政策模式定義：
政策模式定義了算法族，分别封裝起來，讓它們之間可以互相替換，此模式讓算法的變化獨立于使用算法的客戶。
樣例：
UML類圖
Java代碼實作：
Duck.java
/**
* 鴨子超類
* @author LiuJing
*
*/
public abstract class Duck {
FlyBehavior flyBehavior;
QuackBehavior quackBehavior;
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!");
}
// 新加入2個設定行為的方法
public void setFlyBehavior(FlyBehavior fb){
flyBehavior = fb;
}
public void setQuackBehavior(QuackBehavior qb){
quackBehavior = qb;
}
} FlyBehavior.java
/**
* 飛的行為 接口類
* @author LiuJing
*
*/
public interface FlyBehavior {
public void fly();
} FlyWithWings.java
/**
* 用翅膀飛的類
* @author LiuJing
*
*/
public class FlyWithWings implements FlyBehavior{
public void fly(){
System.out.println("I'm flying!!!");
}
} FlyNoWay.java
/**
* 不能飛的類
* @author LiuJing
*
*/
public class FlyNoWay implements FlyBehavior{
public void fly() {
// TODO Auto-generated method stub
System.out.println("I can't fly");
}
} FlyRocketPowered.java
/**
* 用火箭飛的類
* @author LiuJing
*
*/
public class FlyRocketPowered implements FlyBehavior {
public void fly() {
// TODO Auto-generated method stub
System.out.println("I'm flying with a rocket");
}
} QuackBehavoir.java
/**
* 叫的行為 接口
* @author LiuJing
*
*/
public interface QuackBehavior {
public void quack();
} Quack.java
/**
* 嘎嘎叫的類
* @author LiuJing
*
*/
public class Quack implements QuackBehavior{
public void quack() {
// TODO Auto-generated method stub
System.out.println("Quack");
}
} Squeak.java
/**
* 吱吱叫的類
* @author LiuJing
*
*/
public class Squeak implements QuackBehavior{
public void quack() {
// TODO Auto-generated method stub
System.out.println("Squeak");
}
} MuteQuack.java
/**
* 沉默不叫的類
* @author LiuJing
*
*/
public class MuteQuack implements QuackBehavior{
public void quack() {
// TODO Auto-generated method stub
System.out.println("Silence");
}
} MallardDuck.java
/**
* 綠頭鴨
* @author LiuJing
*
*/
public class MallardDuck extends Duck {
public MallardDuck(){
quackBehavior = new Quack();
flyBehavior = new FlyWithWings();
}
@Override
public void display() {
// TODO Auto-generated method stub
System.out.println("I'm a real Mallard duck");
}
} ModelDuck.java
/**
* 模型鴨
* @author LiuJing
*
*/
public class ModelDuck extends Duck {
public ModelDuck(){
flyBehavior = new FlyNoWay();
quackBehavior = new Quack();
}
@Override
public void display() {
// TODO Auto-generated method stub
System.out.println("I'm a model duck");
}
} 現在寫一個測試類，用以測試：
Test.java
/**
* 測試類
* @author LiuJing
*
*/
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
// 測試綠頭鴨
System.out.println("--------測試綠頭鴨--------");
Duck mallard = new MallardDuck();
mallard.performQuack();
mallard.performFly();
// 測試模型鴨
System.out.println("--------測試模型鴨---------");
Duck model = new ModelDuck();
model.performQuack();
model.performFly();
// 改變其飛行行為
model.setFlyBehavior(new FlyRocketPowered());
model.performFly();
}
} 輸出：
--------測試綠頭鴨--------
Quack
I'm flying!!!
--------測試模型鴨---------
Quack
I can't fly
I'm flying with a rocket 政策模式C＃實作樣例：
UML類圖：
C#實作代碼：
Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace PatternTest
{
// 政策抽象類
abstract class Strategy
{
public abstract void AlgorithmInterface();
}
// 算法A
class ConcreteStrategyA : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法A實作");
}
}
// 算法B
class ConcreteStrategyB : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法B實作");
}
}
// 算法C
class ConcreteStrategyC : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法C實作");
}
}
// 具體使用算法的類
class Context
{
Strategy strategy;
public Context(Strategy strategy)
{
this.strategy = strategy;
}
public void ContextInterface()
{
strategy.AlgorithmInterface();
}
}
// 測試代碼
class Program
{
static void Main(string[] args)
{
Context context;
context = new Context(new ConcreteStrategyA());
context.ContextInterface();
context = new Context(new ConcreteStrategyB());
context.ContextInterface();
context = new Context(new ConcreteStrategyC());
context.ContextInterface();
Console.Read();
}
}
} 輸出：
算法A實作
算法B實作
算法C實作 C#具體執行個體：
代碼：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace PatternTest
{
// 現金收費抽象類
abstract class CashSuper
{
public abstract double acceptCash(double money);
}
// 正常收費子類
class CashNormal : CashSuper
{
public override double acceptCash(double money)
{
return money;
}
}
// 打折收費子類
class CashRebate : CashSuper
{
private double moneyRebate = 1d;
public CashRebate(double moneyRebate)
{
this.moneyRebate = moneyRebate;
}
public override double acceptCash(double money)
{
return money * moneyRebate;
}
}
// 返利收費子類
class CashReturn : CashSuper
{
private double moneyCondition = 0.0d;
private double moneyReturn = 0.0d;
public CashReturn(double moneyCondition, double moneyReturn)
{
this.moneyCondition = moneyCondition;
this.moneyReturn = moneyReturn;
}
public override double acceptCash(double money)
{
double result = money;
if (money >= moneyCondition)
{
result = money - Math.Floor(money / moneyCondition) * moneyReturn;
}
return result;
}
}
//class CashFactory
//{
// public static CashSuper createCashAccept(int type)
// {
// CashSuper cs = null;
// switch (type)
// {
// case 1: // "正常收費"
// cs = new CashNormal();
// break;
// case 2: // "滿300返100"
// cs = new CashReturn(300, 100);
// break;
// case 3: // "打8折"
// cs = new CashRebate(0.8);
// break;
// }
// return cs;
// }
//}
// 改進CashFactory,請仔細對比上一個注釋的類，這麼做有什麼好處？
// 好處：
// 隐藏了 CashSuper 對象及其方法 acceptCash
class CashContext
{
private CashSuper cs;
public CashContext(int type)
{
switch (type)
{
case 1: // "正常收費"
cs = new CashNormal();
break;
case 2: // "滿300返100"
cs = new CashReturn(300, 100);
break;
case 3: // "打8折"
cs = new CashRebate(0.8);
break;
}
}
public double getResult(double money)
{
return cs.acceptCash(money);
}
}
// 測試代碼
class Program
{
static void Main(string[] args)
{
//選擇一種折扣類型
// 1,正常收費 2,滿300返100 3,打8折
double total = 0.0d;
double totalPrices = 0d;
//CashSuper csuper = null;
//Console.WriteLine("----------測試正常收費-----------");
//csuper = CashFactory.createCashAccept(1);
//totalPrices = csuper.acceptCash(500);//金額為客人在店裡消費的随機數額 單價*數額 多種
//Console.WriteLine("消費總額為："+ totalPrices);
//total += totalPrices;
//Console.WriteLine("----------測試滿300減100-----------");
//csuper = CashFactory.createCashAccept(2);
//totalPrices = csuper.acceptCash(1400);//金額為客人在店裡消費的随機數額 單價*數額 多種
//Console.WriteLine("消費總額為：" + totalPrices);
//total += totalPrices;
//Console.WriteLine("----------測試8折-----------");
//csuper = CashFactory.createCashAccept(3);
//totalPrices = csuper.acceptCash(1000);//金額為客人在店裡消費的随機數額 單價*數額 多種
//Console.WriteLine("消費總額為：" + totalPrices);
//total += totalPrices;
// 改進代碼後的再測試
CashContext cc = null;
Console.WriteLine("----------測試正常收費-----------");
cc = new CashContext(1);
totalPrices = cc.getResult(500);//金額為客人在店裡消費的随機數額 單價*數額 多種
Console.WriteLine("消費總額為：" + totalPrices);
total += totalPrices;
Console.WriteLine("----------測試滿300減100-----------");
cc = new CashContext(2);
totalPrices = cc.getResult(1400);//金額為客人在店裡消費的随機數額 單價*數額 多種
Console.WriteLine("消費總額為：" + totalPrices);
total += totalPrices;
Console.WriteLine("----------測試8折-----------");
cc = new CashContext(3);
totalPrices = cc.getResult(1000);//金額為客人在店裡消費的随機數額 單價*數額 多種
Console.WriteLine("消費總額為：" + totalPrices);
total += totalPrices;
Console.WriteLine("總消費：" + total);
Console.Read();
}
}
} 輸出：
----------測試正常收費-----------
消費總額為：500
----------測試滿300減100-----------
消費總額為：1000
----------測試8折-----------
消費總額為：800
總消費：2300