Solution 1:

Use FileInputStream:

InputStream is = new FileInputStream("/res/example.xls");

But never read from raw file input stream as this is terribly slow. Wrap it with buffering decorator first:

new BufferedInputStream(is);

BTW leading slash means that the path is absolute, not relative.

Solution 2:

InputStream inputStream = Files.newInputStream(Path);

Solution 3:

Initialize a variable like: Path filePath, and then:

FileInputStream fileStream;
try {
    fileStream = new FileInputStream(filePath.toFile());
} catch (Exception e) {
    throw new RuntimeException(e);
}

Done ! Using Path you can have access to many useful methods.