Design Pattern (GOF): Structural Pattern : Builder

Definition

Convert the existing interfaces to a new interface to achieve compatibility and reusability of the unrelated classes in one application. Also known as Wrapper pattern.

To reuse classes and make new class compatible with existing ones. For example, A clean system is already designed, you want to add more job in, the Extra interface uses adapter pattern to plug in the existing system.

Example

interface Clean {
   public void makeClean();
}
class Office implements Clean{
   public void makeClean() {
       System.out.println("Clean Office");
   }
}
class Workshop implements Clean{
   public void makeClean() {
       System.out.println("Clean Workshop");
   }
}

interface Extra extends Clean{
   public void takeCare();
}
class Facility implements Extra{
   public void makeClean() {
       System.out.println("Clean Facility");
   }
   public void takeCare() {
       System.out.println("Care has been taken");
   }
}
In order to reuse Workshop and Office classes,
we create an adapter interface Extra and
add new job takeCare in the system.

class Test {
  static void Jobs (Extra job) {
      if (job instanceof Clean)
          ((Clean)job).makeClean();
      if (job instanceof Extra)
          ((Extra)job).takeCare();
  }
  public static void main(String[] args) {
      Extra e = new Facility();
      Jobs(e);
      Clean c1 = new Office();
      Clean c2 = new Workshop();
      c1.makeClean();
      c2.makeClean();
      e.makeClean();
  }
}
Author
Kazi Masudul Alam