Multiple type parameters in Kotlin - Mini Project: Build & Apply

Using Multiple Type Parameters in Kotlin

📖 Scenario: Imagine you are building a simple app to store pairs of related information, like a person's name and their age, or a product and its price.

🎯 Goal: You will create a generic class in Kotlin that uses two type parameters to hold pairs of values of different types. Then, you will create an instance of this class and print its contents.

📋 What You'll Learn

Create a generic class called PairBox with two type parameters: A and B

Add two properties to PairBox: first of type A and second of type B

Create a variable called person that is an instance of PairBox holding a String and an Int

Print the values of person.first and person.second in a friendly sentence

💡 Why This Matters

🌍 Real World

Generic classes with multiple type parameters are useful when you want to store or work with pairs or groups of related data of different types, like key-value pairs or coordinate points.

💼 Career

Understanding generics and multiple type parameters is important for writing reusable and type-safe code in Kotlin, which is widely used in Android app development and backend services.

1

Create the generic class with two type parameters

Create a generic class called PairBox with two type parameters A and B. Inside the class, declare two properties: first of type A and second of type B.

Kotlin

# Your code here

Need a hint?

Use the syntax class PairBox(val first: A, val second: B) to define the class.

2

Create an instance of PairBox

Create a variable called person and assign it an instance of PairBox with String and Int as type arguments. Use the values "Alice" for first and 30 for second.

Kotlin

class PairBox(val first: A, val second: B)

# Your code here

Need a hint?

Use val person = PairBox("Alice", 30) to create the instance.

3

Access the properties of the PairBox instance

Write a variable called description that uses string interpolation to create a sentence: "Name: person.first, Age: person.second".

Kotlin

class PairBox(val first: A, val second: B)

val person = PairBox("Alice", 30)

# Your code here

Need a hint?

Use val description = "Name: ${person.first}, Age: ${person.second}" to create the sentence.

4

Print the description

Write a println statement to print the variable description.

Kotlin

class PairBox(val first: A, val second: B)

val person = PairBox("Alice", 30)

val description = "Name: ${person.first}, Age: ${person.second}"

# Your code here

Need a hint?

Use println(description) to show the sentence on the screen.