System.currentTimeMillis() vs. new Date() vs. Calendar.getInstance().getTime()

System.currentTimeMillis()

new Date()

Calendar.getInstance().getTime()

long start = System.currentTimeMillis();
    .... do something ...
 long elapsed = System.currentTimeMillis() -start;

public GregorianCalendar(TimeZone zone, Locale aLocale) {
        super(zone, aLocale);
    gdate = (BaseCalendar.Date) gcal.newCalendarDate(zone);
    setTimeInMillis(System.currentTimeMillis());
}

public Date() {
    this(System.currentTimeMillis());
}