Doing a membership check on a container vs having multiple ifs?

Question

What is better?

if ("a".equals(x) || "b".equals(x)) {
    //do something
}

vs

private static List<String> validAlphabets = ImmutableList.of("a", "b");
if (validAlphabets.contains(x)) {
    //do something
}

The above code sample is in Java, but this applies to any programming language.

Is one approach better than the other?

One other case would be as follows:

if ("a".equals(x)) {
    return "hello a";
}
else if ("b".equals(x)) {
    return "bye b";
}

This can be written as a Map<String,String>

Answer 1

I would argue for the second approach, for the following reasons:

1. There's less chance of making a mistake if you need to add or remove items from the list at some point in the future.
2. Being able to name the variable (validAlphabets in your case) gives you a valuable opportunity to make your code a little more self-documenting.