When to use If-else if-else over switch statements and vice versa [duplicate]

Answer 1

This depends very much on the specific case. Preferably, I think one should use the switch over the if-else if there are many nested if-elses.

The question is how much is many?

Yesterday I was asking myself the same question:

public enum ProgramType {
    NEW, OLD
}

if (progType == OLD) {
    // ...
} else if (progType == NEW) {
    // ...
}

if (progType == OLD) {
    // ...
} else {
    // ...
}

switch (progType) {
case OLD:
    // ...
    break;
case NEW:
    // ...
    break;
default:
    break;
}

In this case, the 1st if has an unnecessary second test. The 2nd feels a little bad because it hides the NEW.

I ended up choosing the switch because it just reads better.

Answer 2

I have often thought that using elseif and dropping through case instances (where the language permits) are code odours, if not smells.

For myself, I have normally found that nested (if/then/else)s usually reflect things better than elseifs, and that for mutually exclusive cases (often where one combination of attributes takes precedence over another), case or something similar is clearer to read two years later.

I think the select statement used by Rexx is a particularly good example of how to do "Case" well (no drop-throughs) (silly example):

Select
    When (Vehicle ¬= "Car") Then
        Name = "Red Bus"
    When (Colour == "Red") Then
        Name = "Ferrari"
    Otherwise
        Name = "Plain old other car"
    End

Oh, and if the optimisation isn't up to it, get a new compiler or language...

Answer 3

If you are switching on the value of a single variable then I'd use a switch every time, it's what the construct was made for.

Otherwise, stick with multiple if-else statements.

Answer 4

The tendency to avoid stuff because it takes longer to type is a bad thing, try to root it out. That said, overly verbose things are also difficult to read, so small and simple is important, but it's readability not writability that's important. Concise one-liners can often be more difficult to read than a simple well laid out 3 or 4 lines.

Use whichever construct best descibes the logic of the operation.