A--- B----
 i |  j  |
[4 |  56]|


class A {
    int i;
    
    A(int i) { this.i = i; }
}

class B extends A {
    int j;

    B() {           // (1)
        super(4);
        j = 56;
    }
}



new B() -> constr (1)

((A)new B()).a



// for (A a : as) {
for (int i = 0; i < as.length(); ++i) {
    A a = as.get(i);
    if (a instanceof B1) {
        B1 b1 = (B1)a;
        b1.someFunction();
    }
}