Map

Optionally returns the value associated with a key.

Creates a new iterator over all key/value pairs of this map

Test two objects for inequality.

Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

Adds key/value pairs to this map, returning a new map.

This method takes two or more key/value pairs. Another overloaded variant of this method handles the case where a single key/value pair is added.

Adds a key/value pair to this map, returning a new map.

Adds all key/value pairs in a traversable collection to this map, returning a new map.

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.

Example:

scala> val a = LinkedList(1)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1)

scala> val b = LinkedList(2)
b: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val c = a ++ b
c: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

scala> val d = LinkedList('a')
d: scala.collection.mutable.LinkedList[Char] = LinkedList(a)

scala> val e = c ++ d
e: scala.collection.mutable.LinkedList[AnyVal] = LinkedList(1, 2, a)

As with ++, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

scala> val x = List(1)
x: List[Int] = List(1)

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

This overload exists because: for the implementation of ++: we should reuse that of ++ because many collections override it with more efficient versions.

Since TraversableOnce has no ++ method, we have to implement that directly, but Traversable and down can use the overload.

As with ++, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

scala> val x = List(1)
x: List[Int] = List(1)

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

Creates a new map from this map with some elements removed.

This method takes two or more elements to be removed. Another overloaded variant of this method handles the case where a single element is removed.

Removes a key from this map, returning a new map.

Creates a new map from this map by removing all elements of another collection.

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

Note: /: is alternate syntax for foldLeft; z /: xs is the same as xs foldLeft z.

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (5 /: a)(_+_)
b: Int = 15

scala> val c = (5 /: a)((x,y) => x + y)
c: Int = 15

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

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

Note: :\ is alternate syntax for foldRight; xs :\ z is the same as xs foldRight z.

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

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (a :\ 5)(_+_)
b: Int = 15

scala> val c = (a :\ 5)((x,y) => x + y)
c: Int = 15

Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

Appends all bindings of this map to a string builder using start, end, and separator strings. The written text begins with the string start and ends with the string end. Inside, the string representations of all bindings of this map in the form of key -> value are separated by the string sep.

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

Example:

scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

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

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

Appends all elements of this map 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 map, separated by the string sep.

Example:

scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

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

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

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of fold and reduce. It has similar semantics, but does not require the result to be a supertype of the element type. It traverses the elements in different partitions sequentially, using seqop to update the result, and then applies combop to results from different partitions. The implementation of this operation may operate on an arbitrary number of collection partitions, so combop may be invoked an arbitrary number of times.

For example, one might want to process some elements and then produce a Set. In this case, seqop would process an element and append it to the list, while combop would concatenate two lists from different partitions together. The initial value z would be an empty set.

pc.aggregate(Set[Int]())(_ += process(_), _ ++ _)

Another example is calculating geometric mean from a collection of doubles (one would typically require big doubles for this).

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

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.

Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.

Note that expression pf.applyOrElse(x, default) is equivalent to

if(pf isDefinedAt x) pf(x) else default(x)

except that applyOrElse method can be implemented more efficiently. For all partial function literals compiler generates applyOrElse implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse the basis for the efficient implementation for many operations and scenarios, such as:

• combining partial functions into orElse/andThen chains does not lead to excessive apply/isDefinedAt evaluation
• lift and unlift do not evaluate source functions twice on each invocation
• runWith allows efficient imperative-style combining of partial functions with conditionally applied actions

For non-literal partial function classes with nontrivial isDefinedAt method it is recommended to override applyOrElse with custom implementation that avoids double isDefinedAt evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.

Cast the receiver object to be of type T0.

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

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

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

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

The factory companion object that builds instances of class Map. (or its Iterable superclass where class Map is not a Seq.)

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

Tests whether this map contains a binding for a key.

Copies elements of this map to an array. Fills the given array xs with at most len elements of this map, starting at position start. Copying will stop once either the end of the current map is reached, or the end of the array is reached, or len elements have been copied.

Copies values of this map to an array. Fills the given array xs with values of this map. Copying will stop once either the end of the current map is reached, or the end of the array is reached.

Copies values of this map to an array. Fills the given array xs with values of this map, beginning at index start. Copying will stop once either the end of the current map is reached, or the end of the array is reached.

Copies all elements of this map to a buffer.

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

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.

Selects all elements except first n ones.

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

Selects all elements except last n ones.

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

Drops longest prefix of elements that satisfy a predicate.

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

The empty map of the same type as this map

Tests whether the argument (arg0) is a reference to the receiver object (this).

The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

• It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
• For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
• null.eq(null) returns true.

When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

Compares two maps structurally; i.e. checks if all mappings contained in this map are also contained in the other map, and vice versa.

Tests whether a predicate holds for some of the elements of this map.

Selects all elements of this map which satisfy a predicate.

Filters this map by retaining only keys satisfying a predicate.

Returns a new map obtained by removing all key/value pairs for which the predicate p returns true.

Note: This method works by successively removing elements for which the predicate is true from this set. If removal is slow, or you expect that most elements of the set will be removed, you might consider using filter with a negated predicate instead.

Called by the garbage collector on the receiver object when there are no more references to the object.

The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

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

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

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

For example:

def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")

The type of the resulting collection is guided by the static type of map. This might cause unexpected results sometimes. For example:

// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)

// lettersOf will return a Set[Char], not a Seq
def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq)

// xs will be a an Iterable[Int]
val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)

// ys will be a Map[Int, Int]
val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)

Converts this map of traversable collections into a map formed by the elements of these traversable collections.

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

val xs = List(Set(1, 2, 3), Set(1, 2, 3))
// xs == List(1, 2, 3, 1, 2, 3)

val ys = Set(List(1, 2, 3), List(3, 2, 1))
// ys == Set(1, 2, 3)

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

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

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

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

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

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

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

Applies a function f to all elements of this map.

Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.

Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

The generic builder that builds instances of Map at arbitrary element types.

A representation that corresponds to the dynamic class of the receiver object.

The nature of the representation is platform dependent.

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

Partitions this map into a map of maps according to some discriminator function.

Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new map.

Partitions elements in fixed size maps.

Tests whether this map 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.

Note: many collection methods will not work on collections of infinite sizes.

The hashCode method for reference types. See hashCode in scala.Any.

Selects the first element of this map.

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

Optionally selects the first element.

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

Selects all elements except the last.

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

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

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

Tests whether the map is empty.

Test whether the dynamic type of the receiver object is T0.

Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

Tests whether this map can be repeatedly traversed.

Collects all keys of this map in a set.

Collects all keys of this map in an iterable collection.

Creates an iterator for all keys.

Selects the last element.

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

Optionally selects the last element.

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

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

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

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

Finds the largest element.

Finds the smallest element.

Displays all elements of this map in a string.

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

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

Equivalent to !(this eq that).

A common implementation of newBuilder for all maps in terms of empty. Overridden for mutable maps in mutable.MapLike.

Tests whether the map is not empty.

Wakes up a single thread that is waiting on the receiver object's monitor.

Wakes up all threads that are waiting on the receiver object's monitor.

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

Returns a parallel implementation of this collection.

For most collection types, this method creates a new parallel collection by copying all the elements. For these collection, par takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.

Specific collections (e.g. ParArray or mutable.ParHashMap) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

All parallel collections return a reference to themselves.

The default par implementation uses the combiner provided by this method to create a new parallel collection.

Partitions this map in two maps according to a predicate.

Multiplies up the elements of this collection.

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

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

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

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

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

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

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

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

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

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

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

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

The collection of type map underlying this TraversableLike object. By default this is implemented as the TraversableLike object itself, but this can be overridden.

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.

Checks if the other iterable collection contains the same elements in the same order as this map.

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

Computes a prefix scan of the elements of the collection.

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

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

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

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

Example:

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

A version of this collection with all of the operations implemented sequentially (i.e. in a single-threaded manner).

This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.

The size of this map.

Selects an interval of elements. The returned collection is made up of all elements x which satisfy the invariant:

from <= indexOf(x) < until

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

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.)

Splits this map into a prefix/suffix pair according to a predicate.

Note: c span p is equivalent to (but possibly more efficient than) (c takeWhile p, c dropWhile p), provided the evaluation of the predicate p does not cause any side-effects.

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

Splits this map into two at a given position. Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n).

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

Defines the prefix of this object's toString representation.

Sums up the elements of this collection.

Selects all elements except the first.

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

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

Selects first n elements.

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

Selects last n elements.

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

Takes longest prefix of elements that satisfy a predicate.

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

The underlying collection seen as an instance of Map. By default this is implemented as the current collection object itself, but this can be overridden.

Converts this map into another by copying all elements.

Converts this map to an array.

Converts this map to a mutable buffer.

A conversion from collections of type Repr to Map objects. By default this is implemented as just a cast, but this can be overridden.

Converts this map to an indexed sequence.

Converts this map to an iterable collection. Note that the choice of target Iterable is lazy in this default implementation as this TraversableOnce may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).

Returns an Iterator over the elements in this map. Will return the same Iterator if this instance is already an Iterator.

Converts this map to a list.

Converts this map to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.

Converts this map to a sequence. As with toIterable, it's lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.

Converts this map to a set.

Converts this map to a stream.

Converts this map to a string.

Converts this map to an unspecified Traversable. Will return the same collection if this instance is already Traversable.

Converts this map to a Vector.

Transposes this map of traversable collections into a map of maps.

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

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

Creates a new map obtained by updating this map with a given key/value pair.

Collects all values of this map in an iterable collection.

Creates an iterator for all values in this map.

Creates a non-strict view of a slice of this map.

Note: the difference between view and slice is that view produces a view of the current map, whereas slice produces a new map.

Note: view(from, to) is equivalent to view.slice(from, to)

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

Creates a non-strict view of this map.

Creates a non-strict filter of this map.

Note: the difference between c filter p and c withFilter p is that the former creates a new collection, whereas the latter only restricts the domain of subsequent map, flatMap, foreach, and withFilter operations.

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

Returns a map formed from this map 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.

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

Returns a map formed from this map 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.

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

Zips this map with its indices.

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

A syntactic sugar for out of order folding. See fold.

Example:

scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (a /:\ 5)(_+_)
b: Int = 15