Java: Reading characters from a text file

chief_officer · 03-25-2007, 01:40 PM

Friends,

I am totally confused...

I am trying to write a small Java program that reads data from a text file. So far, I am able to read the entire file, however I want to group the values in the text file and write with headers.

Step 1 - Here is my text file:

Quote:

MYTEXTFILE
1 XXXX1234567 LINMACWIN*
1 YYYY8901234 DOSOS2YOU*

Step 2 - The explanation of the text file:

The first string (MYTEXTFILE) is an indicator that the file that will be opened is a native file of the application.
The lines ending with * are individual lines.
Each line has different data. From the sample file above:
1: count, as integer
XXXX1234567, YYYY8901234: IDs.
LIN: property 1
MAC: property 2
WIN: property 3
*: end of line character

In fact, all the lines ending with * are character arrays. Inside the arrays, the data are to be read by file specifications; e.g. 3 characters to count, 11 characters IDs, 3 spaces, 3 characters for property 1, 3 characters for property 2, 3 characters for property 3 etc. until *.

Code:

package textfileread;

import java.io.*;

public class Main {
    
    public Main() {
    }
    
    public static void main(String[] args) throws Exception
    {
  
    FileReader conts = new FileReader ("pmlfile.pml");
    BufferedReader br = new BufferedReader (conts);
    String s;
    
    while ((s=br.readLine())!=null)
    {
          
        System.out.println(s);
    }
    conts.close();
    }

These are the only lines that I could code. I am trying to insert CharArrayReader into the code to read characters from the text file, but somehow

Code:

CharArrayReader item_01 = new CharArrayReader(0,0,3)

gives me lots of errors.

I am googling for hours and I have come to a state that I am unable to understand what I read.

Can anyone give me a helping hand?

Regards.

nadroj · 03-25-2007, 04:12 PM

ive never used CharArrayReader, but from the API:

Quote:

CharArrayReader(char[] buf, int offset, int length)

and your passing 3 ints instead of char[], int, int.

after fixing this, post the _error messages_ you recieve so we can try to further help.

rednuht · 03-25-2007, 04:13 PM

its been a while since I used Java but this might help

Code:

                byte dataBuffer[];
		int amountRead=0;

		dataBuffer = new byte[VMIfileSize];
  		try {
      	      BufferedInputStream disi = null;
              disi = new BufferedInputStream(in);

      	      amountRead = (int)disi.read(dataBuffer,0,VMIfileSize);

I am of course refering to the read(buffer,start,end) call.

chief_officer · 03-26-2007, 11:28 AM

@rednuht

Code:

package textfileread;

import java.io.*;

public class Main {
    
    public Main() {
    }
    
    public static void main(String[] args) throws Exception
    {
    int amount_read = 0;
   
    FileReader conts = new FileReader ("pmlfile.pml");
    BufferedReader br = new BufferedReader (conts);
    dataBuffer = new byte [VMIfileSize];

    
    while ((s=br.readLine())!=null)
    {
        BufferedInputStream disi = null;
        disi = new BufferedInputStream(in);
        amountread = (int)disi.read(databuffer,0,VMIfilesize);
    }
    conts.close();
    }
    
}

Quote:

deps-jar:
Compiling 1 source file to /home/diablo/java_codes/textfileread_01/build/classes
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:26: cannot find symbol
symbol : variable dataBuffer
location: class textfileread.Main
dataBuffer = new byte [VMIfileSize];
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:26: cannot find symbol
symbol : variable VMIfileSize
location: class textfileread.Main
dataBuffer = new byte [VMIfileSize];
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:29: cannot find symbol
symbol : variable s
location: class textfileread.Main
while ((s=br.readLine())!=null)
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:32: cannot find symbol
symbol : variable in
location: class textfileread.Main
disi = new BufferedInputStream(in);
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:34: cannot find symbol
symbol : variable amountread
location: class textfileread.Main
amountread = (int)disi.read(databuffer,0,VMIfilesize);
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:34: cannot find symbol
symbol : variable databuffer
location: class textfileread.Main
amountread = (int)disi.read(databuffer,0,VMIfilesize);
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:34: cannot find symbol
symbol : variable VMIfilesize
location: class textfileread.Main
amountread = (int)disi.read(databuffer,0,VMIfilesize);
7 errors
BUILD FAILED (total time: 0 seconds)

@nadroj

Code:

package textfileread;

/**
 *
 * @author diablo
 */

import java.io.*;

public class Main {
    
    /** Creates a new instance of Main */
    public Main() {
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception
    {
    //int c[] = new char[cont_no];
    
    FileReader conts = new FileReader ("pmlfile.pml");
    BufferedReader br = new BufferedReader (conts);
    String s;
    
    while ((s=br.readLine())!=null)
    {
        BufferedInputStream disi = null;
        CharArrayReader input = new CharArrayReader(3, 1, 4);
        System.out.println(input);
    }
    conts.close();
    }
    
}

the error is:

Quote:

nit:
deps-jar:
Compiling 1 source file to /home/diablo/java_codes/textfileread_01/build/classes
/home/diablo/java_codes/textfileread_01/src/textfileread_01/Main.java:30: cannot find symbol
symbol : constructor CharArrayReader(int,int,int)
location: class java.io.CharArrayReader
CharArrayReader input = new CharArrayReader(3, 1, 3);
1 error
BUILD FAILED (total time: 0 seconds)

I am thinking that I am close, that was what I tried to the yesterday before posting. As per the API, I should be able to read 3 characters with CharArrayReader(3, 1, 4). However, I am getting the error above.

What is going wrong? Text files are the simplest files that can be read and written. Reading them should not be so hard.

nadroj · 03-26-2007, 06:42 PM

Quote:

As per the API, I should be able to read 3 characters with CharArrayReader(3, 1, 4). However, I am getting the error above.

from the API page:

Quote:

Constructor Summary
..CharArrayReader(char[] buf)
............Create an CharArrayReader from the specified array of chars.
..CharArrayReader(char[] buf, int offset, int length)
............Create an CharArrayReader from the specified array of chars.

(i added the .'s to keep everything lined up).

you have to pass 'char[], int, int', not 'int,int,int'

EDIT:
regarding errors from your previous post directed to rednuht
- line 16:

Code:

dataBuffer = new byte [VMIfileSize];

do you mean to use ()s instead of []s? Also, where is VMIfileSize declared?

- line 19:

Code:

while ((s=br.readLine())!=null)

where is 's' declared?

- line 22:

Code:

disi = new BufferedInputStream(in);

where is 'in' declared?

- line 23:

Code:

amountread = (int)disi.read(databuffer,0,VMIfilesize);

'databuffer' isnt declared, do you mean 'dataBuffer'? remember java is cASe SENsiTIve.

indienick · 03-26-2007, 07:04 PM

Might I suggest just using a different input class altogether?
I make *almost* exclusive use of java.util.Scanner in every Java application I write.

Code:

import java.util.Scanner;
public class Blarg {
  // To read in from a file:
  Scanner inStream = new Scanner(new File("/path/to/file"));
  ArrayList buf = new ArrayList();

  // To read in from user-typed responses:
  Scanner userInput = new Scanner(System.in);
  String input;
  public static void main(String[] args) {
    while (inStream.hasNext() == true) buf.add(inStream.nextLine());
    System.out.print("Display contents of file (y/n)? ");
    input = userInput.nextLine();
    if (input.equalsIgnoreCase("y")) {
      for (int i = 0; i < buf.size(); i++) {
        System.out.println(buf.get(i).toString());
      }
    } else System.exit(0);
  }
}

Now, the Scanner.nextLine() and Scanner.next() methods return strings. If you want chars, use the following:

Code:

char c = Scanner.findInLine(".").charAt(0);

Which, literally, means find character . at element 0 in the string. Think of the string as an array; the period, ".", is treated as a wildcard character.