public static Long offsetFromFile(File file) {
        return offsetFromFileName(file.getName());
    }
Returns the offset from the given file. The file name is of the form: {number}.{suffix}. This method extracts
the number from the given file's name.

@param file file with the offset information as part of its name.
@return offset of the given file
storage/src/main/java/org/apache/kafka/storage/internals/log/LogFileUtils.java