java – 将SuperClass的对象转换为子类

超级

public class Actual {
    public int x = 123;
}

子类

public class Super extends Actual{
    public int x = 999;
    public int y = 12345;
}


public class Sub extends Super {
    public int x = 144;
}

问题是我可以将超类的对象转换为子类吗？
这是对这个问题的权利,我试过了什么？

public class Mid1Prob1 {
    public static void main(String[] args) {
        System.out.println("Testing...");
        int x = 3;
        Actual actual = new Super();
        System.out.println(actual.x);


        Super super1 = new Super();
        System.out.println(super1.x);


        Actual act = new Actual();

        act = new Sub();
        System.out.println(act.x);
    }
}

但它给出了Class Cast异常.