Scala 3/API/scala.collection.concurrent/Map

Map

trait Map[K, V] extends Map[K, V]

A template trait for mutable maps that allow concurrent access.

A template trait for mutable maps that allow concurrent access.

This is a base trait for all Scala concurrent map implementations. It provides all of the methods a Map does, with the difference that all the changes are atomic. It also describes methods specific to concurrent maps.

Note: The concurrent maps do not accept null for keys or values.

Type Params
K

the key type of the map

V

the value type of the map

See also

"Scala's Collection Library overview" section on Concurrent Maps for more information.

trait Map[K, V]
trait MapOps[K, V, [K, V] =>> Map[K, V], Map[K, V]]
trait Shrinkable[K]
trait Builder[(K, V), Map[K, V]]
trait Growable[(K, V)]
trait Clearable
trait Cloneable[Map[K, V]]
trait Cloneable
trait Map[K, V]
trait Equals
trait MapFactoryDefaults[K, V, [K, V] =>> Map[K, V], [A] =>> Iterable[A]]
trait MapOps[K, V, [K, V] =>> Map[K, V], Map[K, V]]
trait K => V
trait Iterable[(K, V)]
trait Iterable[(K, V)]
trait IterableFactoryDefaults[(K, V), [A] =>> Iterable[A]]
trait IterableOps[(K, V), [A] =>> Iterable[A], Map[K, V]]
trait IterableOnceOps[(K, V), [A] =>> Iterable[A], Map[K, V]]
trait IterableOnce[(K, V)]
class Object
trait Matchable
class Any
class TrieMap[K, V]

Value members

Abstract methods

def putIfAbsent(k: K, v: V): Option[V]

Associates the given key with a given value, unless the key was already associated with some other value.

Associates the given key with a given value, unless the key was already associated with some other value.

This is an atomic operation.

Value Params
k

key with which the specified value is to be associated with

v

value to be associated with the specified key

Returns

Some(oldvalue) if there was a value oldvalue previously associated with the specified key, or None if there was no mapping for the specified key

def remove(k: K, v: V): Boolean

Removes the entry for the specified key if it's currently mapped to the specified value.

Removes the entry for the specified key if it's currently mapped to the specified value.

This is an atomic operation.

Value Params
k

key for which the entry should be removed

v

value expected to be associated with the specified key if the removal is to take place

Returns

true if the removal took place, false otherwise

def replace(k: K, oldvalue: V, newvalue: V): Boolean

Replaces the entry for the given key only if it was previously mapped to a given value.

Replaces the entry for the given key only if it was previously mapped to a given value.

This is an atomic operation.

Value Params
k

key for which the entry should be replaced

newvalue

value to be associated with the specified key

oldvalue

value expected to be associated with the specified key if replacing is to happen

Returns

true if the entry was replaced, false otherwise

def replace(k: K, v: V): Option[V]

Replaces the entry for the given key only if it was previously mapped to some value.

Replaces the entry for the given key only if it was previously mapped to some value.

This is an atomic operation.

Value Params
k

key for which the entry should be replaced

v

value to be associated with the specified key

Returns

Some(v) if the given key was previously mapped to some value v, or None otherwise

Concrete methods

override def getOrElseUpdate(key: K, op: => V): V
Definition Classes
override def updateWith(key: K)(remappingFunction: Option[V] => Option[V]): Option[V]

Update a mapping for the specified key and its current optionally-mapped value (Some if there is current mapping, None if not).

Update a mapping for the specified key and its current optionally-mapped value (Some if there is current mapping, None if not).

If the remapping function returns Some(v), the mapping is updated with the new value v. If the remapping function returns None, the mapping is removed (or remains absent if initially absent). If the function itself throws an exception, the exception is rethrown, and the current mapping is left unchanged.

If the map is updated by another concurrent access, the remapping function will be retried until successfully updated.

Value Params
key

the key value

remappingFunction

a partial function that receives current optionally-mapped value and return a new mapping

Returns

the new value associated with the specified key

Definition Classes

Inherited methods

final def ++[B >: (K, V)](suffix: IterableOnce[B]): Iterable[B]

Alias for concat

Alias for concat

Inherited from
IterableOps
def ++[V2 >: V](xs: IterableOnce[(K, V2)]): Map[K, V2]

Alias for concat

Alias for concat

Inherited from
MapOps
final def ++=(xs: IterableOnce[(K, V)]): Map[K, V]

Alias for addAll

Alias for addAll

Inherited from
Growable
final def +=(elem: (K, V)): Map[K, V]

Alias for addOne

Alias for addOne

Inherited from
Growable
final def --=(xs: IterableOnce[K]): Map[K, V]

Alias for subtractAll

Alias for subtractAll

Inherited from
Shrinkable
final def -=(elem: K): Map[K, V]

Alias for subtractOne

Alias for subtractOne

Inherited from
Shrinkable
def addAll(xs: IterableOnce[(K, V)]): Map[K, V]

Adds all elements produced by an IterableOnce to this growable collection.

Adds all elements produced by an IterableOnce to this growable collection.

Value Params
xs

the IterableOnce producing the elements to add.

Returns

the growable collection itself.

Inherited from
Growable
def addOne(elem: (K, V)): Map[K, V]

Adds a single element to this growable collection.

Adds a single element to this growable collection.

Value Params
elem

the element to add.

Returns

the growable collection itself

Inherited from
Growable
final def addString(b: StringBuilder): StringBuilder

Appends all elements of this collection to a string builder.

Appends all elements of this collection to a string builder. The written text consists of the string representations (w.r.t. the method toString) of all elements of this collection without any separator string.

Example:

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = new StringBuilder()
b: StringBuilder =

scala> val h = a.addString(b)
h: StringBuilder = 1234
Value Params
b

the string builder to which elements are appended.

Returns

the string builder b to which elements were appended.

Inherited from
IterableOnceOps
final def addString(b: StringBuilder, sep: String): StringBuilder

Appends all elements of this collection to a string builder using a separator string.

Appends all elements of this collection to a string builder using a separator string. The written text consists of the string representations (w.r.t. the method toString) of all elements of this collection, separated by the string sep.

Example:

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = new StringBuilder()
b: StringBuilder =

scala> a.addString(b, ", ")
res0: StringBuilder = 1, 2, 3, 4
Value Params
b

the string builder to which elements are appended.

sep

the separator string.

Returns

the string builder b to which elements were appended.

Inherited from
IterableOnceOps
override def addString(sb: StringBuilder, start: String, sep: String, end: String): StringBuilder
Definition Classes
Inherited from
MapOps
def andThen[C](k: PartialFunction[V, C]): PartialFunction[K, C]

Composes this partial function with another partial function that gets applied to results of this partial function.

Composes this partial function with another partial function that gets applied to results of this partial function.

Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.

Type Params
C

the result type of the transformation function.

Value Params
k

the transformation function

Returns

a partial function with the domain of this partial function narrowed by other partial function, which maps arguments x to k(this(x)).

Inherited from
PartialFunction
override def andThen[C](k: V => C): PartialFunction[K, C]

Composes this partial function with a transformation function that gets applied to results of this partial function.

Composes this partial function with a transformation function that gets applied to results of this partial function.

If the runtime type of the function is a PartialFunction then the other andThen method is used (note its cautions).

Type Params
C

the result type of the transformation function.

Value Params
k

the transformation function

Returns

a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments x to k(this(x)).

Definition Classes
Inherited from
PartialFunction
@throws(scala.throws.$lessinit$greater$default$1[scala.NoSuchElementException])
def apply(key: K): V

Retrieves the value which is associated with the given key.

Retrieves the value which is associated with the given key. This method invokes the default method of the map if there is no mapping from the given key to a value. Unless overridden, the default method throws a NoSuchElementException.

Value Params
key

the key

Returns

the value associated with the given key, or the result of the map's default method, if none exists.

Inherited from
MapOps
override def applyOrElse[K1 <: K, V1 >: V](x: K1, default: K1 => V1): V1
Definition Classes
Inherited from
MapOps
def canEqual(that: Any): Boolean
Inherited from
Map
def clear(): Unit
Inherited from
MapOps
override def clone(): Map[K, V]
Definition Classes
Inherited from
MapOps
def collect[B](pf: PartialFunction[(K, V), B]): Iterable[B]
Inherited from
IterableOps
def collect[K2, V2](pf: PartialFunction[(K, V), (K2, V2)]): Map[K2, V2]

Builds a new collection by applying a partial function to all elements of this map on which the function is defined.

Builds a new collection by applying a partial function to all elements of this map on which the function is defined.

Type Params
K2

the key type of the returned map.

V2

the value type of the returned map.

Value Params
pf

the partial function which filters and maps the map.

Returns

a new map resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.

Inherited from
MapOps
def collectFirst[B](pf: PartialFunction[(K, V), B]): Option[B]

Finds the first element of the collection for which the given partial function is defined, and applies the partial function to it.

Finds the first element of the collection for which the given partial function is defined, and applies the partial function to it.

Note: may not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Value Params
pf

the partial function

Returns

an option value containing pf applied to the first value for which it is defined, or None if none exists.

Example

Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)

Inherited from
IterableOnceOps
def compose[R](k: PartialFunction[R, K]): PartialFunction[R, V]

Composes another partial function k with this partial function so that this partial function gets applied to results of k.

Composes another partial function k with this partial function so that this partial function gets applied to results of k.

Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.

Type Params
R

the parameter type of the transformation function.

Value Params
k

the transformation function

Returns

a partial function with the domain of other partial function narrowed by this partial function, which maps arguments x to this(k(x)).

Inherited from
PartialFunction
def compose[A](g: A => K): A => V

Composes two instances of Function1 in a new Function1, with this function applied last.

Composes two instances of Function1 in a new Function1, with this function applied last.

Type Params
A

the type to which function g can be applied

Value Params
g

a function A => T1

Returns

a new function f such that f(x) == apply(g(x))

Inherited from
Function1
def concat[B >: (K, V)](suffix: IterableOnce[B]): Iterable[B]

Returns a new iterable collection containing the elements from the left hand operand followed by the elements from the right hand operand.

Returns a new iterable collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the iterable collection is the most specific superclass encompassing the element types of the two operands.

Type Params
B

the element type of the returned collection.

Value Params
suffix

the traversable to append.

Returns

a new iterable collection which contains all elements of this iterable collection followed by all elements of suffix.

Inherited from
IterableOps
def concat[V2 >: V](suffix: IterableOnce[(K, V2)]): Map[K, V2]

Returns a new map containing the elements from the left hand operand followed by the elements from the right hand operand.

Returns a new map containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the map is the most specific superclass encompassing the element types of the two operands.

Value Params
suffix

the traversable to append.

Returns

a new map which contains all elements of this map followed by all elements of suffix.

Inherited from
MapOps
def contains(key: K): Boolean

Tests whether this map contains a binding for a key.

Tests whether this map contains a binding for a key.

Value Params
key

the key

Returns

true if there is a binding for key in this map, false otherwise.

Inherited from
MapOps
def copyToArray[B >: (K, V)](xs: Array[B], start: Int, len: Int): Int

Copy elements to an array, returning the number of elements written.

Copy elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with at most len elements of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached, or len elements have been copied.

Type Params
B

the type of the elements of the array.

Value Params
len

the maximal number of elements to copy.

start

the starting index of xs.

xs

the array to fill.

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from
IterableOnceOps
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B >: (K, V)](xs: Array[B], start: Int): Int

Copy elements to an array, returning the number of elements written.

Copy elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with values of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

Type Params
B

the type of the elements of the array.

Value Params
start

the starting index of xs.

xs

the array to fill.

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from
IterableOnceOps
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B >: (K, V)](xs: Array[B]): Int

Copy elements to an array, returning the number of elements written.

Copy elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with values of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

Type Params
B

the type of the elements of the array.

Value Params
xs

the array to fill.

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from
IterableOnceOps
def corresponds[B](that: IterableOnce[B])(p: ((K, V), B) => Boolean): Boolean

Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

Note: will not terminate for infinite-sized collections.

Type Params
B

the type of the elements of that

Value Params
p

the test predicate, which relates elements from both collections

that

the other collection

Returns

true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false

Inherited from
IterableOnceOps
def count(p: (K, V) => Boolean): Int

Counts the number of elements in the collection which satisfy a predicate.

Counts the number of elements in the collection which satisfy a predicate.

Note: will not terminate for infinite-sized collections.

Value Params
p

the predicate used to test elements.

Returns

the number of elements satisfying the predicate p.

Inherited from
IterableOnceOps
@throws(scala.throws.$lessinit$greater$default$1[scala.NoSuchElementException])
def default(key: K): V

Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.

Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.

Value Params
key

the given key value for which a binding is missing.

Inherited from
MapOps
def drop(n: Int): Map[K, V]
Inherited from
IterableOps
def dropRight(n: Int): Map[K, V]

Selects all elements except last n ones.

Selects all elements except last n ones.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Value Params
n

the number of elements to drop from this iterable collection.

Returns

a iterable collection consisting of all elements of this iterable collection except the last n ones, or else the empty iterable collection, if this iterable collection has less than n elements. If n is negative, don't drop any elements.

Inherited from
IterableOps
def dropWhile(p: (K, V) => Boolean): Map[K, V]
Inherited from
IterableOps
def elementWise: ElementWiseExtractor[K, V]

Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

Example

val firstChar: String => Option[Char] = _.headOption
Seq("foo", "bar", "baz") match {
  case firstChar.unlift.elementWise(c0, c1, c2) =>
    println(s"$c0, $c1, $c2") // Output: f, b, b
}
Inherited from
PartialFunction
override def empty: Map[K, V]
Definition Classes
Inherited from
MapFactoryDefaults
override def equals(o: Any): Boolean
Definition Classes
Map -> Equals -> Any
Inherited from
Map
def exists(p: (K, V) => Boolean): Boolean

Tests whether a predicate holds for at least one element of this collection.

Tests whether a predicate holds for at least one element of this collection.

Note: may not terminate for infinite-sized collections.

Value Params
p

the predicate used to test elements.

Returns

true if the given predicate p is satisfied by at least one element of this collection, otherwise false

Inherited from
IterableOnceOps
def filter(pred: (K, V) => Boolean): Map[K, V]
Inherited from
IterableOps
def filterInPlace(p: (K, V) => Boolean): Map[K, V]

Retains only those mappings for which the predicate p returns true.

Retains only those mappings for which the predicate p returns true.

Value Params
p

The test predicate

Inherited from
MapOps
def filterNot(pred: (K, V) => Boolean): Map[K, V]
Inherited from
IterableOps
def find(p: (K, V) => Boolean): Option[(K, V)]

Finds the first element of the collection satisfying a predicate, if any.

Finds the first element of the collection satisfying a predicate, if any.

Note: may not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Value Params
p

the predicate used to test elements.

Returns

an option value containing the first element in the collection that satisfies p, or None if none exists.

Inherited from
IterableOnceOps
def flatMap[B](f: (K, V) => IterableOnce[B]): Iterable[B]
Inherited from
IterableOps
def flatMap[K2, V2](f: (K, V) => IterableOnce[(K2, V2)]): Map[K2, V2]

Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.

Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.

Value Params
f

the function to apply to each element.

Returns

a new map resulting from applying the given collection-valued function f to each element of this map and concatenating the results.

Inherited from
MapOps
def flatten[B](asIterable: (K, V) => IterableOnce[B]): Iterable[B]
Inherited from
IterableOps
def fold[A1 >: (K, V)](z: A1)(op: (A1, A1) => A1): A1

Folds the elements of this collection using the specified associative binary operator.

Folds the elements of this collection using the specified associative binary operator. The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Note: will not terminate for infinite-sized collections.

Type Params
A1

a type parameter for the binary operator, a supertype of A.

Value Params
op

a binary operator that must be associative.

z

a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g., Nil for list concatenation, 0 for addition, or 1 for multiplication).

Returns

the result of applying the fold operator op between all the elements and z, or z if this collection is empty.

Inherited from
IterableOnceOps
def foldLeft[B](z: B)(op: (B, (K, V)) => B): B

Applies a binary operator to a start value and all elements of this collection, going left to right.

Applies a binary operator to a start value and all elements of this collection, 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 or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

z

the start value.

Returns

the result of inserting op between consecutive elements of this collection, going left to right with the start value z on the left: op(...op(z, x1), x2, ..., xn) where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.

Inherited from
IterableOnceOps
def foldRight[B](z: B)(op: ((K, V), B) => B): B

Applies a binary operator to all elements of this collection and a start value, going right to left.

Applies a binary operator to all elements of this collection and a start value, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

z

the start value.

Returns

the result of inserting op between consecutive elements of this collection, going right to left with the start value z on the right: op(x1, op(x2, ... op(xn, z)...)) where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.

Inherited from
IterableOnceOps
def forall(p: (K, V) => Boolean): Boolean

Tests whether a predicate holds for all elements of this collection.

Tests whether a predicate holds for all elements of this collection.

Note: may not terminate for infinite-sized collections.

Value Params
p

the predicate used to test elements.

Returns

true if this collection is empty or the given predicate p holds for all elements of this collection, otherwise false.

Inherited from
IterableOnceOps
def foreach[U](f: (K, V) => U): Unit

Apply f to each element for its side effects Note: [U] parameter needed to help scalac's type inference.

Apply f to each element for its side effects Note: [U] parameter needed to help scalac's type inference.

Inherited from
IterableOnceOps
def foreachEntry[U](f: (K, V) => U): Unit

Apply f to each key/value pair for its side effects Note: [U] parameter needed to help scalac's type inference.

Apply f to each key/value pair for its side effects Note: [U] parameter needed to help scalac's type inference.

Inherited from
MapOps
override protected def fromSpecific(coll: IterableOnce[(K, V)]): Map[K, V]
Definition Classes
Inherited from
MapFactoryDefaults
def get(key: K): Option[V]

Optionally returns the value associated with a key.

Optionally returns the value associated with a key.

Value Params
key

the key value

Returns

an option value containing the value associated with key in this map, or None if none exists.

Inherited from
MapOps
def getOrElse[V1 >: V](key: K, default: => V1): V1

Returns the value associated with a key, or a default value if the key is not contained in the map.

Returns the value associated with a key, or a default value if the key is not contained in the map.

Type Params
V1

the result type of the default computation.

Value Params
default

a computation that yields a default value in case no binding for key is found in the map.

key

the key.

Returns

the value associated with key if it exists, otherwise the result of the default computation.

Inherited from
MapOps
def groupBy[K](f: (K, V) => K): Map[K, Map[K, V]]

Partitions this iterable collection into a map of iterable collections according to some discriminator function.

Partitions this iterable collection into a map of iterable collections according to some discriminator function.

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type Params
K

the type of keys returned by the discriminator function.

Value Params
f

the discriminator function.

Returns

A map from keys to iterable collections such that the following invariant holds:

(xs groupBy f)(k) = xs filter (x => f(x) == k)

That is, every key k is bound to a iterable collection of those elements x for which f(x) equals k.

Inherited from
IterableOps
def groupMap[K, B](key: (K, V) => K)(f: (K, V) => B): Map[K, Iterable[B]]

Partitions this iterable collection into a map of iterable collections according to a discriminator function key.

Partitions this iterable collection into a map of iterable collections according to a discriminator function key. Each element in a group is transformed into a value of type B using the value function.

It is equivalent to groupBy(key).mapValues(_.map(f)), but more efficient.

case class User(name: String, age: Int)

def namesByAge(users: Seq[User]): Map[Int, Seq[String]] =
  users.groupMap(_.age)(_.name)

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type Params
B

the type of values returned by the transformation function

K

the type of keys returned by the discriminator function

Value Params
f

the element transformation function

key

the discriminator function

Inherited from
IterableOps
def groupMapReduce[K, B](key: (K, V) => K)(f: (K, V) => B)(reduce: (B, B) => B): Map[K, B]

Partitions this iterable collection into a map according to a discriminator function key.

Partitions this iterable collection into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the f function and then reduced into a single value with the reduce function.

It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce)), but more efficient.

def occurrences[A](as: Seq[A]): Map[A, Int] =
  as.groupMapReduce(identity)(_ => 1)(_ + _)

Note: Even when applied to a view or a lazy collection it will always force the elements.

Inherited from
IterableOps
def grouped(size: Int): Iterator[Map[K, V]]

Partitions elements in fixed size iterable collections.

Partitions elements in fixed size iterable collections.

Value Params
size

the number of elements per group

Returns

An iterator producing iterable collections of size size, except the last will be less than size size if the elements don't divide evenly.

See also
Inherited from
IterableOps
override def hashCode(): Int
Definition Classes
Map -> Any
Inherited from
Map
def head: (K, V)

Selects the first element of this iterable collection.

Selects the first element of this iterable collection.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Returns

the first element of this iterable collection.

Throws
NoSuchElementException

if the iterable collection is empty.

Inherited from
IterableOps
def headOption: Option[(K, V)]

Optionally selects the first element.

Optionally selects the first element.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Returns

the first element of this iterable collection if it is nonempty, None if it is empty.

Inherited from
IterableOps
def init: Map[K, V]

The initial part of the collection without its last element.

The initial part of the collection without its last element.

Note: Even when applied to a view or a lazy collection it will always force the elements.

Inherited from
IterableOps
def inits: Iterator[Map[K, V]]

Iterates over the inits of this iterable collection.

Iterates over the inits of this iterable collection. The first value will be this iterable collection and the final one will be an empty iterable collection, with the intervening values the results of successive applications of init.

Note: Even when applied to a view or a lazy collection it will always force the elements.

Returns

an iterator over all the inits of this iterable collection

Example

List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)

Inherited from
IterableOps
def isDefinedAt(key: K): Boolean

Tests whether this map contains a binding for a key.

Tests whether this map contains a binding for a key. This method, which implements an abstract method of trait PartialFunction, is equivalent to contains.

Value Params
key

the key

Returns

true if there is a binding for key in this map, false otherwise.

Inherited from
MapOps
def isEmpty: Boolean

Tests whether the collection is empty.

Tests whether the collection is empty.

Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when isEmpty is called.

Returns

true if the collection contains no elements, false otherwise.

Inherited from
IterableOnceOps
override def isTraversableAgain: Boolean
Definition Classes
Inherited from
IterableOps
override def iterableFactory: IterableFactory[[A] =>> Iterable[A]]
Definition Classes
Inherited from
Iterable
def iterator: Iterator[(K, V)]

Iterator can be used only once

Iterator can be used only once

Inherited from
IterableOnce
def keySet: Set[K]

Collects all keys of this map in a set.

Collects all keys of this map in a set.

Returns

a set containing all keys of this map.

Inherited from
MapOps
def keyStepper[S <: Stepper[_]](shape: StepperShape[K, S]): S

Returns a Stepper for the keys of this map.

Returns a Stepper for the keys of this map. See method stepper.

Inherited from
MapOps
def keys: Iterable[K]

Collects all keys of this map in an iterable collection.

Collects all keys of this map in an iterable collection.

Returns

the keys of this map as an iterable.

Inherited from
MapOps
def keysIterator: Iterator[K]

Creates an iterator for all keys.

Creates an iterator for all keys.

Returns

an iterator over all keys.

Inherited from
MapOps
override def knownSize: Int
Definition Classes
Inherited from
MapOps
def last: (K, V)

Selects the last element.

Selects the last element.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Returns

The last element of this iterable collection.

Throws
NoSuchElementException

If the iterable collection is empty.

Inherited from
IterableOps
def lastOption: Option[(K, V)]

Optionally selects the last element.

Optionally selects the last element.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Returns

the last element of this iterable collection$ if it is nonempty, None if it is empty.

Inherited from
IterableOps
def lazyZip[B](that: Iterable[B]): LazyZip2[(K, V), B, Map[K, V]]

Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

Calls to lazyZip can be chained to support higher arities (up to 4) without incurring the expense of constructing and deconstructing intermediary tuples.

val xs = List(1, 2, 3)
val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d)
// res == List(4, 8, 12)
Type Params
B

the type of the second element in each eventual pair

Value Params
that

the iterable providing the second element of each eventual pair

Returns

a decorator LazyZip2 that allows strict operations to be performed on the lazily evaluated pairs or chained calls to lazyZip. Implicit conversion to Iterable[(A, B)] is also supported.

Inherited from
Iterable
def lift: K => Option[V]

Turns this partial function into a plain function returning an Option result.

Turns this partial function into a plain function returning an Option result.

Returns

a function that takes an argument x to Some(this(x)) if this is defined for x, and to None otherwise.

See also

Function.unlift

Inherited from
PartialFunction
def map[B](f: (K, V) => B): Iterable[B]
Inherited from
IterableOps
def map[K2, V2](f: (K, V) => (K2, V2)): Map[K2, V2]

Builds a new map by applying a function to all elements of this map.

Builds a new map by applying a function to all elements of this map.

Value Params
f

the function to apply to each element.

Returns

a new map resulting from applying the given function f to each element of this map and collecting the results.

Inherited from
MapOps
override def mapFactory: MapFactory[[K, V] =>> Map[K, V]]
Definition Classes
Map -> Map -> MapOps
Inherited from
Map
def mapResult[NewTo](f: Map[K, V] => NewTo): Builder[(K, V), NewTo]

A builder resulting from this builder my mapping the result using f.

A builder resulting from this builder my mapping the result using f.

Inherited from
Builder
def mapValuesInPlace(f: (K, V) => V): Map[K, V]

Applies a transformation function to all values contained in this map.

Applies a transformation function to all values contained in this map. The transformation function produces new values from existing keys associated values.

Value Params
f

the transformation to apply

Returns

the map itself.

Inherited from
MapOps
def max[B >: (K, V)](ord: Ordering[B]): (K, V)

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

the largest element of this collection with respect to the ordering ord.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def maxBy[B](f: (K, V) => B)(cmp: Ordering[B]): (K, V)

Finds the first element which yields the largest value measured by function f.

Finds the first element which yields the largest value measured by function f.

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns

the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def maxByOption[B](f: (K, V) => B)(cmp: Ordering[B]): Option[(K, V)]

Finds the first element which yields the largest value measured by function f.

Finds the first element which yields the largest value measured by function f.

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns

an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

Inherited from
IterableOnceOps
def maxOption[B >: (K, V)](ord: Ordering[B]): Option[(K, V)]

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

an option value containing the largest element of this collection with respect to the ordering ord.

Inherited from
IterableOnceOps
def min[B >: (K, V)](ord: Ordering[B]): (K, V)

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

the smallest element of this collection with respect to the ordering ord.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def minBy[B](f: (K, V) => B)(cmp: Ordering[B]): (K, V)

Finds the first element which yields the smallest value measured by function f.

Finds the first element which yields the smallest value measured by function f.

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns

the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def minByOption[B](f: (K, V) => B)(cmp: Ordering[B]): Option[(K, V)]

Finds the first element which yields the smallest value measured by function f.

Finds the first element which yields the smallest value measured by function f.

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns

an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

Inherited from
IterableOnceOps
def minOption[B >: (K, V)](ord: Ordering[B]): Option[(K, V)]

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

an option value containing the smallest element of this collection with respect to the ordering ord.

Inherited from
IterableOnceOps
final def mkString: String

Displays all elements of this collection in a string.

Displays all elements of this collection in a string.

Delegates to addString, which can be overridden.

Returns

a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection follow each other without any separator string.

Inherited from
IterableOnceOps
final def mkString(sep: String): String

Displays all elements of this collection in a string using a separator string.

Displays all elements of this collection in a string using a separator string.

Delegates to addString, which can be overridden.

Value Params
sep

the separator string.

Returns

a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.

Example

List(1, 2, 3).mkString("|") = "1|2|3"

Inherited from
IterableOnceOps
final def mkString(start: String, sep: String, end: String): String

Displays all elements of this collection in a string using start, end, and separator strings.

Displays all elements of this collection in a string using start, end, and separator strings.

Delegates to addString, which can be overridden.

Value Params
end

the ending string.

sep

the separator string.

start

the starting string.

Returns

a string representation of this collection. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.

Example

List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

Inherited from
IterableOnceOps
override protected def newSpecificBuilder: Builder[(K, V), Map[K, V]]
Definition Classes
Inherited from
MapFactoryDefaults
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")
def nonEmpty: Boolean

Tests whether the collection is not empty.

Tests whether the collection is not empty.

Returns

true if the collection contains at least one element, false otherwise.

Inherited from
IterableOnceOps
def orElse[A1 <: K, B1 >: V](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]

Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

Type Params
A1

the argument type of the fallback function

B1

the result type of the fallback function

Value Params
that

the fallback function

Returns

a partial function which has as domain the union of the domains of this partial function and that. The resulting partial function takes x to this(x) where this is defined, and to that(x) where it is not.

Inherited from
PartialFunction
def partition(p: (K, V) => Boolean): (Map[K, V], Map[K, V])

A pair of, first, all elements that satisfy predicate p and, second, all elements that do not.

A pair of, first, all elements that satisfy predicate p and, second, all elements that do not. Interesting because it splits a collection in two.

The default implementation provided here needs to traverse the collection twice. Strict collections have an overridden version of partition in StrictOptimizedIterableOps, which requires only a single traversal.

Inherited from
IterableOps
def partitionMap[A1, A2](f: (K, V) => Either[A1, A2]): (Iterable[A1], Iterable[A2])

Applies a function f to each element of the iterable collection and returns a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Applies a function f to each element of the iterable collection and returns a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Example:

val xs = Iterable(1, "one", 2, "two", 3, "three") partitionMap {
 case i: Int => Left(i)
 case s: String => Right(s)
}
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three))
Type Params
A1

the element type of the first resulting collection

A2

the element type of the second resulting collection

Value Params
f

the 'split function' mapping the elements of this iterable collection to an scala.util.Either

Returns

a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Inherited from
IterableOps
def product[B >: (K, V)](num: Numeric[B]): B

Multiplies up the elements of this collection.

Multiplies up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type Params
B

the result type of the * operator.

Value Params
num

an implicit parameter defining a set of numeric operations which includes the * operator to be used in forming the product.

Returns

the product of all elements of this collection with respect to the * operator in num.

Inherited from
IterableOnceOps
def put(key: K, value: V): Option[V]

Adds a new key/value pair to this map and optionally returns previously bound value.

Adds a new key/value pair to this map and optionally returns previously bound value. If the map already contains a mapping for the key, it will be overridden by the new value.

Value Params
key

the key to update

value

the new value

Returns

an option value containing the value associated with the key before the put operation was executed, or None if key was not defined in the map before.

Inherited from
MapOps
def reduce[B >: (K, V)](op: (B, B) => B): B

Reduces the elements of this collection using the specified associative binary operator.

Reduces the elements of this collection using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Type Params
B

A type parameter for the binary operator, a supertype of A.

Value Params
op

A binary operator that must be associative.

Returns

The result of applying reduce operator op between all the elements if the collection is nonempty.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def reduceLeft[B >: (K, V)](op: (B, (K, V)) => B): B

Applies a binary operator to all elements of this collection, going left to right.

Applies a binary operator to all elements of this collection, 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 or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

the result of inserting op between consecutive elements of this collection, going left to right: op( op( ... op(x1, x2) ..., xn-1), xn) where x1, ..., xn are the elements of this collection.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def reduceLeftOption[B >: (K, V)](op: (B, (K, V)) => B): Option[B]

Optionally applies a binary operator to all elements of this collection, going left to right.

Optionally applies a binary operator to all elements of this collection, 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 or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

an option value containing the result of reduceLeft(op) if this collection is nonempty, None otherwise.

Inherited from
IterableOnceOps
def reduceOption[B >: (K, V)](op: (B, B) => B): Option[B]

Reduces the elements of this collection, if any, using the specified associative binary operator.

Reduces the elements of this collection, if any, using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Type Params
B

A type parameter for the binary operator, a supertype of A.

Value Params
op

A binary operator that must be associative.

Returns

An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.

Inherited from
IterableOnceOps
def reduceRight[B >: (K, V)](op: ((K, V), B) => B): B

Applies a binary operator to all elements of this collection, going right to left.

Applies a binary operator to all elements of this collection, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

the result of inserting op between consecutive elements of this collection, going right to left: op(x1, op(x2, ..., op(xn-1, xn)...)) where x1, ..., xn are the elements of this collection.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def reduceRightOption[B >: (K, V)](op: ((K, V), B) => B): Option[B]

Optionally applies a binary operator to all elements of this collection, going right to left.

Optionally applies a binary operator to all elements of this collection, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

Type Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

an option value containing the result of reduceRight(op) if this collection is nonempty, None otherwise.

Inherited from
IterableOnceOps
def remove(key: K): Option[V]

Removes a key from this map, returning the value associated previously with that key as an option.

Removes a key from this map, returning the value associated previously with that key as an option.

Value Params
key

the key to be removed

Returns

an option value containing the value associated previously with key, or None if key was not defined in the map before.

Inherited from
MapOps
def result(): Map[K, V]
Inherited from
MapOps
protected def reversed: Iterable[(K, V)]
Inherited from
IterableOnceOps
def runWith[U](action: V => U): K => Boolean

Composes this partial function with an action function which gets applied to results of this partial function.

Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.

Note that expression pf.runWith(action)(x) is equivalent to

if(pf isDefinedAt x) { action(pf(x)); true } else false

except that runWith is implemented via applyOrElse and thus potentially more efficient. Using runWith avoids double evaluation of pattern matchers and guards for partial function literals.

Value Params
action

the action function

Returns

a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.

See also

applyOrElse.

Inherited from
PartialFunction
def scan[B >: (K, V)](z: B)(op: (B, B) => B): Iterable[B]

Computes a prefix scan of the elements of the collection.

Computes a prefix scan of the elements of the collection.

Note: The neutral element z may be applied more than once.

Type Params
B

element type of the resulting collection

Value Params
op

the associative operator for the scan

z

neutral element for the operator op

Returns

a new iterable collection containing the prefix scan of the elements in this iterable collection

Inherited from
IterableOps
def scanLeft[B](z: B)(op: (B, (K, V)) => B): Iterable[B]
Inherited from
IterableOps
def scanRight[B](z: B)(op: ((K, V), B) => B): Iterable[B]

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

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.

Note: Even when applied to a view or a lazy collection it will always force the elements.

Example:

List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
Type Params
B

the type of the elements in the resulting collection

Value Params
op

the binary operator applied to the intermediate result and the element

z

the initial value

Returns

collection with intermediate results

Inherited from
IterableOps
def size: Int

The size of this collection.

The size of this collection.

Note: will not terminate for infinite-sized collections.

Returns

the number of elements in this collection.

Inherited from
IterableOnceOps
def sizeCompare(that: Iterable[_]): Int

Compares the size of this iterable collection to the size of another Iterable.

Compares the size of this iterable collection to the size of another Iterable.

Value Params
that

the Iterable whose size is compared with this iterable collection's size.

Returns

A value x where

x <  0       if this.size <  that.size
x == 0       if this.size == that.size
x >  0       if this.size >  that.size

The method as implemented here does not call size directly; its running time is O(this.size min that.size) instead of O(this.size + that.size). The method should be overridden if computing size is cheap and knownSize returns -1.

Inherited from
IterableOps
def sizeCompare(otherSize: Int): Int

Compares the size of this iterable collection to a test value.

Compares the size of this iterable collection to a test value.

Value Params
otherSize

the test value that gets compared with the size.

Returns

A value x where

x <  0       if this.size <  otherSize
x == 0       if this.size == otherSize
x >  0       if this.size >  otherSize

The method as implemented here does not call size directly; its running time is O(size min otherSize) instead of O(size). The method should be overridden if computing size is cheap and knownSize returns -1.

See also
Inherited from
IterableOps
final def sizeHint(coll: IterableOnce[_], delta: Int): Unit

Gives a hint that one expects the result of this builder to have the same size as the given collection, plus some delta.

Gives a hint that one expects the result of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection has a known size Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

Value Params
coll

the collection which serves as a hint for the result's size.

delta

a correction to add to the coll.size to produce the size hint.

Inherited from
Builder
def sizeHint(size: Int): Unit

Gives a hint how many elements are expected to be added when the next result is called.

Gives a hint how many elements are expected to be added when the next result is called. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

Value Params
size

the hint how many elements will be added.

Inherited from
Builder
final def sizeHintBounded(size: Int, boundingColl: Iterable[_]): Unit

Gives a hint how many elements are expected to be added when the next result is called, together with an upper bound given by the size of some other collection.

Gives a hint how many elements are expected to be added when the next result is called, together with an upper bound given by the size of some other collection. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

Value Params
boundingColl

the bounding collection. If it is an IndexedSeqLike, then sizes larger than collection's size are reduced.

size

the hint how many elements will be added.

Inherited from
Builder
final def sizeIs: SizeCompareOps

Returns a value class containing operations for comparing the size of this iterable collection to a test value.

Returns a value class containing operations for comparing the size of this iterable collection to a test value.

These operations are implemented in terms of sizeCompare(Int), and allow the following more readable usages:

this.sizeIs < size     // this.sizeCompare(size) < 0
this.sizeIs <= size    // this.sizeCompare(size) <= 0
this.sizeIs == size    // this.sizeCompare(size) == 0
this.sizeIs != size    // this.sizeCompare(size) != 0
this.sizeIs >= size    // this.sizeCompare(size) >= 0
this.sizeIs > size     // this.sizeCompare(size) > 0
Inherited from
IterableOps
def slice(from: Int, until: Int): Map[K, V]
Inherited from
IterableOps
def sliding(size: Int, step: Int): Iterator[Map[K, V]]

Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

The returned iterator will be empty when called on an empty collection. The last element the iterator produces may be smaller than the window size when the original collection isn't exhausted by the window before it and its last element isn't skipped by the step before it.

Value Params
size

the number of elements per group

step

the distance between the first elements of successive groups

Returns

An iterator producing iterable collections of size size, except the last element (which may be the only element) will be smaller if there are fewer than size elements remaining to be grouped.

See also
Example

List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))

List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))

Inherited from
IterableOps
def sliding(size: Int): Iterator[Map[K, V]]

Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

An empty collection returns an empty iterator, and a non-empty collection containing fewer elements than the window size returns an iterator that will produce the original collection as its only element.

Value Params
size

the number of elements per group

Returns

An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.

See also
Example

List().sliding(2) = empty iterator

List(1).sliding(2) = Iterator(List(1))

List(1, 2).sliding(2) = Iterator(List(1, 2))

List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))

Inherited from
IterableOps
def span(p: (K, V) => Boolean): (Map[K, V], Map[K, V])
Inherited from
IterableOps
override def splitAt(n: Int): (Map[K, V], Map[K, V])
Definition Classes
Inherited from
IterableOps
def stepper[S <: Stepper[_]](shape: StepperShape[(K, V), S]): S

Returns a scala.collection.Stepper for the elements of this collection.

Returns a scala.collection.Stepper for the elements of this collection.

The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.

The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.

Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.

Inherited from
IterableOnce
def subtractAll(xs: IterableOnce[K]): Map[K, V]

Removes all elements produced by an iterator from this shrinkable collection.

Removes all elements produced by an iterator from this shrinkable collection.

Value Params
xs

the iterator producing the elements to remove.

Returns

the shrinkable collection itself

Inherited from
Shrinkable
def subtractOne(elem: K): Map[K, V]

Removes a single element from this shrinkable collection.

Removes a single element from this shrinkable collection.

Value Params
elem

the element to remove.

Returns

the shrinkable collection itself

Inherited from
Shrinkable
def sum[B >: (K, V)](num: Numeric[B]): B

Sums up the elements of this collection.

Sums up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type Params
B

the result type of the + operator.

Value Params
num

an implicit parameter defining a set of numeric operations which includes the + operator to be used in forming the sum.

Returns

the sum of all elements of this collection with respect to the + operator in num.

Inherited from
IterableOnceOps
def tail: Map[K, V]

The rest of the collection without its first element.

The rest of the collection without its first element.

Inherited from
IterableOps
def tails: Iterator[Map[K, V]]

Iterates over the tails of this iterable collection.

Iterates over the tails of this iterable collection. The first value will be this iterable collection and the final one will be an empty iterable collection, with the intervening values the results of successive applications of tail.

Returns

an iterator over all the tails of this iterable collection

Example

List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)

Inherited from
IterableOps
def take(n: Int): Map[K, V]
Inherited from
IterableOps
def takeRight(n: Int): Map[K, V]

Selects the last n elements.

Selects the last n elements.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Value Params
n

the number of elements to take from this iterable collection.

Returns

a iterable collection consisting only of the last n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements. If n is negative, returns an empty iterable collection.

Inherited from
IterableOps
def takeWhile(p: (K, V) => Boolean): Map[K, V]

Takes longest prefix of elements that satisfy a predicate.

Takes longest prefix of elements that satisfy a predicate.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Value Params
p

The predicate used to test elements.

Returns

the longest prefix of this iterable collection whose elements all satisfy the predicate p.

Inherited from
IterableOps
override def tapEach[U](f: (K, V) => U): Map[K, V]
Definition Classes
Inherited from
IterableOps
def to[C1](factory: Factory[(K, V), C1]): C1

Given a collection factory factory, convert this collection to the appropriate representation for the current element type A.

Given a collection factory factory, convert this collection to the appropriate representation for the current element type A. Example uses:

xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]

Inherited from
IterableOnceOps
def toArray[B >: (K, V)](`evidence$1`: ClassTag[B]): Array[B]

Convert collection to array.

Convert collection to array.

Implementation note: DO NOT call Array.from from this method.

Inherited from
IterableOnceOps
final def toBuffer[B >: (K, V)]: Buffer[B]
Inherited from
IterableOnceOps
def toIndexedSeq: IndexedSeq[(K, V)]
Inherited from
IterableOnceOps
final def toIterable: Map[K, V]
Inherited from
Iterable
def toList: List[(K, V)]
Inherited from
IterableOnceOps
def toMap[K, V](ev: (K, V) <:< (K, V)): Map[K, V]
Inherited from
IterableOnceOps
def toSeq: Seq[(K, V)]
Returns

This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.

Inherited from
IterableOnceOps
def toSet[B >: (K, V)]: Set[B]
Inherited from
IterableOnceOps
override def toString(): String
Definition Classes
Map -> Function1 -> Iterable -> Any
Inherited from
Map
def toVector: Vector[(K, V)]
Inherited from
IterableOnceOps
def transpose[B](asIterable: (K, V) => Iterable[B]): Iterable[Iterable[B]]

Transposes this iterable collection of iterable collections into a iterable collection of iterable collections.

Transposes this iterable collection of iterable collections into a iterable collection of iterable collections.

The resulting collection's type will be guided by the static type of iterable collection. For example:

val xs = List(
           Set(1, 2, 3),
           Set(4, 5, 6)).transpose
// xs == List(
//         List(1, 4),
//         List(2, 5),
//         List(3, 6))

val ys = Vector(
           List(1, 2, 3),
           List(4, 5, 6)).transpose
// ys == Vector(
//         Vector(1, 4),
//         Vector(2, 5),
//         Vector(3, 6))

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type Params
B

the type of the elements of each iterable collection.

Value Params
asIterable

an implicit conversion which asserts that the element type of this iterable collection is an Iterable.

Returns

a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.

Throws
IllegalArgumentException

if all collections in this iterable collection are not of the same size.

Inherited from
IterableOps
def unapply(a: K): Option[V]

Tries to extract a B from an A in a pattern matching expression.

Tries to extract a B from an A in a pattern matching expression.

Inherited from
PartialFunction
def unzip[A1, A2](asPair: (K, V) => (A1, A2)): (Iterable[A1], Iterable[A2])

Converts this iterable collection of pairs into two collections of the first and second half of each pair.

Converts this iterable collection of pairs into two collections of the first and second half of each pair.

val xs = Iterable(
           (1, "one"),
           (2, "two"),
           (3, "three")).unzip
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three))
Type Params
A1

the type of the first half of the element pairs

A2

the type of the second half of the element pairs

Value Params
asPair

an implicit conversion which asserts that the element type of this iterable collection is a pair.

Returns

a pair of iterable collections, containing the first, respectively second half of each element pair of this iterable collection.

Inherited from
IterableOps
def unzip3[A1, A2, A3](asTriple: (K, V) => (A1, A2, A3)): (Iterable[A1], Iterable[A2], Iterable[A3])

Converts this iterable collection of triples into three collections of the first, second, and third element of each triple.

Converts this iterable collection of triples into three collections of the first, second, and third element of each triple.

val xs = Iterable(
           (1, "one", '1'),
           (2, "two", '2'),
           (3, "three", '3')).unzip3
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three),
//        Iterable(1, 2, 3))
Type Params
A1

the type of the first member of the element triples

A2

the type of the second member of the element triples

A3

the type of the third member of the element triples

Value Params
asTriple

an implicit conversion which asserts that the element type of this iterable collection is a triple.

Returns

a triple of iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.

Inherited from
IterableOps
def update(key: K, value: V): Unit

Adds a new key/value pair to this map.

Adds a new key/value pair to this map. If the map already contains a mapping for the key, it will be overridden by the new value.

Value Params
key

The key to update

value

The new value

Inherited from
MapOps
def valueStepper[S <: Stepper[_]](shape: StepperShape[V, S]): S

Returns a Stepper for the values of this map.

Returns a Stepper for the values of this map. See method stepper.

Inherited from
MapOps
def values: Iterable[V]

Collects all values of this map in an iterable collection.

Collects all values of this map in an iterable collection.

Returns

the values of this map as an iterable.

Inherited from
MapOps
def valuesIterator: Iterator[V]

Creates an iterator for all values in this map.

Creates an iterator for all values in this map.

Returns

an iterator over all values that are associated with some key in this map.

Inherited from
MapOps
override def view: MapView[K, V]
Definition Classes
Inherited from
MapOps
def withDefault(d: K => V): Map[K, V]

The same map with a given default function.

The same map with a given default function. Note: The default is only used for apply. Other methods like get, contains, iterator, keys, etc. are not affected by withDefaultValue.

Invoking transformer methods (e.g. map) will not preserve the default value.

Value Params
d

the function mapping keys to values, used for non-present keys

Returns

a wrapper of the map with a default value

Inherited from
Map
def withDefaultValue(d: V): Map[K, V]

The same map with a given default value.

The same map with a given default value. Note: The default is only used for apply. Other methods like get, contains, iterator, keys, etc. are not affected by withDefaultValue.

Invoking transformer methods (e.g. map) will not preserve the default value.

Value Params
d

default value used for non-present keys

Returns

a wrapper of the map with a default value

Inherited from
Map
override def withFilter(p: (K, V) => Boolean): WithFilter[K, V, [A] =>> Iterable[A], [K, V] =>> Map[K, V]]
Definition Classes
Inherited from
MapFactoryDefaults
def zip[B](that: IterableOnce[B]): Iterable[((K, V), B)]

Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.

Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.

Type Params
B

the type of the second half of the returned pairs

Value Params
that

The iterable providing the second half of each result pair

Returns

a new iterable collection containing pairs consisting of corresponding elements of this iterable collection and that. The length of the returned collection is the minimum of the lengths of this iterable collection and that.

Inherited from
IterableOps
def zipAll[A1 >: (K, V), B](that: Iterable[B], thisElem: A1, thatElem: B): Iterable[(A1, B)]

Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.

Returns a iterable collection formed from this iterable collection and another iterable collection 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.

Value Params
that

the iterable providing the second half of each result pair

thatElem

the element to be used to fill up the result if that is shorter than this iterable collection.

thisElem

the element to be used to fill up the result if this iterable collection is shorter than that.

Returns

a new collection of type That containing pairs consisting of corresponding elements of this iterable collection and that. The length of the returned collection is the maximum of the lengths of this iterable collection and that. If this iterable collection is shorter than that, thisElem values are used to pad the result. If that is shorter than this iterable collection, thatElem values are used to pad the result.

Inherited from
IterableOps
def zipWithIndex: Iterable[((K, V), Int)]
Inherited from
IterableOps

Deprecated and Inherited methods

@deprecated("Use ++ with an explicit collection argument instead of + with varargs", "2.13.0")
def +[V1 >: V](elem1: (K, V1), elem2: (K, V1), elems: (K, V1)*): Map[K, V1]
Deprecated
Inherited from
MapOps
@deprecated("Consider requiring an immutable Map or fall back to Map.concat.", "2.13.0")
def +[V1 >: V](kv: (K, V1)): Map[K, V1]
Deprecated
Inherited from
MapOps
@deprecated("Use ++ instead of ++: for collections of type Iterable", "2.13.0")
def ++:[B >: (K, V)](that: IterableOnce[B]): Iterable[B]
Deprecated
Inherited from
IterableOps
@deprecated("Use ++ instead of ++: for collections of type Iterable", "2.13.0")
def ++:[V1 >: V](that: IterableOnce[(K, V1)]): Map[K, V1]
Deprecated
Inherited from
MapOps
@deprecated("Use `++=` aka `addAll` instead of varargs `+=`; infix operations with an operand of multiple args will be deprecated", "2.13.0") @inline
final def +=(elem1: (K, V), elem2: (K, V), elems: (K, V)*): Map[K, V]

Adds two or more elements to this growable collection.

Adds two or more elements to this growable collection.

Value Params
elem1

the first element to add.

elem2

the second element to add.

elems

the remaining elements to add.

Returns

the growable collection itself

Deprecated
Inherited from
Growable
@deprecated("Use -- or removeAll on an immutable Map", "2.13.0")
final def -(key1: K, key2: K, keys: K*): Map[K, V]
Deprecated
Inherited from
MapOps
@deprecated("Use - or remove on an immutable Map", "2.13.0")
final def -(key: K): Map[K, V]
Deprecated
Inherited from
MapOps
@deprecated("Consider requiring an immutable Map.", "2.13.0") @inline
def --(keys: IterableOnce[K]): Map[K, V]
Deprecated
Inherited from
MapOps
@deprecated("Use `--=` aka `subtractAll` instead of varargs `-=`; infix operations with an operand of multiple args will be deprecated", "2.13.3")
def -=(elem1: K, elem2: K, elems: K*): Map[K, V]

Removes two or more elements from this shrinkable collection.

Removes two or more elements from this shrinkable collection.

Value Params
elem1

the first element to remove.

elem2

the second element to remove.

elems

the remaining elements to remove.

Returns

the shrinkable collection itself

Deprecated
Inherited from
Shrinkable
@deprecated("Use foldLeft instead of /:", "2.13.0") @inline
final def /:[B](z: B)(op: (B, (K, V)) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use foldRight instead of :\\", "2.13.0") @inline
final def :\[B](z: B)(op: ((K, V), B) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("`aggregate` is not relevant for sequential collections. Use `foldLeft(z)(seqop)` instead.", "2.13.0")
def aggregate[B](z: => B)(seqop: (B, (K, V)) => B, combop: (B, B) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use iterableFactory instead", "2.13.0") @deprecatedOverriding("Use iterableFactory instead", "2.13.0") @inline
def companion: IterableFactory[[A] =>> Iterable[A]]
Deprecated
Inherited from
IterableOps
@deprecated("Use `dest ++= coll` instead", "2.13.0") @inline
final def copyToBuffer[B >: (K, V)](dest: Buffer[B]): Unit
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use .view.filterKeys(f). A future version will include a strict version of this method (for now, .view.filterKeys(p).toMap).", "2.13.0")
def filterKeys(p: K => Boolean): MapView[K, V]

Filters this map by retaining only keys satisfying a predicate.

Filters this map by retaining only keys satisfying a predicate.

Value Params
p

the predicate used to test keys

Returns

an immutable map consisting only of those key value pairs of this map where the key satisfies the predicate p. The resulting map wraps the original map without copying any elements.

Deprecated
Inherited from
MapOps
@deprecated("Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)", "2.13.0")
def hasDefiniteSize: Boolean

Tests whether this collection is known to have a finite size.

Tests whether this collection is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as Stream, the predicate returns true if all elements have been computed. It returns false if the stream is not yet evaluated to the end. Non-empty Iterators usually return false even if they were created from a collection with a known finite size.

Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that hasDefiniteSize returns true. However, checking hasDefiniteSize can provide an assurance that size is well-defined and non-termination is not a concern.

Returns

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

See also

method knownSize for a more useful alternative

Deprecated

This method is deprecated in 2.13 because it does not provide any actionable information. As noted above, even the collection library itself does not use it. When there is no guarantee that a collection is finite, it is generally best to attempt a computation anyway and document that it will not terminate for infinite collections rather than backing out because this would prevent performing the computation on collections that are in fact finite even though hasDefiniteSize returns false.

Inherited from
IterableOnceOps
@deprecated("Use .view.mapValues(f). A future version will include a strict version of this method (for now, .view.mapValues(f).toMap).", "2.13.0")
def mapValues[W](f: V => W): MapView[K, W]

Transforms this map by applying a function to every retrieved value.

Transforms this map by applying a function to every retrieved value.

Value Params
f

the function used to transform values of this map.

Returns

a map view which maps every key of this map to f(this(key)). The resulting map wraps the original map without copying any elements.

Deprecated
Inherited from
MapOps
@deprecated("Use coll instead of repr in a collection implementation, use the collection value itself from the outside", "2.13.0")
final def repr: Map[K, V]
Deprecated
Inherited from
IterableOps
@deprecated("Use filterInPlace instead", "2.13.0") @inline
final def retain(p: (K, V) => Boolean): Map[K, V]
Deprecated
Inherited from
MapOps
@deprecated("Iterable.seq always returns the iterable itself", "2.13.0")
def seq: Map[K, V]
Deprecated
Inherited from
Iterable
@deprecated("Use .iterator instead of .toIterator", "2.13.0") @inline
final def toIterator: Iterator[(K, V)]
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use .to(LazyList) instead of .toStream", "2.13.0") @inline
final def toStream: Stream[(K, V)]
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use toIterable instead", "2.13.0")
final def toTraversable: Iterable[(K, V)]

Converts this iterable collection to an unspecified Iterable.

Converts this iterable collection to an unspecified Iterable. Will return the same collection if this instance is already Iterable.

Returns

An Iterable containing all elements of this iterable collection.

Deprecated
Inherited from
IterableOps
@deprecated("Use mapValuesInPlace instead", "2.13.0") @inline
final def transform(f: (K, V) => V): Map[K, V]
Deprecated
Inherited from
MapOps
@deprecated("Use m.clone().addOne((k,v)) instead of m.updated(k, v)", "2.13.0")
def updated[V1 >: V](key: K, value: V1): Map[K, V1]
Deprecated
Inherited from
MapOps
@deprecated("Use .view.slice(from, until) instead of .view(from, until)", "2.13.0")
def view(from: Int, until: Int): View[(K, V)]

A view over a slice of the elements of this collection.

A view over a slice of the elements of this collection.

Deprecated
Inherited from
IterableOps