Hacks 1-3

public class Bottle {
    private String matterState;
    private String material;

    // Parent constructor
    public Bottle(String matterState, String material) {
        this.matterState = matterState;
        this.material = material;
    }

    // Two different methods called sayHello, but with different constructors (or method signatures)
    public void sayHello() {
        System.out.println("I am a bottle");
    }

    public void sayHello(String name) {
        System.out.println("I am a bottle called " + name);
    }
}

public class WaterBottle extends Bottle {
    private String liquid;
    
    // Child constructor; note how it uses super() to automatically initialize some of the attributes
    public WaterBottle(String matterState, String material, String liquid) {
        super(matterState, material);
        this.liquid = liquid;
    }

    // Overriding a method
    @Override
    public void sayHello() {
        System.out.println("I am a water bottle");
    }

    // Overriding a method
    @Override
    public void sayHello(String name) {
        System.out.println("I am a water bottle called " + name);
    }
}

Notes

Classes are allowed to inherit attributes and methods from other classes using the "extends" keyword
- Class inheriting is the child class, class being inherited from is the parent class
super() can be used to call methods (and constructors) from the parent class inside the child class
- Subclass constructor can use super() to quickly set attributes originally from the parent class
Polymorphism
- Child class can be treated as an instance of its parent class (referencing superclass of object)
  - Child won't be able to access its own methods this way
- Methods can be overriden with new definitions
  - @Override keyword
- Methods can be overloaded with different function signatures
  - Same name, different parameters
Late binding - Methods are searched for by the compiler during runtime, not during the compilation of the code. Think about overriding the method
Abstract class + methods
- Abstraction
- Cannot create an object from it directly, must be created using a child class inheriting from the abstract class
- Abstract methods originally only have their signature created and must be fully established in the child class definition
Standard methods - methods inherited from the original Object class
- toString() - will usually print out the memory address of an object, can be overriden to print more specific information about the object in question
- equals() - checks if two objects are equal using "==" (which checks if the two memory addresses point to the same object); can also be overriden for more specific terms of being equal
- hashCode() - generates a unique numeric ID for each object, which can be used to check if they're equal to one another; can also be overriden for more specific terms