class Point
{   protected int x,y;
    Point(int a,int b)
    {   setPoint(a,b);
    }
    public void setPoint(int a,int b)
    {   x=a;
        y=b;
    }
}

class Line extends Point
{   protected int x,y;
    Line(int a,int b)
    {   super(a,b);
        setLine(a,b);
    }
    public void setLine(int x,int y)
    {   this.x=x+x;
        this.y=y+y;
    }
    public double length( )
    {   int x1=super.x,y1=super.y,x2=this.x,y2=this.y;
        return Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
    }
    public String toString( )
    {   return "直線端點:["+super.x+"."+super.y+"]["+x+"."+y+"]直線長度:"+this.length( );
    }
}
public class ThisDemo
{   public static void main(String args[ ])
    {   Line line=new Line(20,20);
        System.out.println("\n"+line.toString( ));
    }
}