我们不太可能使用jdk8以后就把原来的代码都改成新api。所以新旧日期类会共存一段时间。

这篇提供他们之间的转换。

public static void main(String[] args) {        //Date 转 Instant        Instant timestamp = new Date().toInstant();        //其他类都有ofInstant方法用来转换Instant        LocalDateTime date = LocalDateTime.ofInstant(timestamp, ZoneId.of(ZoneId.SHORT_IDS.get("CTT")));        System.out.println(date);        //Calendar 转 Instant        Instant time = Calendar.getInstance().toInstant();        System.out.println(time);        //TimeZone 转 ZoneId        ZoneId defaultZone = TimeZone.getDefault().toZoneId();        System.out.println(defaultZone);        //Calendar 转 ZonedDateTime        ZonedDateTime gregorianCalendarDateTime = new GregorianCalendar().toZonedDateTime();        System.out.println(gregorianCalendarDateTime);        //兼容API        Date dt = Date.from(Instant.now());        System.out.println(dt);        TimeZone tz = TimeZone.getTimeZone(defaultZone);        System.out.println(tz);        GregorianCalendar gc = GregorianCalendar.from(gregorianCalendarDateTime);        System.out.println(gc);    }