OO Concepts – Encapsulation

One of the building blocks of OOP, Encapsulation can have either of 2 meanings (thanks, Wikipedia) :

1. “A language mechanism for restricting access to some of the object’s components.”
2. “A language construct that facilitates the bundling of data with the methods (or other functions) operating on that data.”

Information Hiding
Generally, when we talk about encapsulation in OOP we are talking about Information hiding – closely related to abstraction. As an example, we may want to get a value from an object without worrying about its internal representation.

Here is an example:

public class Person {
  private final String firstName;
  private final String lastName;
 
  public Person(final String firstName, final String lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }

  public String getFullName() {
     return firstName + " " + lastName;
  }
}

In this example we can get a full name for the person regardless of how the first and last names are stored internally inside the Person object. This is the OO version of encapsulation.

In a nutshell, we are protected from changes in the internal representation of data, it is hidden from clients of the Person class – hence the private modifier.

For an alternative take on encapsulation – storing data with the methods working on it – you can look here: http://www.javaworld.com/article/2075271/core-java/encapsulation-is-not-information-hiding.html

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