举动型模式-解释器模式（Interpreter）

行为型模式--解释器模式（Interpreter）

Context类是一个上下文环境类，Plus和Minus分别是用来计算的实现，代码如下：

?

[java]?view plaincopy

1. public?interface?Expression?{??
2. ????public?int?interpret(Context?context);??
3. }??

[java]?view plaincopy

1. public?class?Plus?implements?Expression?{??
2. ??
3. ????@Override??
4. ????public?int?interpret(Context?context)?{??
5. ????????return?context.getNum1()+context.getNum2();??
6. ????}??
7. }??

[java]?view plaincopy

1. public?class?Minus?implements?Expression?{??
2. ??
3. ????@Override??
4. ????public?int?interpret(Context?context)?{??
5. ????????return?context.getNum1()-context.getNum2();??
6. ????}??
7. }??

[java]?view plaincopy

1. public?class?Context?{??
2. ??????
3. ????private?int?num1;??
4. ????private?int?num2;??
5. ??????
6. ????public?Context(int?num1,?int?num2)?{??
7. ????????this.num1?=?num1;??
8. ????????this.num2?=?num2;??
9. ????}??
10. ??????
11. ????public?int?getNum1()?{??
12. ????????return?num1;??
13. ????}??
14. ????public?void?setNum1(int?num1)?{??
15. ????????this.num1?=?num1;??
16. ????}??
17. ????public?int?getNum2()?{??
18. ????????return?num2;??
19. ????}??
20. ????public?void?setNum2(int?num2)?{??
21. ????????this.num2?=?num2;??
22. ????}??
23. ??????
24. ??????
25. }??

[java]?view plaincopy

1. public?class?Test?{??
2. ??
3. ????public?static?void?main(String[]?args)?{??
4. ??
5. ????????//?计算9+2-8的值??
6. ????????int?result?=?new?Minus().interpret((new?Context(new?Plus()??
7. ????????????????.interpret(new?Context(9,?2)),?8)));??
8. ????????System.out.println(result);??
9. ????}??
10. }??

最后输出正确的结果：3。

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