Mutable and Immutable Collections

In Scala, collections are fundamental data structures used for storing and manipulating elements. Scala collections can be categorized into mutable and immutable collections based on their mutability characteristics.

Immutable Collections: Immutable collections, such as List, Set, Map, and others, cannot be modified after creation. Operations on immutable collections return new collections without modifying the original, ensuring thread safety and promoting functional programming principles. Immutable collections are preferred for scenarios where data needs to remain unchanged or shared across concurrent tasks without the risk of unintended modifications.

Mutable Collections: Mutable collections, including ArrayBuffer, MutableList, HashMap, and others, allow elements to be added, removed, or updated after creation. Mutable collections provide direct modification capabilities, suitable for scenarios where in-place modifications are necessary for performance or specific use cases. However, mutable collections require careful handling to avoid unintended side effects, especially in concurrent environments.

Understanding the differences between s is essential for writing scalable, safe, and maintainable Scala code. Choosing the appropriate collection type based on mutability requirements ensures efficient data manipulation and supports different programming paradigms within Scala, such as functional and imperative styles.

The following figure shows all collections in package:

A useful convention if you want to use both mutable and immutable versions of collections is to import just the package collection.mutable.