[Applied] Build a Simple Inventory Management Tool

In this lesson you will build a simple inventory management program using a Kotlin map, putting everything you have learned together. This is for anyone searching for "Kotlin inventory management applied implementation".

Combine the maps and functions you have learned so far into a program that tracks stock levels. A map looks up and updates values quickly by key, which makes it one of the most heavily used data structures in real applications.

The sample code creates a map for stock with mutableMapOf<String, Int>(), sets quantities by product name as in items["apple"] = 10, and reduces stock with items.getValue("apple") - 3. Notice how for ((name, qty) in items) destructures the key and the value together.

A common stumbling block for beginners is what happens when you reach for a key that does not exist. getValue() throws on a missing key while [] access returns null, and not knowing that difference leads to confusing results.

The classes, error handling, and lists you have learned here are core Kotlin skills that carry over directly into real Android and backend development. Well done for getting this far.

📖 Reference code

fun main() {
    val items = mutableMapOf<String, Int>()
    items["apple"] = 10
    items["orange"] = 5
    items["apple"] = items.getValue("apple") - 3
    for ((name, qty) in items) {
        println("${name}: ${qty}")
    }
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).