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(); }