Draw rectangle line by line

Question

I want to draw rectangle by hline and vline in Java. I faced some problem to draw it, I don't know exactly, but I think it's at hline1 and vline1 methods.

There is no error, just a problem in algorithm within the parameter.

Here is the code ..

 package hw1;
 import java.awt.*;
 import java.awt.geom.*;
 import java.awt.event.*;

 public class main extends Frame {

Graphics2D g2d;
main()
{
    addWindowListener(new hw1.main.MyFinishWindow());
}

public class MyFinishWindow extends WindowAdapter
{
    public void windowClosing(WindowEvent e)
    {
        System.exit(0);
    }
}

public void paint (Graphics g)
{
    g2d=(Graphics2D)g;

    hline(0,40,250,40);
    vline(250,40 , 250 , 80);
    hline1(250,80,0,80);
    vline1(0,80 , 0 , 40);

}

public void hline(int x1,int y1 , int x2 , int y2)
{
    for(int x=x1 ; x<=x2 ; x++)
        putpixel(x,y1,Color.blue);
}

public void vline(int x1 ,int y1 , int x2 , int y2 )
{
    for(int y=y1;y<=y2;y++)
        putpixel(x1,y,Color.blue);
}

 public void hline1(int x1,int y1 , int x2 , int y2)
{
    for(int x=x1 ; x<=x2 ; x++)
        putpixel(x,x1,Color.blue);
}

public void vline1(int x1 ,int y1 , int x2 , int y2 )
{
    for(int y=y1;y<=y2;y++)
        putpixel(x1,y,Color.blue);
}

public void putpixel(int x , int y , Color c)

{
    g2d.setColor(c);
    g2d.drawLine(x, y, x, y);
}

 public void putpixel(int x , int y , Color c , int rad)
 {
     g2d.setColor(c);
     if(rad>4) rad=4;
     if(rad<=0) rad=1;
     g2d.drawOval(x-rad/2, y-rad/2, rad, rad);
 }


public static void main(String[] args) {
    // TODO code application logic here

    main f=new main();
    f.setTitle("Computer Graphics:Java 2D prpgram");
    Dimension screenSize=
            Toolkit.getDefaultToolkit().getScreenSize();
    int width=(int) screenSize.getWidth();
    int height=(int) screenSize.getHeight();
    f.setSize(width, height);
    f.setVisible(true);
}

}

Why AWT rather than Swing? See this answer on [Swing extras over AWT](http://stackoverflow.com/a/6255978/418556) for many good reasons to abandon using AWT components. If you need to support older AWT based APIs, see [Mixing Heavyweight and Lightweight Components](http://www.oracle.com/technetwork/articles/java/mixing-components-433992.html). — Andrew Thompson, Oct 01 '13 at 10:11
*"I want to draw rectangle by `hline` and `vline` in Java."* BTW - why that way particularly, as opposed to the (now 2) other good ways to draw a box? If it is 'specified by teacher', it might be best to make that clear. Programmers have a tendency to 'reach for the easiest tool' when programming, and the way you are going about it is *not* the easiest way. — Andrew Thompson, Oct 01 '13 at 10:17

ppeterka · Answer 1 · 2013-10-01T10:27:01.157

The main issue is you always increment the loop variables - without taking into account which boundary value is bigger than the other...

   vline1(0,80 , 0 , 40);

This will start y from 80, and increment it until it gets to 40...

This at least does what it should

public void vline(int x1 ,int y1 , int x2 , int y2 )
{
    //use min and max
    for(int y=Math.min(y1, y2);y<=Math.max(y1,y2);y++) { //always use brackets!!!
        putpixel(x1,y,Color.blue);
    }
}

Also, be sure to implement this for the hline() too...

Other issues

you don't need two functions for the vertical lines, and two for the horizontal. The purpose of methods is reusing code - if you want to preserve this structure for some reason unknown to us, use 1 function for the horizontal line, and one for the vertical.
You shouldn't have any unused parameters in a method.
```
hline(y, x1, x2)
vline(x, y1, y2)
```
would be totally enough.
Not to mention, taking this to a next level: it would be great to have 1 method for all kinds of lines: and that is the drawLine(), as @ling.s pointed out. And that handles all sorts of lines properly...

Moral of the story: know your API, and don't reinvent the wheel (unless this is for school, where the assignment is to reinvent it...)

the solution must be without any extra functions , and i think the problem is in putpixel fun at hline1 and vline1 , how exactly to call putpixel fun in it. may be replace x1 with y , like this. — Khalil Shawahin, Oct 01 '13 at 13:10

score 1 · Answer 2 · answered Oct 01 '13 at 10:07

1

Try drawLine()

public void paint (Graphics g)
{
g2d=(Graphics2D)g;

g.drawLine(0,40,250,40);
g.drawLine(250,40 , 250 , 80);
g.drawLine(250,80,0,80);
g.drawLine(0,80 , 0 , 40);

}

answered Oct 01 '13 at 10:07

Linga

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we must use an algorithm of hline and vline , we can't use drawline fun. – Khalil Shawahin Oct 01 '13 at 13:07

score 0 · Answer 3 · answered Oct 01 '13 at 10:10

As a side note, you can use java.awt.Polygon.

  Polygon p;

   p = new Polygon();
   p.addPoint(10, 10);
   p.addPoint(100,10);       
   p.addPoint(100,100);
   p.addPoint(10,100);

 .....

  public void paintComponent(Graphics g){
    super.paintComponent(g);
    setBackground(Color.white);
    g.fillPolygon(p);   
}

Draw rectangle line by line

3 Answers3

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