Private method of call from Child Object

Question

class Parent {
    public Parent() {
        System.out.println("Parent Default..");
        System.out.println("Object type : " + this.getClass().getName());
        this.method();
    }

    private void method() {
        System.out.println("private method");
    }
}

class Child extends Parent {
    public Child() {
        System.out.println("Child Default..");
    }

    public static void main(String[] args) {
        new Child();
    }
}

When I run this code it prints the class name of "this" = Child but the "this" object is able to call the private method of parent class why?

Answer 1

First of all, when calling new Child(), since there is not a declared non-argument constructor in Child class, it will simple call super() which is invoking the Parent constructor.

Then, when executing this.getClass().getName(), here this stands for a Child instance, this is why you get "Child" as the result. Remember, Object#getClass() returns the most specific class the object belongs to. see more from here.

About why this.method() works. First, because Child extends Parent, the Child instance is also a Parent instance. The java scope modifier controls where the methods or fields can be accessed. Taking Parent#method() as the example, the private modifier indicates that this method can only be accessed (invoked) inside the Parent class. And this is exactly how you code does. it invokes the method inside the constructor of Parent class, which compiles the rule. See more about java access control from here