策略 + 工厂
| package strategy; |
| public abstract class Strategy { |
| public abstract double getResult(); |
| } |
| package strategy; |
| |
| public class StrategyA extends Strategy{ |
| @Override |
| public double getResult() { |
| System.out.println("策略A实现了"); |
| return 1.0; |
| } |
| } |
| package strategy; |
| |
| public class StrategyB extends Strategy{ |
| @Override |
| public double getResult() { |
| System.out.println("策略B实现了"); |
| return 2.0; |
| } |
| } |
| package strategy; |
| |
| public class StrategyC extends Strategy{ |
| @Override |
| public double getResult() { |
| System.out.println("策略C实现了"); |
| return 3.0; |
| } |
| } |
| package strategy; |
| |
| |
| |
| |
| public class Context { |
| private Strategy strategy; |
| public Context(String type){ |
| switch (type){ |
| case "A": |
| strategy = new StrategyA(); |
| break; |
| case "B": |
| strategy = new StrategyB(); |
| break; |
| case "C": |
| strategy = new StrategyC(); |
| break; |
| } |
| } |
| public double getResult(){ |
| return strategy.getResult(); |
| } |
| } |
| package strategy; |
| |
| |
| |
| |
| public class TestStrategy { |
| public static void main(String[] args) { |
| Context context = new Context("A"); |
| double result = context.getResult(); |
| System.out.println("result = " + result); |
| } |
| } |
商场收银软件:
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图片来自《大话设计模式》
优点
- 修改Context不会影响客户端和strategy,修改strategy也不会影响到客户端和其他strategy
- 可以单独对某一strategy进行单元测试
- 修改哪个模块,只需要编译对应的模块
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