Beginner Level:

1. What is Kotlin? How does it differ from Java?
   Kotlin is a statically typed programming language developed by JetBrains. It runs on the Java Virtual Machine (JVM) and can also be compiled to JavaScript or native code. Kotlin differs from Java in several ways, including concise syntax, null safety, extension functions, and enhanced support for functional programming constructs.
2. Explain the basic syntax and structure of a Kotlin program.
   A basic Kotlin program consists of one or more files containing Kotlin code. It typically starts with a package declaration followed by import statements. The entry point of the program is usually a main function declared at the top level. Inside the main function or other functions, you write the logic of your program.
3. What are the advantages of using Kotlin over Java?
   Advantages of Kotlin over Java include concise syntax, null safety, extension functions, interoperability with existing Java codebases, coroutines for asynchronous programming, and various language features that enhance developer productivity.
4. How do you declare variables in Kotlin? What are the different types of variables?
   Variables in Kotlin are declared using the val keyword for immutable variables (constants) and the var keyword for mutable variables. Kotlin supports different types of variables, including primitive types (such as Int, Boolean, Double), nullable types (e.g., Int?), and user-defined types (e.g., class instances).
5. What are nullable types in Kotlin? How do you handle nullability?
   Nullable types in Kotlin are types that can hold a null reference. They are declared by appending ? to the type name (e.g., String?). To handle nullability, Kotlin provides safe calls (?.), the Elvis operator (?:), and the safe cast operator (as?). Additionally, Kotlin encourages the use of non-nullable types whenever possible to prevent NullPointerExceptions.
6. Describe the basic control flow structures in Kotlin.
   Kotlin supports traditional control flow structures such as if, else, when (similar to switch-case in Java), for, while, and do-while. Kotlin’s when expression is more powerful than Java’s switch statement, as it can handle arbitrary expressions as branch conditions.
7. How do you define functions in Kotlin? Explain the differences between top-level functions and member functions.
   Functions in Kotlin are declared using the fun keyword followed by the function name, parameters, return type (if any), and body. Top-level functions are declared outside of any class and can be called directly. Member functions are declared inside classes and are called on instances of the class using dot notation (object.method()).
8. What are data classes in Kotlin? How do they differ from regular classes?
   Data classes in Kotlin are classes that are designed to hold data. They automatically generate equals(), hashCode(), toString(), copy(), and componentN() methods based on the properties declared in the primary constructor. This eliminates the need for boilerplate code when working with data objects.
9. Explain the use of the ‘when’ expression in Kotlin.
   The whenexpression in Kotlin is used as a replacement for the traditional switch statement in Java. It allows you to check a value against multiple conditions and execute the corresponding branch. It can handle both simple and complex conditions, making it more versatile than switch.
10. How do you perform type checking and casting in Kotlin?
    Type checking in Kotlin is done using the is operator, which checks whether an object is of a specific type. Type casting is performed using the as operator for safe casts and the as? operator for safe casts that return null if the cast is not possible. Additionally, Kotlin provides the !is operator for negated type checks.
11. Explain the concept of type inference in Kotlin. How does Kotlin determine the type of variables?
    Type inference in Kotlin allows the compiler to automatically deduce the type of variables based on the context in which they are used. Kotlin determines the type of variables by analyzing the expressions on the right-hand side of variable declarations. For example:
    

    val number = 10 // Compiler infers the type of 'number' as Int 
    val message = "Hello" // Compiler infers the type of 'message' as String

12. What are the primary collections types in Kotlin? Briefly explain each one and provide examples of their usage. Kotlin’s primary collection types include List, Set, and Map.
    
    List: Ordered collection of elements that allows duplicate elements.
    Example: val list = listOf(1, 2, 3)
Set: Unordered collection of unique elements.
    Example: val set = setOf(1, 2, 3)
Map: Collection of key-value pairs where each key is unique. Example: val map = mapOf("key" to "value", "foo" to "bar")
13. Discuss the use of ranges in Kotlin. How are they declared and used in practice? Ranges in Kotlin are used to represent a sequence of values between a start and an end. They are declared using the .. operator. For example:
    

    val range = 1..5 // Represents the range from 1 to 5 (inclusive)
    for (i in range) {
        println(i) // Output: 1, 2, 3, 4, 5
    }