Read a large size text file

how can i read a large size text file in multiple parts without lossin any data ?
Ben

Why are you afraid of losing data? There's no reason that you would lose data if you are reading a large text file.
You should use the various Reader and Writer classes in package java.io to read and write text files. Here's an example of how you can read a text file line by line:
BufferedReader r = new BufferedReader(new FileReader("myfile.txt));
int lineno = 1;
String line;
while ((line = r.readLine()) != null) {
System.out.printf("%d: %s%n", i, line);
i++;
r.close();

Similar Messages

Read data from a text file, one line at a time.

I need to read data from a text file, and display each line in a String Indicator on Front Panel. It displays each line, but I get Error 4, End Of Line, unless I enter an extra line of data in the file that I don't need. I tried Read From Text File.vi, made by Nat Instr, and it gave the same error.

The Read from Text File.vi reads data from a text file line by line until the user stops the VI manually with the Stop button on the front panel, or until an error (such as "Error 4, End of file") occurs. If an error occurs, the Simple Error Handler.vi pops up a dialog that tells you which error occurred.
The Read from Text File.vi uses a while loop, but if you knew how many lines you wanted to read, you could replace the while loop with a for loop set to read that many lines from the file.
If you need something more dynamic because the number of lines in your files vary, then you could change the code of the Read from Text File.vi to the expect "Error 4, End of file" and handle it appropriately. This would require unbundling the error cluster that comes fro
m the Read File function with the Unbundle By Name function, so that you can expose the individual error "status" and error "code" values stored in the cluster. If the value of the error "code" is 4, then you can change the error "status" from true to false, and you can rebundle the cluster with the Bundle by Name function. Setting the error "status" to false instructs the Simple Error Handler to ignore the error. Otherwise, pass the original error cluster to the Simple Error Handler.vi, so that you can see what the error is.
Of course, if you're not interested in what the errors are, you could just remove the Simple Error Handler.vi, but then you wouldn't see any error messages.
Best of Luck,
Dieter
Dieter Schweiss
Applications Engineer
National Instruments

Shell scripts to read data from a text file and to load it into a table

Hi All,
I have a text file consisting of rows and columns as follows,
GEF001 000093625 MKL002510 000001 000000 000000 000000 000000 000000 000001
GEF001 000093625 MKL003604 000001 000000 000000 000000 000000 000000 000001
GEF001 000093625 MKL005675 000001 000000 000000 000000 000000 000000 000001 My requirement is that, i should read the first 3 columns of this file using a shell script and then i have to insert the data into a table consisting of 3 rows in oracle .
the whole application is deployed in unix and that text file comes from mainframe. am working in the unix side of the application and i cant access the data directly from the mainframe. so am required to write a script which reads the data from text file which is placed in certain location and i have to load it to oracle database.
so I can't use SQL * loader.
Please help me something with this...
Thanks in advance.

1. Create a dictionary object in Oracle and assign it to the folder where your file resides
2. Write a little procedure which opens the file in the newly created directory object using ULT_FILE and inside the FOR LOOP and do INSERTs to table you want
3. Create a shell script and call that procedure
You can use the post in my Blog for such issues
[Using Oracle UTL_FILE, UTL_SMTP packages and Linux Shell Scripting and Cron utility together|http://kamranagayev.wordpress.com/2009/02/23/using-oracle-utl_file-utl_smtp-packages-and-linux-shell-scripting-and-cron-utility-together-2/]
Kamran Agayev A. (10g OCP)
http://kamranagayev.wordpress.com

Need to read data from a text file

I need to read data from a text file and create my own hash table out of it. I'm not allowed to use the built in Java class, so how would I go implementing my own reading method and hash table class?

It's not possible to read from a file without using classes from the core API*. You'll have to get clarification from your instructor as to which classes are and are not allowed.
[http://java.sun.com/docs/books/tutorial/essential/io/]
*Unless you write a bunch of JNI code to replicate what the java.io classes are doing.

Reading variables from a text file into a flash projector exe

I am using Flash CS4 and my script is in ActionScript2.
I am developing a flash projector file that runs when a user puts in a cd to guide them through the steps they need to install a program and then kicks off the installer.
I use fscommand to run a utility that reads the users registry to determine the PCs regional settings and then writes this to a text file in the users %temp% directory.
I then use the LoadVariablesNum command to read in the text file and get the variables.
This was working fine when I had the text file stored in a different directory, but when I try and refer to the %temp% directory, I get an Error opening file message.
Is there anyway to get flash to look in the %Temp% directory?
Thanks in advance,
Carol Lutz

Code-tags sometimes cause wonders, I replaced # with *, as the code tags interprets # as comment, which looks odd:
******...*.........To your code: Did you test it step by step, to find out about what is read? You could either use a debugger (e.g., if you have an IDE) or system outs to get a clue. First thing to check would be, if the maze size is read correctly. Further, the following loops look odd:for(int i = 0; i < maze.length; i++) {
    for(int x = 0; x < maze.length; x++) {
        if (input.hasNextLine()) {
            String insert = input.nextLine();
            maze[x] = insert.charAt(x);
}Shouldn't the nextLine test and assignment be in the outer loop? And assignment be to each maze's inner array? Like so:for(int i = 0; i < maze.length; i++) {
    if (input.hasNextLine()) {
        String insert = input.nextLine();
        for(int x = 0; x < insert.size(); x++) {
            maze[i][x] = insert.charAt(x);
}Otherwise, only one character per line is read and storing a character actually should fail.

Reading characters from a text file into a multidimensional array?

I have an array, maze[][] that is to be filled with characters from a text file. I've got most of the program worked out (i think) but can't test it because I am reading my file incorrectly. However, I'm running into major headaches with this part of the program.
The text file looks like this: (It is meant to be a maze, 19 is the size of the maze(assumed to be square). is free space, # is block, s is start, x is finish)
This didn't paste evenly, but thats not a big deal. Just giving an idea.
19
5..................
And my constructor looks like follows, I've tried zillions of things with the input.hasNext() and hasNextLine() to no avail.
Code:
//Scanner to read file
Scanner input = null;
try{
input = new Scanner(fileName);
}catch(RuntimeException e) {
System.err.println("Couldn't find the file");
System.exit(0);
//Set the size of the maze
while(input.hasNextInt())
size = input.nextInt();
//Set Limits on coordinates
Coordinates.setLimits(size);
//Set the maze[][] array equal to this size
maze = new char[size][size];
//Fill the Array with maze values
for(int i = 0; i < maze.length; i++)
for(int x = 0; x < maze.length; x++)
if(input.hasNextLine())
String insert = input.nextLine();
maze[i][x] = insert.charAt(x);
Any advice would be loved =D

Code-tags sometimes cause wonders, I replaced # with *, as the code tags interprets # as comment, which looks odd:
******...*.........To your code: Did you test it step by step, to find out about what is read? You could either use a debugger (e.g., if you have an IDE) or system outs to get a clue. First thing to check would be, if the maze size is read correctly. Further, the following loops look odd:for(int i = 0; i < maze.length; i++) {
    for(int x = 0; x < maze.length; x++) {
        if (input.hasNextLine()) {
            String insert = input.nextLine();
            maze[x] = insert.charAt(x);
}Shouldn't the nextLine test and assignment be in the outer loop? And assignment be to each maze's inner array? Like so:for(int i = 0; i < maze.length; i++) {
    if (input.hasNextLine()) {
        String insert = input.nextLine();
        for(int x = 0; x < insert.size(); x++) {
            maze[i][x] = insert.charAt(x);
}Otherwise, only one character per line is read and storing a character actually should fail.

How do I read and write to text files on a remote computer's hard drive

I would like to read and write data to a text file on a remote computer. This is easily accomplished using one of the file functions such as "write characters to file.vi". If I am already connected to the remote computer, all I need to do is specify the path to the particular file and it will work fine.
My problem is that I want to connect to the remote computer programatically within LabVIEW (I do not want to have to use the computer's OS to establish the connection. Is there a function that I can use to do this?
Thomas D. Schaefer
Wells Manufacturing Corp

Yariv,
You should really start a new thread with a new question like this, so that more people see it. Some people look primarily at threads that have no responses yet. Also, don't post the exact same question in multiple places. Or, if you must cross-post to some other forum, make sure to mention it in your question text.
I'm happy to be a brick in your Western Wall, but I'm not sure what the main objective is here. Is the main problem really getting access to the "X bytes received in Y seconds at Z bytes/sec" string? Or is it accomplishing the file transfer? And what OS and LabVIEW version are you running?
I think your problem is that you the LabVIEW System Exec command does not allow for the degree of interactivity that you need if you want to issue a sequence of commands to a command-line executable. However, under Windows XP (and, presumably, other Windows versions, though I can't check), you can tell the FTP executable to use commands from a textfile script by using the -s switch, and you can override the prompts during multiple file transfers with the -i switch:
ftp -i -s:FILEPATH SERVERNAME
If you issue a command in this format to System Exec, and make sure to create a file at FILEPATH with your command sequence (one per line), then you should at least accomplish the FTP actions. This won't give you the transfer details in the standard output, unfortunately. However, if you just want a general sense of how much was transferred and how quickly it happened, you can code that in LabVIEW by getting the resulting file sizes and using Tick Count before and after the System Exec call to see how long the transfer took.
Hope that helps,
John

Parse large (2GB) text file

Hi all,
I would like your expert tips on efficient ways (speed and memory considerations) for parsing large text files (~2GB) in Java.
Specifically, the text files in hand contain mobility traces that I need to process. Traces have a predefined format, and each trace is given on a new line in the text file.
To obtain the attribues of each trace i use java.util.regex.Pattern and java.util.regex.Matcher.
Thanks in advance,
Nick

Memory mapped files are faster when you need random access and you don't need to load all the data, however here it just add complexity you don't need IMHO.
I suspect most of the time is taken by the parser so if you customise your parser it could be faster. Here is a simple custom parser
public static void main(String... args) throws IOException {
    String template = "tr at %.1f \"$obj(1) pos 123.20 270.98 0.0 2.4\"%n";
    File file = new File("/tmp/deleteme.txt");
//        if(!file.exists()) {
        System.out.println(new Date()+": Writing to "+file);
        PrintWriter pw = new PrintWriter(file);
        for(int i=0;i<Integer.MAX_VALUE/template.length();i++)
            pw.printf(template, i/10.0);
        pw.close();
        System.out.println(new Date()+": ... finished writing to " + file + " length= " + file.length() / 1024 / 1024 + " MB.");
    long start = System.nanoTime();
    final BufferedReader br = new BufferedReader(new FileReader(file), 64 * 1024);
    for(String line;(line = br.readLine()) != null;) {
        int pos = 6;
        int end = line.indexOf(' ', pos);
        double time = Double.parseDouble(line.substring(pos, end));
        pos = line.indexOf('s', end+12)+2;
        end = line.indexOf(' ', pos+1);
        double x = Double.parseDouble(line.substring(pos, end));
        pos = end+1;
        end = line.indexOf(' ', pos+1);
        double y = Double.parseDouble(line.substring(pos, end));
        pos = end+1;
        end = line.indexOf(' ', pos+1);
        double z = Double.parseDouble(line.substring(pos, end));
        pos = end+1;
        end = line.indexOf('"', pos+1);
        double velocity = Double.parseDouble(line.substring(pos, end));
    br.close();
    long time = System.nanoTime() - start;
    System.out.printf(new Date()+": Took %,f sec to read %s%n", time / 1e9, file.toString());
{code}
prints
{code}
Sun May 08 09:38:02 BST 2011: Writing to /tmp/deleteme.txt
Sun May 08 09:42:15 BST 2011: ... finished writing to /tmp/deleteme.txt length= 2208 MB.
Sun May 08 09:43:21 BST 2011: Took 66.610883 sec to read /tmp/deleteme.txt
{code}

How to read long line from text file

Hi,
I just faced problem when reading a big text file.
BufferedReader br = new BufferedReader(new FileReader("D:\\afile.txt"));
String str;
int i;
while ((str = br.readLine())!=null)
i++;
//do some work here...
...This code throws exception:
Exception in thread "main" java.lang.OutOfMemoryError: Java heap spaceSo I thought file line is very long. When I opened it in FAR it only displays no more than 4096 characters as a line.
Help me to read a text file that's line is very long?

try,
$ java -X
-Xmixed mixed mode execution (default)
-Xint interpreted mode execution only
-Xbootclasspath:<directories and zip/jar files separated by ;>
set search path for bootstrap classes and resources
-Xbootclasspath/a:<directories and zip/jar files separated by ;>
append to end of bootstrap class path
-Xbootclasspath/p:<directories and zip/jar files separated by ;>
prepend in front of bootstrap class path
-Xnoclassgc disable class garbage collection
-Xincgc enable incremental garbage collection
-Xloggc:<file> log GC status to a file with time stamps
-Xbatch disable background compilation
-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size
-Xprof output cpu profiling data
-Xrunhprof[:help]|[:<option>=<value>, ...]
perform JVMPI heap, cpu, or monitor profiling
-Xdebug enable remote debugging
-Xfuture enable strictest checks, anticipating future default
-Xrs reduce use of OS signals by Java/VM (see documentation)
-Xcheck:jni perform additional checks for JNI functions
The -X options are non-standard and subject to change without notice.

How can we read a column from text file

hai,
the Text file contains :
m1 m2 m4 89
m1 m2 m4 89
m0 m4 m2 90
I need one array for each column
m[0]= m1,m1,m0 (first column from text file)
m[1]= m2,m2,m2 (second column from text file)
m[2]= 89,89,90 (third column from text file)
andvance thanks

If a 2D array is OK (instead of 4 separate arrays), try something like this
import java.io.*;
import java.util.ArrayList;
class FileReadColumns
public static void main(String args[]) throws IOException, FileNotFoundException
    String line;
    ArrayList lines = new ArrayList();
    BufferedReader in = new BufferedReader(new FileReader("data.txt"));
    while ((line = in.readLine()) != null) lines.add(line);
    String bits[];
    bits = lines.get(0).toString().split(" ");
    String grid[][] = new String[bits.length][];
    for(int i=0;i<grid.length;i++)grid[i] = new String[lines.size()];
    for(int i = 0; i < lines.size(); i++)
      bits = lines.get(i).toString().split(" ");
      for(int ii = 0; ii < bits.length; ii++) grid[ii] = bits[ii];
for(int i = 0; i < grid.length; i++)
for(int ii=0;ii<grid[i].length;ii++)System.out.print(grid[i][ii]+" ");
System.out.println();
System.exit(0);

Read words from a text file into an undefined array

Dear all,
Does anyone know how to read words in text file, seperated by all types of spaces ("_", "\n", "\t","\r","\f") and put them into a string array to be used later?
So far I can read the words using the Tokenizer but can't assign to array:
public class reader
StringTokenizer tokenizer = new StringTokenizer(input);
String[ ] array= null; //unknown size of array
int i=0;
               while(tokenizer.hasMoreTokens())
                         array[i] = tokenizer.nextToken();
                         i++;
Any suggestions welcome!
thanks in advance!

Hi
sorry wrote in a hurry ;) din c the problem clearly
there are two approaches
1) best approach for your problem is Vector or ArrayList, these would make life easy for you.
Always collections are better approach over arrays when the size is dynamic. However in your case the size cant be said to be DYNAMIC. coz the number of words will not grow / shrink during the runtime.. i know that number of words are not fixed but dynamic is something which will grow/shrink during runtime. but still collection is better approach.
2)dirty approach
use double dimensional array
String arr[][] = null;
then use one tokenizer for StringTokenizer(str,"\n");
using countTokens on this will give you number of lines.
use this to initialize array
arr = new String[lineCount][];
then iterate from 1 to lineCount and use 1 more tokenizer to get number of words for that line. use this number to initialize the column size for arr[i] like
arr[i] = new String[wordCount];
then store the token using nested for loops in this array
go for the 1st one ;) 2nd one is hedious n time consuming but both will work ;)
cheers
amey

How do you read data from a text file into a JTextArea?

I'm working on a blogging program and I need to add data from a text file named messages.txt into a JTextArea named messages. How do I go about doing this?

Student_Coder wrote:
1) Read the file messages.txt into a String
2) Initialize messages with the String as the textSwing text components are designed to use Unix-style linefeeds (\n) as line separators. If the text file happens to use a different style, like DOS's carriage-return+linefeed (\r\n), it needs to be converted. The read() method does that, and it saves the info about the line separator style in the Document so the write() method can re-convert it.
lethalwire wrote:
They have 2 different ways of importing documents in this link:
http://java.sun.com/docs/books/tutorial/uiswing/components/editorpane.html
Neither of those methods applies to JTextAreas.

How to store data into database by reading sql statements from text file

how to write java program for storing data into database by reading sql statements from text file

Step 1: Create a property file to add various queries.
Step 2: Read the properties file using ResourceBundle
Step 3: Use the jdbc to execute the query read from the property file.
So in future if you need to change query no need do any modifications in java program. But depends on how you use the property file.

How to read data from a text file

I have saved a text file on my hard drive, and would like to read the file. Once read I would like to copy it to another file. I think I am suppose to use the BufferedReader, and FileReader classes. I am not sure what sequence to follow in order to do this. Could some one give me some feed back on what is needed, and in what sequence to perform this task?

Where do I store my file within my Platform(Eclipe), in order to read or access the file. Whenever I use the declaration below. I get an FileNotFoundException. I understand the code, but am not sure where to store the file, so that the line of code below will recognize it..
FileReader in = new FileReader("data1.txt");
BufferedReader a = new BufferedReader(in);

How to read characters from a text file in java program ?

Sir,
I have to read the characters m to z listed in a text file .
I must compare the character read from the file.
And if any of the characters between m to z is matched i have to replace it with a hexadecimal value.
Any help or suggesstions in this regard would be very useful.
Thanking you,
khurram

Hai,
The requirement is like this
There is an input file, the contents of the file are as follows, you can assume any name for the file.
#Character mappings for Japanese Shift-JIS character set
#ASCII character Mapped Shift-JIS character
m 227,128,133 #Half width katakana letter small m
n 227,128,134 #Half width katakana letter small n
o 227,129,129
p 227,129,130
q 227,129,131
r 227,129,132
s 227,129,133
t 227,129,134
u 227,129,135
v 227,129,136
w 227,129,137
x 227,129,138
y 227,129,139
z 227,129,142
The contents of the above file are to be read as input.
On encountering any character between m to z, i have to do a replacement with a hexadecimal code point value for the multibyte representation in the second column in the input file.
I have the code to get the unicode codepoint value from the multibyte representation, but not from a file.
So if you could please tell me how to get the characters in the second column, it would be very useful for me.
The character # is used to represent the beginning of a comment in the input file.
And comment lines are to be ignored while reading the file.
Say i have a string str="message";
then i should replace the m with the unicode code point value.
Thanking you,
khurram

Read a large size text file

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