Scala interview questions

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.

• Apply method- this method is used to assemble an object from its components. For eg.- if an employee object needs to be created, then the two components namely- first name and last name should be used and should be composed using the apply method.
• Unapply method- when we want to decompose the objects from its components, then we make use of this unapply method. Reverse process is followed while making use of the unapply method. So, the employee object can be decomposed into two components namely- first name and last name.

• An array is a sequential mutable data structure. Whereas, a list is an immutable recursive data structure.
• In scala, an array is an invariant. Whereas, a list is a covariant data structure.
• The size of an array is fixed and cannot be changed easily. Whereas, the size of a list may increase or decrease based on the operations performed by it.

• 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.

• As the name suggests, it is a scalable programming language. It is highly scalable. Its high maintainability, productivity, and testability features make it more usable which turns out to be an advantage and hence it is preferred more.
• Scala consists of singleton and companion objects. These objects in scala, unlike the JVM languages provide a clearer solution to every problem.
• The need of ternary operator gets eliminated in scala as “if blocks”, “for-yield loops”, and “code” in braces return a value.

• 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.