There are several types of collections in Scala.
Iterable() creates an empty collection.
List() creates an empty list.
Vector(20,130), creates a vector with two elements
130 in it.
List(20,130), creates a list with two elements
130 in it.
Iterator(1, 2, 3), an iterator containing three numbers.
Set(Apples, oranges) creates a set of two fruits.
Hashset(Apples, oranges) creates a hashset of two fruits.
Map('apple' -> 23 , 'banana' -> 45) creates a map of key-value pairs to map from characters to integers.
In Scala, a programmer can easily create a collection by defining a collection name and initializing the values of a collection in parentheses. For examples,
Map('apple' -> 23 , 'banana' -> 45)creates a map with some key value pairs.
Now let’s see how does it work. When you write
List(23,45), a function,
List.apply(23, 45) is called. This
apply() method is a companion object of the Class List. The function
apply takes some arguments and creates a list of the passed argument. The companion object is then applied to all the collections: lists, lazylists, Vectors, Seq, Set, Map, Iterables, etc.
.apply(), all collections also have another companion object,
.empty, to create an empty collection.
The companion objects provide several methods in a collection such as
concat (to join two collections together,
fill (for generating collections of a given dimension: single dimension, multi-dimension, etc.),
range (create a range of numbers).
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