Void class

https://docs.oracle.com/javase/7/docs/api/java/lang/Void.html

The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.

Say you want to have a generic that returns void for something:

제너릭 리턴타입을 void로 가지고싶을 때

abstract class Foo<T>{ abstract T bar();}class Bar extends Foo<Void>{ Void bar() { return (null); }}

또는

It also contains Void.TYPE, useful for testing return type with reflection:

리플렉션에서 void 타입을 검증할 때

public void foo() {}...if (getClass().getMethod("foo").getReturnType() == Void.TYPE) ...