Don't create supperclass instance in contructor of subclass, but fully legal

Question

I read in scjp guide as following

In fact, you can't make a new object without invoking not just the constructor of the object's actual class type, but also the constructor of each of its superclasses!

For example

public class Person{

}

public class Employee extends Person{
   public Employee(){
}
}

I don't create a Person instance but it is legal.

Please explain for me, thank for your help.

Answer 1

Whenever you instantiate a subclass, it'll call your superclass' constructor first.

You can find more about this here: JSL §8.8.7

Person.java

public class Person {
    public Person() {
        System.out.println("Super class constructor called");
    }
}

Employee.java

public class Employee extends Person {
    public Employee() {
        System.out.println("Sub class constructor called");
    }
}

If you then instantiate your Employee:

Employee e = new Employee();

Output:

Super class constructor called

Sub class constructor called