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1. What is Kotlin, and how does it differ from Java?

  • Kotlin is a statically typed programming language that runs on the Java Virtual Machine (JVM). It differs from Java in several ways, including concise syntax, enhanced null safety, support for functional programming, and improved type inference. Kotlin is interoperable with Java, making it easier to migrate existing Java codebases to Kotlin.

2. Explain how Kotlin’s null safety feature helps prevent null pointer exceptions.

  • Kotlin’s null safety feature ensures that variables are explicitly declared as nullable or non-nullable. This prevents null pointer exceptions by requiring developers to handle null values explicitly, reducing the risk of accidental null references. Null safety is enforced at compile time, making code more robust.

3. How do you declare different data types in Kotlin?

  • In Kotlin, you declare data types using keywords like Int, String, Boolean, etc. For example, to declare an integer variable, you can use: val age: Int = 30. Kotlin supports a wide range of primitive and user-defined data types.

4. Explain how you define a variable in Kotlin using the val and var keywords.

  • In Kotlin, you use the val keyword to define read-only (immutable) variables and the var keyword for mutable variables. For example, val pi: Double = 3.14159 creates an immutable variable for the value of pi, while var count: Int = 5 creates a mutable variable for counting.

5. Describe how Kotlin range expressions work and how they are used.

  • Kotlin range expressions are used to represent a range of values. For example, 1..10 represents a range from 1 to 10, inclusive. Ranges are commonly used in loops and conditional statements to iterate over or check values within a specified range.

6. What is the purpose of the when expression in Kotlin, and how does it differ from a switch statement in Java?

  • The when expression in Kotlin serves a similar purpose as the switch statement in Java, allowing you to make decisions based on the value of an expression. However, when is more powerful and expressive, as it can handle various data types and conditions in a concise and readable manner.

7. What is type inference in Kotlin, and how does it work?

  • Type inference in Kotlin is the ability of the compiler to automatically determine the data type of a variable based on its initialization value. This feature reduces the need for explicit type declarations, making code cleaner and more concise. For example, val name = “John” infers the type of name as String.

8. How do you create and use a basic Kotlin function?

  • To create a basic Kotlin function, you use the fun keyword, followed by the function name, parameters, and return type. For example, fun add(a: Int, b: Int): Int { return a + b } defines a function that adds two integers and returns the result. You can call the function by its name with arguments, like add(3, 5).

9. What is a lambda expression in Kotlin, and how is it used?

  • A lambda expression in Kotlin is an anonymous function that can be used as an argument to other functions. It is concise and often used for defining functions on the fly. For example, val square = { x: Int -> x * x } defines a lambda expression for squaring a number. Lambdas are commonly used in functions like map and filter to process collections.

10. Compare and contrast the use of val and var when declaring properties in a class.

  • In Kotlin, val is used to declare read-only (immutable) properties, while var is used for mutable properties. A val property can be initialized once and cannot be changed afterward, ensuring immutability. In contrast, a var property can have its value modified after initialization.