While this Question is likely too broad for Stack Overflow, a few thoughts.
Enums
You may not fully understand the enum facility in Java. See the Oracle Tutorial, and see the Enum class doc.
An enum is a class, a regular Java class, a subclass of Enum. The only thing special is that syntactic sugar that automatically instantiates the static instances you define and name. Otherwise, they are normal classe:
- Your enums can carry member variables.
- Your enums can have constructors, and you can pass arguments to those constructors.
- Your enums can offer other methods, and you can pass arguments to those methods.
- You can even pass instances of one enum as arguments to methods of another enum’s instances – just as you might pass instances of an enum to instances of other non-enum classes. Each enum instance is just an object, plain and simple, saved as a static reference on the enum-defining class.
Example:
public enum Food { HERBIVORE, OMNIVORE, CARNIVORE ; } // Syntactic sugar for automatically instantiating these named static instances of this class type.
…and…
public enum Animal {
RABBIT( Food.HERBIVORE ) ,
DOG( Food.OMNIVORE ) ,
CAT( Food.CARNIVORE ) ;
// Member variables.
public Food eats ;
// Constructor
Animal( Food foodType ) {
this.eats = foodType ; // Assign an instance of another enum to this instance of this enum.
}
}
Limitations of enums
While more powerful and useful than in other languages, there are limitations.
Compile-time
Firstly, enums are defined at compile-time. If your values change at runtime, perhaps you want to add or delete items, then enums are not appropriate.
Permanently in memory
Also, enums are static. This means when first used, all the objects of that enum class are instantiated immediately and held in memory throughout the execution of your app. So they are never retired from memory until program ends. So having an enormous number of them might be a burden on memory.
Understand that your can collect enum instances. See the EnumSet and EnumMap classes for fast-to-execute and low-memory usage collections of enum instances. Search Stack Overflow for much coverage on this topic. And be aware that every enum carries a values() method that returns an array of its values, yet this method is mysteriously not listed in the JavaDoc.
As for your mention inheritance, your enums by definition are subclasses of Enum class. So they cannot inherit from any other class you may have in mind, as Java does not support multiple-inheritance. Your enums can implement one or more interfaces. In later version of Java, an inheritance can carry implementation code by way of new default methods, so you can pass along some code that way.
Internationalization
Internationalization and localization seems to be an orthogonal issue. You can add a method on your enum to generate localized String representation of their value. As an example, see DayOfWeek::getDisplayName and Month::getDisplayName enum methods.
Database
If you want to dynamically define your values at runtime, or you have zillions of them, then a database is the way to go. A serious database such as Postgres is designed to manage memory, handle concurrency, and execute efficiently.
You can even combine enums with the database. For example, localization. You might have enum values defined at compile-time, but their getDisplayName method does a lookup into a database to find the French or Arabic translation. That translation value in the database can be updated during runtime by running SQL INSERT or UPDATE commands via JDBC.
Recursive hierarchical relationships
If you are trying to represent relationships of a hierarchy of arbitrary depth, that is a whole other topic I'll not address here other than to say that is often implemented with recursion. Search Stack Overflow and other sources to learn more.
