SimpleDateFormat 你还在用？赶快尝试一下JDK1.8的LocalDateTime、LocalDate...(内有1.8的时间工具类)

日常开发中，我们经常需要使用时间相关类，想必大家对SimpleDateFormat并不陌生。主要用它进行时间的格式化输出和解析，挺方便快捷的，但是SimpleDateFormat并不是一个线程安全的类。在多线程情况下，会出现异常，想必有经验的小伙伴也遇到过。

接下来看看《阿里巴巴开发手册》对SimpleDateFormat是怎么看待的？

【强制】SimpleDateFormat是线程不安全的类，一般不要定义位static变量，如果定义为static，必须加锁，或者使用DateUtils工具类。
正例：注意线程安全，使用DateUtils。亦推荐如下处理
private static final ThreadLocal df = new ThreadLocal(){
    @Override
    protected DateFormat initialValue(){
        return new SimpleDateFormat("yyyy-MM-dd");
    }
};
说明:如果是JDK8的应用，可以使用Instant代替Date，LocalDateTime代替Calendar,DateTimeFormatter 代替SimpleDateFormat，官方给出解释：simple beautiful strong immutable thread-safe

JDK8 DateUtils

个人总结：

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalAdjusters;
import java.util.Date;

/**
 * @ClassName DateUtils
 * @Description 时间工具类 1.8版本
 * @Author QiMing
 * @Date 2019/4/30 8:45
 * @Version 1.0
 */
public class DateUtils {

	/**
	 * 缺省的日期显示格式： yyyy-MM-dd
	 */
	public static final String DEFAULT_DATE_FORMAT = "yyyy-MM-dd";

	/**
	 * 用做单号
	 */
	public static final String DEFAULT_DATE_FORMAT_ORDER = "yyyyMMdd";

	/**
	 * 缺省的日期显示格式： yyyy-MM
	 */
	public static final String DEFAULT_YYMM_FORMAT = "yyyy-MM";
	/**
	 * 缺省的日期时间显示格式：yyyy-MM-dd HH:mm:ss
	 */
	public static final String DEFAULT_DATETIME_FORMAT = "yyyy-MM-dd HH:mm:ss";
	/**
	 * 缺省的日期时间显示格式：yyyy-MM-dd HH:mm:ss:sss
	 */
	public static final String YMDHMSS = "yyyy-MM-dd HH:mm:ss:sss";
	/**
	 * 字符串时间
	 */
	public static final String YMDHMS = "yyyyMMddHHmmss";
	/**
	 * 当前时间
	 */
	public static Date DATE_NOW = new Date();

	/**
	 * 当前时间
	 */
	public static LocalDate localDate = LocalDate.now();

	/**
	 * @Title getDay
	 * @Description 获取年月日（当天）
	 * @Param []
	 * @Return java.lang.String
	 * @Date 2019/6/4 15:26
	 * @Author QiMing
	 */
	public static String getDay() {
		LocalDate date = LocalDate.now();
		DateTimeFormatter fmt = DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT);
		return date.format(fmt);
	}

	/**
	 * @Title getDayTime
	 * @Description 年月日时分秒 （当天） 此方法不支持毫秒
	 * @Param []
	 * @Return java.lang.String
	 * @Date 2019/6/4 15:28
	 * @Author QiMing
	 */
	public static String getDayTime() {
		LocalDateTime date = LocalDateTime.now();
		DateTimeFormatter fmt = DateTimeFormatter.ofPattern(DEFAULT_DATETIME_FORMAT);
		return date.format(fmt);
	}

	/**
	 * @Title getDateToString
	 * @Description date类型转换字符串
	 * @Param [date]
	 * @Return java.lang.String
	 * @Date 2019/7/8 11:07
	 * @Author QiMing
	 */
	public static String getDateToString(Date date) {
		LocalDateTime localDateTime = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
		DateTimeFormatter fmt = DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT_ORDER);
		return localDateTime.format(fmt);
	}

	/**
	 * @Title getLocalDateToString
	 * @Description LocalDate转换String
	 * @Param [localDate]
	 * @Return java.lang.String
	 * @Date 2019/7/8 11:10
	 * @Author QiMing
	 */
	public static String getLocalDateToString(LocalDate localDate) {
		DateTimeFormatter fmt = DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT_ORDER);
		return localDate.format(fmt);
	}

	/**
	 * @Title getFixedTime
	 * @Description 自定固定时间
	 * @Param [year, month, day, hour, minute, second]
	 * @Return java.time.LocalDateTime
	 * @Date 2019/7/8 15:23
	 * @Author QiMing
	 */
	public static LocalDateTime getFixedTime(int year, int month, int day, int hour, int minute, int second) {
		return LocalDateTime.of(year, month, day, hour, minute, second);
	}

	/**
	 * @Title settingsTime
	 * @Description 设置固定时间
	 * @Param [year, month, day, hour, minute, second]
	 * @Return java.time.LocalDateTime
	 * @Date 2019/7/8 15:29
	 * @Author QiMing
	 */
	public static LocalDateTime settingsTime(int year, int month, int day, int hour, int minute, int second) {
		return LocalDateTime.now().withYear(year).withMonth(month).withDayOfMonth(day).withHour(hour).withMinute(minute).withSecond(second);
	}

	/**
	 * @Title firstToMonth
	 * @Description 当月第一天
	 * @Param []
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 15:31
	 * @Author QiMing
	 */
	public static LocalDate firstToMonth() {
		return localDate.with(TemporalAdjusters.firstDayOfMonth());
	}

	/**
	 * @Title lastToMonth
	 * @Description 本月最后一天
	 * @Param []
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 15:33
	 * @Author QiMing
	 */
	public static LocalDate lastToMonth() {
		return localDate.with(TemporalAdjusters.lastDayOfMonth());
	}

	/**
	 * @Title firstNextMonth
	 * @Description 下个月第一天
	 * @Param []
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 15:35
	 * @Author QiMing
	 */
	public static LocalDate firstNextMonth() {
		return localDate.with(TemporalAdjusters.firstDayOfNextMonth());
	}

	/**
	 * @Title firstToYear
	 * @Description 本年第一天
	 * @Param []
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 15:36
	 * @Author QiMing
	 */
	public static LocalDate firstToYear() {
		return localDate.with(TemporalAdjusters.firstDayOfYear());
	}

	/**
	 * @Title lastToYear
	 * @Description 本年最后一天
	 * @Param []
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 15:37
	 * @Author QiMing
	 */
	public static LocalDate lastToYear() {
		return localDate.with(TemporalAdjusters.lastDayOfYear());
	}

	/*———————————————————   时间相差 start    ———————————————————————*/

	/**
	 * @Title difference
	 * @Description 相差分钟
	 * @Param [localTime, localTime1]
	 * @Return long
	 * @Date 2019/7/8 15:43
	 * @Author QiMing
	 */
	public static long difference(LocalTime localTime, LocalTime localTime1) {
		return Duration.between(localTime, localTime1).getSeconds();
	}

	/**
	 * @Title aFewYearsApart
	 * @Description 相差几年
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:47
	 * @Author QiMing
	 */
	public static long aFewYearsApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.YEARS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewMonthsApart
	 * @Description 相差几个月
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:49
	 * @Author QiMing
	 */
	public static long aFewMonthsApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.MONTHS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewWEEKSApart
	 * @Description 相差多少周
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:50
	 * @Author QiMing
	 */
	public static long aFewWEEKSApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.WEEKS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewDAYSApart
	 * @Description 相差多少天
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:51
	 * @Author QiMing
	 */
	public static long aFewDAYSApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.DAYS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewHOURSApart
	 * @Description 相差多少小时
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:52
	 * @Author QiMing
	 */
	public static long aFewHOURSApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.HOURS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewHOURSApart
	 * @Description 相差多少分钟
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:52
	 * @Author QiMing
	 */
	public static long aFewMINUTESApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.MINUTES.between(oldDate, newDate);
	}

	/**
	 * @Title aFewSECONDSApart
	 * @Description 相差多少秒
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:54
	 * @Author QiMing
	 */
	public static long aFewSECONDSApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.SECONDS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewMILLISApart
	 * @Description 相差多少毫秒
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:55
	 * @Author QiMing
	 */
	public static long aFewMILLISApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.MILLIS.between(oldDate, newDate);
	}

	/**
	 * @Title aFewMILLISApart
	 * @Description 相差多少纳秒
	 * @Param [oldDate, newDate]
	 * @Return long
	 * @Date 2019/7/8 15:55
	 * @Author QiMing
	 */
	public static long aFewNANOSApart(LocalDateTime oldDate, LocalDateTime newDate) {
		return ChronoUnit.NANOS.between(oldDate, newDate);
	}

	/*———————————————————   时间相差 end    ———————————————————————*/

	/**
	 * @Title getTimestamp
	 * @Description 获取时间戳13位
	 * @Param []
	 * @Return long
	 * @Date 2019/7/8 15:59
	 * @Author QiMing
	 */
	public static long getTimestamp() {
		return Clock.systemDefaultZone().millis();
	}

	/*———————————————————————   时间转换 Start   ——————————————————————*/

	/**
	 * @Title dateToLocalDateTime
	 * @Description date转换LocalDateTime
	 * @Param [date]
	 * @Return java.time.LocalDateTime
	 * @Date 2019/7/8 16:05
	 * @Author QiMing
	 */
	public static LocalDateTime dateToLocalDateTime(Date date) {
		// LocalDateTime.ofInstant(date.toInstant(),ZoneId.systemDefault());
		return date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
	}

	/**
	 * @Title dateToLocalDate
	 * @Description date转换LocalDate
	 * @Param [date]
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 16:08
	 * @Author QiMing
	 */
	public static LocalDate dateToLocalDate(Date date) {
		return date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
	}

	/**
	 * @Title dateToLocalTime
	 * @Description date转换LocalTime
	 * @Param [date]
	 * @Return java.time.LocalTime
	 * @Date 2019/7/8 16:08
	 * @Author QiMing
	 */
	public static LocalTime dateToLocalTime(Date date) {
		return date.toInstant().atZone(ZoneId.systemDefault()).toLocalTime();
	}

	/**
	 * @Title localDateTimeToDate
	 * @Description LocalDateTime转为Date
	 * @Param [localDateTime]
	 * @Return java.util.Date
	 * @Date 2019/7/8 16:10
	 * @Author QiMing
	 */
	public static Date localDateTimeToDate(LocalDateTime localDateTime) {
		return Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
	}

	/**
	 * @Title localDateToDate
	 * @Description LocalDate -> Date，时间默认都是00
	 * @Param [localDate]
	 * @Return java.util.Date
	 * @Date 2019/7/8 16:13
	 * @Author QiMing
	 */
	public static Date localDateToDate(LocalDate localDate) {
		return Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());
	}
	/*———————————————————————   时间转换 End     ——————————————————————*/

	/*————————————————————————  日期与字符串、字符串与时间转换  Start ——————————————————————————*/

	/**
	 * @Title stringConversionLocalDate
	 * @Description 字符串转LocalDate
	 * @Param [ymd]
	 * @Return java.time.LocalDate
	 * @Date 2019/7/8 16:19
	 * @Author QiMing
	 */
	public static LocalDate stringConversionLocalDate(String ymd) {
		return LocalDate.parse(ymd, DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT));
	}

	/**
	 * @Title stringConversionLocalDateTime
	 * @Description 字符串转LocalDateTime
	 * @Param [ymdhms]
	 * @Return java.time.LocalDateTime
	 * @Date 2019/7/8 16:22
	 * @Author QiMing
	 */
	public static LocalDateTime stringConversionLocalDateTime(String ymdhms) {
		return LocalDateTime.parse(ymdhms, DateTimeFormatter.ofPattern(DEFAULT_DATETIME_FORMAT));
	}

	/**
	 * @Title localDateConversionString
	 * @Description localDate转字符串
	 * @Param [localDate]
	 * @Return java.lang.String
	 * @Date 2019/7/8 16:24
	 * @Author QiMing
	 */
	public static String localDateConversionString(LocalDate localDate) {
		return localDate.format(DateTimeFormatter.ofPattern(DEFAULT_DATE_FORMAT));
	}

	/**
	 * @Title localDateTimeConversionString
	 * @Description localDateTime转字符串
	 * @Param [localDateTime]
	 * @Return java.lang.String
	 * @Date 2019/7/8 16:25
	 * @Author QiMing
	 */
	public static String localDateTimeConversionString(LocalDateTime localDateTime) {
		return localDateTime.format(DateTimeFormatter.ofPattern(DEFAULT_DATETIME_FORMAT));
	}

	/**
	 * @Title localDateTimeToString
	 * @Description localDateTime转字符串
	 * @Param [localDateTime]
	 * @Return java.lang.String
	 * @Date 2019/7/8 16:28
	 * @Author QiMing
	 */
	public static String localDateTimeToString(LocalDateTime localDateTime) {
		return DateTimeFormatter.ofPattern(DEFAULT_DATETIME_FORMAT).format(localDateTime);
	}
	/*————————————————————————  日期与字符串、字符串与时间转换  end   ——————————————————————————*/

	/**
	 * @Title timestampConversionLocalDateTime
	 * @Description 时间戳转换Localdatetime
	 * @Param [timeMillis]
	 * @Return java.time.LocalDateTime
	 * @Date 2019/7/8 16:32
	 * @Author QiMing
	 */
	public static LocalDateTime timestampConversionLocalDateTime(long timeMillis) {
		Instant instant = Instant.ofEpochMilli(timeMillis);
		return LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
	}

	/**
	 * @Title localDateTimeConversiontimestamp
	 * @Description localDateTime 转换时间戳
	 * @Param [localDateTime]
	 * @Return long
	 * @Date 2019/7/8 16:34
	 * @Author QiMing
	 */
	public static long localDateTimeConversiontimestamp(LocalDateTime localDateTime) {
		return localDateTime.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
	}

	/**
	 * @Title getWeek
	 * @Description 获取周几
	 * @Param [localDate]
	 * @Return java.lang.String
	 * @Date 2019/7/8 17:08
	 * @Author QiMing
	 */
	public static String getWeek(LocalDate localDate) {
		String week = String.valueOf(localDate.getDayOfWeek());
		switch (week) {
			case "MONDAY":
				week = "周一";
				break;
			case "TUESDAY":
				week = "周二";
				break;
			case "WEDNESDAY":
				week = "周三";
				break;
			case "THURSDAY":
				week = "周四";
				break;
			case "FRIDAY":
				week = "周五";
				break;
			case "SATURDAY":
				week = "周六";
				break;
			case "SUNDAY":
				week = "周日";
				break;
		}
		return week;
	}

	/**
	 * @Title localDateTimeChangeTen
	 * @Description LocalDateTime转换10位时间戳
	 * @Param [localDateTime]
	 * @Return long
	 * @Date  2019/7/9 8:39
	 * @Author QiMing
	 */
	public static long localDateTimeChangeTen(LocalDateTime localDateTime) {
		long lon = localDateTimeConversiontimestamp(localDateTime) / 1000;
		return Long.valueOf(String.format("%010d", lon));
	}
}