Java By Comparison

Avoid NullPointerException in Conditionals

class Logbook {

    void writeMessage(String message, Path location) throws IOException {
        if (Files.isDirectory(location)) {
            throw new IllegalArgumentException("The path is invalid!");
        }
        if (message.trim().equals("") || message == null) {
            throw new IllegalArgumentException("The message is invalid!");
        }
        String entry = LocalDate.now() + ": " + message;
        Files.write(location, Collections.singletonList(entry),
                StandardCharsets.UTF_8, StandardOpenOption.CREATE,
                StandardOpenOption.APPEND);
    }
}

The first exception that beginners in Java typically see is the NullPointerException. It’s triggered if you call a method or access an attribute on a reference that is ...