What methods exist to improve code efficiency and cleanliness in Kotlin?

To improve the efficiency and cleanliness of Kotlin code, the following methods can be used:

• Using extension functions: Allow adding new functions to existing classes without inheritance.

• Using data classes: For automatic generation of equals(), hashCode(), toString(), and copy methods.

• Using lambdas and functional operations: For concise and expressive code (e.g., map, filter, fold).

• Using sealed classes: For safe handling of a limited set of types, which improves readability and safety.

• Using inline functions: To reduce overhead when using lambdas.

• Using apply, also, let, run, and with: To improve readability and reduce code duplication.

• Avoiding the !! operator: To prevent NullPointerException and use safe calls ?..

• Using coroutines: For asynchronous and non-blocking code.

Example of using extension functions and apply:

fun String.isEmailValid(): Boolean {
    return this.contains("@") && this.contains(".")
}

val user = User().apply {
    name = "John"
    age = 30
}

These methods help write cleaner, more readable, and maintainable code.