CODEWITHSUNDEEP
javavariablesswitch-statement
leif_good
leif_good

Reputation: 386

An adjustable/variable switch case in java

I have a lot of methods that look like the following:

switch(myEnum) {
    case a :
    case b :
    case c :
    case d :
        modifier = 1.1;
        break;
    default :
        break;
}

It would be perfect if i had the opportunity to make every case and the modifier variable, so i can have one method with 6 parameters, 4 for the cases and 2 for the modifier. Something like the following (pseudo):

public void setModifier(case1, case2, case3, case4, modifier, value) {
    switch(myEnum) {
        case case1 :
        case case2 :
        case case3 :
        case case4 :
            modifier = value;
            break;
        default :
            break;
    }
}

modifier and value shouldnt be a problem, but how do i solve the variable switch cases? Is this even possible in java with a switch-statement?

Upvotes: 2

Views: 1680

Answers (1)

Arne Burmeister
Arne Burmeister

Reputation: 20614

There are multiple problems with this approach:

  • You cannot change the value of a parameter passed so that the value is changed for the calling code (in Java, except for a holder kind type like AtomicReference etc).
  • Trying to make code generic because of possible reuse is not always a good idea, this tends to create complex generic code instead of readable specific.
  • It looks like your code is mostly an if, so why note write it in this way?

If I understand your snippet right, I would try the following inline approach:

if (EnumSet.of(a, b, c, d).contains(myEnum)) {
  modifier = 1.1;
}

This is from my perspective much cleaner and therefore has less need to extract it in a general way and very flexible (any number of enum values and any kind of action possible).

If you really need such an approach, a functional interface can do the job:

setModifier(myEnum, () -> modifier = 1.1, a, b, c, d);

public <E extends Enum<E>> void setModifier(E current, Runnable action, E... allowed) {
  Arrays.stream(allowed)
      .filter(one -> one == current)
      .findAny()
      .ifPresent(found -> action.run());
}

As you can see this creates a lot more code which is not necessary if not used spread around classes very often. The code above only works for modifier being a member not a local variable due to implicit final behavior.

Upvotes: 5

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