why encapsulation is used in java code example

Example 1: what is encapsulation java

Encapsulation in Java is a mechanism to wrap up variables and methods together
as a single unit. It is the process of hiding information details and protecting
data and behavior of the object. It is one of the four important OOP concepts. 
 The encapsulate class is easy to test, so it is also better for unit testing.

Example 2: encapsulation in java programs

// java program on encapsulation
class EncapsulationExample
{
   private int ID;
   private String stuName;
   private int stuAge;
   // getter and setter methods
   public int getStudentID()
   {
      return ID;
   }
   public String getStudentName()
   {
      return stuName;
   }
   public int getStudentAge()
   {
      return stuAge;
   }
   public void setStudentAge(int number)
   {
      stuAge = number;
   }
   public void setStudentName(String number)
   {
      stuName = number;
   }
   public void setStudentID(int number)
   {
      ID = number;
   }
}
public class ExampleForEncapsulation
{
   public static void main(String[] args)
   {
      EncapsulationExample student = new EncapsulationExample();
      student.setStudentName("Virat");
      student.setStudentAge(5);
      student.setStudentID(2353);
      System.out.println("Student Name: " + student.getStudentName());
      System.out.println("Student ID: " + student.getStudentID());
      System.out.println("Student Age: " + student.getStudentAge());
   }
}