Develop Reference

Modify the feet to meters program to read from, write to a file. The input file named “feet.txt” and the output file “meters.txt” [duplicate]

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".

Output of Reading the file is not getting as Expected? [duplicate]

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".

Java : File get delete with Files.delete(path), when I try create same file name in next line it will create the old one(content will delete )

I have this code
Files.delete(Paths.get("a.txt"));
FileWriter f = new FileWriter("a.txt");
First line will delete file,
second line will create file but when i checked file created date it will give old one.

It is not because you declare a new instance of FileWriter that the underlying file is affected or even created in any ways.
According to the Javadoc, the constructor will throw an IOException in these cases (java 7)
IOException - if the named file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason
Try writing something in your file.
Also, you should be consistent and use Paths.get either in both statements or not at all. AFAIK Paths.get is filesystem dependent (in other words you may not be deleting the file that you are trying to recreate).

Can I make a Netbeans "empty file" part of compiled jar file?

I have 80,000 words for a crossword (among others) puzzle word pattern matcher. (User inputs "ba??" and gets, among other things, "ball, baby, bank, ..." or enters "ba*" and gets the aforementioned as well as "bat, basket, babboon...".)
I stuck the words in a Netbeans "empty file" and named it "dictionary". The file's contents are just (80,000) words, one per line. This code works like a charm to read the dictionary (code that filters is omitted):
static void showMatches(String pattern, String legal, String w) throws IOException
{
Path p = Paths.get("C:\\Users\\Dov\\Documents\\NetBeansProjects\\Masterwords\\src\\masterwords\\dictionary");
String word;
Scanner sc = new Scanner(p).useDelimiter("\r");
while(sc.hasNext()){
word = sc.next().substring(1);
gui.appendOutput(word);
}
sc.reset();
}
Is there a way to make the file (named "dictionary") become part of the compiled jar file so that I only need to "ship" one file to new, (largely helpless) users?
In another matter of curiosity...
Is it possible to make the argument to Paths.get(...) something like "masterwords/src/dictionary" to make the connection for the Scanner object to be able read it? I'm wondering if this might relate to an answer my first question. (If there's a way, I can't stumble onto it. Whatever similar string I use, I get no error, no output, no "build successful"--gotta click Run > Stop build/run.)

I'm not certain, based on your description, that my solution addresses your issue, but let me restate the problem as I understand it: You have a .jar file that relies on a dictionary resource. That resource is subject to change, and you'd like to be able to update it without having to ship out a whole new .jar containing a new dictionary.
If I'm reading you correctly, you want something like:
private File getInstallPath()
{
return new File(MyClass.class.getProtectionDomain().getCodeSource().getLocation().getPath());
}
This will return the install directory of your .jar file, which is where you can put your dictionary resource so that the .jar knows where to find it. Of course, now you have a bit of a training issue, because users can move, delete or misplace your dictionary file.
Part II:
Now that you've clarified your question, let me again restate: You want to be able to read an arbitrary file included in your .jar file. Fine. You're probably trying to open the file as a file, but once the file is in your .jar, you need to treat it as a resource.
Try using:
Class myClass = Class.forName("MyClass");
ClassLoader myLoader = myclass.getClassLoader();
InputStream myStream = myLoader.getResourceAsStream(myFile);
Do you really need me to explain what "myClass," "myLoader," etc. refer to? Hint: "myClass" is whatever your class is that needs to read the file.

After leaving this thread in frustration for a couple of weeks, yesterday I found a similar question at this forum, which led me to Google "java resource files" and visit ((this URL)).
Between the two I figured out how to read a file named 'dictionary' that was created as a Netbeans "empty Java file", which was located in Source Packages ... [default package] (as shown in Netbeans Projects window) and stored as C:\Users\Dov\!Docs\Documents\NetBeansProjects\WordPatternHelp\src\dictionary:
File file = new File("src/dictionary");
...
p = file.toPath();
sc = new Scanner(p).useDelimiter("\r");
Success. Hooray.
But after compiling and executing the .jar file from a DOS command line, 'dictionary' couldn't be found. So the above only works from within Netbeans IDE.
After mostly erroneous attempts caused by the above 'success', I finally got success using #Mars' second suggestion like so:
package masterwords;
public class Masterwords
...
InputStream myStream = Class.forName("masterwords.Masterwords").
getClassLoader().getResourceAsStream("dictionary");
sc = new Scanner(myStream).useDelimiter("\r"); // NULL PTR EXCEPTION HERE
So, for whatever it might be worth, a very belated thanks (and another apology) to #Mars. It was as straightforward as he indicated. Wish I'd tried it 2 weeks ago, but I'd never seen any of the methods and didn't want to take the time to learn how they work back then with other more pressing issues at hand. So I had no idea Mars had actually written the exact code I needed (except for the string arguments). Boy, do I know how the methods work now.

both File.isFile() and File.isDirectory() is returning false

I have a file with name "aaaäaa.xls"
For this, File.isFile() and File.isDirectory() is returning false? why it is returning false in Linux?

Please try the following code example
if(!pFile.exists()){
throw new FileNotFoundException();
}
boolean isDir = pFile.isDirectory();
boolean isFile = pfile.isFile();
the file is not a file
if it is not a directory and, in addition, satisfies other system-dependent criteria
if the exception is thrown, you have to check the file path.

According to the documentation:
public boolean isFile()
Returns:
true if and only if the file denoted by this abstract pathname exists and is
a normal file; false otherwise.
From this basis, your file either doesn't exist or is not a normal file.
Possible reasons of the 1st:
file doesn't exist;
file can't be accessed;
file name is mistyped;
the character encoding used in your program isn't the
same as that used when you created the file.
Possible reasons of the 2nd:
it's not a regular file.
Or it's a bug in JVM. It's also possible though unlikely. For example at once I had problems with an exclamation mark in path names - Bug 4523159.
If you want to access the file in any way, consider calling dir.listFiles() and work with its return value.
(answer is partially based on this thread)

Check the permissions of the parent directories of this file. Some of these directories may not have execute permission for the current user.
The execute bit of directory allows the affected user to enter it and access files and directories inside

I know that this question was asked five years ago, in fact, I got to it because I had the same problem, I am creating a List of all the files in a given path, like this:
File files = Paths.get(path).toFile();
List<String> filenames = Arrays.asList(files.list());
The thing is, that path contains a directory which is called testing_testing, which is being returned as part of the list.
Then when I do the following test:
for (String filename : filenames) {
if (Files.isDirectory(Paths.get(filename))) {
System.out.println(filename + " is a directory.");
} else {
if(filename.equals("testing_testing")) {
System.out.println("Is this a directory?: " + Files.isDirectory(Paths.get(filename)));
System.out.println("Does the file exists?: " + Files.exists(Paths.get(filename)));
System.out.println("Is this a regular file?: " + Files.isRegularFile(Paths.get(filename)));
System.out.println("Is this a symbolic link?: " + Files.isSymbolicLink(Paths.get(filename)));
}
}
}
It is returning false for Files.isDirectory() and for Files.exists().
Tinkering around for a bit, I noticed that I was only getting the filenames, without the full path to them, which meant that I was only passing testing_testing to Paths.get() instead of passing the full path to get to it, that's why it didn't exists and returned false for both scenarios.
I changed the code to:
Paths.get("C:\test", filename);
And now the tests return the proper values. I don't know if you've already figured this out, because it's been five years since you asked. But for anyone with the same problem, make sure that you're passing the correct path to your files, and then try the other things suggested in previous answers on this same question.

I've also had problems with file.isFile() returning false on files, presumably because the file is not "regular", as noted in other responses to this question. As a workaround, I use file.listFiles() != null, which seems to provide the functionality I need. According to the Java File API:
If this abstract pathname does not denote a directory, then this method returns null. Otherwise an array of File objects is returned.

I got same error when i was testing isFile() on a .txt file.
The problem was the file i created had something.txt with .txt on the name.
Then i renamed something.txt to something
I was really mad with myself

The character encoding used by Java in your case is different from the character encoding in the source file, so the symbol "ä" in the file name cannot be properly decoded by Java, resulting in a different file name. That's why Java cannot find the file. Therefore, the file manipulation functions over this file return "False".
As the safest way to work properly in different build environments, to avoid setting Java character encoding option and also make handling source files easier, use US-ASCII only (7-bit) characters in the source code. As for the other characters, use their Unicode numbers, e.g., instead of "ä" use "\u00e4". So, your filename would become "aaa\u00e4aa.xls".

I've had this issue several times and if everything has been tried then it might be that you have issues with pathing. Any space character is replaced by %20, and it results in an issue.
Therefore, whereas this doesn't work:
File file = new File(Objects.requireNonNull(getClass().getResource(/path/to/file).getPath());
This actually does:
File file = new File(Objects.requireNonNull(getClass().getResource(/path/to/file).getPath().replace("%20", " "));