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FileReader info -> drawLine in graph

Posted on 1998-11-14
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Last Modified: 2010-03-30
Anyone have an example of reading data from a data file
(FileReader, BufferedReader) then graphing the data
in an Applet (paint, drawLine)?

rjcole@clearsail.net
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Question by:robjay
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4 Comments
 
LVL 16

Accepted Solution

by:
heyhey_ earned 400 total points
ID: 1227432
here is some code - how to read some data from file and draw into the screen . Only Applications can access files on the local disk, if want to use this code in Applet you' have to change FileInputStream with new URL(...) and URL.getStream(); (so you'll get the information from the remote host)

data.txt
---start
10,10
100,10
100 100 10 100 10 10 50 50
---end

the app code
-- start

import java.util.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;


public class PaintTest extends Panel
{
    Vector data;

public PaintTest() {
    super();
 }

 public void paint(Graphics g)
 {
    if (data == null) return;
    int len = data.size();
    if (len < 2) return;
    int[] cur;
    int[] next;
    cur = (int[]) data.elementAt(0);
    next = (int[]) data.elementAt(0);
    for (int i = 1; i < len; i++)
    {
        cur = next;
        next = (int[]) data.elementAt(i);
        g.drawLine(cur[0], cur[1], next[0], next[1]);
    }
    cur = (int[]) data.elementAt(0);
    g.drawLine(cur[0], cur[1], next[0], next[1]);
 }

 public void loadFile (String name)
 {
    data = new Vector();
    int x,y;
    int[] cur;
    String st;
   
    try {
        FileInputStream is = new FileInputStream(name);
        StreamTokenizer t = new StreamTokenizer(is);
        t.whitespaceChars(',', ',');
        while (true) {
       
            if (t.nextToken() == StreamTokenizer.TT_EOF) return;
    //        st = t.sval;
            x = (int) t.nval;
            System.out.println("\nnext token = " + x);
            if (t.nextToken() == StreamTokenizer.TT_EOF) return;
            y = (int)t.nval;
            System.out.println("\nnext token = " + y);
            cur = new int[2];
            cur[0] = x;
            cur[1] = y;
            data.addElement(cur);    
        }
    } catch (Exception e )
    {
        System.out.println("Error caught");
        e.printStackTrace();
    }
 }

public static void main (String[] args) {
    Frame f = new Frame();
    f.setLayout(new BorderLayout());
    PaintTest test = new PaintTest();
    test.loadFile("c:\\data.txt");

    f.add(test , BorderLayout.CENTER);
    f.setSize(150,150);
    f.addWindowListener(
    new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    }
    );
//    f.pack();
    f.show();

}
}
--- end

hope this helps
  heyhey

P.S. if you need more information on applets post a question here
 
0
 

Author Comment

by:robjay
ID: 1227433
This looks like the right direction - but I definately need to get this to the web browser -
(you can look at my attempt at http://www.clearsail.net/~robjay/Graph3Applet.java)
a gif would be OK, but presentation in an applet would be better - can you explain a little
more how I can do this in an applet or my best alternative?
Thanks

0
 

Author Comment

by:robjay
ID: 1227434
As I have looked at this a little more, could you write the exact code that you would use to replace this line, and say yourfile is out there at www.somewhere.com/data.txt :

FileInputStream is = new FileInputStream(name);

As I understand this, as long as my file is accessible via the internet, I can download the contents?


0
 
LVL 16

Expert Comment

by:heyhey_
ID: 1227435
haven't tested it, but

URL url = new URL("www.somewhere.com/data.txt");
InputStream = URL.getStream();

should work. Your browser sends HTTP reuqest to the web-server at www.somewhere.com, handles the response and gives you only the body of the message (which is your data.txt file)
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