Encapsulation Program in Java

Encapsulation Program in Java

Encapsulation program in Java demonstrates the technique to bind methods and fields in a single unit. The term encapsulation is inspired by the word ‘capsule’, which is made up of different varieties of medicine mixed together. Encapsulation acts as the protective barrier that stops the outside code to directly access the data (fields) of a Java class. The common way to achieve encapsulation is to declare fields of a class as private and exposing only the methods of that class to the outside world in order to access the fields. Consider the following example.

FileName: EcapsulationExample.java

 // A Java program that illustrates the encapsulation
class Employee
{
    // The following class fields/ variables are declared as private
    // The public methods of the class access these private variables
    private int empAge;
    private int empId;
    private String empName;
    // public method getEmpAge() to access the private field empAge
    public int getEmpAge() { return empAge; }
    // public method getEmpId() to access the private field empId
    public int getEmpId() { return empId; }
    // public method getEmpName() to access the private field empName
    public String getEmpName() { return empName; }
    // public method setEmpAge() to set the private field empAge
    public void setEmpAge(int newAge) { empAge = newAge; }
    // public method setEmpId() to set the private field empId
    public void setEmpId(int newId) { empId = newId; }
    // public method setEmpName() to set the private field empName
    public void setEmpName(String newName)
    {
        empName = newName;
    }
}
public class EncapsulationExample
{
    // driver method
    public static void main(String argvs[])
    {
        // creating an object of the class Employee
        Employee emp = new Employee();
        // Using set method to sett values of the fields
        emp.setEmpName("Amit Bansal");
        emp.setEmpAge(19);
        emp.setEmpId(9051);
        // Using get methods to access the various fields of the class Employee
        System.out.println("The name of the employee is: "  + emp.getEmpName() );
        System.out.println("Age of the employee is: " + emp.getEmpAge() );
        System.out.println("Employee Id of the employee is: " + emp.getEmpId() );
    }
} 

Output:

 The name of the employee is: Amit Bansal
Age of the employee is: 19
Employee Id of the employee is: 9051 

Explanation: All the fields of the class Employee have been encapsulated. Thus, direct access of the fields i.e., emp.empAge, emp.empName, or emp.empId leads to the compilation error. Therefore, we need the public methods(getEmpName(), setEmpName(), setEmpAge(), and getEmpId() etc.) to access or manipulate the values of the private fields of the class employee.

Importance of Encapsulation

• Encapsulation helps in data hiding. In the above example, the outer world has no idea how the age, name, and employee id of an employee is getting stored. One can never see the implementation of it since the fields are private.
• Encapsulation enhances flexibility. In the above example, we can make the fields write-only or read-only based on the requirement. If we comment out the setter methods (setEmpName(), setEmpId(), setEmpAge()) then, we can only access the value of the fields but can not change it (read-only). If we comment out the code of getter methods (getEmpName(), getEmpId(), getEmpAge()) we find that we can manipulate values of the fields but can not access it (write-only).