Enum Singleton: Constructor-less Instance vs Static Methods - Which Approach to Choose?

Deciding Between Enum Singleton Instance and Static Method Approaches

When using an Enum to create a singleton in Java, there are two common approaches: utilizing a constructor-less enum with instance methods, or employing a static method within the enum. Each approach offers its own nuances.

Constructor-less Enum with Instance Methods

<code class="java">public enum Elvis {
    INSTANCE;
    private int age;

    public int getAge() {
        return age;
    }
}</code>

In this example, the singleton is accessed via Elvis.INSTANCE.getAge(). This approach provides a clear instance of the object, allowing access to both instance-specific variables and methods.

Enum with Static Methods

<code class="java">public enum Elvis {
    INSTANCE;
    private int age;

    public static int getAge() {
        return INSTANCE.age;
    }
}</code>

In this case, the singleton is accessed using Elvis.getAge(). This approach emphasizes static methods, which are convenient when the singleton's behavior doesn't rely heavily on instance-specific variables.

Deciding Between the Approaches

The choice between these approaches depends on the specific requirements:

• Need for an Instance: If you require a specific instance with its own variables and methods, use the constructor-less enum with instance methods.
• Sufficiency of Static Methods: If static methods suffice for accessing the singleton's functionality, then the enum with static methods is a simpler solution.

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