(1) Drawing {
    (2);
    (3);
}

class DP1 {
    static public void draw_a_line(double x1, double y1, double x2, double y2) { /* 代码省略 */ }
    static public void draw_a_circle(double x, double y, double r) { /* 代码省略 */ }
}

class DP2 { 
    static public void drawline(double x1, double y1, double x2 ,double y2) { /* 代码省略 */ }
    static public void drawcircle (double x, double y, double r) { /* 代码省略 */ }
}

class V1Drawing implements Drawing {
    public void drawLine(double x1, double y1, double x2 ,double y2) { /* 代码省略 */ }
    public void drawCircle(double x, double y, double r) { (4); }
}

class V2Drawing implements Drawing {
    public void drawLine(double x1, double y1, double x2 ,double y2) { /* 代码省略 */ }
    public void drawCircle (double x, double y, double r) {（5）;} 
}

abstract class Shape {
    private Drawing _dp;
    (6);
    Shape(Drawing dp) { _dp = dp; }
    public void drawLine(double x1, double y1, double x2 ,double y2) { _dp.drawLine(x1, y1, x2, y2); }
    public void drawCircle (double x, double y, double r) { _dp.drawCircle(x, y, r); }
}

class Rectangle extends Shape {
    private double _x1, _x2, _y1, _y2;
    public Rectangle(Drawing dp, double x1, double y1, double x2, double y2) { /* 代码省略 */ }
    public void draw() { /* 代码省略 */ }
}

class Circle extends Shape {
    private double _x, _y, _r;
    public Circle(Drawing dp, double x, double y, double r) { /* 代码省略 */ }
    public void draw() { drawCircle(_x, _y, _r); }
}