(IS A ) and (HAS A) relationship in Java

                                                 Relationship  between the classes.

                                                   ----------------------------------------

                                                                    

   ( IS A ) relationship --   Parent class  doesn’t  depend  on child.

                Class   Animal {    }

                 Class  Dog {}

                  Class    Dog extends Animal {

                                                   // tightly coupled  all properties inherited of Animal

                           }

 ( Has A ) relationship --- 

        Association :--

                 Class   Bank  {    }

                  Class    Employee {}

                   Class      OpenBank  {

                             Bank      axis =new Bank () ;            //  Independent  //loosely coupled

                              Employee  manager =new Employee( ); //Independent

                               }

                        

       Composition :--     

                          Class    Car {    }

                         Class       Engine {}

                         Class      MusicPlayer{}

                         Class     CarMove  {

                            Engine   a=new  Engine() ;  // Most needed /dependent

                                      }

 Engine is most essential component   to car move. So its composition. Engine can be change.

      

          Aggregation  :-- 

                                  Class   CarMove {

                                           MusicPlayer  mp=new MusicPlayer(); // Not essential

                                                     

                                                 Engine  e =new Engine();               //

                                                                }

    Music Player not essential component  but overall  it part of car . Aggregate future of car.

                                       

    Diagram which shows  the   Has A  relations .

          Composition and Aggregation are   Associations.