Variables in Kotlin

1. What is the difference between val and var in Kotlin?

val is used for immutable variables (read-only), while var is used for mutable variables (read-write).

2. Explain the concept of type inference in Kotlin.

Kotlin can automatically infer the data type of a variable based on its initialization value, eliminating the need to explicitly specify the type.

3. How is null handled in Kotlin, and what is the purpose of the nullable types?

In Kotlin, variables cannot be null by default. To allow null values, you need to explicitly declare a variable as nullable using the ? modifier.

4. What is the difference between a property and a variable in Kotlin?

A property is a class member that encapsulates a value, while a variable is a general term for a named memory location that can hold data.

5. Explain the concept of late initialization in Kotlin.

Late initialization allows declaring a non-nullable variable without initializing it immediately, deferring the initialization to a later point in the code.

6. What is the purpose of the const keyword in Kotlin?

The const keyword is used to declare compile-time constants. These must be initialized with a value known at compile time.

7. How does Kotlin handle primitive data types compared to Java?

Kotlin does not have primitive data types; everything is an object. However, it can optimize certain types internally for better performance.

8. Explain the difference between val and const val in terms of runtime initialization.

While val is evaluated at runtime, const val is evaluated at compile time, and the value must be known at compile time.

9. What is the purpose of the by lazy delegate in Kotlin?

by lazy is used for lazy initialization of properties. The value is computed only once, the first time the property is accessed.

10. How is the scope of a variable determined in Kotlin?

The scope of a variable is determined by where it is declared. Variables declared inside a block or function are only accessible within that scope.

11. Explain the concept of type casting in Kotlin.

Type casting is the process of converting a variable from one data type to another. Kotlin supports both safe and unsafe type casting.

12. What is the purpose of the this keyword in Kotlin?

this refers to the instance of the current class. It is used to differentiate between class members and parameters with the same name.

13. How does Kotlin handle string interpolation, and what is the syntax for it?

String interpolation in Kotlin is done using the ${} syntax. It allows embedding expressions directly within string literals.

14. What are extension functions in Kotlin, and how are they useful with respect to variables?

Extension functions allow adding new functions to existing classes without modifying their code. They can be used to enhance the functionality of variables.

15. Explain the difference between == and === in Kotlin.

== checks for structural equality (content), while === checks for referential equality (memory address) when dealing with objects.

16. How are ranges used in Kotlin, and how can they be applied to variables?

Ranges in Kotlin are defined using the .. operator. They can be used to iterate over a sequence of values or to check if a variable falls within a specific range.

17. What is the purpose of the when expression in Kotlin, and how can it be used with variables?

when is a powerful replacement for the traditional switch statement in Java. It can be used with variables to provide concise and expressive conditional logic.

18. Explain the concept of smart casts in Kotlin.

Smart casts in Kotlin automatically cast a variable to a more specific type within a certain scope if certain conditions are met, eliminating the need for explicit casting.

19. How does Kotlin handle default values for function parameters, and how can they be utilized with variables?

Kotlin allows specifying default values for function parameters, making it possible to call functions without providing values for all parameters.

20. What is the purpose of the lateinit modifier in Kotlin, and when should it be used?

lateinit is used for late initialization of mutable properties. It should only be used with var properties, and the value must be assigned before accessing it.