源碼和圖片來自 head first 設計模式
一. 開閉原則
類應該對擴展開放, 對修改關閉;
二. 裝飾者模式描述
裝飾者模式, 動態地將責任附加到對象上.若要擴展功能, 裝飾者提供了比繼承更有彈性的替代方案
完整代碼下載
二. 代碼
高層抽象 Beverage
public abstract class Beverage {
String description = "Unknown Beverage";
public String getDescription() {
return description;
}
public abstract double cost();
}
public class Espresso extends Beverage {
public Espresso() {
description = "Espresso";
}
@Override
public double cost() {
return 1.99;
}
}
裝飾器 CondimentDecorator
public abstract class CondimentDecorator extends Beverage {
public abstract String getDescription();
}
public class Milk extends CondimentDecorator {
Beverage beverage;
public Milk(Beverage beverage) {
super();
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + " ," + "Milk";
}
@Override
public double cost() {
return .33 + beverage.cost();
}
}
四. 測試代碼
public class StarbuzzCoffee {
public static void main(String[] args) {
Beverage beverage = new Espresso();
System.out.println(beverage.getDescription() + " $" + beverage.cost());
Beverage beverage2 = new DarkRoast();
beverage2 = new Mocha(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
System.out.println(beverage2.getDescription() + " $" + beverage2.cost());
Beverage beverage3 = new HouseBlend();
beverage3 = new Mocha(beverage3);
beverage3 = new Soy(beverage3);
beverage3 = new Whip(beverage3);
System.out.println(beverage3.getDescription() + " $" + beverage3.cost());
}
}
輸出:
Espresso $1.99
Dark Roast Coffee, Mocha, Mocha ,Whip $1.06
House Blend Coffee, Mocha ,Soy ,Whip $2.08
五. 裝飾 java.io 類
實現轉小寫的出入流
public class LowerCaseInputStream extends FilterInputStream {
public LowerCaseInputStream(InputStream inputStream) {
super(inputStream);
}
@Override
public int read() throws IOException {
int c = super.read();
return (c == -1 ? c : Character.toLowerCase((char)c));
}
}
測試代碼
public static void toLower() {
int c;
try {
InputStream in = new LowerCaseInputStream(
new BufferedInputStream(
new FileInputStream("count.txt")));
StringBuilder sb = new StringBuilder();
while((c = in.read()) != -1) {
sb.append((char)c);
}
System.out.println(sb.toString());
in.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
輸出:
APP.CHEN.COM
1
app.chen.com
1