greeting.java

public static String greeting() {
    Calendar c = Calendar.getInstance();
    int timeOfDay = c.get(Calendar.HOUR_OF_DAY);

    if (timeOfDay >= 0 && timeOfDay < 12) {
        return "Good Morning";
    } else if (timeOfDay >= 12 && timeOfDay < 16) {
        return "Good Afternoon";
    } else if (timeOfDay >= 16 && timeOfDay < 21) {
        return "Good Evening";
    } else if (timeOfDay >= 21 && timeOfDay < 24) {
        return "Good Night";
    } else {
        return "Hello";
    }
}