// Java program to show the difference between aggregation and composition
// Engine class is used by car, so the class Car will have a field of Engine type.
class AvsC {
  public static void main ( String[ ] args ) {
    // Making an engine by creating an instance of Engine class
    Engine engine1 = new Engine( args[0] );
    Engine engine2 = new Engine( args[1] );

    // Making a car with engine, so we are passing an engine
    // instance as an argument while creating instace of Car
    Car car1 = new Car( args[2], engine1 );
    Car car2 = new Car( args[2], engine2 );
    car2.move( engine1 );
  }
}

class Engine {
  String name;
  Engine( String name ) { this.name = name; }

  // Starting an engine
  public void work( ) { System.out.println( this.name ); } 	
}

final class Car { 
  String name;
  /*-------------------------------------------------*
   * For a car to move, it needs to have a engine.   *
   * Have to comment out either one of the following *
   * two commands.                                   *
   *-------------------------------------------------*/ 
  private Engine engine;          // Aggregation
  private final Engine engine;    // Composition 
	
  Car( String name, Engine engine ) {
    this.name   = name;
    this.engine = engine;
  }

  // Car starts moving by starting engine. 
  public void move( Engine engine ) { 
    if ( engine != null ) { 
      this.engine = engine;
      System.out.print( this.name + " " + enging.name ); 
    } 
  }
}