Encapsulation

   Wrapping up(combing) of data(variable) and functions(method) into a single unit(class) is known as encapsulation. It also means hiding data and methods within an Object. Only the class methods can access the class data. Outside of class methods can not access the data members of another class. It provide the security of class data members and class methods. Encapsulation provides the security that keeps data and methods safe from inadvertent(needless) changes.

• Technically in encapsulation, the variables or data of a class is hidden from any other class and can be accessed only through any member function of own class in which they are declared.
• As in encapsulation, the data in a class is hidden from other classes, so it is also known as data-hiding.
• Encapsulation can be achieved by: Declaring all the variables in the class as private and writing public methods in the class to set and get the values of variables.

// Java program to demonstrate encapsulation
public class Encapsulate
{
    // private variables declared
    // these can only be accessed by
    // public methods of class
    private String geekName;
    private int geekRoll;
    private int geekAge;

    // get method for age to access
    // private variable geekAge
    public int getAge()
    {
    return geekAge;
    }

    // get method for name to access
    // private variable geekName
    public String getName()
    {
    return geekName;
    }
   
    // get method for roll to access
    // private variable geekRoll
    public int getRoll()
    {
    return geekRoll;
    }

    // set method for age to access
    // private variable geekage
    public void setAge( int newAge)
    {
    geekAge = newAge;
    }

    // set method for name to access
    // private variable geekName
    public void setName(String newName)
    {
    geekName = newName;
    }
   
    // set method for roll to access
    // private variable geekRoll
    public void setRoll( int newRoll)
    {
    geekRoll = newRoll;
    }
}

In the above program the class EncapsulateDemo is encapsulated as the variables are declared as private. The get methods like getAge() , getName() , getRoll() are set as public, these methods are used to access these variables. The setter methods like setName(), setAge(), setRoll() are also declared as public and are used to set the values of the variables.

The program to access variables of the class EncapsulateDemo is shown below:

public class TestEncapsulation
{   
    public static void main (String[] args)
    {
        Encapsulate obj = new Encapsulate();
       
        // setting values of the variables
        obj.setName("Harsh");
        obj.setAge(19);
        obj.setRoll(51);
       
        // Displaying values of the variables
        System.out.println("Geek's name: " + obj.getName());
        System.out.println("Geek's age: " + obj.getAge());
        System.out.println("Geek's roll: " + obj.getRoll());
       
        // Direct access of geekRoll is not possible
        // due to encapsulation
        // System.out.println("Geek's roll: " + obj.geekName);       
    }
}

Advantages of Encapsulation:

• Data Hiding: The user will have no idea about the inner implementation of the class. It will not be visible to the user that how the class is storing values in the variables. He only knows that we are passing the values to a setter method and variables are getting initialized with that value.
• Increased Flexibility: We can make the variables of the class as read-only or write-only depending on our requirement. If we wish to make the variables as read-only then we have to omit the setter methods like setName(), setAge() etc. from the above program or if we wish to make the variables as write-only then we have to omit the get methods like getName(), getAge() etc. from the above program
• Reusability: Encapsulation also improves the re-usability and easy to change with new requirements.
• Testing code is easy: Encapsulated code is easy to test for unit testing.