java8时间工具类

优点：

1.方便。

Date 只能是日期加时间的格式，这样在存储显示的时候是非常不方便的，而 LocalDate 、LocalTime、LocalDateTime 

分别代表日期，时间，日期+时间，非常灵活。再就是后者在日期计算及格式化方面非常简单易用，而Date要繁琐很多。

2.线程安全。

传统时间类不支持多线程安全。

缺点<目前发现的坑>：

1.在比较日期相隔天数时，不要使用Period.between()方法,这个只是当月相隔天数。其实就是：a月b日  -  c月d日  =   (b-d)日

注意：

比较时，会需要传接口Temporal作为参数，可用它的实现类，比如localDateTime即可。

如果比较相隔的时、分、毫秒时，需要将格式转成精确到小时以后<相隔的时、分、秒都可以只格式化到小时yyyy-MM-dd HH即可不报错>

附工具类代码：

public class DateUtil {

    public static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("HHmmss");
    public static final DateTimeFormatter MONTH_FORMATTER = DateTimeFormatter.ofPattern("yyyyMM");
    public static final DateTimeFormatter SHORT_DATE_FORMATTER = DateTimeFormatter.ofPattern("yyMMdd");
    public static final DateTimeFormatter SHORT_DATETIME_FORMATTER = DateTimeFormatter.ofPattern("yyMMddHHmmss");
    public static final DateTimeFormatter DATETIME_FORMATTER =  DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
    public static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd");

    /**
     * 返回当前的日期
     * @return
     */
    public static LocalDate getCurrentLocalDate() {
        return LocalDate.now();
    }

    /**
     * 返回当前时间
     * @return
     */
    public static LocalTime getCurrentLocalTime() {
        return LocalTime.now();
    }

    /**
     * 返回当前日期时间
     * @return
     */
    public static LocalDateTime getCurrentLocalDateTime() {
        return LocalDateTime.now();
    }

    /**
     * yyyyMMdd
     *
     * @return
     */
    public static String getCurrentDateStr() {
        return LocalDate.now().format(DATE_FORMATTER);
    }

    /**
     * yyMMdd
     *
     * @return
     */
    public static String getCurrentShortDateStr() {
        return LocalDate.now().format(SHORT_DATE_FORMATTER);
    }

    public static String getCurrentMonthStr() {
        return LocalDate.now().format(MONTH_FORMATTER);
    }

    /**
     * yyyyMMddHHmmss
     * @return
     */
    public static String getCurrentDateTimeStr() {
        return LocalDateTime.now().format(DATETIME_FORMATTER);
    }

    /**
     * yyMMddHHmmss
     * @return
     */
    public static String getCurrentShortDateTimeStr() {
        return LocalDateTime.now().format(SHORT_DATETIME_FORMATTER);
    }

    /**
     * HHmmss
     * @return
     */
    public static String getCurrentTimeStr() {
        return LocalTime.now().format(TIME_FORMATTER);
    }

    public static String getCurrentDateStr(String pattern) {
        return LocalDate.now().format(DateTimeFormatter.ofPattern(pattern));
    }

    public static String getCurrentDateTimeStr(String pattern) {
        return LocalDateTime.now().format(DateTimeFormatter.ofPattern(pattern));
    }

    public static String getCurrentTimeStr(String pattern) {
        return LocalTime.now().format(DateTimeFormatter.ofPattern(pattern));
    }

    public static LocalDate parseLocalDate(String dateStr, String pattern) {
        return LocalDate.parse(dateStr, DateTimeFormatter.ofPattern(pattern));
    }

    public static LocalDateTime parseLocalDateTime(String dateTimeStr, String pattern) {
        return LocalDateTime.parse(dateTimeStr, DateTimeFormatter.ofPattern(pattern));
    }

    public static LocalTime parseLocalTime(String timeStr, String pattern) {
        return LocalTime.parse(timeStr, DateTimeFormatter.ofPattern(pattern));
    }

    public static String formatLocalDate(LocalDate date, String pattern) {
        return date.format(DateTimeFormatter.ofPattern(pattern));
    }

    public static String formatLocalDateTime(LocalDateTime datetime, String pattern) {
        return datetime.format(DateTimeFormatter.ofPattern(pattern));
    }

    public static String formatLocalTime(LocalTime time, String pattern) {
        return time.format(DateTimeFormatter.ofPattern(pattern));
    }

    public static LocalDate parseLocalDate(String dateStr) {
        return LocalDate.parse(dateStr, DATE_FORMATTER);
    }

    public static LocalDateTime parseLocalDateTime(String dateTimeStr) {
        return LocalDateTime.parse(dateTimeStr, DATETIME_FORMATTER);
    }

    public static LocalTime parseLocalTime(String timeStr) {
        return LocalTime.parse(timeStr, TIME_FORMATTER);
    }

    public static String formatLocalDate(LocalDate date) {
        return date.format(DATE_FORMATTER);
    }

    public static String formatLocalDateTime(LocalDateTime datetime) {
        return datetime.format(DATETIME_FORMATTER);
    }

    public static String formatLocalTime(LocalTime time) {
        return time.format(TIME_FORMATTER);
    }

    /**
     * 日期相隔天数
     * @param startDateInclusive
     * @param endDateExclusive
     * @return
     */
    public static long periodDays(LocalDate startDateInclusive, LocalDate endDateExclusive) {
        return endDateExclusive.toEpochDay() - startDateInclusive.toEpochDay();
    }

    /**
     * 日期相隔小时
     * @param startInclusive
     * @param endExclusive
     * @return
     */
    public static long durationHours(Temporal startInclusive, Temporal endExclusive) {
        return Duration.between(startInclusive, endExclusive).toHours();
    }

    /**
     * 日期相隔分钟
     * @param startInclusive
     * @param endExclusive
     * @return
     */
    public static long durationMinutes(Temporal startInclusive, Temporal endExclusive) {
        return Duration.between(startInclusive, endExclusive).toMinutes();
    }

    /**
     * 日期相隔毫秒数
     * @param startInclusive
     * @param endExclusive
     * @return
     */
    public static long durationMillis(Temporal startInclusive, Temporal endExclusive) {
        return Duration.between(startInclusive, endExclusive).toMillis();
    }

    /**
     * 是否当天
     * @param date
     * @return
     */
    public static boolean isToday(LocalDate date) {
        return getCurrentLocalDate().equals(date);
    }

    /**
     * 获取此日期时间与默认时区<Asia/Shanghai>组合的时间毫秒数
     * @param dateTime
     * @return
     */
    public static Long toEpochMilli(LocalDateTime dateTime) {
        return dateTime.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
    }

    /**
     * 获取此日期时间与指定时区组合的时间毫秒数
     * @param dateTime
     * @return
     */
    public static Long toSelectEpochMilli(LocalDateTime dateTime, ZoneId zoneId) {
        return dateTime.atZone(zoneId).toInstant().toEpochMilli();
    }
}