基类、子类

public interface Car {
	
	public String type();

}

public class Bike implements Car {

	@Override
	public String type() {
		// TODO Auto-generated method stub
		return "Bike";
	}
	public String people(){
		
		return "Bin";
		
	}

}

public class Bus implements Car {

	@Override
	public String type() {
		// TODO Auto-generated method stub
		return "Bus";
	}

}

public class Action {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Car car = new Bike();
		
		System.out.println(car.type());
		
		System.out.println(((Bike)car).people());

	}

}

Bike
Bin