Primary constructor and init blocks in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a primary constructor with a parameter name.

Kotlin

class Person [1](val name: String) {}

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

Avar

Bfun

Cconstructor

Dinit

Attempts:

3 left

💡 Hint

Common Mistakes

Using fun instead of constructor.

Using var or init in the constructor declaration.

In Kotlin, the primary constructor is declared right after the class name using the constructor keyword or directly with parameters. Here, constructor keyword is used explicitly.

2fill in blank

medium

Complete the code to initialize the age property inside the init block.

Kotlin

class Person(val name: String, val age: Int) {
    init {
        println("Age is [1]")
    }
}

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

Aage

Bname

Cthis

Dconstructor

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use this without a property name.

Using name instead of age.

Inside the init block, you can access the primary constructor parameters directly by their names. Here, age is printed.

3fill in blank

hard

Fix the error in the primary constructor declaration by filling the blank.

Kotlin

class Car [1] val model: String, val year: Int) {}

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

A[

B{

C<

D(

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces or square brackets instead of parentheses.

Forgetting the opening parenthesis.

The primary constructor parameters must be enclosed in parentheses after the class name.

4fill in blank

hard

Fill both blanks to create a property color with a default value and print it in the init block.

Kotlin

class Bike(val model: String, val year: Int, val color: String = [1]) {
    init {
        println("Bike color is [2]")
    }
}

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

A"red"

Bcolor

Cmodel

D"blue"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong default value syntax.

Printing model instead of color.

The property color is given a default value "red". Inside the init block, the property color is printed.

5fill in blank

hard

Fill all three blanks to create a class with a primary constructor, an init block that prints a greeting, and a property greeting initialized from the constructor.

Kotlin

class Greeter [1](val name: String) {
    val greeting = "Hello, [2]!"
    init {
        println([3])
    }
}

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

Aconstructor

Bname

Cgreeting

Dinit

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the constructor keyword.

Using init instead of greeting in the print statement.

The primary constructor is declared with constructor. The property greeting uses the name parameter. The init block prints the greeting property.