Compostion,Association and aggregation in java

[anish jain]

I want to know how to implement Compostion,Aggregation and Association in Java.

I searched many time but never got any satisfactroy answer

[Seetharaman Venkatasamy]

Please, SearchFirst

[john sal]

Stephan van Hulst wrote:Please read the message following this post

Composition:

final class Car {

  private final Engine engine;

  Car(EngineSpecs specs) {
    engine = new Engine(specs);
  }

  void move() {
    engine.work();
  }
}

Aggregation:

final class Car {

  private Engine engine;

  void setEngine(Engine engine) {
    this.engine = engine;
  }

  void move() {
    if (engine != null)
      engine.work();
  }
}

In the case of composition, the Engine is completely encapsulated by the Car. There is no way for the outside world to get a reference to the Engine. The Engine lives and dies with the car. With aggregation, the Car also performs its functions through an Engine, but the Engine is not always an internal part of the Car. Engines may be swapped, or even completely removed. Not only that, but the outside world can still have a reference to the Engine, and tinker with it regardless of whether it's in the Car.

[Stephan van Hulst]

John, I appreciate that you're helping other users out; but when you cite material written by someone else, please provide a link to the source.

[john sal]

Sure I will take care of it in future.

Thanks