9.7 Object Superclass

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 Animal {
    private String name;
    private int age;

    public Animal(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Overriding the toString() method from Object class
    @Override
    public String toString() {
        return "Animal{Name='" + name + "', Age=" + age + "}";
    }

    // No override for hashCode(), it will use the original method from Object
}

public class ObjectMethodsExample {
    public static void main(String[] args) {
        Animal animal = new Animal("Leo", 5);

        // Execute the overridden toString() method
        System.out.println("toString() result: " + animal.toString());

        // Execute the unchanged hashCode() method from Object
        System.out.println("hashCode() result: " + animal.hashCode());
    }
}
ObjectMethodsExample.main(null);

toString() result: Animal{Name='Leo', Age=5}
hashCode() result: 2114337902