■ サンプル
import java.io.IOException; import java.net.HttpURLConnection; import java.net.URL; import java.text.DateFormat; import java.text.SimpleDateFormat; import com.ibm.icu.util.Calendar; public class Main { public static void main(String[] args) { Calendar calendar = getDatetimeFromResponseHeader("https://blogs.yahoo.co.jp/dk521123/37095462.html", 10_000); System.out.println(toString(calendar)); } public static Calendar getDatetimeFromResponseHeader(String url, int timeout) { try { URL targetUrl = new URL(url); HttpURLConnection connection = (HttpURLConnection) targetUrl.openConnection(); connection.setConnectTimeout(timeout); connection.setReadTimeout(timeout); connection.setRequestMethod("HEAD"); Calendar returnValue = Calendar.getInstance(); returnValue.setTimeInMillis(connection.getDate()); return returnValue; } catch (IOException exception) { return null; } } public static String toString(Calendar calendar){ DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss SSS"); return dateFormat.format(calendar.getTime()); } }
