Collections

Collections are the container of things that contains a random number of elements.

• Collections are containers of things.
• These containers can be Sequenced, Linear set of items like List, Tuple, Map etc.
• Collections may have an arbitrary number of elements or be bounded to Zero or one element.
• The Scala collection classes are part of scala.collection package and its sub packages.

Scala collections can be of two types basically:

Mutable Collection

• These collections are part of scala.collection.mutable package.
• With these collections, we can add, remove or modify data.

Immutable Collection

• These collections are part of scala.collection.immutable package.
• This doesn’t allow to modify the data.
• Scala imports this package by default.
• To use mutable collection, we need to explicitly import the mutable package
  in code.
• Any change in an immutable collection, produces a new collection without
  modifying the existing collection. 

Most Common Collection types are –

• List
• Map
• Set
• Tuple
• Iterators

 Following is the hierarchy of all collections in package scala.collection