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JavaEncapsulation


Encapsulation is more useful fundamental OOP concepts. The other three are inheritance, polymorphism, and abstraction.


Encapsulation in Java is data variables and methods together as a single unit. In encapsulation, the variables of a class will be hidden from other classes, and can be accessed only through the methods of their current class. Therefore, it is also known as data hiding.
  • Declare the variables of a class as private.
  • Provide public setter and getter methods to modify and view the variables values.

Example
/* File name : EncapTest.java */
public class EncapTest {
   private String name;
   private String idNum;
   private int age;

   public int getAge() {
      return age;
   }

   public String getName() {
      return name;
   }

   public String getIdNum() {
      return idNum;
   }

   public void setAge( int newAge) {
      age = newAge;
   }

   public void setName(String newName) {
      name = newName;
   }

   public void setIdNum( String newId) {
      idNum = newId;
   }
}


The public setXXX() and getXXX() methods are the access points of the instance variables of the EncapTest class
/* File name : RunEncap.java */
public class RunEncap {

   public static void main(String args[]) {
      EncapTest encap = new EncapTest();
      encap.setName("Sophie");
      encap.setAge(28);
      encap.setIdNum("12343ms");

      System.out.print("Name : " + encap.getName() + " Age : " + encap.getAge());
   }
}
Output Name : James Age : 20