• 0

Java: Reading File & Loop help


Question

Hi... I'm a newbie at Java, so I was wondering if you guys could help me out...

I have txt file i'm reading scores and labels off of to make a bar graph.

First line is an integer (score), second line is the label ("Score 1"), and they alternate from then on. I have 5 scores, meaning ten lines in the txt file.

Anyway, I can read the txt file and make the bar graph perfectly, but when i make the loop, i always have to specify how many times to do the loop... I have no idea how to make it count how many items are in the txt file automatically or to stop when there are no more values.

Please help if you can :o

Here is my code for the loop area so far:

 int n = 0;
  int itemCount = 5;

  SimpleReader reader = new SimpleReader( "graphdata.dat" );

  while ( n < itemCount )
 	 {
 	 double number = reader.getInt();
 	 r = new SimpleRectangle( BAR_START, barPos, (int) number, BAR_HEIGHT );
 	 r.setColor( barColor );
 	 r.setToFill();
 	 graphWin.add( r );
 	 total = total + number;
 	 n = n + 1;
 	 barPos = barPos + BAR_HEIGHT + BAR_SPACER;

 	 String word = reader.getString();
 	 lab = new SimpleLabel( LABEL_START, labelPos, LABEL_WIDTH, LABEL_HEIGHT );
 	 lab.setText( word + ": " + (int) number );
 	 graphWin.add( lab );
 	 labelPos = labelPos + LABEL_HEIGHT + LABEL_SPACER;
 	 }
  reader.safeClose();

Link to comment
https://www.neowin.net/forum/topic/62996-java-reading-file-loop-help/
Share on other sites

6 answers to this question

Recommended Posts

  • 0

Well, I've got no idea what SimpleReader is, but if it's extending BufferedReader, reader.ready() will say if the file is ready or not.

So:

while(reader.ready()) {
........

or

while(reader.getInt() != *numberhere*)

If it returns an error number, just put that in the *numberhere*

It's hard though not knowing what your reader does or what methods it has to read the file with.

Edited by kjordan2001
  • 0

Use BufferedReader instead and to for the this question:

"or to stop when there are no more values"

use a while loop if the following code:

while (in.readLine() != null)
{
    //Code execution here
}

This code below is what i did some while back and should give you some hints on how to implement BufferedReader:

/**
 * Read Class - A Class that Read's a Text file
 * @author Saad Mahamood 
 * @version 10/10/02 
 */

import java.io.*;

public class Read  
{

    public Read()
    {
        //Default Constructor
    }


    /**
     * textFile - This method read's a text file and output's
     *            it's content's to the terminal
     *@execption - IOException 
     */
    public void textFile() throws IOException
    {
        File aFile = new File("read.txt");

        if ((!aFile.isFile()) || (!aFile.canRead()))
        {
            // Let's leave
            throw new IOException("File not found");
        }

            
        BufferedReader in = new BufferedReader(new FileReader(aFile));
        
        
        String theString = null;

        for (int i=0;i < 26; i++ ) 
        {
            theString = in.readLine();
            System.out.println(theString);
       	 
        }


    }



	public static void main(String[] args) 
	{
  System.out.println("Reading file");
        System.out.println("***********************");
        Read aread = new Read();
        try
        {
            aread.textFile();
        }
        catch(IOException e)
        {
            System.err.println("Anption occured!");
        }

	}
}

ss1.

  • 0

try {
    BufferedReader oBuffer = new BufferedReader(new FileReader(new File("Path\to\file.txt")));
} catch (FileNotFoundException e) {
    system.out.print("FileFound");
}

String s = null;
while(true) {
    s = oBuffer.readLine();
    if (s == null) break;

    //Do your Rectangle business here
}

BTW: IF you are finding you have to create your own readers and writers and you are a newbie, then you are going down the wrong path. The book "Core Java2" from Sun Press has a good chapter that deals with the intricacies of Readers and Writers (and InputStreams and OutputStreams). I suggest you read it. It will spare you a lot of time later down the line.

Also, try not to initialize your objects inside of a loop. You have a line

String word = reader.getString();

inside your loop. That is not very efficient. While not technically wrong, it is a bad habit to get into.

FREE TIP: (and off-topic) On a related note, careful with string concatenation inside loops. You don't do it on the example you supplied, but if you are reading a file the last thing you want to do is:

String s = new String();
String temp = null;
while (true) {
    temp = oBuffer.readLine();
    if (temp == null) break;
    s += temp;
}

If you read the book above, or any text on the net, you will learn to use a StringBuffer for this kind of operation.

Edited by PeterHammer
  • 0

sorry for the lack of reply the past few days, i haven't had a chance to jump back on the computer...

thanks for all your help... I'm a total newbie to Java, and i just found out how stupid it was to post the code that I have, since I found out that SimpleReader and all that stuff were custom classes from my teacher. sorry about that.

thanks for all your help though, i got it working now =)

thanks for all your help with BifferedReader also, I think i'm gonna study up on that one more... I'll read up a bit more before I ask for the next question.

Thanks again, and I really appreciate all of your help guys. :D

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • Jumping unicorns says that I forgot you. I never grunt.
    • Microsoft can't help break Windows Outlook as even opening an email now sends it crashing by Sayan Sen It is no surprise that right now, Microsoft's priority is to move users onto the New Outlook for Windows if they haven't done so already. The company began default-deployment of the new app on fresh Microsoft 365 systems and also made switching between the New app and the classic app easier. At the same time, the company is also trying to improve the new app as it recently added yet another feature that will allow people to use the app without an internet connection, and it also blocked more file types to improve security. Perhaps as a consequence of this relentless pursuit, the classic Outlook app has become quite prone to bugs and issues in recent times as Microsoft may be losing its focus. For example, in April, the downloads for Classic Outlook broke and more recently, this month, the tech giant confirmed that a major Calendar feature upgrade has broken the app in several different ways. Microsoft has provided workarounds for several of the issues so check this article out if you are having problems. And the bugs just keep on coming as Microsoft earlier today confirmed that opening emails or starting a new email will now crash the application, and it affects all channels. The company explains: Opening a mail on an email client is probably the most common and basic functionality a user is expected to do, so it is annoying to see such a bug not getting caught during testing. Again, this perhaps indicates that Microsoft's focus maybe elsewhere at the moment. The company has shared the Windows Event Viewer Log for the crash and the problematic OLMAPI32 DLL file is related to Microsoft Messaging Application Programming Interface (MAPI). The issue reminds us of the similar OLEAUT32 dll issue fix in our recent ReactOS article. The event viewer log notes: Faulting application name: OUTLOOK.EXE, version: 16.0.14334.20090, time stamp: 0x683fe030 Faulting module name: OLMAPI32.DLL, version: 16.0.14334.20090, time stamp: 0x683ff910 Exception code: 0xc0000409 Fault offset: 0x00196e1c Faulting process id: 0x9100 Faulting application start time: 0x01dbdbe04fe54514 Faulting application path: C:\Program Files (x86)\Microsoft Office\root\Office16\OUTLOOK.EXE Faulting module path: C:\Program Files (x86)\Microsoft Office\root\Office16\OLMAPI32.DLL Thankfully, Microsoft has issued a workaround for the problem as it currently investigates the bug by manually creating a FORMS2 folder which should exist at the following address: C:\Users\\AppData\Local\Microsoft\FORMS2. Microsoft explains: You can find the support article for the issue here on Microsoft's official website.
    • I have no issue with a service not being offered free. That's perfectly understandable. I do have issue with seeing ads literally everywhere these days, though, plastered in layers over every website and in every app. Especially with how annoying they tend to be (hell, many ads these days even promote literal scams). That's why people use ad blockers. Let me choose. Offer an ad-free experience for a couple of bucks (but be reasonable, don't get too greedy) or ads for free access. Don't make it ads or nothing.
    • Yeah, running a site does consume your whole life.
  • Recent Achievements

    • Week One Done
      korostelev earned a badge
      Week One Done
    • Week One Done
      rozermack875 earned a badge
      Week One Done
    • Week One Done
      oneworldtechnologies earned a badge
      Week One Done
    • Veteran
      matthiew went up a rank
      Veteran
    • Enthusiast
      Motoman26 went up a rank
      Enthusiast
  • Popular Contributors

    1. 1
      +primortal
      684
    2. 2
      ATLien_0
      268
    3. 3
      Michael Scrip
      182
    4. 4
      +FloatingFatMan
      177
    5. 5
      Steven P.
      139
  • Tell a friend

    Love Neowin? Tell a friend!