That's right, I forgot a method parameter: jshell> class Foo { void foo(Object o) { System.out.println("Super"); } } | created class Foo jshell> class

That's right, I forgot a method parameter: jshell> class Foo { void foo(Object o) { System.out.println("Super"); } } | created class Foo jshell> class Bar extends Foo { void foo(Integer i) { System.out.println("Sub"); } } | created class Bar jshell> Foo f = new Bar(); f ==> Bar@7f9a81e8 jshell> Integer i = 1; i ==> 1 jshell> f.foo(i) Super jshell> ((Bar)f).foo(i); Sub