Practice 50 Kotlin Null Safety and Smart Casts Coding Questions, TechnoVlogs

Practice 50 Kotlin Null Safety and Smart Casts Coding Questions


Q1. Write a Kotlin program to check if a nullable string is null using the safe call operator (?.).
  Input: val str: String? = "Hello"
  Expected Output: "Hello"

Q2. Write a Kotlin program to print "Not null" if a nullable string is not null using the safe call operator.
  Input: val str: String? = null
  Expected Output: "null"

Q3. Write a Kotlin program to safely access the length of a nullable string using the safe call operator.
  Input: val str: String? = "Kotlin"
  Expected Output: 6

Q4. Write a Kotlin program to use the elvis operator (?:) to provide a default value if a nullable string is null.
  Input: val str: String? = null
  Expected Output: "Default"

Q5. Write a Kotlin program to use the elvis operator (?:) to return a default value for a nullable integer.
  Input: val num: Int? = null
  Expected Output: 0

Q6. Write a Kotlin program to safely access the length of a nullable string and return "null" if it is null.
  Input: val str: String? = null
  Expected Output: "null"

Q7. Write a Kotlin program to check if a nullable string is null or empty.
  Input: val str: String? = "Kotlin"
  Expected Output: false

Q8. Write a Kotlin program to use the !! operator to assert that a nullable value is not null.
  Input: val str: String? = "Hello"
  Expected Output: "Hello"

Q9. Write a Kotlin program to demonstrate a NullPointerException when using the !! operator with a null value.
  Input: val str: String? = null
  Expected Output: NullPointerException

Q10. Write a Kotlin program to use the let function with a nullable value to execute code only if the value is not null.
   Input: val str: String? = "Kotlin"
   Expected Output: "Not null"

Q11. Write a Kotlin program to safely access the value of a nullable integer inside a let block.
   Input: val num: Int? = 5
   Expected Output: 5

Q12. Write a Kotlin program to use the safe call operator with a method on a nullable string.
   Input: val str: String? = "Hello"
   Expected Output: "Hello".toUpperCase()

Q13. Write a Kotlin program to check if a nullable integer is null and return a default value using let.
   Input: val num: Int? = null
   Expected Output: 0

Q14. Write a Kotlin program to perform null safety check and print the length of a nullable string if it's not null.
   Input: val str: String? = "Kotlin"
   Expected Output: 6

Q15. Write a Kotlin program to demonstrate null safety when accessing an element of a nullable list.
   Input: val list: List<String>? = listOf("Kotlin", "Java")
   Expected Output: Kotlin

Q16. Write a Kotlin program to use ? let's print the length of a nullable string if it's not null.
   Input: val str: String? = "Programming"
   Expected Output: 11

Q17. Write a Kotlin program to use the !! operator on a nullable integer and print its value.
   Input: val num: Int? = 5
   Expected Output: 5

Q18. Write a Kotlin program to demonstrate how to use smart casting with a nullable variable.
   Input: val obj: Any? = "Kotlin"
   Expected Output: Kotlin (after smart casting)

Q19. Write a Kotlin program to safely cast an object to a specific type using as?.
   Input: val obj: Any? = 10
   Expected Output: 10

Q20. Write a Kotlin program to use safe casting to Int? and print the result.
   Input: val obj: Any? = "Kotlin"
   Expected Output: null

Q21. Write a Kotlin program to use the smart cast feature to check the type of an object.
   Input: val obj: Any = "Hello"
   Expected Output: "String"

Q22. Write a Kotlin program to check the type of a nullable object using the is operator.
   Input: val obj: Any? = 10
   Expected Output: "Integer"

Q23. Write a Kotlin program to smart cast a nullable type after checking it with the is operator.
   Input: val obj: Any? = "Hello"
   Expected Output: "Hello" (smart cast to String)

Q24. Write a Kotlin program to use smart cast with an else condition in an if statement.
   Input: val obj: Any? = 5
   Expected Output: "Integer"

Q25. Write a Kotlin program to handle a nullable variable using the when expression and smart cast.
   Input: val obj: Any? = 5
   Expected Output: "Integer"

Q26. Write a Kotlin program to safely perform a cast and handle the case where casting is not possible using as?.
   Input: val obj: Any? = "Kotlin"
   Expected Output: null

Q27. Write a Kotlin program to handle nullable variables in a when expression without explicit null checks.
   Input: val obj: Any? = null
   Expected Output: "Null value"

Q28. Write a Kotlin program to use smart casting within a function that checks if an object is of type String.
   Input: val obj: Any? = "Kotlin"
   Expected Output: "Kotlin"

Q29. Write a Kotlin program to safely access a nullable integer and perform arithmetic operations.
   Input: val num: Int? = 10
   Expected Output: 20 (adding 10)

Q30. Write a Kotlin program to handle a nullable object of type String and safely convert it to uppercase.
   Input: val str: String? = "kotlin"
   Expected Output: "KOTLIN"

Q31. Write a Kotlin program to safely access the first element of a nullable list.
   Input: val list: List<String>? = listOf("A", "B")
   Expected Output: "A"

Q32. Write a Kotlin program to use safe calls to perform operations on nullable objects.
   Input: val str: String? = "Kotlin"
   Expected Output: "Kotlin".toLowerCase()

Q33. Write a Kotlin program to use the !! operator on a nullable string and handle potential exceptions.
   Input: val str: String? = null
   Expected Output: NullPointerException

Q34. Write a Kotlin program to check if a nullable string contains a substring using safe calls.
   Input: val str: String? = "Kotlin"
   Expected Output: true

Q35. Write a Kotlin program to use as? to cast an object safely to String and print it.
   Input: val obj: Any? = "Kotlin"
   Expected Output: "Kotlin"

Q36. Write a Kotlin program to use the smart cast feature inside a function to safely cast and access properties.
   Input: val obj: Any? = "Hello"
   Expected Output: "Hello"

Q37. Write a Kotlin program to use the smart cast feature after checking type using is.
   Input: val obj: Any? = 10
   Expected Output: "Integer"

Q38. Write a Kotlin program to handle null safety in a list of nullable integers and print their sum.
   Input: val numbers: List<Int?> = listOf(1, 2, null, 4)
   Expected Output: 7

Q39. Write a Kotlin program to check and cast a nullable object to String using as?.
   Input: val obj: Any? = "Kotlin"
   Expected Output: "Kotlin"

Q40. Write a Kotlin program to use smart casting in a when expression to check the type and print the type name.
   Input: val obj: Any? = 10
   Expected Output: "Integer"

Q41. Write a Kotlin program to check if a nullable integer is positive or negative using null safety.
   Input: val num: Int? = -5
   Expected Output: "Negative"

Q42. Write a Kotlin program to use smart casting inside a when expression to check the type of a variable.
   Input: val obj: Any? = "Kotlin"
   Expected Output: "String"

Q43. Write a Kotlin program to use !! operator to assert that a nullable value is not null and perform an operation.
   Input: val num: Int? = 5
   Expected Output: 10

Q44. Write a Kotlin program to handle nullable values and perform arithmetic operations if the value is not null.
   Input: val num: Int? = 10
   Expected Output: 20

Q45. Write a Kotlin program to safely access the property of a nullable object using the safe call operator.
   Input: val person: Person? = Person("John", 25)
   Expected Output: "John"

Q46. Write a Kotlin program to use the let function with nullable types for null safety.
   Input: val str: String? = "Hello"
   Expected Output: "Hello"

Q47. Write a Kotlin program to safely cast a nullable string to uppercase using safe call operators.
   Input: val str: String? = "kotlin"
   Expected Output: "KOTLIN"

Q48. Write a Kotlin program to use the smart cast feature after checking the type in a conditional statement.
   Input: val obj: Any? = "Hello"
   Expected Output: "Hello"

Q49. Write a Kotlin program to perform a null safety check and print the value if it is not null.
   Input: val str: String? = "Kotlin"
   Expected Output: "Kotlin"

Q50. Write a Kotlin program to demonstrate smart casting in a when statement with multiple branches.
   Input: val obj: Any? = 100
   Expected Output: "Integer"

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