java java中UTC到IST时间的转换在LOCAL中有效，但在CLOUD SERVER中无效
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Conversion of UTC to IST time in java is working in LOCAL but not in CLOUD SERVER
提问by Vicky
I am working in date conversion in java in that i am using following code snippet to convert the UTC time to IST format.It is working properly in the local when i run it but when i deploy it in server its not converting , its displaying only the utc time itself.Is there any configuaration is needed in server side.Please help me out.
我正在 Java 中进行日期转换，因为我正在使用以下代码片段将 UTC 时间转换为 IST 格式。当我运行它时它在本地正常工作，但是当我将它部署到服务器中时它没有转换，它只显示UTC 时间本身。服务器端是否需要任何配置。请帮帮我。
CODE SNIPPET:
代码片段：
DateFormat sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
String pattern = "dd-MM-yyyy HH:mm:ss";
SimpleDateFormat formatter;
formatter = new SimpleDateFormat(pattern);
try {
String formattedDate = formatter.format(utcDate);
Date ISTDate = sdf.parse(formattedDate);
String ISTDateString = formatter.format(ISTDate);
return ISTDateString;
}
采纳答案by Andreas
Java Dateobjects are already/always in UTC. Time Zone is something that is applied when formatting to text. A Datecannot (should not!) be in any time zone other than UTC.
JavaDate对象已经/总是在 UTC 中。时区是在格式化文本时应用的东西。ADate不能（不应该！）位于 UTC 以外的任何时区。
So, the entire concept of converting utcDateto ISTDateis flawed.
(BTW: Bad name. Java conventions says it should be istDate)
因此，转换utcDate为的整个概念ISTDate是有缺陷的。
（顺便说一句：名字不好。Java 约定说它应该是istDate）
Now, if you want the code to return the date as text in IST time zone, then you need to request that:
现在，如果您希望代码将日期作为 IST 时区中的文本返回，那么您需要请求：
DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
formatter.setTimeZone(TimeZone.getTimeZone("Asia/Kolkata")); // Or whatever IST is supposed to be
return formatter.format(utcDate);
回答by Rakesh Chaudhari
Using Java 8 New API,
使用 Java 8 新 API，
Instant s = Instant.parse("2019-09-28T18:12:17Z");
ZoneId.of("Asia/Kolkata");
LocalDateTime l = LocalDateTime.ofInstant(s, ZoneId.of("Asia/Kolkata"));
System.out.println(l);
