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 am attempting to read from a file, however the console gives me this error.
Exception in thread "main" java.io.FileNotFoundException: dataEx.txt (The system cannot find the file specified)
This is the code that I am executing.
import java.io.*;
import java.util.*;
public class ReadTest {
public static void main(String[] args) throws IOException {
BufferedReader f = new BufferedReader(new FileReader("dataEx.txt" ));
}
}
This is my project structure
-project
-ReadTest.java
-dataEx.txt
Working directory
Your path is wrong, thus the reader can not find the file. Whereever you think your current working directory should be, that is not where it is.
Execute the following code to know where it is:
System.out.println(Paths.get("").toAbsolutePath());
That is the path to your current working directory. Then compare that result to your expectation. Realize that your expectation was wrong and correct the path to your file or your working directory settings.
It is hard to guess where your directory might be right now. Maybe in your bin folder, next to the .class files. You will see after executing the above code snippet.
NIO
By the way, not sure what exactly you plan on doing with that BufferedReader but you might be interested in the newer modern file API revolving around Files and Paths:
List<String> lines = Files.readAllLines(Paths.get("myFile.txt"));
It also has other neat utility methods for File IO, much better than the cumbersome File class and the clunky BufferedReader.
I am trying to use the opencsv library however I am getting stuck early on with FileReader not being able to find the csv I am using to test with.
I have the following code:
import java.io.File;
import java.io.FileReader;
public class Test {
public static void main(String[] args) {
File f = new File("demo.csv");
if(f.exists() && !f.isDirectory()) {
System.out.println("File exists");
}
else {
System.out.println("File does not exist");
}
FileReader reader = new FileReader("demo.csv");
}
}
I am getting a FileNotFoundException error on the FileReader:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Unhandled exception type FileNotFoundException at Test.main(Test.java:19)
despite having checked the file exists in the correct directory using f.exist. Done a load of searching and found nothing to explain it.
Can anyone help with this?
check if the file extension is visible and your file is not named demo.csv.csv. Happend to me and took me a while to resolve.
By default, the compiler would look for "demo.csv" in the root directory. Make sure that you clearly specify the path in FileReader parameter.
The same code does work in my case (provided demo.csv in right under the root directory)
I was trying to make a directory and file using java with File object as:
import java.io.*;
class CreateFile{
public static void main(String[] args) throws IOException{
File f = new File("File/handling/file1.txt");
if(!f.exists())
f.createNewFile();
}
}
but its showing error (see below) and unable to make it, the path and file name doesn't existed before execution. I don't know where am I going wrong, someone please clarify whats the mistake and how to resolve it? It might be I need to know something about File object, so please do tell me...
See error:
Exception in thread "main" java.io.IOException: The system cannot find the path
specified
at java.io.WinNTFileSystem.createFileExclusively(Native Method)
at java.io.File.createNewFile(File.java:947)
at CreateFile.main(CreateFile.java:6)
The error is telling you that either there is no File directory relative to where you're running this, or there is but it doesn't have a handling subdirectory. In this case, exists returns false and so you call createNewFile to try to create the file, but the directory in which you're trying to create it doesn't exist, and so it throws an exception.
You can use mkdirs to create the directories if necessary, like so:
import java.io.*;
class CreateFile{
public static void main(String[] args) throws IOException{
File f = new File("File/handling/file1.txt");
if(!f.exists()) {
f.getParentFile().mkdirs(); // This is a no-op if it exists
f.createNewFile();
}
}
}
I have a program that scans a file and then closes the file.
import java.util.*;
import java.io.*;
public class FileTester{
public static void main(String[] args) throws IOException {
File test = new File("MyDatta.in.txt");
Scanner sf = new Scanner(test);
sf.close();
}
}
When I run the program I get an error message like this:
Exception in thread "main" java.io.FileNotFoundException: MyDatta.in.txt (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:120)
at java.util.Scanner.<init>(Scanner.java:636)
at FileTester.main(FileTester.java:6)
I have a mac that runs on Mac OS. I have reason to believe it has to do with the pathway to my file which is in documents. I know in windows one would use C:\folder name\file to scan it but I just don't know with Mac and I cannot find it anywhere
From Java documentation for FileInputStream: "If the named file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading then a FileNotFoundException is thrown."
Maybe file is used by another program?
You should put this as the file path:
~/Documents/MyDatta.in.txt
to tell java that your file is in documents. The ~ is your home folder.