📌 Maps in Kotlin

In Kotlin, a Map is a collection of key-value pairs where keys are unique, and each key is associated with exactly one value. Maps are useful when you want to store data in a key-value format, like a dictionary.

Kotlin provides two types of Maps:

1. Immutable Map (Map) → Read-only (Cannot be modified).

2. Mutable Map (MutableMap) → Can be modified (Add, Remove, or Update key-value pairs).

✅ 1. Creating Maps in Kotlin

📌 Immutable Map

• Use mapOf() to create a read-only map.

kotlin
fun () {    val fruits = mutableMapOf("Apple" to 5, "Banana" to 10, "Orange" to 7)    println(fruits)    // Adding a new key-value pair    fruits["Mango"] = 12    // Removing a key    fruits.remove("Banana")    // Updating a value    fruits["Apple"] = 8    println(fruits)}

Output:

mathematica
{Apple=5, Banana=10, Orange=7}{Apple=8, Orange=7, Mango=12}

• fruits["key"] = value → Add or Update.

• remove() → Remove a key-value pair.

✅ 2. Accessing Map Elements

You can access map elements using the key:

📌 Example:

kotlin
val capitals = mapOf("France" to "Paris", "Italy" to "Rome", "Germany" to "Berlin")println("Capital of France: ${capitals["France"]}") println(Capital of France: ParisCapital of Spain: Not Found

• map[key] → Returns value or null if the key doesn't exist.

• ?: → Provides a default value using the Elvis operator.

✅ 3. Map Functions in Kotlin

✅ 4. Iterating Through a Map

📌 Using For Loop:

kotlin
val students = mapOf(101 to "John", 102 to "Emma", 103 to "Liam")for ((id, name) in students) {    println("Student ID: $id, Name: Student ID: 101, Name: JohnStudent ID: 102, Name: EmmaStudent ID: 103, Name: Liam

• Destructure using (key, value) inside the loop.

📌 Using forEach:

kotlin
students.forEach { (key, value) -> println("$key -> 101 -> John102 -> Emma103 -> Liam

✅ 5. Filtering Maps

You can filter key-value pairs using filter or filterKeys.

📌 Filter by Values:

kotlin
val products = mapOf("Laptop" to 50000, "Phone" to 30000, "Tablet" to 20000)val expensiveProducts = products.filter { it.value > 30000 }println(expensiveProducts)

Output:

{Laptop=50000}

📌 Filter by Keys:

kotlin
val filteredKeys = products.filterKeys { it.startsWith("P") }println(filteredKeys)

Output:

{Phone=30000}

✅ 6. Map Transformations

You can transform maps using mapValues() or mapKeys().

📌 Example:

kotlin
val numbers = mapOf(1 to 10, 2 to 20, 3 to 30)// Double the valuesval doubledValues = numbers.mapValues { it.value * 2 }println(doubledValues)// Prefix keysval prefixedKeys = numbers.mapKeys { "Key${it.key}" }println(prefixedKeys)

Output:

{1=20, 2=40, 3=60}{Key1=10, Key2=20, Key3=30}

✅ 7. Conclusion

• Use mapOf() for immutable maps and mutableMapOf() for mutable ones.

• Access elements using map[key] or get().

• Use filter, mapValues, or mapKeys for transformations.

• Iterate using for loops or forEach.

• Efficient for representing key-value data like dictionaries, configurations, and mappings.