In which cases is it recommended to use built-in functions in the code?

Built-in functions are recommended to be used when:

• You need to improve performance, as built-in functions are often optimized at the compiler or platform level.
• You require the use of standard, proven operations to avoid errors and enhance code readability.
• You want to simplify the code by using ready-made solutions instead of writing custom code.

For example, in Android when working with collections, you can use Kotlin's built-in functions such as map, filter, forEach, which make the code more concise and understandable:

val numbers = listOf(1, 2, 3, 4, 5)
val evenNumbers = numbers.filter { it % 2 == 0 }
evenNumbers.forEach { println(it) }

Using built-in functions also helps follow the idiomatic style of the language and makes code maintenance easier.