class A { }

class B extends A { void bla() { System.out.println("Class B blabla."); } }

class C {

    A a = new A();

    void assign (A[] v) {
	v[0] = a;
    }

    public static void main (String[] args) {
	C c = new C();
	B[] v = new B[1];
	c.assign (v);
	v[0].bla();
    }
}