How can I make an object available to all classes in my project without including it as a field?

Question

I am making a text adventure engine in Java, and in order to save memory, I have a database object that holds all the currently scraped items from an XML document. I want to use it from several different classes. How can I make it available to my classes? Currently I'm using a null static field with an appropriate mutator method.

Answer 1

It might be useful to use a Singleton for this.

Answer 2

You can use a enum type. Joshua Bloch says in his book Efective Java: a single-element enum type is the best way to implement a singleton.

public enum Elvis {
    INSTANCE;
    public void leaveTheBuilding() { ... }
}