策略模式和简单工厂模式的结合使用

1 //策略类，定义所有支持的算法的公共接口
2 public abstract class Strategy {
3     public abstract void algorithmMethod(int numberA,int numberB);
4 }

 1 //具体策略类，封装了具体的算法或行为，继承于Strategy   
 2 //用于加法的算法
 3 public class ConcreteStrategyAdd extends Strategy {
 4 
 5     @Override
 6     public void algorithmMethod(int numberA,int numberB) {
 7         System.out.println(numberA+" + "+numberB+" = "+(numberA+numberB)+";");
 8     }
 9 
10 }

 1 //具体策略类，封装了具体的算法或行为，继承于Strategy
 2 //用于乘法的算法
 3 public class ConcreteStrategyMul extends Strategy {
 4 
 5     @Override
 6     public void algorithmMethod(int numberA,int numberB) {
 7         System.out.println(numberA+" * "+numberB+" = "+(numberA*numberB)+";");
 8     }
 9 
10 }

 1 //具体策略类，封装了具体的算法或行为，继承于Strategy
 2 //用于两个数相减的算法
 3 public class ConcreteStrategySub extends Strategy {
 4 
 5     @Override
 6     public void algorithmMethod(int numberA,int numberB) {
 7         System.out.println(numberA+" - "+numberB+" = "+(numberA-numberB)+";");
 8     }
 9 
10 }

 1 //Context上下文，用一个ConcreteStrategy来配置，维护一个对Strategy对象的引用
 2 public class Context {
 3     private Strategy strategy;
 4 
 5     // 构造方法，注意，参数不是具体的算法策略对象，而是一个字符串，表示策略的类型
 6     public Context(String strategyType) {
 7         
 8         /**
 9          * 将实例化具体策略的过程由客户端转移到Context类中，简单工厂的应用
10          */
11         switch (strategyType) {
12             case "add":
13                 strategy = new ConcreteStrategyAdd();
14                 break;
15             case "sub":
16                 strategy = new ConcreteStrategySub();
17                 break;
18             case "mul":
19                 strategy = new ConcreteStrategyMul();
20                 break;
21         }
22 
23     }
24 
25     // 根据具体的策略对象，调用其算法的方法
26     public void contextInterface(int numberA, int numberB) {
27         strategy.algorithmMethod(numberA, numberB);
28     }
29 
30 }

 1 public class Test {
 2     public static void main(String[] args) {
 3         Context context;
 4         // 我想使用加法算法
 5         /*context = new Context(new ConcreteStrategyAdd());
 6         context.contextInterface(5, 4);*/
 7         context = new Context("add");
 8         context.contextInterface(5, 4);
 9 
10         // 我想使用减法算法
11         /*context = new Context(new ConcreteStrategySub());
12         context.contextInterface(5, 4);*/
13         context = new Context("sub");
14         context.contextInterface(5, 4);
15         
16         // 我想使用乘法算法
17         /*context = new Context(new ConcreteStrategyMul());
18         context.contextInterface(5, 4);*/
19         context = new Context("mul");
20         context.contextInterface(5, 4);
21     }
22 }