Alternative Classes with Different Interfaces.

Two classes perform identical functions but have different method names.

class SmtpMailer {
  private final SmtpTransport transport = new SmtpTransport();
  void send(Message msg) { transport.write(msg); }
}
class EmailSender {
  private final SmtpTransport transport = new SmtpTransport();
  void deliver(Message msg) { transport.write(msg); }
}

The programmer who created one of the classes probably didn’t know that a functionally equivalent class already existed.

• You get rid of unnecessary duplicated code, making the resulting code less bulky.

• Code becomes more readable and understandable (you no longer have to guess the reason for creation of a second class performing the exact same functions as the first one).