GroupBy for categorization in Kotlin - Mini Project: Build & Apply

GroupBy for categorization

📖 Scenario: You work in a bookstore. You have a list of books with their genres. You want to group the books by their genre to organize the store better.

🎯 Goal: Build a Kotlin program that groups a list of books by their genre using groupBy.

📋 What You'll Learn

Create a list of books with exact titles and genres

Create a variable to hold the grouped books

Use groupBy to group books by genre

Print the grouped books

💡 Why This Matters

🌍 Real World

Grouping items by categories is common in organizing data, like sorting books by genre in a bookstore.

💼 Career

Understanding how to group data helps in data analysis, reporting, and building features like filters in apps.

1

Create the list of books

Create a list called books with these exact entries: "The Hobbit" to "Fantasy", "1984" to "Dystopian", "The Catcher in the Rye" to "Classic", "The Lord of the Rings" to "Fantasy", and "Brave New World" to "Dystopian".

Kotlin

# Create the list of books with titles and genres
# Your code here

Need a hint?

Use listOf with pairs of book title and genre using to.

2

Create a variable for grouped books

Create a variable called groupedBooks to hold the result of grouping books by genre.

Kotlin

val books = listOf(
    "The Hobbit" to "Fantasy",
    "1984" to "Dystopian",
    "The Catcher in the Rye" to "Classic",
    "The Lord of the Rings" to "Fantasy",
    "Brave New World" to "Dystopian"
)
# Create a variable called groupedBooks to hold grouped books
# Your code here

Need a hint?

Use groupBy on books and group by the genre, which is the second element of each pair.

3

Group books by genre using groupBy

Use groupBy on books with a lambda that selects the genre (the second element) to group the books. Store the result in groupedBooks.

Kotlin

val books = listOf(
    "The Hobbit" to "Fantasy",
    "1984" to "Dystopian",
    "The Catcher in the Rye" to "Classic",
    "The Lord of the Rings" to "Fantasy",
    "Brave New World" to "Dystopian"
)

val groupedBooks = books.groupBy { it.second }
# Your code here

Need a hint?

The grouping is done by the genre, which is the second part of each pair.

4

Print the grouped books

Print the groupedBooks variable to show the books grouped by genre.

Kotlin

val books = listOf(
    "The Hobbit" to "Fantasy",
    "1984" to "Dystopian",
    "The Catcher in the Rye" to "Classic",
    "The Lord of the Rings" to "Fantasy",
    "Brave New World" to "Dystopian"
)

val groupedBooks = books.groupBy { it.second }

# Print the groupedBooks variable
# Your code here

Need a hint?

Use println(groupedBooks) to display the grouped map.