Enkapsulasi & modifier akses

Pengantar Pemrograman Berorientasi Objek di Java

Sani Yusuf

Lead Software Engineering Content Developer

Memahami enkapsulasi

Enkapsulasi dapat dijelaskan dengan perangkat seluler
Anda hanya mengakses fitur yang diekspos seperti layar, speaker, dll.
Mekanisme internal sepenuhnya tersembunyi dari pengguna

Ponsel

Properti public

Properti bertanda public dapat diakses oleh instance objek


  class Car {
    // Public property
    public String color;


    // Public constructor
    public Car(String color){
      this.color = color;
    }    
  }


    public class Main {

      // main method
      public static void main(String[] args) {
          Car myCar = new Car("brown");
          // Can access public members 
          // from object instance
          System.out.println(
            myCar.color); // Brown
        }
      }

Properti private

Properti bertanda private dapat diakses oleh instance objek
Properti bertanda private hanya dapat digunakan di dalam kelas


  // Car class
  class Car {
     public String color;

     // Private properties 
     private String model;


     public Car(String color){
       this.color = color;
     }
  }


    // Main class
    public class Main {
      // main method
      public static void main(String[] args) {
          Car myCar = new Car("brown");
          // Calling private properties causes errors        
          System.out.println(
            myCar.model); // Java compilation error
        }
      }

Metode public


  // Car class
  class Car {
      public String color;
      private String model;

      public Car(String color){
          this.color = color;
      }

      // Public method
      public String getModel(){
          return this.model;
      }    
  }

Metode private


  class Car {


      // Private method, "calculateSpeed" can only be used within "Car" class
      private calculateSpeed(){
        // Trademarked formula code
      }

      public int getSpeed(){
        // "calculateSpeed" can be used anywhere within "Car" class
        return this.calculateSpeed();
      }
    }

Metode static

Properti bertanda static dapat diakses tanpa instance objek
Umumnya untuk menampung kode/pustaka bersama


   // Formula class 
   static class Formula {

     // Method for calculating square
     static int getSquare(int number) {
        return number * number;
      }
   }


  // Main class 
  public class Main {

    public static void 
      main(String[] args) {
          // We can use "getSquare" 
          // without an object instance
        System.out.println(
          Formula.getSquare(5)); // 25
      }
  }

Ringkasan

Modifier akses: public, private, static
Modifier akses membantu mengamankan aplikasi
static memungkinkan penggunaan kelas tanpa membuat instance

Ayo berlatih!

Pengantar Pemrograman Berorientasi Objek di Java