裝飾器模式

裝飾器模式

適用場景

• 在不改變classA的情況下，給classA動態增加/增強功能

實現方法

• Decorator繼承classA的接口，並依賴classA

public interface A {
    void callA();
}

public class AImpl implements A {
    ......
}

public class Decorator implements A {
    private A a = new AImpl();

    public void callA() {
        // do sth.
        a.callA();
        // do sth.
    }
}

實現例子

• java io: FilterInputStream

public class DecoratorDemo {
    public static void main(String[] args) {
        try(InputStream in = new FileInputStream("a.txt")) {
                FilterInputStream filterInputStream = new DataInputStream(in);
                System.out.println(filterInputStream.read());
            }
    }
}