Class, Object & Creating an object

 Hello I'm going to explain what is, and how to use , A sample code on calling methods & giving values to objects.                                                                                                                                                                                                                                                                                                    

         Object

  • Objects are common features and behaviours.
  • We can classify anything as an object.
    When we take a human, 
 
     The common features\properties.             Behaviors\Functions.
                       height                                              run
                       weight                                             think 
                       hands                                               walk
                       legs                                                  speak
                       hair                                                  jump
                       talents                                              eat
                       color                                                 sing
                       eyes                                                 dance
                       nose
                       age

  • The red color words are values they are changeable.
  • When we take features, the values will only change but the feature is the same.
  • When we take an object the features are common but the behaviors would be changed.

        Class

  • When we're making a template by considering an object using features & behaviors its called a class.

          Object Human
 
        Human block ------- is a Template 
        Features-------- are Variables
        Behaviors -------are Methods
        Object--------is a Class

Consider this code sample:

                      class Human{
                      height;
                      weight;
                      eyes;
                      legs;
                      hands;
                      name;
                      void walk(){
                       }
                      void eat(){
                       }
                      void drive(){

       

          Creating an object

          1. Human amal = new Human();
  
           Indications: RED: Class
                               GREEN: Object Name 
                               BLACK: Keyword (new is a keyword)
                               D.GREEN: Semicolon (code end)
                               BLUE: Parameter (Data In\Out)

       We can write that code line also as:
 
                        2. Human amal;
                            amal = new Human();

Giving values to an object and calling methods

  •       calling means running                                                                                                 call = run

     Consider this sample code:

                            class Human{
                         Human sanija;
                         Human thisum;
                         Human jared;
                         sanija = new Human();
                         thisum = new Human();
                         jared = new Human();
                         height;
                         weight;
                         void walk() {
                         method of walking inside brackets
                         }
                         void drive() {
                         method of driving inside brackets
                         }
                         sanija.walk();
                         jared.drive();
                         thisum.height = "6 feets"
                         thisum.weight = "76 kg"

  • You can see that the line "thisum.height = "6 feets" is connected with the variable called "height;" & you can see the line  "thisum.weight = "76 kg" is connected with the variable called "weight;"
                  
  • You can see the line "sanija.walk();" is connected with the method "void walk()" and also you can see the line  "jared.drive();" is connected with the method "void drive()".
 
-(2nd Article)        
                                                                                                    


Thank You!
                                                                                                           


                                                                                                            
                     
                                                                                                       -Article about Java by Hirun Yapa

                                 
                                                                                      


Comments

Post a Comment

Popular posts from this blog

Interfaces

Image
I have explained you in a past article about Inheritance. But here I'm going to talk about Multiple Inheritance.  Multiple Inheritance is extending one class to many classes. But its not allowed in Java. As a solution OOP gave us Interfaces. Interface is like a class (That means it has all the features that a class have) But Interface is not a class. We can use Interfaces in /java if we need to use multiple inheritance. Java has no limit for multiple inheritance using Interfaces. but when we are inheriting  Interfaces we use the keyword implements not extends Creating an Interface Ex :- 1)        Interface Saman {                                 } We create an interface in the way we are creating a class. Inheriting an Interface to a Class Ex :- 2)    class A {                   }           ...
Read more

Super Keyword

Image
      Refer to this code sample.        class Monkey {        Monkey(){        }        }        class Man extends Monkey{        Man(){         Super();        }        }       Super = Super class         The keyword super is used to call the constructor in the super class when you are in   the sub class. When we are using the super keyword in a constructor of the sub class, the constructor of super class will run in the constructor of the sub class. We can access methods and variables in the super class using the keyword super.
Read more

Abstract Classes

Image
When we're coding, we will meet methods that we can't apply codes, So we can name them as Meaningless Methods . We can't store meaningless methods in an ordinary way. In that situation, We have to make Abstract methods using the keyword "Abstract". We can't store Abstract methods in an ordinary class. Therefore, we have to make the class also an abstract class using Abstract keyword. We can store abstract methods only in abstract classes. But we can store any method in an abstract class. The important thing is, we cannot create objects in an abstract class .  Refer to the code sample given below, Abstract class Vehicle{ abstract void park (); } Abstract class Vehicle { Abstract void park (); void reverse (){ } } There is a code inside the meaningless method highlighted with Orange like , Ex :-  class Vehicle {           void park (){           }           } The part highlighted in blue is a meaningless ...
Read more