Scala interview questions

Scala is a high-level programming language that combines object-oriented and functional programming in one concise. Below are some Scala interview questions and answer

#1 What do you mean by a Scala map?

The collection of key-value pairs where the key can retrieve the values present in a map is known as a scala map. The keys, unlike the values in a scala map are unique. There are two types of maps present in scala:
  • Mutable
  • Immutable

By default, immutable map is supported by scala. To use the mutable map, the programmer needs to import the “scala.collection.mutable”. It is an explicit class. “mutable.map” is the syntax for using the mutable and immutable class in the same program. To access the immutable class, we just have to use the name of the map and it can be accessed.

#2 How does yield work in Scala?

#3 What is the difference between a Java future and a Scala future?

#4 What is "Type Inference" in Scala?

#5 What do you mean by implicit parameters?

#6 Please explain closure is Scala?

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#7 What is a applicative?

#8  Differentiate Nil, Null, None, and Nothing in scala.

The difference between these four attributes in scala is given below:
  • Nil- it is used to initialize an empty list since it is an object which extends list.
  • Null- null in scala is used to provide compatibility with the java null keyword or to provide a type for the null keyword. It also represents the absence of type information for complex types.
  • None- the “none” pattern in scala is used to remove null values from the scala code.
  • Nothing- it is used for providing the return type for the operations that can affect the normal flow of program.

#9 Tell the advantages of companion objects when used in Scala?

Instead of having static methods or variables, scala has singleton or companion objects. These objects are then compiled to classes which have static methods. Some advantages of these companion objects are listed below:

  • These are beneficial as they can be used for encapsulating things. They also act as a bridge and hence functional and object-oriented programs can be written easily.
  • These companion objects also help in keeping the scala programming code more concise because the static keyword need not be added to each and every attribute.
  • A clear separation between the static and non-static methods is maintained with the help of these companion objects.

#10 Explain what is Unit in Scala?

#11  What do you understand by an implicit parameter in Scala ?

Implicit parameters are used when we want to invoke a function without passing all the parameters. The default values of all the parameters or the parameters which we want to use are set as implicit. When implicit parameters are not used the local value of that parameter is used. An implicit keyword needs to be used if want to make a value, function parameter, or a variable as an implicit parameter. Once the value becomes implicit, we need not pass all the parameters to invoke a particular function.

#12 List different types of literals available in Scala?

#13 Which Scala library is used for the functional programming?

pure functional data structure is present in the scala library. It also complements the standard Scala library. It also has a pre-defined set of foundational type classes’ like- Monad, Functor, etc. The standard library of Scala is automatically set as a dependency by default. The Scala library is used for compiling scala sources and for that it needs to be on the classpath.

#14 What is Monad in Scala?

#15 Explain trait in Scala and its uses?

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