데코레이터 패턴

1 개요

decorator pattern
데코레이터 패턴

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2 예제

// the Window abstract class
public abstract class Window {
    public abstract void draw(); // draws the Window
    public abstract String getDescription(); // returns a description of the Window
}
 
// extension of a simple Window without any scrollbars
class SimpleWindow extends Window {
    public void draw() {
        // draw window
    }
 
    public String getDescription() {
        return "simple window";
    }
}

// abstract decorator class - note that it extends Window
abstract class WindowDecorator extends Window {
    protected Window decoratedWindow; // the Window being decorated
 
    public WindowDecorator (Window decoratedWindow) {
        this.decoratedWindow = decoratedWindow;
    }
    public void draw() {
        decoratedWindow.draw(); //delegation
    }
    public String getDescription() {
        return decoratedWindow.getDescription(); //delegation
    }
}
 
// the first concrete decorator which adds vertical scrollbar functionality
class VerticalScrollBarDecorator extends WindowDecorator {
    public VerticalScrollBarDecorator (Window decoratedWindow) {
        super(decoratedWindow);
    }
 
    @Override
    public void draw() {
        super.draw();
        drawVerticalScrollBar();
    }
 
    private void drawVerticalScrollBar() {
        // draw the vertical scrollbar
    }
 
    @Override
    public String getDescription() {
        return super.getDescription() + ", including vertical scrollbars";
    }
}
 
// the second concrete decorator which adds horizontal scrollbar functionality
class HorizontalScrollBarDecorator extends WindowDecorator {
    public HorizontalScrollBarDecorator (Window decoratedWindow) {
        super(decoratedWindow);
    }
 
    @Override
    public void draw() {
        super.draw();
        drawHorizontalScrollBar();
    }
 
    private void drawHorizontalScrollBar() {
        // draw the horizontal scrollbar
    }
 
    @Override
    public String getDescription() {
        return super.getDescription() + ", including horizontal scrollbars";
    }
}

public class DecoratedWindowTest {
    public static void main(String[] args) {
        // create a decorated Window with horizontal and vertical scrollbars
        Window decoratedWindow = new HorizontalScrollBarDecorator (
                new VerticalScrollBarDecorator(new SimpleWindow()));
 
        // print the Window's description
        System.out.println(decoratedWindow.getDescription());
    }
}

3 같이 보기

4 참고 자료

http://en.wikipedia.org/wiki/Decorator_pattern