Review of Greenhorn Code?

[Tina Parks]

I have just started programming, and I would very much like to have someone review my code so that I don't compound mistakes when I modify it. Essentially, I want to know if I am making any fundamental mistakes that could hurt me later when I try to make the code more sophisticated. Is there a forum or service available? Can it be done here?
BTW, the code I wrote is short and easy to understand. And it compiles and works with no errors. But naturally that doesn't mean errors, or substandard programming, don't exist.

[Marilyn de Queiroz]

The Cattle Drive --
cattle drive
about the cattle drive
is the only service like this that I am aware of.

[Junilu Lacar]

Marilyn,
The Cattle Drive is now a fee-based service, right? Do you mean to say that folks can't post non-Cattle Drive related code here and get it nitpicked for free?

[Marilyn de Queiroz]

>Do you mean to say that folks can't post non-Cattle Drive
>related code here and get it nitpicked for free?

That is not what I intended to say. I had the impression that Tina was looking for more than what she can get in the regular forums by posting code here.

[Tina Parks]

How about if I post the code and see? If so, in which forum?

[David O'Meara]

If it's only a page or so I'd dump the code anyway
If it belongs somewhere else you'll find out.
(don't worry about the semi-militant nature 'round these parts, comes from giving ppl guns )
Dave

[Marilyn de Queiroz]

This, Java in General (beginner), is a good forum to begin in.

[Tina Parks]

Okay, here is the code. It is designed to draw vectors with the mouse. I stripped it down quite a bit to shorten it, including the import statements. I am most concerned with the Canvas call (is there a better way?) and the drawRect() method I implemented in order to draw a border around the applet window. (There has to be a better way.) But most importantly, I am concerned about the overall structure -- I want a code that is robust. At any rate, thanks in advance. I loooove this forum!
__________________

<font size=2.5>
public class VectorComponents extends Applet{

public void init()  {
setBackground(Color.white);
setLayout(new BorderLayout());
add(new VCCanvas());
}
}
class VCCanvas extends Canvas implements MouseListener, MouseMotionListener{
int x = 25; int y = 35;
int x0 = 150; int y0 = 150;  /* To shift origin to window center */
public VCCanvas(){
addMouseListener(this);
addMouseMotionListener (this) ;   
}
public void mouseDragged(MouseEvent  e) {
x=e.getX() ;
y=e.getY() ;
repaint(); 
}
public void mousePressed(MouseEvent  e) {
x=e.getX() ;
y=e.getY() ;
repaint(); 
}
public void mouseReleased(MouseEvent  e) {} 
public void mouseEntered(MouseEvent e) {} 
public void mouseExited(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}  
public void mouseClicked(MouseEvent e) {} 
public void paint(Graphics  g) {
g.setPaintMode();
//Draw window border
g.setColor(Color.black);
g.drawRect(0,0,2*x0-1,2*y0-1);
//Refer to Vector() method to draw vectors
g.setColor (Color.black);
drawVector(g,x0,y0,x,y);
g.setColor(Color.red);
drawVector(g,x0,y0,x,y0);
g.setColor(Color.blue);
drawVector(g,x0,y0,x0,y);
}
public void drawVector(Graphics g,int x1,int y1,int x2,int y2){
double theta;
long x, y;
//Draw vector arrow base
theta = Math.atan2(y1-y2,x2-x1);
g.drawLine(x1, y1, x2, y2);
// Draw vector arrowheads
x = Math.round(6*Math.cos(theta+Math.PI/10.));
y = Math.round(6*Math.sin(theta+Math.PI/10.));
g.drawLine(x2, y2, x2-(int)x, y2+(int)y);
x = Math.round(6*Math.cos(theta-Math.PI/10.));
y = Math.round(6*Math.sin(theta-Math.PI/10.));
g.drawLine(x2, y2, x2-(int)x, y2+(int)y);
}
}

(edited by Cindy to format code)
[This message has been edited by Cindy Glass (edited July 28, 2001).]

[Tina Parks]

Should I interpret the lack of responses as a good sign -- that there are no recommendations needed?

[Cindy Glass]

It's just that we are in awe of your wonderful code, and don't want to sound stupid by critiquing it .
Actually it looks pretty good to me.

[Nura Horne]

Yup, I lloked through it also and it has no errors in it that will be detrimental to programming more sophisticated works.
Good luck, A

[Tina Parks]

Great!
I do have one question -- what about the rectangle? In the above code I explicitly tell the program to draw a rectagle to use as a border around the applet window. Is this preferred?

[Cindy Glass]

Well if you switched over to Swing and used a JApplet then you could have a BorderFactory and do cool stuff.
The sun tutorial:
http://java.sun.com/docs/books/tutorial/uiswing/misc/border.html

[Tina Parks]

Thanks, but I have had my fill of Swing.

[Michael Ernest]

Ok, see, now I like Tina just for saying that.
------------------
Michael Ernest, co-author of: The Complete Java 2 Certification Study Guide