Type Casting ??? What is type casting?

class CodeRunner{
    public static void main(String[] args){
        int intNum = 1000;
        //You do not need to specify type casting when you put the value of int, which is a small bowl, in a large bowl, long.
        long longNum = intNum;

        //If you do not explicitly type cast with int as below,
        //posible lossy conversion from long to int error
        intNum = (int)longNum;
    }
}

class CodeRunner{
    public static void main(String[] args){
        //Human who inherited Animal can type casting with Animal
        Human humanObject1 = new Human();
        Animal animalObject1 = humanObject1;

        // However, on the contrary, Human cannot be typecasted as Animal
        // Because Human includes all the functions of Animal 
        // You can say, "Human is Animal"
        // You can't say "Animal" is "Human"
        // The code below has an error
        Animal animalObject2 = new Animal();
        Human humanObject2 = animalObject2;
    }
}

class Animal{
    int age;
}

class Human extends Animal{
    String name;    
}

public class shape {
    public void draw(){}

    public static void doosomthing {

        shape.draw();

        /*
        Subclass circle type parameters 
        There is no compilation error because it was upcast and received as a super class shape.

        A subclass is equal to or larger than a superclass.
        Subclasses are created by inheriting superclasses, so the things that exist in superclasses are basically in subclasses
        It doesn't matter if you omit the type transformation, and there is no compilation error.

        Determines whether a particular method in a subclass should be executed at the time (runtime) the method is executed (dynamic binding)
        You will then run the method of the requested subclass.
         */
    }

    public static void main(String[] args) {
        One circle = new();
        triangle = new triangle();

        DoSomthing(circle); // Execution Result : Draw a circle
        DoSomthing (triangle); // Execution Result: Draw a triangle

        /*
        Pass parameters to the type of subclass circle, triangle.
        The doSomething method upcasts the parameters received into a superclass shape.
         */
    }
}

class one extensions shape {
    @Override
    public void draw() {
        System.out.println ("draw a circle");
    }
}

class triangle extensions shape {
    @Override
    public void draw() {
        System.out.println ("draw a triangle");
    }
}