I've got a loop that reads through a text file and outputs it, now I'm trying to get it to loop through, and write what's printed out into a text file as I want it to display as HTML. This is what I've got so far for this method:
public void hChoice()
{
File fbScores = new File ("P:/SD/Assignment1/fbScores.txt");
String line = "";
try {
Scanner scanScores = new Scanner(fbScores);
while(scanScores.hasNext())
{
line = scanScores.nextLine();
stringArr = line.split(":");
if(stringArr.length == 4)
{
System.out.println("<h1>" + stringArr[0]+" [" +stringArr[2]+"] |" + stringArr[1]+" ["+ stringArr[3]+" ]<br></h1> ");
PrintWriter out = new PrintWriter("P:/SD/Assignment1/HTMLscores.txt");
out.close();
}
}
}
catch (FileNotFoundException e)
{
System.out.println("problem " +e.getMessage());
}
}
I've added the HTML tags in the print out and it prints it out fine, but I've tried several different methods to get it to print to a text file but none have worked. Pretty new to Java so any help would be much appreciated. Thankyou. :)
You've gotten your syntax and code wrong for writing to files.
Please Google and check the right syntax for writing to files using java. Plenty of resources available. You'll learn better if you try it yourself.
FYR, here is one: http://www.tutorialspoint.com/java/java_files_io.htm
Related
I am trying to create an authentication system of sorts that uses a file called Users.dat to store user data. Currently, I am developing a method to remove users by rewriting the Users.dat file, omitting the user specified. The code below works in a basic environment with an all-encompassing directory containing the .java files and the Users.dat file in the same spot. The old Users.dat file is deleted and Users.dat.tmp is renamed to User.dat. (No problems here, everything works as intended).
public static boolean RemoveUser(String userName) {
// TODO remove username from Users.dat
try {
File originalFile = new File("Users.dat");
System.out.println(originalFile.getAbsolutePath());
BufferedReader read = new BufferedReader(new FileReader("Users.dat"));
String line = null;
while ((line = read.readLine()) != null) {
if (line.indexOf(userName) != -1) {
break;
}
}
String[] userInfo = line.split(", ");
if (!userName.equals(userInfo[2])) {
System.out.println("Username not found. No users removed.");
read.close();
return false;
}
File tempFile = new File(originalFile.getAbsolutePath() + ".tmp");
PrintWriter print = new PrintWriter(new FileWriter(tempFile));
String lineToRemove = line;
BufferedReader read2 = new BufferedReader(new FileReader("Users.dat"));
while ((line = read2.readLine()) != null) {
if (!line.trim().equals(lineToRemove)) {
print.println(line);
print.flush();
}
}
print.close();
read.close();
read2.close();
System.out.println(originalFile.getAbsolutePath());
originalFile.delete(); //This line is not executing correctly
tempFile.renameTo(originalFile); //Nor is this line
} catch (FileNotFoundException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
return true;
}
Users.dat file format:
Joe, Last, jlast, 58c536ed8facc2c2a293a18a48e3e120, true
Sam, sone, samsone, 2c2a293a18a48e3e12058c536ed8facc, false
Jane, Best, jbest, 293a18a48e3e12052058c536ed8facc2c, false
Andrew, Estes, Aestes, 63a490d69aa544fd1272a976014ad570, true
Test, User, tuser, 63a490d69aa544fd1272a976014ad570, true
I have two System.out.println(originalFile.getAbsolutePath()) statements, one at the beginning, one at the end to make sure the path isn't getting screwed up in the process of everything somehow.
Like I said, the code works, however, when I try to implement it in my project, it creates the Users.dat.tmp and it writes the correct data to it, but it does not delete the old Users.dat file, nor does it rename the Users.dat.tmp file to replace Users.dat. I'm certain the directory is correct, as I am literally displaying it as the code executes. I can't figure out any other reason why originalFile.delete() and tempFile.renameTo(originalFile) aren't functioning properly.
EDIT:
Using java.nio.file, I was able to produce an error message. it reads:
java.nio.file.FileSystemException: C:\Path\Users.dat: The process cannot access the file because it is being used by another process.
I don't have the file open when this error message is shown, and I don't get this error using java.nio in my testing environment mentioned at the beginning. I'm not sure what other process the message is referring to.
EDIT 2:
I tried running the code on other machines, one a Mac, the other a Windows laptop, and the code functioned on the Mac just fine, but I was still seeing the same issue on the Windows laptop.
I had the similar issue. My problem was not closing all the streams I read and written to the file. Thanks for your Edit #1, that was helpful
When you wrap
BufferedReader read = new BufferedReader(new FileReader("Users.dat"));
don't you need to close the inner readers too?
If not for the author, but for those who stambled upon this question (like me), hope this suggestion will be useful
I had an earlier function that I was calling in main that was accessing Users.dat, but I never closed the BufferredReader in that function.
Currently working on a project which requires me to read in file input of over 50k lines. I am currently using the BufferedReader class to read in the input and present the data in a text area. Currently, the application just reproduces the file in my own HMI similar to a text editor, however where I would like to differ is that there are certain starting words for each line that I would like to not be presented in the text area... I believe my lack of experience with buffers is responsible for my problems. I have tried implementing code along the following lines:
private void insertSyrFile(BufferedReader buffer, JFileChooser chooser) throws IOException{
String line;
//reader = "\n";
try{
reader = new FileReader(chooser.getSelectedFile().toString());
buffer = new BufferedReader(reader);
while ((line = buffer.readLine()) != null){
if (!line.startsWith("Elaborating"))
origSyrTextFeild.read(buffer, null);
}
}catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}
}
This code was implemented with the following button event handler:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
JFileChooser chooser = new JFileChooser();
chooser.showOpenDialog(null);
syrFile.openFile(chooser.getSelectedFile().toString());
try {
insertSyrFile(buffer, chooser); //origSyrTextFeild.setText(syrFile.readFileLine());
} catch (IOException ex) {
Logger.getLogger(ParsingAppMainFrame.class.getName()).log(Level.SEVERE, null, ex);
}
}
... using this code, even though I have if statement to check for a string, the original file is still reproduced with no processing on the file. I am still a beginner in java, however if someone understands what my goal is and has any insight I'd appreciate any ideas!!
I guess you may use " origSyrTextFeild.append(line);" instead of " origSyrTextFeild.read(buffer, null);". Because the if statement checks the "line" but "read" method get contents from the original buffer.
I am working on a function that enables the user to check a single student's assessment result. I use try and catch, but when I run the code, the system runs directly to the catch part, and the file's content is blank. I am not sure the reason about this problem. Here is my code:
System.out.println('\n' + "Please enter the Student's uni that you would like to call. Type 'exit' to leave");
String studentInfo = s.nextLine();
if (studentInfo.equalsIgnoreCase("exit")) {
userSelection = "exit";
}
boolean studentFound = false;
for (int i = 0; i < students.size(); i++) {
if (studentInfo.equalsIgnoreCase(students.get(i).getStudentUI())) {
studentFound = true;
try {
File singleStudentList = new File(studentInfo + " .txt");
PrintWriter writer = new PrintWriter(singleStudentList);
System.out.println(studentUniLists.get(i));
writer.println(studentUniLists.get(students.indexOf(studentInfo)));
writer.close();
} catch (Exception e) {
System.out.println("Problem writing the file. Please make sure the path is correct");
}
}
}
Thanks for helping!
My hunch is that your error is in one of these two lines:
System.out.println(studentUniLists.get(i));
writer.println(studentUniLists.get(students.indexOf(studentInfo)));
You haven't included code as to what studentUniLists is, so there is some guesswork here.
My guess is that students.indexOf(studentInfo) could be returning -1, so then when you do studentUniLists.get(-1) on a List, this is going to give you an IndexOutOfBoundsException. You should really only be catching the IOException, so that you can detect this kind of issue
Probably index out of bounds somewhere, e.g:
System.out.println(studentUniLists.get(i));
Are you sure studentUniLists has the index i?
Since you wrote there is no output and it just goes directly to catch.
As commented elsewhere, printing the actual exception helps.
You catch ANY Exception and you print to the console that this is file related problem. It does not have to be.
I suggest you add into your catch clause e.printStackTrace() to print the real problem. Secondly you should consider avoiding catching Exception as it is too broad. It might be worth catching exception that is related to file problems in the first place and leaving the rest uncaught.
Looking at the documentation - PrintWriter will be unlikely to throw errors. Comstructor may throw FileNotFoundException or SecurityException. CheckErrors is the function you need for checking file related errors.
https://docs.oracle.com/javase/7/docs/api/java/io/PrintWriter.html#checkError(). Yet I believe you have non file related problem like NullPointerException or IndexOutOfBoundsException.
Hope this helps.
First, With Jdk 1.7 when you open the file use the try with ressources to let the jvm do the close automaticly.
File singleStudentList;
try (singleStudentList = new File(studentInfo + " .txt")) {
PrintWriter writer = new PrintWriter(singleStudentList);
}
Second, The error is getting by this : new File(studentInfo + " .txt")
you're always creating the empty file "true .txt"
Third, print the error by ex.printStackTrace();
I wrote a short script to create a file to my Desktop, and the file appeared. I just did it all in main, like so:
import java.io.*;
import java.util.Scanner;
public class FilePractice {
public static void main(String[] args) {
//create a new File object
File myFile = new File("/home/christopher/Desktop/myFile");
try{
System.out.println("Would you like to create a new file? Y or N: ");
Scanner input = new Scanner(System.in);
String choice = input.nextLine();
if(choice.equalsIgnoreCase("Y"))
{
myFile.createNewFile();
}
else
{
//do nothing
}
}catch(IOException e) {
System.out.println("Error while creating file " + e);
}
System.out.println("'myFile' " + myFile.getPath() + " created.");
}
}
I just wanted to make sure the code worked, which it did. After that, I wanted to expand by creating a file with user input, as well as define which directory the user wished to send the file to. I'm on a Linux machine, and I wanted to send it to my Desktop again, so my user input was "/home/christopher/Desktop" for the userPath. Nothing happened. I even cd'd to my Desktop via terminal to "ls" everything there, and still nothing.
Perhaps my syntax is wrong?
If this is a duplicate of anything, my apologies. I tried to do a thorough search before coming here, but I only found info on creating files and sending files to directories that are already defined as a string (e.g. File myFile = new File("/home/User/Desktop/myFileName")).
Here is the expanded attempt:
try {
System.out.println("Alright. You chose to create a new file.\nWhat would you like to name the file?");
String fileName = input.nextLine();
input.nextLine();
System.out.println("Please enter the directory where you would like to save this file.\nFor example: C:\\Users\\YourUserName\\Documents\\");
String userFilePath = input.nextLine();
File userFile = new File(userFilePath, fileName);
System.out.println("Is this the file path you wish to save to? ----> " + userFile.getPath()+"\nY or N: ");
String userChoice = input.nextLine();
if (userChoice.equalsIgnoreCase("Y")) {
userFile.createNewFile();
//print for debug
System.out.println(userFile.getPath());
}
}catch(IOException e) {
System.out.println("Error while attempting to create file " + e);
}
System.out.println("File created successfully");
My print statement for a debug attempt outputs "/home/christopher/Desktop", but not the file name appended to the directory.
Thanks for any help offered. This is just for experimentation while learning Java I/O. Since a hypothetical user may not be on the same OS as me, I can work on those methods later. I'm keeping it on my home machine, hence the Unix filepath names.
Changing input.nextLine() to input.next() solved the problem. The program was not reaching the if statement after asking the user if they were sure their entered path was the desired save point.
I also put in a simple else statement that printed out ("File not created") to verify that it was skipping it.
Anyway, question answered. :-)
I have the basics of my program finished.
The idea is that the user can specify a shape color width height etc. Upon inputting the data, constructors are called which create output, or there are other options which create output that the user can specify.
My goal is to get all of this output into a text file.
Currently I create a scanner for reading:
static Scanner input = new Scanner(System.in);
Then in my main driver method I create a Formatter:
public static void main(String[] args) {
Formatter output = null;
try{
output = new Formatter("output.txt");
}
catch(SecurityException e1){
System.err.println("You don't have" +
" write accress to this file");
System.exit(1);
}
catch(FileNotFoundException e){
System.err.println("Error opening or" +
" creating file.");
System.exit(1);
}
After each time I expect output I have placed this bit of code:
output.format("%s", input.nextLine());
And finally I close the file with
output.close()
The file is created but it is currently blank. I know I'm on the right track, because I've tried doing this:
output.format("%d", i);
where i is an integer of 0 and the file writes correctly.
However, I cannot seem to get it to work for an entire line, or for the output at all.
Please help!
I am not an expert but why can you not just use "FileWriter"?
Is it because you want to catch those exceptions to display useful information to the user?
Or have I misunderstood the question completely? - If so, sorry and just disregard this.
import java.io.FileWriter;
import java.io.IOException;
try
{
FileWriter fout = new FileWriter("output.txt"); // ("output.txt", true) for appending
fout.write(msg); // Assuming msg is already defined
fout.close();
}
catch (IOException e)
{
e.printStackTrace();
}