Calendar cal = Calendar.getInstance();

 int hour = cal.get(Calendar.HOUR_OF_DAY);
 if (hour >= 6 && hour < 8) {
  out.print("早上好");
 } else if (hour >= 8 && hour < 11) {
  out.print("上午好");
 } else if (hour >= 11 && hour < 13) {
  out.print("中午好");
 } else if (hour >= 13 && hour < 18) {
  out.print("下午好");
 } else {
  out.print("晚上好");
 }