[一]Head First设计模式之【策略模式】（鸭子设计的优化历程）

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!”);
}

public void setFlyBehavior(FlyBehavior fb) {
flyBehavior = fb;
}
public void setQuackBehavior(QuackBehavior qb) {
quackBehavior = qb;
}

}

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 class FlyRocketPowered implements FlyBehavior {
public void fly() {
System.out.println(“I’m flying with a rocket!”);
}
}

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 class Squeak implements QuackBehavior {
public void quack() {
System.out.println(“Squeak”);
}
}

public class ModelDuck extends Duck {
public ModelDuck() {
flyBehavior = new FlyNoWay();
quackBehavior = new Quack();
}
public void display() {
System.out.println(“I’m a model duck”);
}
}

public class MiniDuckSimulator {
public static void main(String[] args) {
Duck mallard = new MallardDuck();
mallard.performQuack();
mallard.performFly();

Duck model = new ModelDuck();
model.performFly();
model.setFlyBehavior(new FlyRocketPowered());
model.performFly();

}
}

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。