Question

public class Test {
    class Foo {
        int frob() {
            return 7;
        }
    }

    class Bar extends Foo {
        @Override
        int frob() {
            return 8;
        }
    }

    class Baz extends Foo {
        @Override
        int frob() {
            return 9;
        }
    }

    public static int quux(Bar b) {
        return b.frob();
    }

    public static void main(String[] args) {
        System.out.println(quux(new Bar()));//this line gives non-static variable this cannot be referenced from a static context
    }

}

Answer 1

You can fix this by declaring the nested classes as static, OR by instantiating Bar in the context of an instance of Test.

It fails because (the non-static) Bar must be instantiated in the context of an existing Test class instance; since main is static, there is no such beast.