其他的类和接口都已经写好 不知道如何实现CompositeShape类来重写draw方法画图
```package cn.edu.swun.www.model;
import cn.edu.swun.www.action.Drawable;
import java.util.ArrayList;
import java.util.Iterator;
public class CompositeShape extends Shape implements Drawable {
private ArrayList shapes;
public CompositeShape(String color,ArrayList<Shape> shapes){
this.color=color;
this.shapes=shapes;
}
@Override
public void draw(String penType) {
}
}
@Override
public double getArea() {
return 0;
}
}