Related
I have an assignment for my CS class where it says to read a file with several test scores and asks me to sum and average them. While summing and averaging is easy, I am having problems with the file reading. The instructor said to use this syntax
Scanner scores = new Scanner(new File("scores.dat"));
However, this throws a FileNotFoundException, but I have checked over and over again to see if the file exists in the current folder, and after that, I figured that it had to do something with the permissions. I changed the permissions for read and write for everyone, but it still did not work and it still keeps throwing the error. Does anyone have any idea why this may be occurring?
EDIT: It was actually pointing to a directory up, however, I have fixed that problem. Now file.exists() returns true, but when I try to put it in the Scanner, it throws the FileNotFoundException
Here is all my code
import java.util.Scanner;
import java.io.*;
public class readInt{
public static void main(String args[]){
File file = new File("lines.txt");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
}
There are a number situation where a FileNotFoundException may be thrown at runtime.
The named file does not exist. This could be for a number of reasons including:
The pathname is simply wrong
The pathname looks correct but is actually wrong because it contains non-printing characters (or homoglyphs) that you did not notice
The pathname is relative, and it doesn't resolve correctly relative to the actual current directory of the running application. This typically happens because the application's current directory is not what you are expecting or assuming.
The path to the file is is broken; e.g. a directory name of the path is incorrect, a symbolic link on the path is broken, or there is a permission problem with one of the path components.
The named file is actually a directory.
The named file cannot be opened for reading for some reason.
The good news that, the problem will inevitably be one of the above. It is just a matter of working out which. Here are some things that you can try:
Calling file.exists() will tell you if any file system object exists with the given name / pathname.
Calling file.isDirectory() will test if it is a directory.
Calling file.canRead() will test if it is a readable file.
This line will tell you what the current directory is:
System.out.println(new File(".").getAbsolutePath());
This line will print out the pathname in a way that makes it easier to spot things like unexpected leading or trailing whitespace:
System.out.println("The path is '" + path + "'");
Look for unexpected spaces, line breaks, etc in the output.
It turns out that your example code has a compilation error.
I ran your code without taking care of the complaint from Netbeans, only to get the following exception message:
Exception in thread "main" java.lang.RuntimeException: Uncompilable
source code - unreported exception java.io.FileNotFoundException; must
be caught or declared to be thrown
If you change your code to the following, it will fix that problem.
public static void main(String[] args) throws FileNotFoundException {
File file = new File("scores.dat");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
Explanation: the Scanner(File) constructor is declared as throwing the FileNotFoundException exception. (It happens the scanner it cannot open the file.) Now FileNotFoundException is a checked exception. That means that a method in which the exception may be thrown must either catch the exception or declare it in the throws clause. The above fix takes the latter approach.
The code itself is working correctly. The problem is, that the program working path is pointing to other place than you think.
Use this line and see where the path is:
System.out.println(new File(".").getAbsoluteFile());
Obviously there are a number of possible causes and the previous answers document them well, but here's how I solved this for in one particular case:
A student of mine had this problem and I nearly tore my hair out trying to figure it out. It turned out that the file didn't exist, even though it looked like it did. The problem was that Windows 7 was configured to "Hide file extensions for known file types." This means that if file appears to have the name "data.txt" its actual filename is "data.txt.txt".
Hope this helps others save themselves some hair.
I recently found interesting case that produces FileNotFoundExeption when file is obviously exists on the disk.
In my program I read file path from another text file and create File object:
//String path was read from file
System.out.println(path); //file with exactly same visible path exists on disk
File file = new File(path);
System.out.println(file.exists()); //false
System.out.println(file.canRead()); //false
FileInputStream fis = new FileInputStream(file); // FileNotFoundExeption
The cause of the problem was that the path contained invisible \r\n characters at the end.
The fix in my case was:
File file = new File(path.trim());
To generalize a bit, the invisible / non-printing characters could have include space or tab characters, and possibly others, and they could have appeared at the beginning of the path, at the end, or embedded in the path. Trim will work in some cases but not all. There are a couple of things that you can help to spot this kind of problem:
Output the pathname with quote characters around it; e.g.
System.out.println("Check me! '" + path + "'");
and carefully check the output for spaces and line breaks where they shouldn't be.
Use a Java debugger to carefully examine the pathname string, character by character, looking for characters that shouldn't be there. (Also check for homoglyph characters!)
An easy fix, which worked for me, is moving my files out of src and into the main folder of the project. It's not the best solution, but depending on the magnitude of the project and your time, it might be just perfect.
Reading and writing from and to a file can be blocked by your OS depending on the file's permission attributes.
If you are trying to read from the file, then I recommend using File's setReadable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file;
File f = new File(arbitrary_path);
f.setReadable(true);
data_of_file = Files.readAllBytes(f);
f.setReadable(false); // do this if you want to prevent un-knowledgeable
//programmers from accessing your file.
If you are trying to write to the file, then I recommend using File's setWritable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file = { (byte) 0x00, (byte) 0xFF, (byte) 0xEE };
File f = new File(arbitrary_path);
f.setWritable(true);
Files.write(f, byte_array);
f.setWritable(false); // do this if you want to prevent un-knowledgeable
//programmers from changing your file (for security.)
Apart from all the other answers mentioned here, you can do one thing which worked for me.
If you are reading the path through Scanner or through command line args, instead of copy pasting the path directly from Windows Explorer just manually type in the path.
It worked for me, hope it helps someone :)
I had this same error and solved it simply by adding the src directory that is found in Java project structure.
String path = System.getProperty("user.dir") + "\\src\\package_name\\file_name";
File file = new File(path);
Scanner scanner = new Scanner(file);
Notice that System.getProperty("user.dir") and new File(".").getAbsolutePath() return your project root directory path, so you have to add the path to your subdirectories and packages
You'd obviously figure it out after a while but just posting this so that it might help someone. This could also happen when your file path contains any whitespace appended or prepended to it.
Use single forward slash and always type the path manually. For example:
FileInputStream fi= new FileInputStream("D:/excelfiles/myxcel.xlsx");
What worked for me was catching the exception. Without it the compiler complains even if the file exists.
InputStream file = new FileInputStream("filename");
changed to
try{
InputStream file = new FileInputStream("filename");
System.out.println(file.available());
}
catch (Exception e){
System.out.println(e);
}
This works for me. It also can read files such txt, csv and .in
public class NewReader {
public void read() throws FileNotFoundException, URISyntaxException {
File file = new File(Objects.requireNonNull(NewReader.class.getResource("/test.txt")).toURI());
Scanner sc = new Scanner(file);
while (sc.hasNext()) {
String text = sc.next();
System.out.println(text);
}
}
}
the file is located in resource folder generated by maven. If you have other folders nested in, just add it to the file name like "examples/test.txt".
I have an assignment for my CS class where it says to read a file with several test scores and asks me to sum and average them. While summing and averaging is easy, I am having problems with the file reading. The instructor said to use this syntax
Scanner scores = new Scanner(new File("scores.dat"));
However, this throws a FileNotFoundException, but I have checked over and over again to see if the file exists in the current folder, and after that, I figured that it had to do something with the permissions. I changed the permissions for read and write for everyone, but it still did not work and it still keeps throwing the error. Does anyone have any idea why this may be occurring?
EDIT: It was actually pointing to a directory up, however, I have fixed that problem. Now file.exists() returns true, but when I try to put it in the Scanner, it throws the FileNotFoundException
Here is all my code
import java.util.Scanner;
import java.io.*;
public class readInt{
public static void main(String args[]){
File file = new File("lines.txt");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
}
There are a number situation where a FileNotFoundException may be thrown at runtime.
The named file does not exist. This could be for a number of reasons including:
The pathname is simply wrong
The pathname looks correct but is actually wrong because it contains non-printing characters (or homoglyphs) that you did not notice
The pathname is relative, and it doesn't resolve correctly relative to the actual current directory of the running application. This typically happens because the application's current directory is not what you are expecting or assuming.
The path to the file is is broken; e.g. a directory name of the path is incorrect, a symbolic link on the path is broken, or there is a permission problem with one of the path components.
The named file is actually a directory.
The named file cannot be opened for reading for some reason.
The good news that, the problem will inevitably be one of the above. It is just a matter of working out which. Here are some things that you can try:
Calling file.exists() will tell you if any file system object exists with the given name / pathname.
Calling file.isDirectory() will test if it is a directory.
Calling file.canRead() will test if it is a readable file.
This line will tell you what the current directory is:
System.out.println(new File(".").getAbsolutePath());
This line will print out the pathname in a way that makes it easier to spot things like unexpected leading or trailing whitespace:
System.out.println("The path is '" + path + "'");
Look for unexpected spaces, line breaks, etc in the output.
It turns out that your example code has a compilation error.
I ran your code without taking care of the complaint from Netbeans, only to get the following exception message:
Exception in thread "main" java.lang.RuntimeException: Uncompilable
source code - unreported exception java.io.FileNotFoundException; must
be caught or declared to be thrown
If you change your code to the following, it will fix that problem.
public static void main(String[] args) throws FileNotFoundException {
File file = new File("scores.dat");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
Explanation: the Scanner(File) constructor is declared as throwing the FileNotFoundException exception. (It happens the scanner it cannot open the file.) Now FileNotFoundException is a checked exception. That means that a method in which the exception may be thrown must either catch the exception or declare it in the throws clause. The above fix takes the latter approach.
The code itself is working correctly. The problem is, that the program working path is pointing to other place than you think.
Use this line and see where the path is:
System.out.println(new File(".").getAbsoluteFile());
Obviously there are a number of possible causes and the previous answers document them well, but here's how I solved this for in one particular case:
A student of mine had this problem and I nearly tore my hair out trying to figure it out. It turned out that the file didn't exist, even though it looked like it did. The problem was that Windows 7 was configured to "Hide file extensions for known file types." This means that if file appears to have the name "data.txt" its actual filename is "data.txt.txt".
Hope this helps others save themselves some hair.
I recently found interesting case that produces FileNotFoundExeption when file is obviously exists on the disk.
In my program I read file path from another text file and create File object:
//String path was read from file
System.out.println(path); //file with exactly same visible path exists on disk
File file = new File(path);
System.out.println(file.exists()); //false
System.out.println(file.canRead()); //false
FileInputStream fis = new FileInputStream(file); // FileNotFoundExeption
The cause of the problem was that the path contained invisible \r\n characters at the end.
The fix in my case was:
File file = new File(path.trim());
To generalize a bit, the invisible / non-printing characters could have include space or tab characters, and possibly others, and they could have appeared at the beginning of the path, at the end, or embedded in the path. Trim will work in some cases but not all. There are a couple of things that you can help to spot this kind of problem:
Output the pathname with quote characters around it; e.g.
System.out.println("Check me! '" + path + "'");
and carefully check the output for spaces and line breaks where they shouldn't be.
Use a Java debugger to carefully examine the pathname string, character by character, looking for characters that shouldn't be there. (Also check for homoglyph characters!)
An easy fix, which worked for me, is moving my files out of src and into the main folder of the project. It's not the best solution, but depending on the magnitude of the project and your time, it might be just perfect.
Reading and writing from and to a file can be blocked by your OS depending on the file's permission attributes.
If you are trying to read from the file, then I recommend using File's setReadable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file;
File f = new File(arbitrary_path);
f.setReadable(true);
data_of_file = Files.readAllBytes(f);
f.setReadable(false); // do this if you want to prevent un-knowledgeable
//programmers from accessing your file.
If you are trying to write to the file, then I recommend using File's setWritable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file = { (byte) 0x00, (byte) 0xFF, (byte) 0xEE };
File f = new File(arbitrary_path);
f.setWritable(true);
Files.write(f, byte_array);
f.setWritable(false); // do this if you want to prevent un-knowledgeable
//programmers from changing your file (for security.)
Apart from all the other answers mentioned here, you can do one thing which worked for me.
If you are reading the path through Scanner or through command line args, instead of copy pasting the path directly from Windows Explorer just manually type in the path.
It worked for me, hope it helps someone :)
I had this same error and solved it simply by adding the src directory that is found in Java project structure.
String path = System.getProperty("user.dir") + "\\src\\package_name\\file_name";
File file = new File(path);
Scanner scanner = new Scanner(file);
Notice that System.getProperty("user.dir") and new File(".").getAbsolutePath() return your project root directory path, so you have to add the path to your subdirectories and packages
You'd obviously figure it out after a while but just posting this so that it might help someone. This could also happen when your file path contains any whitespace appended or prepended to it.
Use single forward slash and always type the path manually. For example:
FileInputStream fi= new FileInputStream("D:/excelfiles/myxcel.xlsx");
What worked for me was catching the exception. Without it the compiler complains even if the file exists.
InputStream file = new FileInputStream("filename");
changed to
try{
InputStream file = new FileInputStream("filename");
System.out.println(file.available());
}
catch (Exception e){
System.out.println(e);
}
This works for me. It also can read files such txt, csv and .in
public class NewReader {
public void read() throws FileNotFoundException, URISyntaxException {
File file = new File(Objects.requireNonNull(NewReader.class.getResource("/test.txt")).toURI());
Scanner sc = new Scanner(file);
while (sc.hasNext()) {
String text = sc.next();
System.out.println(text);
}
}
}
the file is located in resource folder generated by maven. If you have other folders nested in, just add it to the file name like "examples/test.txt".
This is an issue I have had in many applications.
I want to change the information inside a file, which has an outdated version.
In this instance, I am updating the file that records playlists after adding a song to a playlist. (For reference, I am creating an app for android.)
The problem is if I run this code:
FileOutputStream output = new FileOutputStream(file);
output.write(data.getBytes());
output.close();
And if an IOException occurs while trying to write to the file, the data is lost (since creating an instance of FileOutputStream empties the file). Is there a better method to do this, so if an IOException occurs, the old data remains intact? Or does this error only occur when the file is read-only, so I just need to check for that?
My only "work around" is to inform the user of the error, and give said user the correct data, which the user has to manually update. While this might work for a developer, there is a lot of issues that could occur if this happens. Additionally, in this case, the user doesn't have permission to edit the file themselves, so the "work around" doesn't work at all.
Sorry if someone else has asked this. I couldn't find a result when searching.
Thanks in advance!
One way you could ensure that you do not wipe the file is by creating a new file with a different name first. If writing that file succeeds, you could delete the old file and rename the new one.
There is the possibility that renaming fails. To be completely safe from that, your files could be named according to the time at which they are created. For instance, if your file is named save.dat, you could add the time at which the file was saved (from System.currentTimeMillis()) to the end of the file's name. Then, no matter what happens later (including failure to delete the old file or rename the new one), you can recover the most recent successful save. I have included a sample implementation below which represents the time as a 16-digit zero-padded hexadecimal number appended to the file extension. A file named save.dat will be instead saved as save.dat00000171ed431353 or something similar.
// name includes the file extension (i.e. "save.dat").
static File fileToSave(File directory, String name) {
return new File(directory, name + String.format("%016x", System.currentTimeMillis()));
}
// return the entire array if you need older versions for which deletion failed. This could be useful for attempting to purge any unnecessary older versions for instance.
static File fileToLoad(File directory, String name) {
File[] files = directory.listFiles((dir, n) -> n.startsWith(name));
Arrays.sort(files, Comparator.comparingLong((File file) -> Long.parseLong(file.getName().substring(name.length()), 16)).reversed());
return files[0];
}
I have an assignment for my CS class where it says to read a file with several test scores and asks me to sum and average them. While summing and averaging is easy, I am having problems with the file reading. The instructor said to use this syntax
Scanner scores = new Scanner(new File("scores.dat"));
However, this throws a FileNotFoundException, but I have checked over and over again to see if the file exists in the current folder, and after that, I figured that it had to do something with the permissions. I changed the permissions for read and write for everyone, but it still did not work and it still keeps throwing the error. Does anyone have any idea why this may be occurring?
EDIT: It was actually pointing to a directory up, however, I have fixed that problem. Now file.exists() returns true, but when I try to put it in the Scanner, it throws the FileNotFoundException
Here is all my code
import java.util.Scanner;
import java.io.*;
public class readInt{
public static void main(String args[]){
File file = new File("lines.txt");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
}
There are a number situation where a FileNotFoundException may be thrown at runtime.
The named file does not exist. This could be for a number of reasons including:
The pathname is simply wrong
The pathname looks correct but is actually wrong because it contains non-printing characters (or homoglyphs) that you did not notice
The pathname is relative, and it doesn't resolve correctly relative to the actual current directory of the running application. This typically happens because the application's current directory is not what you are expecting or assuming.
The path to the file is is broken; e.g. a directory name of the path is incorrect, a symbolic link on the path is broken, or there is a permission problem with one of the path components.
The named file is actually a directory.
The named file cannot be opened for reading for some reason.
The good news that, the problem will inevitably be one of the above. It is just a matter of working out which. Here are some things that you can try:
Calling file.exists() will tell you if any file system object exists with the given name / pathname.
Calling file.isDirectory() will test if it is a directory.
Calling file.canRead() will test if it is a readable file.
This line will tell you what the current directory is:
System.out.println(new File(".").getAbsolutePath());
This line will print out the pathname in a way that makes it easier to spot things like unexpected leading or trailing whitespace:
System.out.println("The path is '" + path + "'");
Look for unexpected spaces, line breaks, etc in the output.
It turns out that your example code has a compilation error.
I ran your code without taking care of the complaint from Netbeans, only to get the following exception message:
Exception in thread "main" java.lang.RuntimeException: Uncompilable
source code - unreported exception java.io.FileNotFoundException; must
be caught or declared to be thrown
If you change your code to the following, it will fix that problem.
public static void main(String[] args) throws FileNotFoundException {
File file = new File("scores.dat");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
Explanation: the Scanner(File) constructor is declared as throwing the FileNotFoundException exception. (It happens the scanner it cannot open the file.) Now FileNotFoundException is a checked exception. That means that a method in which the exception may be thrown must either catch the exception or declare it in the throws clause. The above fix takes the latter approach.
The code itself is working correctly. The problem is, that the program working path is pointing to other place than you think.
Use this line and see where the path is:
System.out.println(new File(".").getAbsoluteFile());
Obviously there are a number of possible causes and the previous answers document them well, but here's how I solved this for in one particular case:
A student of mine had this problem and I nearly tore my hair out trying to figure it out. It turned out that the file didn't exist, even though it looked like it did. The problem was that Windows 7 was configured to "Hide file extensions for known file types." This means that if file appears to have the name "data.txt" its actual filename is "data.txt.txt".
Hope this helps others save themselves some hair.
I recently found interesting case that produces FileNotFoundExeption when file is obviously exists on the disk.
In my program I read file path from another text file and create File object:
//String path was read from file
System.out.println(path); //file with exactly same visible path exists on disk
File file = new File(path);
System.out.println(file.exists()); //false
System.out.println(file.canRead()); //false
FileInputStream fis = new FileInputStream(file); // FileNotFoundExeption
The cause of the problem was that the path contained invisible \r\n characters at the end.
The fix in my case was:
File file = new File(path.trim());
To generalize a bit, the invisible / non-printing characters could have include space or tab characters, and possibly others, and they could have appeared at the beginning of the path, at the end, or embedded in the path. Trim will work in some cases but not all. There are a couple of things that you can help to spot this kind of problem:
Output the pathname with quote characters around it; e.g.
System.out.println("Check me! '" + path + "'");
and carefully check the output for spaces and line breaks where they shouldn't be.
Use a Java debugger to carefully examine the pathname string, character by character, looking for characters that shouldn't be there. (Also check for homoglyph characters!)
An easy fix, which worked for me, is moving my files out of src and into the main folder of the project. It's not the best solution, but depending on the magnitude of the project and your time, it might be just perfect.
Reading and writing from and to a file can be blocked by your OS depending on the file's permission attributes.
If you are trying to read from the file, then I recommend using File's setReadable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file;
File f = new File(arbitrary_path);
f.setReadable(true);
data_of_file = Files.readAllBytes(f);
f.setReadable(false); // do this if you want to prevent un-knowledgeable
//programmers from accessing your file.
If you are trying to write to the file, then I recommend using File's setWritable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file = { (byte) 0x00, (byte) 0xFF, (byte) 0xEE };
File f = new File(arbitrary_path);
f.setWritable(true);
Files.write(f, byte_array);
f.setWritable(false); // do this if you want to prevent un-knowledgeable
//programmers from changing your file (for security.)
Apart from all the other answers mentioned here, you can do one thing which worked for me.
If you are reading the path through Scanner or through command line args, instead of copy pasting the path directly from Windows Explorer just manually type in the path.
It worked for me, hope it helps someone :)
I had this same error and solved it simply by adding the src directory that is found in Java project structure.
String path = System.getProperty("user.dir") + "\\src\\package_name\\file_name";
File file = new File(path);
Scanner scanner = new Scanner(file);
Notice that System.getProperty("user.dir") and new File(".").getAbsolutePath() return your project root directory path, so you have to add the path to your subdirectories and packages
You'd obviously figure it out after a while but just posting this so that it might help someone. This could also happen when your file path contains any whitespace appended or prepended to it.
Use single forward slash and always type the path manually. For example:
FileInputStream fi= new FileInputStream("D:/excelfiles/myxcel.xlsx");
What worked for me was catching the exception. Without it the compiler complains even if the file exists.
InputStream file = new FileInputStream("filename");
changed to
try{
InputStream file = new FileInputStream("filename");
System.out.println(file.available());
}
catch (Exception e){
System.out.println(e);
}
This works for me. It also can read files such txt, csv and .in
public class NewReader {
public void read() throws FileNotFoundException, URISyntaxException {
File file = new File(Objects.requireNonNull(NewReader.class.getResource("/test.txt")).toURI());
Scanner sc = new Scanner(file);
while (sc.hasNext()) {
String text = sc.next();
System.out.println(text);
}
}
}
the file is located in resource folder generated by maven. If you have other folders nested in, just add it to the file name like "examples/test.txt".
I have an assignment for my CS class where it says to read a file with several test scores and asks me to sum and average them. While summing and averaging is easy, I am having problems with the file reading. The instructor said to use this syntax
Scanner scores = new Scanner(new File("scores.dat"));
However, this throws a FileNotFoundException, but I have checked over and over again to see if the file exists in the current folder, and after that, I figured that it had to do something with the permissions. I changed the permissions for read and write for everyone, but it still did not work and it still keeps throwing the error. Does anyone have any idea why this may be occurring?
EDIT: It was actually pointing to a directory up, however, I have fixed that problem. Now file.exists() returns true, but when I try to put it in the Scanner, it throws the FileNotFoundException
Here is all my code
import java.util.Scanner;
import java.io.*;
public class readInt{
public static void main(String args[]){
File file = new File("lines.txt");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
}
There are a number situation where a FileNotFoundException may be thrown at runtime.
The named file does not exist. This could be for a number of reasons including:
The pathname is simply wrong
The pathname looks correct but is actually wrong because it contains non-printing characters (or homoglyphs) that you did not notice
The pathname is relative, and it doesn't resolve correctly relative to the actual current directory of the running application. This typically happens because the application's current directory is not what you are expecting or assuming.
The path to the file is is broken; e.g. a directory name of the path is incorrect, a symbolic link on the path is broken, or there is a permission problem with one of the path components.
The named file is actually a directory.
The named file cannot be opened for reading for some reason.
The good news that, the problem will inevitably be one of the above. It is just a matter of working out which. Here are some things that you can try:
Calling file.exists() will tell you if any file system object exists with the given name / pathname.
Calling file.isDirectory() will test if it is a directory.
Calling file.canRead() will test if it is a readable file.
This line will tell you what the current directory is:
System.out.println(new File(".").getAbsolutePath());
This line will print out the pathname in a way that makes it easier to spot things like unexpected leading or trailing whitespace:
System.out.println("The path is '" + path + "'");
Look for unexpected spaces, line breaks, etc in the output.
It turns out that your example code has a compilation error.
I ran your code without taking care of the complaint from Netbeans, only to get the following exception message:
Exception in thread "main" java.lang.RuntimeException: Uncompilable
source code - unreported exception java.io.FileNotFoundException; must
be caught or declared to be thrown
If you change your code to the following, it will fix that problem.
public static void main(String[] args) throws FileNotFoundException {
File file = new File("scores.dat");
System.out.println(file.exists());
Scanner scan = new Scanner(file);
}
Explanation: the Scanner(File) constructor is declared as throwing the FileNotFoundException exception. (It happens the scanner it cannot open the file.) Now FileNotFoundException is a checked exception. That means that a method in which the exception may be thrown must either catch the exception or declare it in the throws clause. The above fix takes the latter approach.
The code itself is working correctly. The problem is, that the program working path is pointing to other place than you think.
Use this line and see where the path is:
System.out.println(new File(".").getAbsoluteFile());
Obviously there are a number of possible causes and the previous answers document them well, but here's how I solved this for in one particular case:
A student of mine had this problem and I nearly tore my hair out trying to figure it out. It turned out that the file didn't exist, even though it looked like it did. The problem was that Windows 7 was configured to "Hide file extensions for known file types." This means that if file appears to have the name "data.txt" its actual filename is "data.txt.txt".
Hope this helps others save themselves some hair.
I recently found interesting case that produces FileNotFoundExeption when file is obviously exists on the disk.
In my program I read file path from another text file and create File object:
//String path was read from file
System.out.println(path); //file with exactly same visible path exists on disk
File file = new File(path);
System.out.println(file.exists()); //false
System.out.println(file.canRead()); //false
FileInputStream fis = new FileInputStream(file); // FileNotFoundExeption
The cause of the problem was that the path contained invisible \r\n characters at the end.
The fix in my case was:
File file = new File(path.trim());
To generalize a bit, the invisible / non-printing characters could have include space or tab characters, and possibly others, and they could have appeared at the beginning of the path, at the end, or embedded in the path. Trim will work in some cases but not all. There are a couple of things that you can help to spot this kind of problem:
Output the pathname with quote characters around it; e.g.
System.out.println("Check me! '" + path + "'");
and carefully check the output for spaces and line breaks where they shouldn't be.
Use a Java debugger to carefully examine the pathname string, character by character, looking for characters that shouldn't be there. (Also check for homoglyph characters!)
An easy fix, which worked for me, is moving my files out of src and into the main folder of the project. It's not the best solution, but depending on the magnitude of the project and your time, it might be just perfect.
Reading and writing from and to a file can be blocked by your OS depending on the file's permission attributes.
If you are trying to read from the file, then I recommend using File's setReadable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file;
File f = new File(arbitrary_path);
f.setReadable(true);
data_of_file = Files.readAllBytes(f);
f.setReadable(false); // do this if you want to prevent un-knowledgeable
//programmers from accessing your file.
If you are trying to write to the file, then I recommend using File's setWritable method to set it to true, or, this code for instance:
String arbitrary_path = "C:/Users/Username/Blah.txt";
byte[] data_of_file = { (byte) 0x00, (byte) 0xFF, (byte) 0xEE };
File f = new File(arbitrary_path);
f.setWritable(true);
Files.write(f, byte_array);
f.setWritable(false); // do this if you want to prevent un-knowledgeable
//programmers from changing your file (for security.)
Apart from all the other answers mentioned here, you can do one thing which worked for me.
If you are reading the path through Scanner or through command line args, instead of copy pasting the path directly from Windows Explorer just manually type in the path.
It worked for me, hope it helps someone :)
I had this same error and solved it simply by adding the src directory that is found in Java project structure.
String path = System.getProperty("user.dir") + "\\src\\package_name\\file_name";
File file = new File(path);
Scanner scanner = new Scanner(file);
Notice that System.getProperty("user.dir") and new File(".").getAbsolutePath() return your project root directory path, so you have to add the path to your subdirectories and packages
You'd obviously figure it out after a while but just posting this so that it might help someone. This could also happen when your file path contains any whitespace appended or prepended to it.
Use single forward slash and always type the path manually. For example:
FileInputStream fi= new FileInputStream("D:/excelfiles/myxcel.xlsx");
What worked for me was catching the exception. Without it the compiler complains even if the file exists.
InputStream file = new FileInputStream("filename");
changed to
try{
InputStream file = new FileInputStream("filename");
System.out.println(file.available());
}
catch (Exception e){
System.out.println(e);
}
This works for me. It also can read files such txt, csv and .in
public class NewReader {
public void read() throws FileNotFoundException, URISyntaxException {
File file = new File(Objects.requireNonNull(NewReader.class.getResource("/test.txt")).toURI());
Scanner sc = new Scanner(file);
while (sc.hasNext()) {
String text = sc.next();
System.out.println(text);
}
}
}
the file is located in resource folder generated by maven. If you have other folders nested in, just add it to the file name like "examples/test.txt".