Scala - Interview Questions and Answers

21) What is method overloading in Scala?

Scala provides method overloading feature which allows us to define methods of the same name but having different parameters or data types. It helps to optimize code. You can achieve method overloading either by using different parameter list or different types of parameters.

Example

 class Arithmetic{     def add(a:Int, b:Int){         var sum = a+b         println(sum)     }     def add(a:Int, b:Int, c:Int){         var sum = a+b+c         println(sum)     } }  object MainObject{     def main(args:Array[String]){         var a  = new Arithmetic();         a.add(10,10);         a.add(10,10,10);     } } 

22) What is this in Scala?

In Scala, this is a keyword and used to refer a current object. You can call instance variables, methods, constructors by using this keyword.

Example

 class ThisExample{     var id:Int = 0     var name: String = "     def this(id:Int, name:String){         this()         this.id = id         this.name = name     }     def show(){         println(id+" "+name)     } }  object MainObject{     def main(args:Array[String]){         var t = new ThisExample(101,"Martin")         t.show()     } } 

23) What is Inheritance?

Inheritance is an object-oriented concept which is used to reusability of code. You can achieve inheritance by using extends keyword. To achieve inheritance, a class must extend to other class. A class which is extended called super or parent class. A class which extends class is called derived or base class.

Example

 class Employee{     var salary:Float = 10000 }  class Programmer extends Employee{     var bonus:Int = 5000     println("Salary = "+salary)     println("Bonus = "+bonus) }  object MainObject{     def main(args:Array[String]){         new Programmer()     } } 

24) What is method overriding in Scala?

When a subclass has the same name method as defined in the parent class, it is known as method overriding. When subclass wants to provide a specific implementation for the method defined in the parent class, it overrides a method from the parent class.

In Scala, you must use either override keyword or override annotation to override methods from the parent class.

Example

 class Vehicle{     def run(){         println("vehicle is running")     } }  class Bike extends Vehicle{      override def run(){         println("Bike is running")     } }  object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.run()     } } 

25) What is final in Scala?

Final keyword in Scala is used to prevent inheritance of super class members into the derived class. You can declare the final variable, method, and class also.

Scala Final Variable Example

 class Vehicle{      final val speed:Int = 60 } class Bike extends Vehicle{    override val speed:Int = 100     def show(){         println(speed)     } }  object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

26) What is the final class in Scala?

In Scala, you can create a final class by using the final keyword. A final class can't be inherited. If you make a class final, it can't be extended further.

Scala Final Class Example

 final class Vehicle{      def show(){          println("vehicle is running")      }  }  class Bike extends Vehicle{        override def show(){         println("bike is running")     } }  object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

27) What is an abstract class in Scala?

A class which is declared with the abstract keyword is known as an abstract class. An abstract class can have abstract methods and non-abstract methods as well. An abstract class is used to achieve abstraction.

Example

 abstract class Bike{     def run() }  class Hero extends Bike{     def run(){         println("running fine...")     } }  object MainObject{     def main(args: Array[String]){         var h = new Hero()         h.run()     } } 

28) What is Scala Trait?

A trait is like an interface with partial implementation. In Scala, the trait is a collection of abstract and non-abstract methods. You can create a trait that can have all abstract methods or some abstract and some non-abstract methods.

Example

 trait Printable{     def print() }  class A4 extends Printable{     def print(){         println("Hello")     } }  object MainObject{     def main(args:Array[String]){         var a = new A4()         a.print()     } } 

29) What is a trait mixins in Scala?

In Scala, "trait mixins" means you can extend any number of traits with a class or abstract class. You can extend only traits or combination of traits and class or traits and abstract class.

It is necessary to maintain the order of mixins otherwise compiler throws an error.

Example

 trait Print{     def print() }  abstract class PrintA4{     def printA4() }  class A6 extends PrintA4 {     def print(){               				 // Trait print         println("print sheet")     }     def printA4(){              				// Abstract class printA4         println("Print A4 Sheet")     } }  object MainObject{     def main(args:Array[String]){         var a = new A6() with Print				// You can also extend trait during object creation         a.print()         a.printA4()     } } 

30) What is the access modifier in Scala?

Access modifier is used to define accessibility of data and our code to the outside world. You can apply accessibly to class, trait, data member, member method, and constructor, etc. Scala provides the least accessibility to access to all. You can apply any access modifier to your code according to your requirement.

In Scala, there are only three types of access modifiers.

No modifier
Protected
Private

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