CODEWITHSUNDEEP
javamethodstypesargumentsrequired
Erich Jaeger
Erich Jaeger

Reputation: 23

How to set required constants for methods?

I am creating a method called setState and I want to use binary operators for it, but I want to create something to check if the passed argument is a constant defined in the class:

public static final int STATE1 = 0b1;
public static final int STATE2 = 0b10;
public static final int STATE3 = 0b100;
public void setState(int stateType, boolean state){
    if(state){
        this.state |= stateType;
    }else{
        this.state &= ~stateType;
    }
 }

So when I type setState(10, false) it will say: Wrong argument type, found x, required y

Upvotes: 0

Views: 62

Answers (2)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726479

One way to check a value against a group of allowed values is a Set<Integer> that contains all the allowed values. You can construct such set in a static constructor of the class, i.e.

private static final Set<Integer> allowedState = new HashSet<Integer>();
static {
    allowedState.add(STATE1);
    allowedState.add(STATE2);
    allowedState.add(STATE3);
}

Now you can check if the state passed to you is valid by verifying that allowedState contains stateType:

if (!allowedState.contains(stateType)) {
    // Throw an exception
}

To ensure that the allowedState set is immutable use Collcetions.unmodifiableSet(). Modifier final only ensures that the reference cannot be redinded to another object.

However, an approach based on raw int constants is not idiomatic to Java. A better way to achieve the same effect would be wrapping the states in an enum (tutorial), which would make sure that only a valid constant could be passed to your setState method:

public enum State {
    STATE1(0b1)
,   STATE2(0b10)
,   STATE3(0b100);

    private final int bitMask;
    State(int bitMask) { this.bitMask = bitMask; }
    public int getBitMask() { return bitMask; }
}

Upvotes: 1

Jarrett Spiker
Jarrett Spiker

Reputation: 401

you only want stateType to be one of STATE1, STATE2, or STATE3? You could use an enum defined in that class. Something like:

public class MyClass{
    public enum State{
        STATE1 (0b1),
        STATE2(0b10),
        STATE3(0b100);

      public final int value;
      State(int value){
        this.value = value;
      }
    }

   public void setState(State stateType, boolean state){
    if(state){
        this.state |= stateType.value;
    }else{
        this.state &= ~stateType.value;
    }
  }
}

Upvotes: 1

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