lombok
Annotation Type NonNull

@Target(value={FIELD,METHOD,PARAMETER,LOCAL_VARIABLE})
@Retention(value=CLASS)
@Documented
public @interface NonNull

Lombok is smart enough to translate any annotation named @NonNull in any casing and with any package name to the return type of generated getters and the parameter of generated setters and constructors, as well as generate the appropriate null checks in the setter and constructor. You can use this annotation for the purpose, though you can also use JSR305's annotation, findbugs's, pmd's, or IDEA's, or just about anyone elses. As long as it is named @NonNull. WARNING: If the java community ever does decide on supporting a single @NonNull annotation (for example via JSR305), then this annotation will be deleted from the lombok package. If the need to update an import statement scares you, you should use your own annotation named @NonNull instead of this one.