Computer Science Canada

Making a program for parents..need help.
Author:  GUImaster [ Wed Jul 07, 2010 8:40 pm ]
Post subject:  Making a program for parents..need help.
Im making a program for my parents...and i got stuck. a part of what i need to do is
**Using Netbeans 6.8**

*Needs Button*
*Needs TextField*
---------------------------------------------------------------------------------
Check To see if "input.txt" is empty

if "input.txt" is empty then
write "This is Header"
write "----------------"
write (Text in TextField)

if "input.txt" isnt empty then

append at end of file (Text in TextField)
--------------------------------------------------------------------------------


i had a basic idea of what i needed to do but it didnt work out for me

Thanks in Advance
Author:  Zren [ Wed Jul 07, 2010 9:08 pm ]
Post subject:  Re: Making a program for parents..need help.
Here's some code snippets to point you in a general direction of File Input/Output. Buttons are rather easy in netbeans so that shouldn't be the problem. If ya need more details just ask.

To find if the file exist (Copy n Paste, this forum doesn't like the brackets at the end. Or just look for exists yourself): http://download.oracle.com/docs/cd/E17476_01/javase/1.4.2/docs/api/java/io/File.html#exists()

File Size:
Java:
File f = new File("blarg.txt");
long file_size = f.length();


For writing to files: [Source]
Java:

import java.io.*;
class FileWrite {
   public static void main(String args[]) {
      try {
        // Create file
        FileWriter fstream = new FileWriter("out.txt");
        BufferedWriter out = new BufferedWriter(fstream);
        //Trick: BufferedWriter out = new BufferedWriter( new FileWriter("out.txt") );

        out.write("Hello Java");
        //Close the output stream
        out.close();
    } catch (Exception e) { //Catch exception if any
        System.err.println("Error: " + e.getMessage());
    }
  }
}

Don't forget to close or flush the bufferedwriter or nothing will write to file.
Author:  GUImaster [ Wed Jul 07, 2010 9:49 pm ]
Post subject:  Re: Making a program for parents..need help.
i have import.java.io.*;
and this code happens when the button is pressed

code:
try {
            fis = new FileInputStream("input.txt");
           
            in = new DataInputStream(fis);
            temp = in.readLine();
            in.close();
           
            fwriter5 = new FileWriter("input.txt", true);
            bfwriter2 = new BufferedWriter(fwriter5);
            if (temp.compareTo(" ")==0) {
                bfwriter2.write("Hello");
                bfwriter2.write("------------------");
                bfwriter2.write(jTextField1.getText());
               
            } else  {
                 
               // bfwriter2.write(jTextField1.getText());
            }
         
        } catch (IOException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }
           


thats what i have after using netbeans gui bulder... but it doesnt work for me
Author:  Zren [ Wed Jul 07, 2010 10:04 pm ]
Post subject:  RE:Making a program for parents..need help.
Did you clooooo~se the buffered writer?
Author:  GUImaster [ Wed Jul 07, 2010 10:06 pm ]
Post subject:  Re: Making a program for parents..need help.
i dont exactly know where to close it....the try catch things always throw me off

[Update] I closed it in the if statement and i got the same error}

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
Author:  GUImaster [ Wed Jul 07, 2010 10:20 pm ]
Post subject:  Re: Making a program for parents..need help.
I got it working now...Thanks for the help

i changed the if (Temp.compareTo(" ")==0) to if (temp == null)

:


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