父类:
public class TrainCar extends GCompound{ public TrainCar(double size){ engine = new Engine(size); add(engine); } }
子类:
public class Engine extends TrainCar { public Engine (double size){ //继承父类之后,标记这行出错。如果继承 GCompound,则无问题。 GPolygon engine = engine(size); add(engine); } }
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