Resources

Resources loads classpath resources as streams, text, properties, or file-system paths.

All resource lookup methods throw IllegalArgumentException when the requested resource does not exist. They do not return null and do not write diagnostics to standard error.

Streams, text, and properties

Use stream-based APIs for code that must work both from an IDE and from a packaged JAR:

try (InputStream in = Resources.getResource("config/app.yml")) {
    // read resource
}

String text = Resources.getResourceText("templates/page.html");
Properties properties = Resources.getProperties("application.properties");

File-system paths

getResourcesFromClasspath(...) and getResourcesFromClass(...) return paths only for resources backed by a file: URL:

String path = Resources.getResourcesFromClasspath("com/example/config.properties");
String relative = Resources.getResourcesFromClass(MyClass.class, "template.txt");

A resource inside a JAR is not a normal Path; these methods throw UnsupportedOperationException for non-file URLs. Use getResource(...) for JAR content instead of attempting to convert the URL display text into a path.

getClassName(File, String) derives a fully qualified class name from a .class filename, and getJarDir() returns the parent directory of the running code source.