Singletons, Enums and anonymous inner classes

Question

As you may know, some people are declaring singletons with an Enum of 1 instance, because the JVM guarantees that there will always be a single instance with no concurrency

Answer 1

Add

       public String getFormattedPrice(float input) {
        return input + " €";
    }

outside the overrides as the default implementation. (Next to the declaration of getPrice.) And you are good to go.

You can also have enums implement interfaces, to define what everybody needs to implement.