Kotlin ‘Enum.values()’ is recommended to be replaced by ‘Enum.entries’

Kotlin 1.9.2 introduced a new feature Enum.entries. What is it, and why is it preferred over Enum.values()?

How do Enum.values() work?

Enum.values()

It creates a New Mutable Array every time you use it.

1. Every time it is called, a new array is created, which can lead to performance issues if not used properly.
2. It returns an Array, which you probably will want to convert into a list, which leads to even more computing.
3. It’s mutable, which is something you might not expect, and leads to hard-to-fix bugs.

val values = Enum.values() // Can affect performance if too many arrays are created
values[0] = Enum.TWO // Array is mutable meaning it's easy to introduce unexpected bugs

In this example, a new array is created and then one of its elements is replaced.

How do Enum.entries work?

Enum.entries

It returns a Constant Immutable List.

1. It works faster because we don’t need to copy the array we access a defined constant.
2. It’s a List instead of Array, which lets us use all the Collection extensions without creating a List.
3. It’s immutable, which is something you would expect when accessing enums.

val entries = Enum.entries // Returns a constant Immutable List
entries.add(Enum.TWO) // Compilation error
entries[0] = Enum.TWO // Compilation error

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Article based on:

Enum classes | Kotlin