举动型模式-状态模式（State）

行为型模式--状态模式（State）

State类是个状态类，Context类可以实现切换，我们来看看代码：

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1. package?com.xtfggef.dp.state;??
2. ??
3. /**?
4. ?*?状态类的核心类?
5. ?*?2012-12-1?
6. ?*?@author?erqing?
7. ?*?
8. ?*/??
9. public?class?State?{??
10. ??????
11. ????private?String?value;??
12. ??????
13. ????public?String?getValue()?{??
14. ????????return?value;??
15. ????}??
16. ??
17. ????public?void?setValue(String?value)?{??
18. ????????this.value?=?value;??
19. ????}??
20. ??
21. ????public?void?method1(){??
22. ????????System.out.println("execute?the?first?opt!");??
23. ????}??
24. ??????
25. ????public?void?method2(){??
26. ????????System.out.println("execute?the?second?opt!");??
27. ????}??
28. }??

1. package?com.xtfggef.dp.state;??
2. ??
3. /**?
4. ?*?状态模式的切换类???2012-12-1?
5. ?*?@author?erqing?
6. ?*??
7. ?*/??
8. public?class?Context?{??
9. ??
10. ????private?State?state;??
11. ??
12. ????public?Context(State?state)?{??
13. ????????this.state?=?state;??
14. ????}??
15. ??
16. ????public?State?getState()?{??
17. ????????return?state;??
18. ????}??
19. ??
20. ????public?void?setState(State?state)?{??
21. ????????this.state?=?state;??
22. ????}??
23. ??
24. ????public?void?method()?{??
25. ????????if?(state.getValue().equals("state1"))?{??
26. ????????????state.method1();??
27. ????????}?else?if?(state.getValue().equals("state2"))?{??
28. ????????????state.method2();??
29. ????????}??
30. ????}??
31. }??

测试类：

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1. public?class?Test?{??
2. ??
3. ????public?static?void?main(String[]?args)?{??
4. ??????????
5. ????????State?state?=?new?State();??
6. ????????Context?context?=?new?Context(state);??
7. ??????????
8. ????????//设置第一种状态??
9. ????????state.setValue("state1");??
10. ????????context.method();??
11. ??????????
12. ????????//设置第二种状态??
13. ????????state.setValue("state2");??
14. ????????context.method();??
15. ????}??
16. }??

输出：

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execute the first opt!
execute the second opt!

根据这个特性，状态模式在日常开发中用的挺多的，尤其是做网站的时候，我们有时希望根据对象的某一属性，区别开他们的一些功能，比如说简单的权限控制等。