Skip to content
Fix These Errors
java.io.FileNotFoundException

java.io.FileNotFoundException

DodaTech 3 min read

FileNotFoundException is thrown when Java cannot open a file — the path is wrong, the file doesn’t exist, or the process lacks OS permissions to read or write it.

What It Means

A FileInputStream, FileReader, RandomAccessFile, or similar I/O class tried to access a file at the specified path, but the OS returned an error. Java wraps this into FileNotFoundException. The message usually includes the path that was attempted.

Why It Happens

  • The file path is incorrect (typo, wrong directory).
  • The file doesn’t exist at the specified location.
  • The application’s working directory is not what you expect.
  • The file exists but the process doesn’t have read permission.
  • On Windows, another process has the file locked exclusively.
  • You’re using a relative path when an absolute path is needed.

How to Fix It

1. Print the working directory 

// Discover where your app is running from
System.out.println("Working dir: " + System.getProperty("user.dir"));

// Now use a path relative to that directory
File file = new File("data/config.properties");

2. Use absolute paths or build from known locations 

// BUG: relative path may not resolve as expected
FileInputStream fis = new FileInputStream("config.properties");

// FIX: use absolute path
FileInputStream fis = new FileInputStream("/opt/myapp/config.properties");

// Or build from a known base
String home = System.getProperty("user.home");
File config = new File(home, ".myapp/config.properties");

3. Check file existence and handle gracefully 

File file = new File("data/input.txt");

if (!file.exists()) {
    System.err.println("File not found: " + file.getAbsolutePath());
    return;
}

if (!file.canRead()) {
    System.err.println("Cannot read file: " + file.getAbsolutePath());
    return;
}

// Safe to read
try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
    reader.lines().forEach(System.out::println);
}

4. Use getResourceAsStream for bundled files 

// For files bundled in the JAR or classpath
// Good for config files bundled with your app
try (InputStream in = getClass()
        .getResourceAsStream("/config/default.properties")) {
    if (in == null) {
        throw new FileNotFoundException(
            "Resource not found: /config/default.properties"
        );
    }
    Properties props = new Properties();
    props.load(in);
}

5. Create parent directories before writing 

File output = new File("/var/log/myapp/output.log");

// Ensure parent directory exists
File parent = output.getParentFile();
if (parent != null && !parent.exists()) {
    parent.mkdirs();  // creates all missing parent directories
}

try (FileWriter writer = new FileWriter(output)) {
    writer.write("Log entry");
}
What's the difference between FileNotFoundException and NoSuchFileException?
FileNotFoundException (from java.io) is the older checked exception. NoSuchFileException (from java.nio.file) is the newer unchecked exception used by the NIO.2 API. Both mean the file doesn’t exist, but NoSuchFileException provides more details (file type, other attributes).
How do I see which directory Java thinks is the working directory?
Print System.getProperty("user.dir") at the start of your program. This is the directory used as the base for all relative paths. You can also print new File(".").getAbsolutePath() to confirm.
What does 'Permission denied' in the error message mean?
The file exists but the OS user running the Java process doesn’t have read (or write) permission. Check the file’s permissions with ls -la filename on Linux/macOS, or right-click → Properties → Security on Windows. Fix with chmod +r filename or run the process as the correct user.
Previous HTTP 409 Conflict — What It Means & How to Debug Next ValueError: invalid literal for int() with base 10

Built by the developers of DodaTech

Doda Browser, DodaZIP & Durga Antivirus Pro

Home Browse Fix These Errors