Thinking in Java Fourth Edition Bruce Eckel Chapter 6 Exercise 14

Exercise 14: In Car.java add a service( ) method to Engine and call this method in main( ).

class Engine
{
    public void start()
    {
    }
    public void rev()
    {
    }
    public void stop()
    {
    }
    public void service()
    {
        System.out.println("service engine");
    }
}

class Wheel
{
    public void inflate(int psi)
    {
    }
}

class Window
{
    public void rollup()
    {
    }
    public void rolldown()
    {
    }
}

class Door
{
    public Window window = new Window();
    public void open() {}
    public void close() {}
}

public class Car
{
    public Engine engine = new Engine();
    public Wheel[] wheel = new Wheel[4];
    public Door
        left = new Door(),
        right = new Door(); // 2-door
    public Car()
    {
        for(int i = 0; i < 4; i++)
            wheel[i] = new Wheel();
    }
    public static void main(String[] args)
    {
        Car car = new Car();
        car.left.window.rollup();
        car.wheel[0].inflate(72);
        car.engine.service();
    }  
}

Output:

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