ObjectOrientationBasics

/**
 * @author Samuel Finocchio
 * Object Orientation basics
*/
// This is the definition of a class
// class is the keyword used to define ObjectOrientationBasics as a class
public class ObjectOrientationBasics {
    // Here attributes (fields) should be defined
    // Attributes should be declared as private
    // private means that you can't have direct access to the member of the class
    private String attribute;
    // So you can't do something like this:
    // ObjectOrientationBasics.attribute (DOES NOT WORK)
    // ObjectOrientationBasics oob = new ObjectOrientationBasics();
    // oob.attribute (DOES NOT WORK) it is private

    // Public defines attributes visibile outside the local context
    public String publicAttribute;
    // So you can do this
    // ObjectOrientationBasics oob = new ObjectOrientationBasics();
    // oob.publicAttribute; (DOES WORK)

    // In a static context you can reference an attribute directly from the class itself
    public static final double PI = 3.14159;
    // So this works:
    // ObjectOrientationBasics.PI (DOES WORK);
    // But you have no power on it
    // ObjectOrientationBasics.PI = 1.1618; (YOU CAN'T DO THAT)

    // So at the end..
    // visibility modifier - specification of the context (static or not) - type - name;


    // When calling new ClassName();
    // We are calling a constructor method, that means that we are defining the object with a default object of that class type.
    // We can create a constructor like this

    // It MUST have the same name as the referencing class
    public ObjectOrientationBasics() { // It does not have a specified return type
        // We use the constructor to define the default values of the class
        this.publicAttribute = "Hi, i am public";
        this.attribute = "And i am private";

        // This way when we create a new object these attributes will have these strings as default value
        // ObjectOrientationBasics oob = new ObjectOrientationBasics(); // new calls the constructor
        // System.out.println(oob.publicAttribute); // This will print "Hi, i am public" without assigning anything to it
    }

    // Other methods should be defined here
    // Usually methods are defined as public

    // This is something called a get method, it allows to work with private attributes outside the local context
    public String getAttribute()
    {
        return attribute;
    }

    // This is called set method, it allow to edit a private attribute outside the class
    public void setAttribute(String attribute) {
        // this references the class it self so it means that attribute is the one defined on top up there
        this.attribute = attribute;
    }

    // Other random method
    public void sayHi() {
        System.out.println("HI!!");
    }

    // This is method overload, it uses the same name but different attributes and a different code
    public void sayHi(String name) {
        System.out.println("Hi, " +  name + "!!");
    }

    // The constructor can be overloaded too
    public ObjectOrientationBasics(String attribute) {
        this.attribute = attribute;
    }

    // This is a different constructor in witch we can specificy our own default value to attribute
    // ObjectOrientationBasics oob = new ObjectOrientationBasics("Someting else");
    // System.out.println(oob.getAttribute()); // prints "Something else"

    // If we call sayHi(); "HI!!" appears
    // if we call sayHi("John") "Hi, John!!" appears

    // A static method can be called without an object
    public static double average (int a, int b) {
        return (a + b) / 2;
    }

    // This can be done
    // ObjectOrientationBasics.average(4, 9);
}