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

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(Iterable<? extends T> source, Function<? super T, ? extends ID> idMapper, Function<? super T, ? extends ID> parentMapper)	Build a List with roots of Tree from flat source.
default <R> Tree<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.
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 version of this which contains no duplicates.
default Seq<T>	distinctBy(Comparator<? super T> comparator)	Returns a new version of this which contains no duplicates.
default <U> Seq<T>	distinctBy(Function<? super T, ? extends U> keyExtractor)	Returns a new version of this which contains no duplicates.
String	draw()	Creates a neat 2-dimensional drawing of a tree.
default Seq<T>	drop(int n)	Drops the first n elements of this or all elements, if this length < n.
default Seq<T>	dropRight(int n)	Drops the last n elements of this or all elements, if this length < n.
default Seq<T>	dropUntil(Predicate<? super T> predicate)	Drops elements until the predicate holds for the current element.
default Seq<T>	dropWhile(Predicate<? super T> predicate)	Drops elements while the predicate holds for the current element.
static <T> Tree.Empty<T>	empty()	Returns the singleton empty tree.
boolean	equals(Object o)	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.
static <T> Tree<T>	fill(int n, 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(Predicate<? super T> predicate)	Returns a new traversable consisting of all elements which satisfy the given predicate.
default <U> Tree<U>	flatMap(Function<? super T, ? extends Iterable<? extends U>> mapper)	FlatMaps this Traversable.
default <U> U	foldRight(U zero, BiFunction<? super T, ? super U, ? extends U> f)	Folds this elements from the right, starting with zero and successively calling combine.
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(Function<? super T, ? extends C> classifier)	Groups this elements by classifying the elements.
default Iterator<Seq<T>>	grouped(int size)	Groups this Traversable into fixed size blocks.
default boolean	hasDefiniteSize()	Checks if this Traversable is known to have a finite size.
int	hashCode()	Returns the hash code of this collection.
default T	head()	Returns the first element of a non-empty Traversable.
default Seq<T>	init()	Dual of Traversable.tail(), returning all elements except the last.
default Option<Seq<T>>	initOption()	Dual of Traversable.tailOption(), returning all elements except the last as Option.
default boolean	isAsync()	A Tree is computed synchronously.
default boolean	isBranch()	Checks if this Tree is a branch.
default boolean	isDistinct()	Checks if this Traversable may consist of distinct elements only.
default boolean	isLazy()	A Tree is computed eagerly.
boolean	isLeaf()	Checks if this Tree is a leaf.
default boolean	isSequential()	Checks if the elements of this Traversable appear in encounter order.
default boolean	isTraversableAgain()	Checks if this Traversable can be repeatedly traversed.
default Iterator<T>	iterator()	An iterator by means of head() and 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(Function<? super T, ? extends U> mapper)	Maps the elements of this Traversable to elements of a new type preserving their order, if any.
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... values)	Creates a Tree of the given elements.
static <T> Tree.Node<T>	of(T value, Tree.Node<T>... children)	Returns a new Node containing the given value and having the given children.
static <T> Tree.Node<T>	of(T value, Iterable<Tree.Node<T>> children)	Returns a new Node containing the given value and having the given children.
static <T> Tree<T>	ofAll(Iterable<? extends T> iterable)	Creates a Tree of the given elements.
static <T> Tree<T>	ofAll(Stream<? extends T> javaStream)	Creates a Tree that contains the elements of the given Stream.
default Tree<T>	orElse(Iterable<? extends T> other)	Returns this Traversable if it is nonempty, otherwise return the alternative.
default Tree<T>	orElse(Supplier<? extends Iterable<? extends T>> supplier)	Returns this Traversable if it is nonempty, otherwise return the result of evaluating supplier.
default Tuple2<Seq<T>,Seq<T>>	partition(Predicate<? super T> predicate)	Creates a partition of this Traversable by splitting this elements in two in distinct traversables according to a predicate.
default Tree<T>	peek(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, 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(Predicate<? super T> predicate)	Returns a new traversable consisting of all elements which do not satisfy the given predicate.
default Tree<T>	replace(T currentElement, T newElement)	Replaces the first occurrence (if exists) of the given currentElement with newElement.
default Tree<T>	replaceAll(T currentElement, T newElement)	Replaces all occurrences of the given currentElement with newElement.
default Seq<T>	retainAll(Iterable<? extends T> elements)	Keeps all occurrences of the given elements from this.
default Seq<T>	scan(T zero, BiFunction<? super T, ? super T, ? extends T> operation)	Computes a prefix scan of the elements of the collection.
default <U> Seq<U>	scanLeft(U zero, BiFunction<? super U, ? super T, ? extends U> operation)	Produces a collection containing cumulative results of applying the operator going left to right.
default <U> Seq<U>	scanRight(U zero, BiFunction<? super T, ? super U, ? extends U> operation)	Produces a collection containing cumulative results of applying the operator going right to left.
default Iterator<Seq<T>>	slideBy(Function<? super T, ?> classifier)	Slides a non-overlapping window of a variable size over this Traversable.
default Iterator<Seq<T>>	sliding(int size)	Slides a window of a specific size and step size 1 over this Traversable by calling Traversable.sliding(int, int).
default Iterator<Seq<T>>	sliding(int size, int step)	Slides a window of a specific size and step size over this Traversable.
default Tuple2<Seq<T>,Seq<T>>	span(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 String	stringPrefix()	Returns the name of this Value type, which is used by toString().
static <T> Tree<T>	tabulate(int n, 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()	Drops the first element of a non-empty Traversable.
default Option<Seq<T>>	tailOption()	Drops the first element of a non-empty Traversable and returns an Option.
default Seq<T>	take(int n)	Takes the first n elements of this or all elements, if this length < n.
default Seq<T>	takeRight(int n)	Takes the last n elements of this or all elements, if this length < n.
default Seq<T>	takeUntil(Predicate<? super T> predicate)	Takes elements until the predicate holds for the current element.
default Seq<T>	takeWhile(Predicate<? super T> predicate)	Takes elements while the predicate holds for the current element.
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(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(Tree.Order order)	Traverses this tree in a specific order.
default <T1,T2> Tuple2<Tree<T1>,Tree<T2>>	unzip(Function<? super T, Tuple2<? extends T1, ? extends T2>> unzipper)	Unzips this elements by mapping this elements to pairs which are subsequently split into two distinct sets.
default <T1,T2,T3> Tuple3<Tree<T1>,Tree<T2>,Tree<T3>>	unzip3(Function<? super T, Tuple3<? extends T1, ? extends T2, ? extends T3>> unzipper)	Unzips this elements by mapping this elements to triples which are subsequently split into three distinct sets.
default Seq<T>	values()	Traverses this tree values in Tree.Order.PRE_ORDER.
default Seq<T>	values(Tree.Order order)	Traverses this tree values in a specific order.
default <U> Tree<Tuple2<T,U>>	zip(Iterable<? extends U> that)	Returns a traversable formed from this traversable and another Iterable collection by combining corresponding elements in pairs.
default <U> Tree<Tuple2<T,U>>	zipAll(Iterable<? extends U> that, T thisElem, U thatElem)	Returns a traversable formed from this traversable and another Iterable by combining corresponding elements in pairs.
default <U,R> Tree<R>	zipWith(Iterable<? extends U> that, BiFunction<? super T, ? super U, ? extends R> mapper)	Returns a traversable formed from this traversable and another Iterable collection by mapping elements.
default Tree<Tuple2<T,Integer>>	zipWithIndex()	Zips this traversable with its indices.
default <U> Tree<U>	zipWithIndex(BiFunction<? super T, ? super Integer, ? extends U> mapper)	Zips this traversable with its indices by applying mapper provided.

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

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,
 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

static <T> Tree.Node<T> of(T value,
 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... 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(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(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,
 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,
 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,
 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(Iterable<? extends T> source,
 Function<? super T, ? extends ID> idMapper,
 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(PartialFunction<? super T, ? extends R> partialFunction)

Description copied from interface: Traversable

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).

Specified by:

collect in interface Traversable<T>

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

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

Checks if this Traversable may consist of distinct elements only.

Specified by:

isDistinct in interface Traversable<T>

Returns:

true if this Traversable may consist of distinct elements only, 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

Checks if the elements of this Traversable appear in encounter order.

Specified by:

isSequential in interface Traversable<T>

Returns:

true, if the insertion order of elements 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(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(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(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 version of this which contains no duplicates. Elements are compared using equals.

Specified by:

distinct in interface Traversable<T>

Returns:

a new Traversable containing this elements without duplicates

distinctBy

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

Description copied from interface: Traversable

Returns a new version of this which contains no duplicates. Elements are compared using the given comparator.

Specified by:

distinctBy in interface Traversable<T>

Parameters:

comparator - A comparator

Returns:

a new Traversable containing this elements without duplicates

distinctBy

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

Description copied from interface: Traversable

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.

Specified by:

distinctBy in interface Traversable<T>

Type Parameters:

U - key type

Parameters:

keyExtractor - A key extractor

Returns:

a new Traversable containing this elements without duplicates

drop

default Seq<T> drop(int n)

Description copied from interface: Traversable

Drops the first n elements of this or all elements, if this length < n.

Specified by:

drop in interface Traversable<T>

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

default Seq<T> dropRight(int n)

Description copied from interface: Traversable

Drops the last n elements of this or all elements, if this length < n.

Specified by:

dropRight in interface Traversable<T>

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

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

Description copied from interface: Traversable

Drops elements until the predicate holds for the current element.

Specified by:

dropUntil in interface Traversable<T>

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.

dropWhile

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

Description copied from interface: Traversable

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.

Specified by:

dropWhile in interface Traversable<T>

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.

filter

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

Description copied from interface: Traversable

Returns a new traversable consisting of all elements which satisfy the given predicate.

Specified by:

filter in interface Traversable<T>

Parameters:

predicate - A predicate

Returns:

a new traversable

reject

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

Description copied from interface: Traversable

Returns a new traversable consisting of all elements which do not satisfy the given predicate.

The default implementation is equivalent to

filter(predicate.negate()

Specified by:

reject in interface Traversable<T>

Parameters:

predicate - A predicate

Returns:

a new traversable

flatMap

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

Description copied from interface: Traversable

FlatMaps this Traversable.

Specified by:

flatMap in interface Traversable<T>

Type Parameters:

U - The resulting component type.

Parameters:

mapper - A mapper

Returns:

A new Traversable instance.

foldRight

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

Description copied from interface: Foldable

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>

Specified by:

foldRight in interface Traversable<T>

Type Parameters:

U - the type of the folded value

Parameters:

zero - A zero element to start with.

f - A function which combines elements.

Returns:

a folded value

groupBy

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

Description copied from interface: Traversable

Groups this elements by classifying the elements.

Specified by:

groupBy in interface Traversable<T>

Type Parameters:

C - classified class type

Parameters:

classifier - A function which classifies elements into classes

Returns:

A Map containing the grouped elements

See Also:

• Traversable.arrangeBy(Function)

grouped

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

Description copied from interface: Traversable

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 Traversable.sliding(int, int), i.e. grouped(size) is the same as sliding(size, size).

Specified by:

grouped in interface Traversable<T>

Parameters:

size - a positive block size

Returns:

A new Iterator of grouped blocks of the given size

hasDefiniteSize

default boolean hasDefiniteSize()

Description copied from interface: Traversable

Checks if this Traversable is known to have a finite size.

This method should be implemented by classes only, i.e. not by interfaces.

Specified by:

hasDefiniteSize in interface Traversable<T>

Returns:

true, if this Traversable is known to have a finite size, false otherwise.

head

default T head()

Description copied from interface: Traversable

Returns the first element of a non-empty Traversable.

Specified by:

head in interface Traversable<T>

Returns:

The first element of this Traversable.

init

default Seq<T> init()

Description copied from interface: Traversable

Dual of Traversable.tail(), returning all elements except the last.

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

Dual of Traversable.tailOption(), returning all elements except the last as Option.

Specified by:

initOption in interface Traversable<T>

Returns:

Some(traversable) or None if this is empty.

isTraversableAgain

default boolean isTraversableAgain()

Description copied from interface: Traversable

Checks if this Traversable can be repeatedly traversed.

This method should be implemented by classes only, i.e. not by interfaces.

Specified by:

isTraversableAgain in interface Traversable<T>

Returns:

true, if this Traversable is known to be traversable repeatedly, false otherwise.

iterator

default Iterator<T> iterator()

Description copied from interface: Traversable

An iterator by means of head() and tail(). Subclasses may want to override this method.

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 of this Traversable elements.

map

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

Description copied from interface: Traversable

Maps the elements of this Traversable to elements of a new type preserving their order, if any.

Specified by:

map in interface Traversable<T>

Specified by:

map in interface Value<T>

Type Parameters:

U - Component type of the target Traversable

Parameters:

mapper - A mapper.

Returns:

a mapped Traversable

orElse

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

Description copied from interface: Traversable

Returns this Traversable if it is nonempty, otherwise return the alternative.

Specified by:

orElse in interface Traversable<T>

Parameters:

other - An alternative Traversable

Returns:

this Traversable if it is nonempty, otherwise return the alternative.

orElse

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

Description copied from interface: Traversable

Returns this Traversable if it is nonempty, otherwise return the result of evaluating supplier.

Specified by:

orElse in interface Traversable<T>

Parameters:

supplier - An alternative Traversable supplier

Returns:

this Traversable if it is nonempty, otherwise return the result of evaluating supplier.

partition

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

Description copied from interface: Traversable

Creates a partition of this Traversable by splitting this elements in two in distinct traversables according to a predicate.

Specified by:

partition in interface Traversable<T>

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.

peek

default Tree<T> peek(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 (if exists) of the given currentElement with newElement.

Specified by:

replace in interface Traversable<T>

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

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

Description copied from interface: Traversable

Replaces all occurrences of the given currentElement with newElement.

Specified by:

replaceAll in interface Traversable<T>

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

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

Description copied from interface: Traversable

Keeps all occurrences of the given elements from this.

Specified by:

retainAll in interface Traversable<T>

Parameters:

elements - Elements to be kept.

Returns:

a Traversable containing all occurrences of the given elements.

scan

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

Description copied from interface: Traversable

Computes a prefix scan of the elements of the collection. Note: The neutral element z may be applied more than once.

Specified by:

scan in interface Traversable<T>

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

scanLeft

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

Description copied from interface: Traversable

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.

Specified by:

scanLeft in interface Traversable<T>

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

scanRight

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

Description copied from interface: Traversable

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.

Specified by:

scanRight in interface Traversable<T>

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

slideBy

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

Description copied from interface: Traversable

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]]

Specified by:

slideBy in interface Traversable<T>

Parameters:

classifier - A function which classifies elements into classes

Returns:

A new Iterator of windows of the grouped elements

sliding

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

Description copied from interface: Traversable

Slides a window of a specific size and step size 1 over this Traversable by calling Traversable.sliding(int, int).

Specified by:

sliding in interface Traversable<T>

Parameters:

size - a positive window size

Returns:

a new Iterator of windows of a specific size using step size 1

sliding

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

Description copied from interface: Traversable

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],[4]]

Specified by:

sliding in interface Traversable<T>

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

span

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

Description copied from interface: Traversable

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.

Specified by:

span in interface Traversable<T>

Parameters:

predicate - A predicate.

Returns:

a Tuple containing the longest prefix of elements that satisfy p and the 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

Drops the first element of a non-empty Traversable.

Specified by:

tail in interface Traversable<T>

Returns:

A new instance of Traversable containing all elements except the first.

tailOption

default Option<Seq<T>> tailOption()

Description copied from interface: Traversable

Drops the first element of a non-empty Traversable and returns an Option.

Specified by:

tailOption in interface Traversable<T>

Returns:

Some(traversable) or None if this is empty.

take

default Seq<T> take(int n)

Description copied from interface: Traversable

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.

Specified by:

take in interface Traversable<T>

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

default Seq<T> takeRight(int n)

Description copied from interface: Traversable

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.

Specified by:

takeRight in interface Traversable<T>

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

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

Description copied from interface: Traversable

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.

Specified by:

takeUntil in interface Traversable<T>

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.

takeWhile

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

Description copied from interface: Traversable

Takes elements while the predicate holds for the current element.

Specified by:

takeWhile in interface Traversable<T>

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.

unzip

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

Description copied from interface: Traversable

Unzips this elements by mapping this elements to pairs which are subsequently split into two distinct sets.

Specified by:

unzip in interface Traversable<T>

Type Parameters:

T1 - 1st element type of a pair returned by unzipper

T2 - 2nd element type of a pair returned by unzipper

Parameters:

unzipper - a function which converts elements of this to pairs

Returns:

A pair of set containing elements split by unzipper

unzip3

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

Description copied from interface: Traversable

Unzips this elements by mapping this elements to triples which are subsequently split into three distinct sets.

Specified by:

unzip3 in interface Traversable<T>

Type Parameters:

T1 - 1st element type of a triplet returned by unzipper

T2 - 2nd element type of a triplet returned by unzipper

T3 - 3rd element type of a triplet returned by unzipper

Parameters:

unzipper - a function which converts elements of this to pairs

Returns:

A triplet of set containing elements split by unzipper

zip

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

Description copied from interface: Traversable

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.

Specified by:

zip in interface Traversable<T>

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.

zipWith

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

Description copied from interface: Traversable

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.

Specified by:

zipWith in interface Traversable<T>

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.

zipAll

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

Description copied from interface: Traversable

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.

Specified by:

zipAll in interface Traversable<T>

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.

zipWithIndex

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

Description copied from interface: Traversable

Zips this traversable with its indices.

Specified by:

zipWithIndex in interface Traversable<T>

Returns:

A new traversable containing all elements of this traversable paired with their index, starting with 0.

zipWithIndex

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

Description copied from interface: Traversable

Zips this traversable with its indices by applying mapper provided.

Specified by:

zipWithIndex in interface Traversable<T>

Type Parameters:

U - The type of the mapped elements.

Parameters:

mapper - a mapper.

Returns:

a new traversable containing elements of this traversable, zipped with indices, and mapped with mapper provided.

equals

boolean equals(Object o)

Description copied from interface: Traversable

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 Traversable<T>

Specified by:

equals in interface Value<T>

Overrides:

equals in class Object

Parameters:

o - an object, may be null

Returns:

true, if this collection equals the given object according to the rules described above, false otherwise.

hashCode

int hashCode()

Description copied from interface: Traversable

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 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.