21. How do you create a coroutine in Kotlin, and what are the key coroutine building blocks?

  • To create a coroutine in Kotlin, you use the launch or async functions. The key coroutine building blocks include suspend functions, which can be suspended and resumed, and CoroutineScope, which defines the scope and context in which the coroutine runs.

22. Compare and contrast the usage of suspend and runBlocking in the context of coroutines.

  • Suspend is used to mark functions that can be called from a coroutine to suspend execution, while runBlocking is a function used to create a new coroutine that blocks the current thread until the coroutine is completed. suspend is used within a coroutine, while runBlocking is typically used for testing and main functions.

23. What is the purpose of the Kotlin Standard Library, and name a few common functions it provides.

  • The Kotlin Standard Library provides a set of functions and classes to extend the capabilities of the language. It includes functions like map, filter, let, and apply for working with collections and improving code expressiveness and readability.

24. How do you perform asynchronous operations using the async and await functions in Kotlin coroutines?

  • To perform asynchronous operations using Kotlin coroutines, you can use the async function to launch concurrent tasks and the await function to wait for their results. This allows you to perform multiple operations concurrently while maintaining readability and control.

25. Explain the difference between Kotlin’s primary constructor and secondary constructor in classes.

  • The primary constructor in Kotlin is defined in the class header and is used to initialize properties. Secondary constructors are additional constructors within the class and are used to provide alternative ways to create instances. Primary constructors are called first and can delegate to secondary constructors if needed.

26. How do you handle resource management and cleanup in Kotlin using the use function?

  • The use function in Kotlin is used for resource management and cleanup, particularly with resources that need to be closed after use, like files or database connections. It ensures that the resource is properly closed once the operation is completed or an exception is thrown.

27. Discuss sealed classes and data classes in Kotlin, and when should you use them?

  • Sealed classes are used for managing restricted hierarchies of types, ensuring that all possible subclasses are explicitly defined. Data classes are used for storing data and automatically generate useful functions. You should use sealed classes when you have a closed set of subclasses, and data classes when you need to store and manipulate data with minimal boilerplate.

28. How can you implement property delegation in Kotlin, and what built-in delegates are available?

  • Property delegation in Kotlin allows you to offload the implementation of property access and modification to another object. You can implement custom delegates or use built-in delegates like lazy, observable, and vetoable to add behavior to properties without modifying their code.

29. What is the Kotlin Android Extension (Android KTX), and how does it simplify Android app development?

  • The Kotlin Android Extension (Android KTX) is a set of extensions for the Android framework that simplifies Android app development when using Kotlin. It enhances the Android API by providing more idiomatic and concise Kotlin syntax, improving code readability and developer productivity.

30. How do you work with collections in Kotlin, and what are some common functions for filtering and transforming data?

  • In Kotlin, you work with collections using functions like filter, map, and reduce. filter is used to select elements that meet a certain condition, map is used to transform elements, and reduce is used to combine elements into a single result. These functions make working with collections more expressive and efficient.