How to read file from relative path in Java project? java.io.File cannot find the path specified

java

file-reading

relative-paths

classloader

byAnton Shumikhin·Dec 10, 2024

For reading a file from a relative path in Java, you can use either Class.getResourceAsStream("/relativePath") or new File("relativePath"). The former is when your file is stored within the classpath, while the latter is when your file is located relative to the project root. Replace "relativePath" with the actual path to your file.

InputStream stream = YourClass.class.getResourceAsStream("/file.txt"); // Somewhere in the classpath

File file = new File("file.txt"); // Close to the project root

If your file resides within the classpath, refrain from using new File() as it might fail when your application is packaged into a JAR. Rather, opt for a URL or InputStream. If your file is formatted with key=value pairs, Properties.load() is a handy method for reading.

Decoding file paths and resources

Resource retrieval within classpath

When your file is sealed within your application as a resource, it’s similar to saying you’re working in the classpath. This can be compared to the well-organized filing system of an application.

URL resourceURL = YourClass.class.getResource("/config/sample-config.json"); // Get that mysterious file!

With this approach, you can conveniently access resources packed inside JAR files or other elements of the classpath, like a virtual file system or network placeholders.

File in properties format? No problem!

In case your file is conveniently set up as a properties file with key=value pairs, you can simplify the reading process enormously:

Properties properties = new Properties();
properties.load(new InputStreamReader(
    YourClass.class.getResourceAsStream("/config/app.properties"), StandardCharsets.UTF_8)); // Key and values, sitting on a tree!

This handy trick does wonders in combating familiar issues when it comes to file encodings and the grandeur of proper formatting.

Access within static context

public static void someMethod() {
    InputStream stream = YourClass.class.getResourceAsStream("/file.txt"); // Like grabbing a beer from the fridge!
    //...
}

Don't forget, in a static context, YourClass.class is crucial to reference the correct class loader.

Setting the record straight on relative paths

Your relative path must include the trail of shreds after "./" when using methods like Class.getResource().

Verifying paths against project labyrinth

Always verify that the path you're traversing matches the blueprint of your project (package structure) to avoid diving headfirst into the FileNotFoundException.

Reading buffet using `BufferedReader`

try (BufferedReader reader = new BufferedReader(new InputStreamReader(
    YourClass.class.getResourceAsStream("/data.txt"), StandardCharsets.UTF_8))) {
    reader.lines().forEach(System.out::println); // Let's sing the file content!
}