java.util.Objects utility class comes with a useful null-check assertions:
Instead of checking a variable with if-statements you can use the built-in method:
import static java.util.Objects.requireNonNull;
requireNonNull(this.script, "Cannot initialize ScriptableSink without script.");
The sample above was borrowed from enhydrator.
See you at Java EE Workshops at Munich Airport, Terminal 2 or Virtual Dedicated Workshops / consulting. Is Munich's airport too far? Learn from home: effectivejavaee.com.