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介绍
装饰模式，可称为装饰器模式或修饰模式，是面向对象编程领域中，一种动态地往一个类中添加新的行为的设计模式。在原有的基础上进行功能增强。就功能而言，装饰模式相比生成子类更为灵活，这样可以给某个对象而不是整个类添加一些功能。特点是用来增强原有对象功能，依附于原有对象。应用在用于需要对原有对象增加功能而不是完全覆盖的场景。
角色
| 角色 | 说明 |
|---|---|
| Component | 抽象构件 |
| ConcreteComponent | 具体构件 |
| Decorator | 抽象装饰类 |
| ConcreteDecorator | 具体装饰类 |
角色示例
| 类名 | 担任角色 | 说明 |
|---|---|---|
| Soldier | Component | 士兵 |
| LandSoldier | ConcreteComponent | 陆军 |
| SeaSoldier | ConcreteComponent | 海军 |
| SoldierArsenal | Decorator | 士兵军火库 |
| M4a1 | ConcreteDecorator | M4a1枪支 |
| Ak47 | ConcreteDecorator | Ak47枪支 |
UML类图
2020-09-04_5f51e8aa3d4aa.jpg
代码
abstract class Soldier {
String weapon = "no weapon";
public String getWeapon(){
return weapon;
}
}
class LandSoldier extends Soldier {
public LandSoldier() {
weapon = "+LandSoldier";
}
}
class SeaSoldier extends Soldier {
public SeaSoldier() {
weapon = "+SeaSoldier";
}
}
abstract class SoldierArsenal extends Soldier {
public abstract String getWeapon();
}
class M4a1 extends SoldierArsenal {
private Soldier soldier;
public M4a1(Soldier s) {
soldier = s;
}
@Override
public String getWeapon() {
return soldier.getWeapon() + "+with M4a1";
}
}
class Ak47 extends SoldierArsenal {
private Soldier soldier;
public Ak47(Soldier s) {
soldier = s;
}
@Override
public String getWeapon() {
return soldier.getWeapon() + "+with Ak47";
}
}
public class SoldierTest {
public static void main(String[] args) {
Soldier s1 = new LandSoldier();
System.out.println(s1.getWeapon());
M4a1 s2 = new M4a1(s1);
System.out.println(s2.getWeapon());
Ak47 s3 = new Ak47(s2);
System.out.println(s3.getWeapon());
}
}
创建 SoldierTest.java，内容如上。
执行
$ javac SoldierTest.java
$ java SoldierTest
+LandSoldier
+LandSoldier+with M4a1
+LandSoldier+with M4a1+with Ak47
