Java设计形式之组合模式

Java设计模式之组合模式

COMPOSITE?（Object Structural）?
Purpose?
Facilitates the creation of object hierarchies where each object?
can be treated independently or as a set of nested objects?
through the same interface.?
Use When?
1 Hierarchical representations of objects are needed..?
2 Objects and compositions of objects should be treated uniformly.?
Example?
Sometimes the information displayed in a shopping cart is the?
product of a single item while other times it is an aggregation?
of multiple items. By implementing items as composites we can?
treat the aggregates and the items in the same way, allowing us?
to simply iterate over the tree and invoke functionality on each?
item. By calling the getCost() method on any given node we?
would get the cost of that item plus the cost of all child items,?
allowing items to be uniformly treated whether they were single?
items or groups of items.?
Java代码?

1. package?javaPattern.composite;??
2. ??
3. import?java.util.ArrayList;??
4. ??
5. ??
6. interface?Component{??
7. ????public?void?operation();??
8. }??
9. public?class?Composite?implements?Component{??
10. ????private?ArrayList<Component>?al?=?new?ArrayList<Component>();??
11. ????@Override??
12. ????public?void?operation()?{??
13. ????????System.out.println("Composite's?operation...");??
14. ??????????
15. ????}??
16. ????public?void?add(Component?c){??
17. ????????al.add(c);??
18. ????}??
19. ????public?void?remove(Component?c){??
20. ????????al.remove(c);??
21. ????}??
22. ????public?Component?getChild(int?index){??
23. ????????return?al.get(index);??
24. ????}??
25. }??
26. class?Leaf?implements?Component{??
27. ??
28. ????@Override??
29. ????public?void?operation()?{??
30. ????????System.out.println("leaf's?operation..");??
31. ??????????
32. ????}??
33. ??????
34. }??
35. class?Client{??
36. ????public?static?void?main(String[]?args)?{??
37. ????????Composite?composite?=?new?Composite();??
38. ????????Component?component1?=?new?Leaf();??
39. ????????Component?component2?=?new?Leaf();??
40. ????????composite.add(component1);??
41. ????????composite.add(component2);??
42. ????}??
43. } ?