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。
public interface FlyBehavior {
public void fly();
}
public class FlyWithWings implements FlyBehavior{
@Override
public void fly() {
System.out.println("i'm flying");
}
}public class FlyNoWay implements FlyBehavior{
@Override
public void fly() {
System.out.println(" cannot fly");
}
}public interface QuackBehavior {
public void quack();
}public class Quack implements QuackBehavior{
@Override
public void quack() {
System.out.println("quack");
}
}public class MuteQuack implements QuackBehavior{
@Override
public void quack() {
System.out.println("<<silence>>");
}
}public class Squeak implements QuackBehavior{
@Override
public void quack() {
System.out.println("squeak");
}
}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 FlyBehavior getFlyBehavior() {
return flyBehavior;
}
public void setFlyBehavior(FlyBehavior flyBehavior) {
this.flyBehavior = flyBehavior;
}
public QuackBehavior getQuackBehavior() {
return quackBehavior;
}
public void setQuackBehavior(QuackBehavior quackBehavior) {
this.quackBehavior = quackBehavior;
}
}public class MallardDuck extends Duck{
public MallardDuck(){
flyBehavior = new FlyWithWings();
quackBehavior = new Quack();
}
@Override
public void display() {
System.out.println("I am a mallard duck");
}
}public class MiniDuckSimulator {
public static void main(String[] args){
Duck mallard = new MallardDuck();
mallard.performFly();
mallard.performQuack();
mallard.setFlyBehavior(new FlyNoWay());
mallard.performFly();
}
}public class MiniDuckSimulator {
public static void main(String[] args){
Duck mallard = new MallardDuck();
mallard.performFly();
mallard.performQuack();
mallard.setFlyBehavior(new FlyNoWay());
mallard.performFly();
}
}