Maps

Maps are a type of collection in Kotlin that store key-value pairs. Unlike arrays and lists, which use indices to access elements, maps use keys to look up values. This section will guide you through the basics of working with maps in Kotlin.

Defining Maps

Syntax

The basic syntax for defining a map in Kotlin is as follows:

val mapName = mapOf(key1 to value1, key2 to value2, ...)

Example

Here's a simple map that associates names with ages.

val ageMap = mapOf("Alice" to 30, "Bob" to 25, "Charlie" to 40)

Accessing Elements

Syntax

You can access the value associated with a key using the following syntax:

mapName[key]

Example

Fetching the age of "Alice" from the ageMap.

val aliceAge = ageMap["Alice"]  // Result: 30

Mutable Maps

Syntax

Kotlin also provides mutable maps that allow you to add or remove key-value pairs.

val mutableMap = mutableMapOf(key1 to value1, key2 to value2, ...)

Example

val mutableAgeMap = mutableMapOf("Alice" to 30, "Bob" to 25)
mutableAgeMap["Charlie"] = 40  // Adds "Charlie" with age 40 to the map

Removing Elements

Syntax

To remove a key-value pair from a mutable map, you can use the remove method.

mutableMap.remove(key)

Example

mutableAgeMap.remove("Alice")  // Removes "Alice" from the map

Summary and Best Practices

• Use maps when you need to associate keys with values for quick lookups.
• Prefer using mapOf for read-only maps and mutableMapOf for maps that will be modified.
• Always specify the types of keys and values explicitly for better readability.

Maps are a powerful tool for storing key-value pairs in Kotlin. They are especially useful in scenarios where you need fast access to data based on some unique identifiers, making them invaluable in Android Native development and data manipulation tasks.