JAVA设计模式之策略模式

策略模式：定义了算法族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化独立于使用算法的客户。

例子：设计一个鸭子类，有的鸭子会飞但有的不会飞；有的鸭子会叫但有的不会叫；所有的鸭子都有一个不同的外观。

public interface FlyBehavior
{
    public void fly();
}

public class FlyWithWings implements FlyBehavior
{
    public void fly() 
    {
        System.out.println("I'm flying!");
    }
}

public class FlyNoWay implements FlyBehavior
{
    public void fly() 
    {
        System.out.println("I can't fly!");
    }
}

public interface QuackBehavior 
{
    public void quack();
}

public class Quack implements QuackBehavior
{
    public void quack() 
    {
        System.out.println("Quack!");
    }
}

public class MuteQuack implements QuackBehavior
{
    public void quack() 
    {
        System.out.println("<Silence>");
    }
}

public abstract class Duck 
{
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;
    
    public abstract void display();
    
    public void performFly()
    {
        flyBehavior.fly();
    }
    
    public void performQuack()
    {
        quackBehavior.quack();
    }
}

public class MallardDuck extends Duck
{
    public MallardDuck(FlyBehavior flyBehavior, QuackBehavior quackBehavior)
    {
        this.quackBehavior = quackBehavior;
        this.flyBehavior = flyBehavior;
    }

    @Override
    public void display() 
    {
        System.out.println("I'm a real Mallard Duck!");
    }
}

public class test 
{
    public static void main(String[] args)
    {
        Duck duck = new MallardDuck(new FlyWithWings(), new MuteQuack());
        duck.performFly();
        duck.performQuack();
        duck.display();
    }
}

参考：《headfirst设计模式》、http://yangguangfu.iteye.com/blog/815107