用Java在Dos下，用纯字符画图

教女朋友Java时，让她做经典的空心菱形输出的题目。忽然想到写个用字符画各种图形的程序让她练习，于是就写了这个程序让她参考。

DrawCharShape.java

public class DrawCharShape
{
    public static void main(String[] args)
    {
        Screen sc=new Screen('.');
        DrawShape ds=new DrawShape(sc,0.5);
        ds.DrawCircle(new Point(30,18),18);
        ds.DrawCircle(new Point(10,10),10);
        ds.DrawCircle(new Point(23,15),8);
        ds.DrawLine(new Point(0,0),new Point(0,38));
        ds.DrawLine(new Point(0,0),new Point(79,0));
        ds.DrawLine(new Point(10,10),new Point(70,30));
        ds.DrawCircle(new Point(79,0),20);
        ds.DrawRect(new Point(10,10),new Point(65,25));
        sc.PrintScreen();
    }
}
class DrawShape  //画图类
{
    private Screen screen;
    private double linewidth;
    public DrawShape(Screen screen)
    {
        this(screen,1);
    }
    public DrawShape(Screen screen,double linewidth)
    {
        this.screen=screen;
        this.linewidth=linewidth;
    }
    public void DrawLine(Point a,Point b)
    {
        if(b.x==a.x) //如果是竖线，直接画
        {            
            if(a.y>b.y)
            {
                int temp;
                temp=a.y;
                a.y=b.y;
                b.y=temp;
            }
            for(int i=a.y;i<b.y;i++)
                screen.setPoint(a.x,i);
            return;
        }
        if(b.y==a.y) //如果是横线，直接画
        {
            if(a.x>b.x)
            {
                int temp;
                temp=a.x;
                a.x=b.x;
                b.x=temp;
            }
            for(int i=a.x;i<b.x;i++)
                screen.setPoint(i,a.y);
            return;
        }
        //斜线，纵坐标分成小数步长。
        double ystep=((double)b.y-a.y)/((double)b.x-a.x); 
        if(a.x>b.x)
            {
                Point temp;
                temp=a;
                a=b;
                b=temp;
            }
        //横坐标以1为单位，纵坐标以小数步长为单位。
        for(double i=a.x,j=a.y;i<b.x;i++,j+=ystep)
                screen.setPoint((int)i,(int)j);
    }
    public void DrawCircle(Point o,int r)
    {
        for(int i=0;i<80;i++)
            for(int j=0;j<39;j++)
            if(Math.abs(o.getDistanceFrom(new Point(i,j))-r)<this.linewidth) //如果某点与圆心间的距离，与半径之差小于线宽，则把该点点亮以画圆。
                screen.setPoint(i,j);
    }
    public void DrawRect(Point lefttop,Point rightbottom) //画矩形
    {
        for(int i=lefttop.x;i<=rightbottom.x;i++) //画上下两条边
        {
            screen.setPoint(i,lefttop.y);
            screen.setPoint(i,rightbottom.y);
        }
        for(int i=lefttop.y;i<=rightbottom.y;i++) //画左右两条边
        {
            screen.setPoint(lefttop.x,i);
            screen.setPoint(rightbottom.x,i);
        }
    }
}
class Point  //点类
{
    int x;
    int y;
    public Point()
    {
        this(0,0);
    }
    public Point(int x,int y)
    {
        this.x=x;
        this.y=y;
    }
    public double getDistanceFrom(Point another) //得到与另一点之间的距离，平面几何中。点与点的距离为：开根((x1-x2)平方+(y1-y2)平方)
    {
        return Math.sqrt(Math.pow(another.x-this.x,2)+Math.pow(another.y-this.y,2));
    }
}
class Screen //虚拟屏幕类
{
    private char[][] screen; //屏幕上的点
    private char pointchar;
    public Screen(char point)
    {
        this.pointchar=point;
        screen=new char[39][80]; //规定，虚拟屏幕上，共有39x80个点。（和Dos屏幕点对点）左上角点为（0,0)
    }
    public void setPoint(int x,int y) //把屏幕的某一点点亮
    {
        screen[y][x]=pointchar;
    }
    public void setPoint(Point p)
    {
        this.setPoint(p.x,p.y);
    }
    public void clearPoint(int x,int y) //把屏幕的某一点熄灭
    {
        screen[y][x]=' ';
    }
    public void clearPoint(Point p)  
    {
        this.clearPoint(p.x,p.y);
    }
    public void PrintScreen() //将虚拟屏幕内容输出到Dos控制台屏幕。
    {
        for(int i=0;i<39;i++)
            for(int j=0;j<80;j++)
                System.out.print(screen[i][j]);
    }
}