Singleton – the proper way

Question

public enum YourSingleton {
    INSTANCE;

    public void doStuff(String stuff) {
        System.out.println("Doing " + stuff);
    }
}

YourSingleton.INSTANCE.doStuff("some stuff");

Here is the original link, http://electrotek.wordpress.com/2008/08/06/singleton-in-java-the-proper-way/

I am asking why we can call the function doStuff this way in Java.

Answer 1

In Java, enum can do everything that class can [1]. YourSingleton.INSTANCE creates an instance of YourSingleton, so you can then invoke methods as if it were a regular class instance, which it basically is.

See the official Java docs for a more in-depth discussion on Enum Types: http://download.oracle.com/javase/tutorial/java/javaOO/enum.html

[1] enum does not have a practical implementation of inheritance. Since all enum types implicity inherit java.lang.Enum and Java does not support multiple inheritance, you cannot extend anything else.