How to mark a method obligatory?

Question

Suppose you create a class names Person using the builder pattern, and suppose the Builder class contains methods body(), head(), arms()

Answer 1

No way with the compiler.

You can do is throw a runtime exception from the build() method that the builder is not properly initialized (and have a test that is invoked in the maven test phase)

But you can also have build(..) accept a HeadDetails object. That way tou can't invoke build without specifying the obligatory parameters.