스파르타 spring 2기 TIL day16

// ==================================================
// STUDY: note about static method hiding
// ==================================================

class Static {
    static class Parent {
        // static methods can't be an abstract method, WHY?:
        // abstract public static void sayHi() { // deosn't compile
        public static void sayHi() {
            System.out.println("Hi, I'm parent.");
        }
    }

    static class Child extends Parent{
        // it also can't be overriden, WHY??
        // @Override
        public static void sayHi() {
            System.out.println("Hi, I'm child.");
        }
    }

    public static void main(String[] args) {
        // let's see this example
        Child child = new Child(); 
        child.sayHi(); // this prints "Hi, I'm child.", as expected

        Parent who = new Child();
        who.sayHi();

        // but guess who is going to say?
        // IT SAYS "Hi, I'm parent."!!!
        //
        // It's because java deduce which static method to call at compile time using type.
        // 
        // Meaning it can't get the information on Object's class since that's runtime information.
    }
}