问为什么这个导入不能在Eclipse中跨包工作？

EN

package car;

import engine.Engine;

    public class Car {
        private Engine engine;

        /***
         * Constructor
         * @param engine The engine that the car object will have
         */
        Car(Engine engine) {
            engine = new Engine(engine);    // Use the Engine copy constructor
        }
    }

package engine;

public class Engine {
    private String name;
    private int displacement;

    public Engine(String name, int displacement) throws Exception {
        setName(name);
        setDisplacement(displacement);
    }
    public String getName() {return name;}
    public int getDisplacement() {return displacement;}

    private void setName(String name) throws Exception {
        if (name.trim().length() == 0) {
            throw new Exception("Engine name cannot be blank");
        }
    }
    private void setDisplacement(int displacement) throws Exception {
        if (displacement < 0) {
            throw new Exception("Engine displacement cannot be zero or negative");
        }
    }
}