

Some(traversable) if non-empty, or None if this Traversable is empty

isTraversableAgain

default boolean isTraversableAgain()

Description copied from interface: Traversable

Checks if this Traversable can be traversed multiple times without side effects.

Implementations should provide the correct behavior; this is not meant for interfaces alone.

Specified by:

isTraversableAgain in interface Traversable<T>

Returns:

true if this Traversable is guaranteed to be repeatably traversable, false otherwise

iterator

default @NonNull Iterator<T> iterator()

Description copied from interface: Traversable

Returns an iterator over the elements of this Traversable, implemented via Traversable.head() and Traversable.tail(). Subclasses may override for a more efficient implementation.

Specified by:

iterator in interface Iterable<T>

Specified by:

iterator in interface Traversable<T>

Specified by:

iterator in interface Value<T>

Returns:

a new Iterator over the elements of this Traversable

map

default <U> Tree<U> map(@NonNull Function<? super T, ? extends U> mapper)

Description copied from interface: Traversable

Transforms the elements of this Traversable to a new type, preserving order if defined.

Specified by:

map in interface Traversable<T>

Specified by:

map in interface Value<T>

Type Parameters:

U - the target element type

Parameters:

mapper - a mapping function

Returns:

a new Traversable containing the mapped elements

mapTo

default <U> Tree<U> mapTo(U value)

Description copied from interface: Value

Maps the underlying value to another fixed value.

Specified by:

mapTo in interface Traversable<T>

Specified by:

mapTo in interface Value<T>

Type Parameters:

U - The new component type

Parameters:

value - value to replace the contents with

Returns:

A new value

mapToVoid

default Tree<Void> mapToVoid()

Description copied from interface: Value

Maps the underlying value to Void

Specified by:

mapToVoid in interface Traversable<T>

Specified by:

mapToVoid in interface Value<T>

Returns:

A new value of type Void

orElse

default Tree<T> orElse(@NonNull Iterable<? extends T> other)

Description copied from interface: Traversable

Returns this Traversable if it is non-empty; otherwise, returns the given alternative.

Specified by:

orElse in interface Traversable<T>

Parameters:

other - an alternative Traversable to return if this is empty

Returns:

this Traversable if non-empty, otherwise other

orElse

default Tree<T> orElse(@NonNull Supplier<? extends Iterable<? extends T>> supplier)

Description copied from interface: Traversable

Returns this Traversable if it is non-empty; otherwise, returns the result of evaluating the given supplier.

Specified by:

orElse in interface Traversable<T>

Parameters:

supplier - a supplier of an alternative Traversable if this is empty

Returns:

this Traversable if non-empty, otherwise the result of supplier.get()

partition

default Tuple2<Seq<T>,Seq<T>> partition(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Splits this Traversable into two partitions according to a predicate.

The first partition contains all elements that satisfy the predicate, and the second contains all elements that do not. The original iteration order is preserved.

Specified by:

partition in interface Traversable<T>

Parameters:

predicate - a predicate used to classify elements

Returns:

a Tuple2 containing the two resulting Traversable instances

peek

default Tree<T> peek(@NonNull 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 Traversable<T>

Specified by:

peek in interface Value<T>

Parameters:

action - The action that will be performed on the element(s).

Returns:

this instance

replace

default Tree<T> replace(T currentElement,
 T newElement)

Description copied from interface: Traversable

Replaces the first occurrence of currentElement with newElement, if it exists.

Specified by:

replace in interface Traversable<T>

Parameters:

currentElement - the element to be replaced

newElement - the replacement element

Returns:

a new Traversable with the first occurrence of currentElement replaced by newElement

replaceAll

default Tree<T> replaceAll(T currentElement,
 T newElement)

Description copied from interface: Traversable

Replaces all occurrences of currentElement with newElement.

Specified by:

replaceAll in interface Traversable<T>

Parameters:

currentElement - the element to be replaced

newElement - the replacement element

Returns:

a new Traversable with all occurrences of currentElement replaced by newElement

retainAll

default Seq<T> retainAll(@NonNull Iterable<? extends T> elements)

Description copied from interface: Traversable

Retains only the elements from this Traversable that are contained in the given elements.

Specified by:

retainAll in interface Traversable<T>

Parameters:

elements - the elements to keep

Returns:

a new Traversable containing only the elements present in elements, in their original order

scan

default Seq<T> scan(T zero,
 @NonNull BiFunction<? super T, ? super T, ? extends T> operation)

Description copied from interface: Traversable

Computes a prefix scan of the elements of this Traversable.

The neutral element zero may be applied more than once.

Specified by:

scan in interface Traversable<T>

Parameters:

zero - the neutral element for the operator

operation - an associative binary operator

Returns:

a new Traversable containing the prefix scan of the elements

scanLeft

default <U> Seq<U> scanLeft(U zero,
 @NonNull BiFunction<? super U, ? super T, ? extends U> operation)

Description copied from interface: Traversable

Produces a collection containing cumulative results of applying the operator from left to right.

Will not terminate for infinite collections. The results may vary across runs unless the collection is ordered.

Specified by:

scanLeft in interface Traversable<T>

Type Parameters:

U - the type of the resulting elements

Parameters:

zero - the initial value

operation - a binary operator applied to the intermediate result and each element

Returns:

a new Traversable containing the cumulative results

scanRight

default <U> Seq<U> scanRight(U zero,
 @NonNull BiFunction<? super T, ? super U, ? extends U> operation)

Description copied from interface: Traversable

Produces a collection containing cumulative results of applying the operator from right to left.

The head of the resulting collection is the last cumulative result. Will not terminate for infinite collections. Results may vary across runs unless the collection is ordered.

Specified by:

scanRight in interface Traversable<T>

Type Parameters:

U - the type of the resulting elements

Parameters:

zero - the initial value

operation - a binary operator applied to each element and the intermediate result

Returns:

a new Traversable containing the cumulative results

slideBy

default Iterator<Seq<T>> slideBy(@NonNull Function<? super T, ?> classifier)

Description copied from interface: Traversable

Partitions this Traversable into consecutive non-overlapping windows according to a classification function.

Each window contains elements with the same class, as determined by classifier. Two consecutive elements belong to the same window only if classifier returns equal values for both. Otherwise, the current window ends and a new window begins with the next element.

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]]

Specified by:

slideBy in interface Traversable<T>

Parameters:

classifier - A function classifying elements into groups

Returns:

An Iterator of windows (grouped elements)

sliding

default Iterator<Seq<T>> sliding(int size)

Description copied from interface: Traversable

Slides a window of a given size over this Traversable with a step size of 1.

This is equivalent to calling Traversable.sliding(int, int) with a step size of 1.

Specified by:

sliding in interface Traversable<T>

Parameters:

size - a positive window size

Returns:

An Iterator of windows, each containing up to size elements

sliding

default Iterator<Seq<T>> sliding(int size,
 int step)

Description copied from interface: Traversable

Slides a window of a specific size with a given step 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],[4]]

Specified by:

sliding in interface Traversable<T>

Parameters:

size - a positive window size

step - a positive step size

Returns:

an Iterator of windows with the given size and step

span

default Tuple2<Seq<T>,Seq<T>> span(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Splits this Traversable into a prefix and remainder according to the given predicate.

The first element of the returned Tuple is the longest prefix of elements satisfying predicate, and the second element is the remaining elements.

Specified by:

span in interface Traversable<T>

Parameters:

predicate - a predicate used to determine the prefix

Returns:

a Tuple containing the prefix and remainder

stringPrefix

default String stringPrefix()

Description copied from interface: Value

Returns the name of this Value type, which is used by toString().

Specified by:

stringPrefix in interface Value<T>

Returns:

This type name.

tail

default Seq<T> tail()

Description copied from interface: Traversable

Returns a new Traversable without its first element.

Specified by:

tail in interface Traversable<T>

Returns:

a new Traversable containing all elements except the first

tailOption

default Option<Seq<T>> tailOption()

Description copied from interface: Traversable

Returns a new Traversable without its first element as an Option.

Specified by:

tailOption in interface Traversable<T>

Returns:

Some(traversable) if non-empty, otherwise None

take

default Seq<T> take(int n)

Description copied from interface: Traversable

Returns the first n elements of this Traversable, or all elements if n exceeds the length.

Equivalent to sublist(0, max(0, min(length(), n))), but safe for n < 0 or n > length().

If n < 0, an empty instance is returned. If n > length(), the full instance is returned.

Specified by:

take in interface Traversable<T>

Parameters:

n - the number of elements to take

Returns:

a new Traversable containing the first n elements

takeRight

default Seq<T> takeRight(int n)

Description copied from interface: Traversable

Returns the last n elements of this Traversable, or all elements if n exceeds the length.

Equivalent to sublist(max(0, length() - n), length()), but safe for n < 0 or n > length().

If n < 0, an empty instance is returned. If n > length(), the full instance is returned.

Specified by:

takeRight in interface Traversable<T>

Parameters:

n - the number of elements to take from the end

Returns:

a new Traversable containing the last n elements

takeUntil

default Seq<T> takeUntil(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Takes elements from this Traversable until the given predicate holds for an element.

Equivalent to takeWhile(predicate.negate()), but useful when using method references that cannot be negated directly.

Specified by:

takeUntil in interface Traversable<T>

Parameters:

predicate - a condition tested sequentially on the elements

Returns:

a new Traversable containing all elements before the first one that satisfies the predicate

takeWhile

default Seq<T> takeWhile(@NonNull Predicate<? super T> predicate)

Description copied from interface: Traversable

Takes elements from this Traversable while the given predicate holds.

Specified by:

takeWhile in interface Traversable<T>

Parameters:

predicate - a condition tested sequentially on the elements

Returns:

a new Traversable containing all elements up to (but not including) the first one that does not satisfy the predicate

unzip

default <T1,T2> Tuple2<Tree<T1>,Tree<T2>> unzip(@NonNull Function<? super T, Tuple2<? extends T1, ? extends T2>> unzipper)

Description copied from interface: Traversable

Unzips the elements of this Traversable by mapping each element to a pair and splitting them into two separate Traversable collections.

Specified by:

unzip in interface Traversable<T>

Type Parameters:

T1 - type of the first element in the resulting pairs

T2 - type of the second element in the resulting pairs

Parameters:

unzipper - a function that maps elements of this Traversable to pairs

Returns:

a Tuple2 containing two Traversable collections with the split elements

unzip3

default <T1,T2,T3>
Tuple3<Tree<T1>,Tree<T2>,Tree<T3>> unzip3(@NonNull Function<? super T, Tuple3<? extends T1, ? extends T2, ? extends T3>> unzipper)

Description copied from interface: Traversable

Unzips the elements of this Traversable by mapping each element to a triple and splitting them into three separate Traversable collections.

Specified by:

unzip3 in interface Traversable<T>

Type Parameters:

T1 - type of the first element in the resulting triples

T2 - type of the second element in the resulting triples

T3 - type of the third element in the resulting triples

Parameters:

unzipper - a function that maps elements of this Traversable to triples

Returns:

a Tuple3 containing three Traversable collections with the split elements

zip

default <U> Tree<Tuple2<T,U>> zip(@NonNull Iterable<? extends U> that)

Description copied from interface: Traversable

Returns a Traversable formed by pairing elements of this Traversable with elements of another Iterable. Pairing stops when either collection runs out of elements; any remaining elements in the longer collection are ignored.

The length of the resulting Traversable is the minimum of the lengths of this Traversable and that.

Specified by:

zip in interface Traversable<T>

Type Parameters:

U - the type of elements in the second half of each pair

Parameters:

that - an Iterable providing the second element of each pair

Returns:

a new Traversable containing pairs of corresponding elements

zipWith

default <U,R> Tree<R> zipWith(@NonNull Iterable<? extends U> that,
 BiFunction<? super T, ? super U, ? extends R> mapper)

Description copied from interface: Traversable

Returns a Traversable by combining elements of this Traversable with elements of another Iterable using a mapping function. Pairing stops when either collection runs out of elements.

The length of the resulting Traversable is the minimum of the lengths of this Traversable and that.

Specified by:

zipWith in interface Traversable<T>

Type Parameters:

U - the type of elements in the second parameter of the mapper

R - the type of elements in the resulting Traversable

Parameters:

that - an Iterable providing the second parameter of the mapper

mapper - a function that combines elements from this and that into a new element

Returns:

a new Traversable containing mapped elements

zipAll

default <U> Tree<Tuple2<T,U>> zipAll(@NonNull Iterable<? extends U> that,
 T thisElem,
 U thatElem)

Description copied from interface: Traversable

Returns a Traversable formed by pairing elements of this Traversable with elements of another Iterable, filling in placeholder elements when one collection is shorter than the other.

The length of the resulting Traversable is the maximum of the lengths of this Traversable and that.

If this Traversable is shorter than that, thisElem is used as a filler. Conversely, if that is shorter, thatElem is used.

Specified by:

zipAll in interface Traversable<T>

Type Parameters:

U - the type of elements in the second half of each pair

Parameters:

that - an Iterable providing the second element of each pair

thisElem - the element used to fill missing values if this Traversable is shorter than that

thatElem - the element used to fill missing values if that is shorter than this Traversable

Returns:

a new Traversable containing pairs of elements, including fillers as needed

zipWithIndex

default Tree<Tuple2<T,Integer>> zipWithIndex()

Description copied from interface: Traversable

Zips this Traversable with its indices, starting at 0.

Specified by:

zipWithIndex in interface Traversable<T>

Returns:

a new Traversable containing each element paired with its index

zipWithIndex

default <U> Tree<U> zipWithIndex(@NonNull BiFunction<? super T, ? super Integer, ? extends U> mapper)

Description copied from interface: Traversable

Zips this Traversable with its indices and maps the resulting pairs using the provided mapper.

Specified by:

zipWithIndex in interface Traversable<T>

Type Parameters:

U - the type of elements in the resulting Traversable

Parameters:

mapper - a function mapping an element and its index to a new element

Returns:

a new Traversable containing the mapped elements

equals

boolean equals(Object o)

Description copied from interface: Traversable

Determines whether this collection is equal to the given object.

In Vavr, there are four basic collection types:

• Seq – sequential elements
• Set – distinct elements
• Map – key-value pairs
• Multimap – keys mapped to multiple values

Two collections are considered equal if and only if:

• They are of the same collection type (Seq, Set, Map, Multimap)
• They contain the same elements
• For Seq, the element order is the same

For Map and Multimap, two entries (key1, value1) and (key2, value2) are equal if both their keys and values are equal.

Additional notes:

• No collection equals null (e.g., Queue(1) != null)
• Null elements are allowed and treated as expected (e.g., List(null, 1) == Stream(null, 1), HashMap((null,1)) == LinkedHashMap((null,1)))
• Element order matters only for Seq
• Other collection classes are equal if their types and elements (in iteration order) are equal
• Iterators are compared by reference only

Specified by:

equals in interface Traversable<T>

Specified by:

equals in interface Value<T>

Overrides:

equals in class Object

Parameters:

o - the object to compare with, may be null

Returns:

true if the collections are equal according to the rules above, false otherwise

hashCode

int hashCode()

Description copied from interface: Traversable

Returns the hash code of this collection.

Vavr distinguishes between collections with predictable iteration order (like Seq) and collections with arbitrary iteration order (like Set, Map, and Multimap). In all cases, the hash of an empty collection is defined as 1.

For collections with predictable iteration order, the hash is computed as:

int hash = 1;
for (T t : this) {
    hash = hash * 31 + Objects.hashCode(t);
}

For collections with arbitrary iteration order, the hash is computed to be independent of element order:

int hash = 1;
for (T t : this) {
    hash += Objects.hashCode(t);
}

Note that these algorithms may change in future Vavr versions. Hash codes are generally not cached, unlike size/length, because caching would increase memory usage due to persistent tree-based structures. Computing the hash code is linear in time, O(n). For frequently re-used collections (e.g., as HashMap keys), caching can be done externally using a wrapper, for example:

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; }

    @Override
    public boolean equals(Object o) {
        if (o == key) return true;
        if (key != null && o instanceof Hashed) return key.equals(((Hashed<?>) o).key);
        return false;
    }

    @Override
    public int hashCode() { return hashCode.get(); }

    @Override
    public String toString() { return "Hashed(" + key + ")"; }
}

Specified by:

hashCode in interface Traversable<T>

Specified by:

hashCode in interface Value<T>

Overrides:

hashCode in class Object

Returns:

the hash code of this collection

toString

String toString()

Description copied from interface: Value

Clarifies that values have a proper toString() method implemented.

See Object.toString().

Specified by:

toString in interface Value<T>

Overrides:

toString in class Object

Returns:

A String representation of this object

draw

String draw()

Creates a neat 2-dimensional drawing of a tree. Unicode characters are used to draw node junctions.

Returns:

A nice string representation of the tree.