Read lines from text file to java prog

how can I read lines from input file to java prog ?
I need to read from input text file, line after line
10x !

If you search in THIS forum with e.g. read lines from file, you will find answers like this one:
Hi ! This is the answer for your query. This program prints as the output itself reading line by line.......
import java.io.*;
public class readfromfile
public static void main(String a[])
if you search in THIS forum, with e.g. read lines from text file
try{
BufferedReader br = new BufferedReader(new FileReader(new File("readfromfile.java")));
while(br.readLine() != null)
System.out.println(" line read :"+br.readLine());
}catch(Exception e)
e.printStackTrace();
}

Similar Messages

Read lines from text-file in specified [ITEM]

Hello,
are there any functions integrated in Labview to read a text-file which looks like this:
[ITEM-NAME_01]
parameter1 = here
parameter2 = 1123
parameter3 = a453
[ITEM-NAME_02]
parameter4 = here
parameter5 = 1123
parameter6 = a453
Can this be done easy, or do i have to manually search the file for the "["-character ?
At the end i want a VI where i pass the file-name and the item-name as input, and as output i want one array with the parameter-names and the other array with the values.
How can this be done?
Thanks for your help

Hi OnlyOne,
you are talking about Configuration files?
Look in the file palette, sub-palette "configuration files". It's all in there!
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

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.

Read lines from a file

With "ApartmentFileHandler" I can write Apartment-objects to a file and read them from a file.
To write I loop through each room in the apartment and write its size
and type. I put 1 Room per line.
To read I read each line of the file and recreate the room stored
there. When there are no lines left in the file I pass the Rooms from
the file to the Apartment constructor and return the new Apartment.
Only one Apartment is stored in each file. (Apartment doesn?t implement
Serializable, so I cant write straight Apartment-objects to a file.)
So in the file, there are stored one "Room" per line: String type,
double size
QUESTION: How am I able to read all lines: first line first -> make a new room of
it, and store to a roomArray? Then second -> do same as I did to the
first.
Now my read()-method doesn't read all lines. How to change it to read next line?
Thanks in advance.
public class Room extends Space
public Room(String type, double area)
public String getType()
public double getSize()
public class Apartment extends Space
public static final String KITCHEN
public Apartment(Room[] rooms)
public String getType()
public double getSize()
public Room[] getRooms()
public class ApartmentFileHandler extends Object {
     private FileOutputStream ostream;
     private ObjectOutputStream op;
     private FileInputStream istream;
     private ObjectInputStream ip;
     private String filepath;
public ApartmentFileHandler (String filepath) {
                          this.filepath = filepath;
public Apartment read()
                                  throws InvalidApartmentFile,
                                             IOException {
      istream = new FileInputStream(filepath);
      ip = new ObjectInputStream(istream);
                              // count how many rows in the file ie. rooms
                       String lineThatIsRead = ip.readLine();
                       int count =0;
                       while (lineThatIsRead != null) {
                                count =count +1;
                                lineThatIsRead =ip.readLine();
     Room room;
     Room roomArray[ ] = new Room[count];
      for(int i =0; i<count; i++) {
                              String type =ip.readUTF();
          double size =ip.readDouble();
                               room =new Room(type, size);
          roomArray[ i ] =room;
                            Apartment apartment = new Apartment(roomArray);
                            return apartment;
        public void write(Apartment apartment)
              throws IOException {
                ostream = new FileOutputStream(filepath);
                op = new ObjectOutputStream(ostream);
                int numberOfRooms =apartment.getRooms().length;
                Room[] allRooms =apartment.getRooms();
                for (int i=0; i< numberOfRooms; i++) {
                     op.writeUTF( allRooms[ i ].getType() );
                     op.writeDouble( allRooms[ i ].getSize() );
                     op.writeChars("\n");

Hi,
I recommend using java.io.BufferedReader in conjunction with java.io.FileReader:
BufferedReader reader=new BufferedReader(new FileReader(filepath));
java.io.BufferedReader provides the method public java.lang.String readLine() throws java.io.IOException which lets you read a complete line from the underlying java.io.Reader object. Furthermore, BufferedReader will - as the name implies - buffer your IO-operations which will help you improve the program's performance. In order to read all the lines contained in a text file you might want to apply a loop:
String line;
while((line=reader.readLine())!=null && line.length()!=0){
//process data in string line (parse into string and double)
Of course, everything must be contained within a try-catch-block in order to be able to handle upcoming IOException objects.
Regards,
Michael

How to replace a line ina text file using java?

Hi ALL,
Does anybody know how to replace a line in a text file uisng java.

use this thing:
http://doesthatevencompile.com/current-projects/code-sniplets/ASCIIFile.htm
open the file,
read its contents, replace the text you need in the contents, set the contents back into the file.
it takes care of the IO for you.

Read words from text file by delimiter as columns and rows

Hi All,
I need your help as i have a problem with reading string by delimiter. i have used various tech in java, but i can not get the result as expected.
Please help me to get the string from text file and write into excel . i have used a text file.
problem
get the below as string by delimiter
OI.ID||'|'||OI.IDSIEBEL||'|'||OI.IDTGU||'|'||OI.WORKTYPE||'|'||OI.UTR_FK
read the below as string by delimiter
"50381|TEST_7.15.2.2|09913043548|Attivazione|07-SEP-10
now i need to write the above into excel file as columns and rows.
there are 5 columns and each corresponding values
the outut excel should be
OI.ID OI.IDSIEBEL OI.IDSIEBEL OI.WORKTYPE OI.UTR_FK
50381 TEST_7.15.2.2 09913043548 Attivazione 07-SEP-10
i tried in diffrerent techinq but not able to get the resule. pls help me
Thanks,
Jasmin
Edited by: user13836688 on Jan 22, 2011 8:13 PM

First of all, when posting code, put it between two tags.
Second of all, the pipe is a special character in regex, so you need to escape it as
.split("\ \|");
Erh. So 2 backslashes before the pipe character. Stupid forum won't post it.
Edited by: Kayaman on Jan 24, 2011 9:35 AM
Edited by: Kayaman on Jan 24, 2011 9:35 AM
Edited by: Kayaman on Jan 24, 2011 9:36 AM

Reading a remote text file in java

All,
I have a text file on a server where I work which I want to read. To connect to the server I'm using ssh (need to provide user & pass)
I use the j2ssh tool and can get access via my Java code, but I couldn't find how can I read the file. I can download the file from the remote server
to my local computer, but I only want to read it line by line exactly the way I read local files.
Thanks!

ravivg wrote:
I'm trying to avoid downloading it. How can I have the server read it?
thanks!I think I thought I told you already... you can't! That's not how it works. Sheesh.

Read char from text file

I am trying to read in questions, possible answers and the correct answer from a text file.
The text file looks like this
1. what is blah blah blah?
a. something
b. something else
c. none of the above
b
where the last line of the file is a character which is the correct answer.
I can read all these in as a string but I have to read the last line in as a character .
can you please help.

I'm not sure if this is what you need but, take a look:
import java.io.*;
public class questions
public static void main(String[] args)
try
Question a=new Question();
ObjectOutputStream out=new ObjectOutputStream(new FileOutputStream(new File("answers.txt")));
out.writeObject(a);
ObjectInputStream in=new ObjectInputStream(new FileInputStream(new File("answers.txt")));
Question b=(Question)in.readObject();
char answer=b.getAnswer();
System.out.println(answer);
catch(IOException e)
System.out.println(e);
catch(ClassNotFoundException e)
System.out.println(e);
class Question implements Serializable
String q;
String a1;
String a2;
String a3;
char c;
public Question()
q=new String("The Question");
a1=new String("1st possible choise");
a2=new String("2st possible choise");
a3=new String("3st possible choise");
c='c';
public void setQuestion(String que)
q=que;
public void setAnswer1(String an1)
a1=an1;
public void setAnswer2(String an2)
a2=an2;
public void setAnswer3(String an3)
a3=an3;
public void setAnswer(char an)
c=an;
public char getAnswer()
return c;
Ofcource all methods in Question class should be adapted to the needs of your program.
If i helped help me too.. (duke $)

Read comlumn from text file

i have a text file of record some thing like
last name first name email
how can i make it read the text file column by column
i created a class with linkedlist to put it in but can't make it recognize which is which
(code)
public void NewTail( String i, String f, String l, String m, String p)
if (stu == null)
stu = new ListNode(i, f, l, m, p, null);
else
ListNode temp = stu;
while ( temp.next != null)
temp = temp.next;
temp.next = new ListNode(i, f, l, m, p, null);
}(/code)

then from the class i use
record st = new record();
         FileReader file = new FileReader( "student.txt");
         BufferedReader inputFile = new BufferedReader( file);
         int ID = new Integer( inputFile.readLine()).intValue();
         while( ID > 0)
            String first = inputFile.readLine();
            String last = inputFile.readLine();
            String email = inputFile.readLine();
            String phone = inputFile.readLine();
            st.NewTail(ID, first, last, major, numcoursepre);
            ID = new Integer( inputFile.readLine()).intValue();
         }but this only read line by line it won't read by column i mean i read the whole likne but i can't make it distinglish which is which which is first name and which is last name
i want to be able to get email if i just want email but can't get thing to know please help thank you

Read pixel from text file

Hi, is it possible to retrieve an image just by reading some parameters or its pixel from a text file? If yes, could anyone give me some ideas on how to do that? How do you also retrieve a specific line or value from a text file?
Thanks.

Hi Fred,
it seems you started a new thread for that very same topic - again...
Why can't you keep things in one place? Why do we have to hop between several threads of yours to get all relevant information?
"if I want to read line 13 of my text file"
Same question as in the other thread: Where do you start to count? 0 or 1?
Have you tried to wire a "13" to the ReadLine function?
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Read data from text file one by one using for loop

Dear Forum
I want to read data of single colum of text file inside the for loop one by one(for each iteration value must be replaced by another value of text file).This value is used by a formula inside for loop. also after completion of iterations the values must be plotted on xy graph. How to do it.? please help me.
profravi

It's not very efficient to read a file line by line. Much simpler to read it all at once and then auto-index the results inside a for loop. The image below shows a generic solution to your problem. This assumes that the data in the file is in a single column.
I would also recomend checking ou the learning LabVIEW resources here.
I would aslos suggest that since this type of question is not specific to either NI-Elvis or the LabVIEW SE, you should post similar questions to the LabVIEW board. If you have problems, attaching a sample of the text file would help.
Message Edited by Dennis Knutson on 10-18-2007 09:11 AM
Attachments:
XY Graph From File.PNG ‏4 KB

Student in distress: Read data from text file to fill a JTable

I'm already late 2 weeks for my project and I still can't figure this out :(
The project is made of 3 classes; the main one is Viewer.java; it creates the interface, Menu.java that manages the menu and the methods related to it and finally JTableData.java that extends JTable ( This is the part that I don't really understand)
In the class MENU.JAVA I wrote the method jMenuOpen_actionPerformed(...) for the button OUVRIR (Open) that let's me select the file to read, then puts the content in a 2D table. Here' s my problem: I have to somehow update the content of the table created in VIEWER.JAVA with the content read from the file (cvs file delimited by ";") using a JTableData object (?)
//THIS IS THE FIRST CLASS VIEWER.JAVA THAT CONTAINS THE MAIN METHOD
//AND CREATES THE INTERFACE
package viewer;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Viewer extends JFrame {
public Menu menu = null;
GridLayout gridLayout1 = new GridLayout();
JTabbedPane jTabbedPane = new JTabbedPane();
JTableData jTableInfo = new JTableData(30, 7);
public Viewer() {
          addWindowListener(new WindowAdapter()
          {               public void windowClosing(WindowEvent e)
                    dispose();
                    System.exit(0);
        try
            jbInit();
            this.setSize(1000, 700);
            this.setVisible(true);
        catch(Exception e)
            e.printStackTrace();
public static void main(String[] args) {
      Viewer viewer = new Viewer();
private void jbInit() throws Exception {
    menu = new Menu(this);
    gridLayout1.setColumns(1);
    this.setTitle("Viewer");
    this.getContentPane().setLayout(gridLayout1);
    jTableInfo.setMaximumSize(new Dimension(0, 64));
    jTableInfo.setPreferredSize(new Dimension(0, 64));
    //TO DO Partie de droite
    JTabbedPane webViewerTabs = new JTabbedPane();
    //972 3299
    //java.net.URL URL1 = new java.net.URL("http://www.nba.com");
    //java.net.URL URL2 = new java.net.URL("http://www.insidehoops.com");
    //java.net.URL URL3 = new java.net.URL("http://www.cnn.com");
    JEditorPane webViewer01 = new JEditorPane();
    webViewer01.setEditable(false);
    //webViewer01.setPage(URL1);
    JEditorPane webViewer02 = new JEditorPane();
    webViewer02.setEditable(false);
    //webViewer02.setPage(URL2);
    JEditorPane webViewer03 = new JEditorPane();
    webViewer03.setEditable(false);
    //webViewer03.setPage(URL3);
    webViewerTabs.addTab("Site01", webViewer01);
    webViewerTabs.addTab("Site02", webViewer02);
    webViewerTabs.addTab("Site03", webViewer03);
    jTabbedPane.add(webViewerTabs);
        //End TO DO
    this.getContentPane().add(jTableInfo);
    this.getContentPane().add(jTabbedPane);
    this.setJMenuBar(menu);
//This is the MENU.JAVA CLASS WHERE I OPEN THE FILE, READ THE
//CONTENT AND WHERE I SHOULD SEND THE DATA TO THE TABLE.
//Title:        Menu
//Author:       Luc Duong
package viewer;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
public class Menu extends JMenuBar {
JMenu jMenu1 = new JMenu();
JMenuItem jMenuNew = new JMenuItem();
JMenuItem jMenuOpen = new JMenuItem();
JMenuItem jMenuSave = new JMenuItem();
JMenuItem jMenuExit = new JMenuItem();
JMenuItem jMenuApropos = new JMenuItem();
JFileChooser fileChooser = new JFileChooser();
Viewer viewer = null;
boolean isFileChanged = false;
private File fileName;
static String data [][] = new String[7][9];
public int lineCount;
public Menu(Viewer viewer) {
    try {
      jbInit();
      this.viewer = viewer;
      this.add(jMenu1);
    catch(Exception e) {
      e.printStackTrace();
private void jbInit() throws Exception {
    jMenu1.setText("Fichier");
    jMenuNew.setText("Nouveau");
    jMenuNew.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jMenuNew_actionPerformed(e);
    jMenuOpen.setText("Ouvrir");
    jMenuOpen.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jMenuOpen_actionPerformed(e);
    jMenuSave.setText("Sauvegarder");
    jMenuSave.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jMenuSave_actionPerformed(e);
    jMenuExit.setText("Quitter");
    jMenuExit.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jMenuExit_actionPerformed(e);
    jMenuApropos.setText("A propos");
    jMenuApropos.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jMenuApropos_actionPerformed(e);
    jMenu1.add(jMenuNew);
    jMenu1.add(jMenuOpen);
    jMenu1.add(jMenuSave);
    jMenu1.add(jMenuExit);
    jMenu1.add(jMenuApropos);
void jMenuNew_actionPerformed(ActionEvent e) {
//THIS IS THE METHOD I'M WORKING ON RIGHT NOW
void jMenuOpen_actionPerformed(ActionEvent e) {
      fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
      int result = fileChooser.showOpenDialog(this);
      if (result == JFileChooser.CANCEL_OPTION) return;
      if (result == JFileChooser.APPROVE_OPTION)
          //[email protected]
          File chosenFile = fileChooser.getSelectedFile();
          String path = chosenFile.getPath();
          String nom = chosenFile.getName();
          boolean exist = chosenFile.exists();
          try
            FileReader fr = new FileReader(chosenFile);
            BufferedReader reader = new BufferedReader(fr);
            System.out.println("Opening File Successful!" + chosenFile.getName());
            //String qui contient la ligne courante
            String currentLine = new String();
            StringTokenizer currentLineTokens = new StringTokenizer("");
            int row = 0;
            int column = 0;
            while( (currentLine = reader.readLine() ) != null)
                currentLineTokens = new StringTokenizer(currentLine,";");
                System.out.println("Now reading line index: " + row);
                while(currentLineTokens.hasMoreTokens())
                    data[row][column] = currentLineTokens.nextToken();
                    System.out.println(column + "\t" + data[row][column]);
                    if(column>=8) column=-1;
                    column++;
                row++;
            lineCount = row-1;
            System.out.println("\nNombre total de lignes: " + lineCount);
        catch(Exception ex)
            System.out.println("Test: " + ex.getMessage());
            JOptionPane.showMessageDialog(this, "Erreur d'ouverture du fichier", "Erreur d'ouverture du fichier", JOptionPane.ERROR_MESSAGE);
void jMenuSave_actionPerformed(ActionEvent e) {
      if (JFileChooser.APPROVE_OPTION == fileChooser.showSaveDialog(this))
            System.err.println("Save: " + fileChooser.getSelectedFile().getPath());
void jMenuExit_actionPerformed(ActionEvent e) {
    if (!isFileChanged)
       System.exit(1);
    else
        JOptionPane.showConfirmDialog(null, "Do you want to save now?", "Save?", JOptionPane.YES_NO_OPTION);
      // ask the user if he want to save
      // yes or no?
      // yes
       jMenuSave_actionPerformed(e);
      // no
      System.exit(1);
void jMenuApropos_actionPerformed(ActionEvent e) {
//THIS IS THE JTABLEDATA.JAVA CLASS THAT EXTENDS JTable. I'm not sure
// how this works :(//Title: JTableData
//Author: Luc Duong
package viewer;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JTableData extends JTable {
public JTableData(int row, int col)
super(row, col);

Hi, Salut
you should use JTable's DataModel to update your table.
data[row][column] = currentLineTokens.nextToken();
jTableInfo.getModel().setValueAt(data[row][column], row, column);
jTableInfo.repaint();BEWARE CSV files and StringTokenizer, i've had problems with it (for example ;;Test; is not tokenized "", "", "Test")
StringTokenizer ignores separator when in first position, and ignores double separators. I use this piece of code before tokenize a String :
private static char _separator = ';';
private static String checkCsvString(String s) {
         * V�rification du s�parateur inital, perdu par le StringTokenizer et
         * pourtant bien important
        if (s.startsWith("" + _separator)) {
            s = " " + s;
         * V�rification des doubles s�parateurs, perdus par le StringTokenizer
        int index;
        while ((index = s.indexOf("" + _separator + _separator)) >= 0) {
            s = s.substring(0, index) + _separator + " " + _separator + s.substring(index + 2);
        return s;
    }hope it helps
Nico

Read value from text file to JTextField

Hi,
I think this is the right place to post this. Although maybe it is not it could be classed as I/O issues?
I have a JFrame with a JTextField which requires the user to enter a value. When they click a JButton "OK". It writes the value to a text file and closes the frame using FileWriter. If they click clear button it writes the value "" to the file. What I want to do is when the frame opens it reads the value from the text file. I have been trying to use FileReader but have not been able to write the code correctly. Any help would be greatly appreciated.
Thanks

File f = yourfile;
BufferedReader br = new BufferedReader(new FileReader(f));
String value = br.readLine();Alex.

Read data from text file and displaying on Webdynpro

Hi all,
I need some help. I have a text file with set of name, phonenumbers . I want to know how to display the data using Webdynpro. Could some one help me. help is appreciated and I promise to award points for right answer.
Thank you
Maruti

Hi Maruti,
just open the file and loop on the rows, here an example::
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
FileReader f = new FileReader("c:
FileName.ext");
while ((s = in.readLine()) != null)
//Here you can put the line into a WD context structure, i.e:
wdContext.currentContoEconomicoFormElement().setField(s);
}catch (Exception e) {.....}
in.close();
f.close();
For any others questions, please, let me know.
Vito

Read url from text file

I am new to Adobe Air. I was able to load a web browser as an Air app with the following line:
<mx:HTML id="myBrowser" width="100%" height="100%" location="http://www.google.com"/>
My question is this: is it possible to add a text file to the project (to be stored locally) that can be read by the application so that the location attribute (URL) can be dynamically populated?
I want the user to be able to change the starting URL by manually editing this text file.
Any help I can get is appreciated!
Note: I am aware that a URL bar can simply be added to the app, but that is really not the solution that I'm looking for. I don't want the user to be able to change the url using the GUI.

Great, thank you for your response!
Could you give me a sugestion on how to aproch the code. Specifically how to read the file itself. Would it require a specific format?
Thanks you.

Read lines from text file to java prog

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