import java.net.InetAddress;
import java.text.SimpleDateFormat;
import java.util.Date;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.NtpV3Packet;
import org.apache.commons.net.ntp.TimeInfo;
SimpleDateFormat formater = new SimpleDateFormat("HH:mm:ss.SSS");
NTPUDPClient client = new NTPUDPClient();
try {
client.open();
InetAddress host = InetAddress.getByName(NTP_SERVER);
TimeInfo info = client.getTime(host);
info.computeDetails();
Date exactTime = new Date(System.currentTimeMillis() + info.getOffset());
System.out.println("正しい時刻\n" + formater.format(exactTime) + "\n");
} catch (Exception e) {
e.printStackTrace();
} finally {
client.close();
}