从超类Java实例化子类

Question

I want to try and instantiate a Child object that extends Parent with the properties of a previously instantiated parent object. So something like this:

class Parent {
    ClassName property1;

    // Setters and getters
}

class Child extends Parent {
    public Child(Parent parent) {
        this.property1 = parent.getProperty1();
        // + other properties
    }
}

Parent parent = new Parent();
parent.setProperty1(prop);

Child object = (Child)parent; // Casting exception
Child object2 = new Child(parent); // This is not ideal

Is there any other way to achieve this?

Answer 1

First look up polymorphism. It seems you're not familiar with one of the main features of an OOP language.

Second, you need to instantiate your parent like this

Parent p = new Child();

Child c = (Child) p;