head first design patterns problem

[dick kromkamp]

Hello everybody,

I started to read the book 'head first design patterns', but
I already got a problem.

public abstract class Duck {
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;
 
    public Duck() {
    }
 
    public abstract void display();
 
    public void performFly () {
        flyBehavior.fly();
    }
 
    public void performQuack() {
        quackBehavior.quack();
    }
 
    public void swim() {
        System.out.println("All ducks float, even decoys!");
    }
}

I want to compile this code, but then it said:

C:\test1>javac Duck.java
Duck.java:11: cannot find symbol
symbol  : method fly()
location: class Duck
        flyBehavior = fly();
                      ^
Duck.java:15: cannot find symbol
symbol  : method quack()
location: class Duck
        quackBehavior = quack();

How do you compile this?

greetz
[ September 29, 2008: Message edited by: dick kromkamp ]

[tapeshwar sharma]

The book gives only that part of the code that is necessary to make the reader understand the concept.The fly() etc. methods are a "don't care" vis-a-vis driving the concept home.
However, since you have raised this question, it makes me think that may be you are jumping ahead of yourself by reading Design Patterns. May be you should read Java basics first.

[dick kromkamp]

That's not true,
I only posted a part of the code on page18.
The fly() methods etc are in the FlyBehavier and QuickBehavier.
Anyone can help who had read this book?

[ September 28, 2008: Message edited by: dick kromkamp ]
[ September 28, 2008: Message edited by: dick kromkamp ]

[Steve Luke]

Originally posted by dick kromkamp:
That's not true,
I only posted a part of the code on page18.
The fly() methods etc are in the FlyBehavier and QuickBehavier.
Anyone can help who had read this book?

[ September 28, 2008: Message edited by: dick kromkamp ]

[ September 28, 2008: Message edited by: dick kromkamp ]

So if fly() is part of the FlyBehavior object, how do you think you should call the fly() method from that object? As a hint, the code you posted IS NOT the code that is on page 18 of the book. You screwed up copying it. Can you see where? If you had a solid knowledge of Java Basics, as has previously been suggested, you should have been able to see the error right away.
[ September 28, 2008: Message edited by: Steve Luke ]