Java8 LocalDate/LocalDateTime常用方法

简单来说，LocalDate就是不带时分秒（为0）的日期，而LocalDateTime则有时分秒。

新东西当然就得用，下面是一些常用的方法，做个笔记。

获取当前时间

LocalDate now = LocalDate.now();
LocalDate now = LocalDate.now(ZoneId.systemDefault());
LocalDateTime now = LocalDateTime.now();
LocalDateTime now = LocalDateTime.now(ZoneId.systemDefault());

获取指定日期的时间

LocalDate now = LocalDate.of(2017, 9, 22);
LocalDateTime now = LocalDateTime.of(2017, 9, 22, 15, 40, 00);

Date转换为LocalDate/LocalDateTime

Date date = new Date();
LocalDate now = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
LocalDateTime nowTime = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();

LocalDate/LocalDateTime转换为Date

LocalDate now = LocalDate.now(ZoneId.systemDefault());
Date date = Date.from(now.atStartOfDay(ZoneId.systemDefault()).toInstant());

LocalDateTime now = LocalDateTime.now(ZoneId.systemDefault());
Date date = Date.from(now.atZone(ZoneId.systemDefault()).toInstant());

获取两个LocalDate的相差天数

/**
* 如果是 now.until(before, ChronoUnit.DAYS), 返回的结果是负数
*/
LocalDate before = LocalDate.of(2017, 9, 22);
LocalDate now = LocalDate.now(ZoneId.systemDefault());
long betweenDays = before.until(now, ChronoUnit.DAYS);