What is encapsulation? How does it actually hide data?

Question

Searching turns up a simple definition: data hiding.

But, consider the following two examples:

1) First Example:

Class Emp         


        

Answer 1

Say I use your code like this:

Employee employee = new Employee();
int age = employee.getAge();
// Do something with age

Here, unless I look at your source code, I have absolutely no idea how Employee has calculated its age. For all I know, getAge() could look like this:

public int getAge() {
    return new java.util.Random().nextInt( 100 );
}

or perhaps something even more complicated. I just don't know.

So in your second example, the fact that getAge() just returns a private member variable is completely hidden from me.