Scala Interview Questions and Answers
Scalable Language, or Scala, is a general-purpose, hybrid functional programming language. Integrating the features of other technical and object-oriented languages, Scala is designed to run on JVM (Java Virtual Machine). This means Scala will enable you to use all the classes of Java SDK, including custom classes, of your Java open source projects. This information is often asked in Scala interview questions. Being used in most of the enterprise-level web apps, Scala provides lightweight syntax that helps developers define anonymous functions. The language supports high-level functions and allows nesting of those functions. Scala will enable developers to write general programming patterns efficiently by reducing the number of lines. This language also empowers the developers to write immutable codes, thus making it easy to apply parallelism and concurrency.
If you are preparing for the Scala language job interview, we have one of the biggest collection of Scala Interview Questions and Answers.
Most Frequently Asked Scala Interview Questions
| S.no | Scala | Java |
|---|---|---|
| 1. | Includes implicit | Includes widening and casting |
| 2. | variables immutable | variables mutable by default |
| 3. | Pattern matching | Switch statements |
| 4. | Allows related type to be defined as one file | Does not allow related types to be described in one file |
Option in Scala is a container that holds zero or one element of a specific type. It represents values that either exist or do not exist. The Option is used to wrap missing values and is a replacement to return null values. This question has the most likelihood of being asked in Scala interview questions for experienced professionals.
A trait in Scala is a unique kind of Class that enables developers to use multiple inheritances. Although a trait can extend to only one class, a class can have many traits. However, unlike classes in Scala, you cannot instantiate traits.
Traits are often used when the user requires dependency injection (DI). In Scala, you do not have annotations or special packages for import. You must initialize the class with trait and dependency gets injected.
There are times when programmers have to write functions that are recursive, where the critical problem that such functions eat up the entire allocated stack space. To overcome this challenge, Scala provides a “tail recursion” mechanism.
This mechanism optimizes recursive functions so that they do not create new stack space and use the existing stack space.
| S.no | Array | List |
|---|---|---|
| 1. | The sequential and mutable data structure | The recursive and immutable data structure |
| 2. | Invariant | Covariant |
| 3. | Fixed size | Variable size |
Akka is a runtime and toolkit for building concurrent, fault-tolerant and distributed applications on Java Virtual Machine. Though Akka is written in Scala, it contains language bindings for both Scala and Java. Its approach to handling concurrency is built on Actor Model.
Here are some of the limitations of Scala:
- Online community support is limited.
- Difficult to learn.
- Challenge to find professionals for real Scala development.
- Backward compatibility is limited.
REPL in Scala, or Read-Evaluate-Print Loop, is pronounced as ‘ripple.’ It acts as an Interpreter for executing code from the command prompt. This is the reason REPL is called as Scala Command Line Interface (CLI).
The key use of REPL is to develop and test snippets of code for practice purposes. It is useful for Beginner developers to practice low-level programs.
Latest version of Scala is 2.12.11, which was released in March 16, 2020.
Here are some of the points here Scala scores over other programming languages:
- Functional Plus OOP language.
- Allows developers to write reactive apps.
- Runs on JVM.
- Cross compatible with Java
- Cleaner, elegant and more concise code
Key Features of Scala Language
- Singleton object
- Concurrency control
- Traits
- Case classes and Pattern matching
- String interpolation
- Lazy computation
Classes and inheritance - two features that stand out in object-oriented programming (OOP) language - are supported in Scala. This enables the development and maintenance of modular software. Some other key features include objects, traits, and case classes.
The unique feature that makes Scala standout from the rest is its ability to scale and expand. Considered as one of the “future-proof” languages, it has almost eliminated the common problems associated with other popular languages. Regardless of the nature of the project you are handling, trust Scala to handle it.
Designed to compensate for the faults of Java, JVM views Scala and Java as same languages.
Development History of Scala Language
Martin Odersky started the design process of Scala at the EPFL in Switzerland in 2001. Odersky followed the work dome on Funnel, a programming language that combined ideas from Petri nets and functional programming. After an internal delay, the first version of Scala was publicly released in 2004 on the Java platform.
Latest Version
Latest version is 2.12.8, which was released in Dec 2018. With its first 2.12 release, Scala license got changed to Apache v2.0.