Object Superclass

Learning Targets:

  • What is the Object class
  • Why is the Object class important to remember

Every class and object created without the extends keyword will be implicitly extended from the Object Superclass. This means it will inherit some basic methods. Some notable methods are:

  1. getClass()
  2. toString()
  3. equals()

So What?

Well its important to keep in mind when writing out your class. If you are planning to have a method in your class/object that matches the basic Object, then it must be a public override because all of the Object methods are public.

  • are some methods from Object such as getClass() that you cannot override.
// this will return an error
class Shape {
    String toString(){
        return "Shape";
    }
}

// this will be fine
class Shape{
    @Override
    public String toString(){
        return "Shape";
    }
}

Popcorn Hacks

Create an example where you execute an unchanged method from Object, then execute a different method from Object that you changed.

class Shape {
    // Overriding the toString() method from the Object class
    @Override
    public String toString() {
        return "This is a Shape object.";
    }
}

public class Main {
    public static void main(String[] args) {
        Shape myShape = new Shape();

        // Executing an unchanged method from Object class: getClass()
        System.out.println("Class: " + myShape.getClass());

        // Executing the overridden toString() method from Object class
        System.out.println(myShape.toString());
    }
}