CODEWITHSUNDEEP
javaconstants
fxmasa
fxmasa

Reputation: 834

Define constants in Java and use them in a collection

I have a class similar to this:

class DomainTypes {
  public static final DomainType DOMAIN_1 = DomainType.of("example1.com");
  public static final DomainType DOMAIN_2 = DomainType.of("example2.com");
  public static final DomainType DOMAIN_3 = DomainType.of("example3.com");

  public static Set<DomainType> getDomainTypes() {
    return ImmutableSet.of(
      DOMAIN_1, DOMAIN_2, DOMAIN_3
    );
  }
}

But this is error prone. In case somebody adds a domain as a new constant, she can forget to add it into getDomainTypes() method. I don't want to use reflection if possible.

I need to have DomainType class in different module (jar) - kind of API module - let's say dns-api module, than DomainTypes. DomainTypes is rather configuration and it is in web-app module, which is dependent on dns-api module. With enum, I couldn't separate configuration from the object with implemented logic and I wouldn't be able to reuse dns-api module in another application. So I think tha using enum is not a solution for me.

Upvotes: 1

Views: 803

Answers (1)

Jesper
Jesper

Reputation: 206796

Use an enum instead of a class with constants:

public enum DomainType {
    DOMAIN_1("example1.com"),
    DOMAIN_2("example2.com"),
    DOMAIN_3("example3.com");

    private final String url;

    DomainType(String url) {
        this.url = url;
    }

    public String getUrl() {
        return url;
    }
}

Enums automatically have a values() method which gives you an array of all the values:

DomainType[] domainTypes = DomainType.values();

Upvotes: 1

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