How to implement thread-safe lazy initialization?

Question

What are some recommended approaches to achieving thread-safe lazy initialization? For instance,

// Not thread-safe
public Foo getI         


        

Answer 1

If you use lombok in your project, you can use a feature described here.

You just create a field, annotate it with @Getter(lazy=true) and add initialization, like this: @Getter(lazy=true) private final Foo instance = new Foo();

You'll have to reference field only with getter (see notes in lombok docs), but in most cases that's what we need.