Type constraints with upper bounds in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic function with an upper bound on type parameter T.

Kotlin

fun <T [1] Number> printNumber(value: T) {
    println(value)
}

Drag options to blanks, or click blank then click option'

A<:

B:

C>:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' instead of '<:' for upper bounds.

Using '>' or '=' symbols which are incorrect here.

In Kotlin, to specify an upper bound for a generic type parameter, use the '<:' symbol.

2fill in blank

medium

Complete the code to declare a class with a generic type parameter T that must be a subtype of Comparable<T>.

Kotlin

class Box<T [1] Comparable<T>> {
    fun compareTo(other: T): Int {
        return 0
    }
}

Drag options to blanks, or click blank then click option'

A:

B>:

C<:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' instead of '<:'.

Confusing upper bound syntax with inheritance syntax.

The '<:' symbol is used to specify that T must be a subtype of Comparable.

3fill in blank

hard

Fix the error in the generic function declaration to correctly specify the upper bound for T.

Kotlin

fun <T [1] Any> printValue(value: T) {
    println(value)
}

Drag options to blanks, or click blank then click option'

A<:

B:

C>:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' which is incorrect for upper bounds.

Using '=' or '>' symbols.

The correct syntax for upper bounds in Kotlin generics is '<:'.

4fill in blank

hard

Fill both blanks to declare a generic function where T is a subtype of Number and R is a subtype of Comparable<R>.

Kotlin

fun <T [1] Number, R [2] Comparable<R>> process(value: T, other: R) {
    println(value)
    println(other)
}

Drag options to blanks, or click blank then click option'

A<:

B:

C>:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing ':' and '<:' symbols.

Using '>' or '=' which are incorrect.

Both T and R use '<:' to specify their upper bounds in Kotlin generics.

5fill in blank

hard

Fill all three blanks to declare a generic class with T, R, and S having upper bounds Number, Comparable<R>, and Any respectively.

Kotlin

class Container<T [1] Number, R [2] Comparable<R>, S [3] Any> {
    fun display(t: T, r: R, s: S) {
        println(t)
        println(r)
        println(s)
    }
}

Drag options to blanks, or click blank then click option'

A<:

B:

C>:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' or other symbols instead of '<:'.

Inconsistent symbols for different type parameters.

All type parameters use '<:' to specify their upper bounds in Kotlin generics.