java 1.8 时间戳localdatetime转换

java 1.8 中 关于LocalDateTime 的与long 的转换，在1.8 localdateTime 中对于时区设置是敏感的，这个需要留意

public static void main(String[] args) {
Period sixMonths = Period.ofMonths(1);
LocalDate date = LocalDate.now();
LocalDate future = date.minus(sixMonths);
System.out.println(future);
LocalDateTime d =
LocalDateTime.ofInstant(Instant.ofEpochMilli(System.currentTimeMillis()), ZoneId.systemDefault());

System.out.println(d.minus(sixMonths).atZone(ZoneId.systemDefault()).toInstant().toEpochMilli());
ZoneId zoneId = ZoneId.systemDefault(); // or: ZoneId.of("Europe/Oslo");
long epoch = date.atStartOfDay(zoneId).toEpochSecond();
System.out.println(epoch);
System.out.println(new Date(1490585496969l));
System.out.println(ZoneId.systemDefault());
Set<String> set = new HashSet<>();
if (set.isEmpty()){
System.out.println("true");
}
}