例如，现有的类（例如java.util.Date和SimpleDateFormatter）不是线程安全的，这会导致用户潜在的并发问题。而新的LocalDate、LocalDateTime、DateTimeFormatter是不可变值类。
LocalDate和LocalTime。它们是本地的，它们从观察者的角度表示日期和时间，例如书桌上的日历或墙上的时钟。还有一种称为复合类LocalDateTime，这是一个配对LocalDate和LocalTime。
下面是一个简单的思维导图和一个基于LocalDate、LocalDateTime...实现的日期工具类可以帮助我们记住一些类、API...,日期工具类中引入了gvava工具包。maven依赖如下
<dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>28.1-jre</version></dependency>import com.google.common.base.Strings;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.sql.Timestamp;import java.time.*;import java.time.format.DateTimeFormatter;import java.time.format.DateTimeParseException;import java.time.temporal.*;import java.util.*;public class Date8Util { private static final Logger logger = LoggerFactory.getLogger(Date8Util.class); public static final HashMap<String,String> fomatMap = new HashMap(); static { fomatMap.put("DATE_FORMAT_DEFAULT","yyyy-MM-dd HH:mm:ss"); fomatMap.put("FORMATE1","yyyy-MM-dd hh:mm:ss"); fomatMap.put("DATE_FORMAT_YYYYMMDD","yyyy-MM-dd"); fomatMap.put("DATE_FORMAT_YYYYMMDDHHSSMS","yyyyMMddHHmmssms"); fomatMap.put("DATE_FORMAT_YYYYMMDDHHSS","yyyyMMddHHmmss"); fomatMap.put("DATE_FORMAT_YYYY_MM_DD","yyyyMMdd"); fomatMap.put("DATE_FORMAT_YYYY_MM","yyyyMM"); fomatMap.put("DATE_FORMAT_HHmmss","HHmmss"); fomatMap.put("DATE_FORMAT_JQUERY_DATEPICKER_DEFAULT","yyyy/MM/dd"); fomatMap.put("FORMATE_PATTERN_C_YYYYMMDD","yyyy年MM月dd日"); fomatMap.put("FORMATE_PATTERN_C_MMDD","MM月dd日"); fomatMap.put("FORMATE_PATTERN_C_YYYYMM","yyyy年MM月"); } /** * 获取当前日期时间 yyyy-MM-dd HH:mm:ss * @return */ public static String getTime(){ LocalDateTime date = LocalDateTime.now(); DateTimeFormatter dtf = DateTimeFormatter.ofPattern(fomatMap.get("DATE_FORMAT_DEFAULT"), Locale.CHINA); return date.format(dtf); } /** * 当前日期 字符串日期格式 * @return Date */ public static Date getNowDate(){ return Timestamp.valueOf(getTime()); } /** * 当前日期.yyyy-MM-dd * @return */ public static String getCurrentDate(){ return LocalDate.now().format(DateTimeFormatter.ofPattern(fomatMap.get("DATE_FORMAT_YYYYMMDD"), Locale.CHINA)); } /** * @Description 当前日期时间 yyyyMMddHHmmssms * @return */ public static String getCurrDate(){ return LocalDateTime.now().format(DateTimeFormatter.ofPattern(fomatMap.get("DATE_FORMAT_YYYYMMDDHHSSMS"), Locale.CHINA)); } public static String getNowDate(String fomat){ return LocalDateTime.now().format(DateTimeFormatter.ofPattern(fomat,Locale.CHINA)); } /** * 字符串转日期 * @param aMask * @param aDate * @return */ public static String convertDateToString(String aMask, Date aDate){ //Date 转化位 LocalDateTime LocalDateTime dateTime = LocalDateTime.ofInstant(aDate.toInstant(),ZoneId.systemDefault()); return getDateTime(aMask, dateTime); } public static String convertDateToString(String aMask, LocalDateTime dateTime){ return getDateTime(aMask, dateTime); } /** * 获取date time * @param fmt * @param dateTime * @return */ private static String getDateTime(String fmt, LocalDateTime dateTime) { DateTimeFormatter dtf = null; String str = ""; if(dateTime != null){ dtf = DateTimeFormatter.ofPattern(fmt,Locale.CHINA); str = dateTime.format(dtf); } return str; } /** * 日期字符串转 日期 * @param fmt * @param dateStr * @return */ public static LocalDate convertStringToDate(String fmt,String dateStr){ if (Strings.isNullOrEmpty(fmt) || Strings.isNullOrEmpty(dateStr)) { return null; } else { DateTimeFormatter sdf = DateTimeFormatter.ofPattern(fmt,Locale.CHINA); try { return LocalDate.parse(dateStr,sdf); } catch (DateTimeParseException var4) { logger.error("ParseException[" + fmt + "] for:" + dateStr, var4); return null; } } } /** * 获取 日期所在月份的第一天 date为空传当前月 * @param date * @return */ public static LocalDate getFirstDayOfMonth(LocalDate date){ return Optional.ofNullable(date).map(dt -> dt.with(TemporalAdjusters.firstDayOfMonth())).orElse(null); } /** * 获取 日期所在月份的最后一天，date为空传当前月 * @param date * @return */ public static LocalDate getLastDayOfMonth(LocalDate date){ return Optional.ofNullable(date).map(dt -> dt.with(TemporalAdjusters.lastDayOfMonth())).orElse(null); } /** * 获取上一个月的这个时候，例如当前日期2002-09-11，则返回2020-08-11 * @param date * @return */ public static LocalDate getMonthOfMonth(LocalDate date){ return Optional.ofNullable(date).map(dt -> dt.minusMonths(1)).orElse(null); } /** * 获取系统日期时间 * @return */ public static LocalDateTime getSystemTime(){ return LocalDateTime.ofInstant(Instant.now(),ZoneId.systemDefault()); } /** * 日期时间 转字符串 * @param dateTime * @param pattern * @return */ public static String dateTimeToString(LocalDateTime dateTime, String pattern){ if(dateTime == null || Strings.isNullOrEmpty(pattern)){ return null; } DateTimeFormatter dtf = DateTimeFormatter.ofPattern(pattern,Locale.CHINA); return dateTime.format(dtf); } /** * 两个日期相隔的天数 * @param startdate * @param endDate * @return */ public static int daysOfTwo(LocalDate startdate, LocalDate endDate){ return (int) startdate.until(endDate, ChronoUnit.DAYS); } public static int daysOfTwo(String startdate, String endDate, String dateFormat){ DateTimeFormatter dtf = DateTimeFormatter.ofPattern(dateFormat,Locale.CHINA); LocalDate smDate = LocalDate.parse(startdate,dtf); LocalDate bDate = LocalDate.parse(endDate,dtf); return (int)smDate.until(bDate,ChronoUnit.DAYS); } /** * 昨天日期 * @return */ public static String getYesterday(){ LocalDate now = LocalDate.now(); return now.minusDays(1).format(DateTimeFormatter.ofPattern("yyyy-MM-dd",Locale.CHINA)); } /** * 比较日期大小 * @param date1 * @param date2 * @return */ public static int compare(String date1, String date2){ DateTimeFormatter dtf = null; if(date1.indexOf(":") > -1 && date2.indexOf(":") > -1){ dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss",Locale.CHINA); LocalDateTime dateTime1 = LocalDateTime.parse(date1,dtf); LocalDateTime dateTime2 = LocalDateTime.parse(date2,dtf); if(dateTime1.isBefore(dateTime2)){ return -1; } return dateTime1.isAfter(dateTime2) ? 1:0; }else{ dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd",Locale.CHINA); LocalDate dt1 = LocalDate.parse(date1,dtf); LocalDate dt2 = LocalDate.parse(date2,dtf); if(dt1.isBefore(dt2)){ return -1; } return dt1.isAfter(dt2) ? 1:0; } } /** * 获取日期 x年x月x日 * @param date * @return */ public static String getFormatDate(String date){ DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy年MM月dd日"); DateTimeFormatter dtf2 = DateTimeFormatter.ofPattern("yyyy-MM-dd"); LocalDate localDate = LocalDate.parse(date,dtf2); return localDate.format(dtf); } /** * data1 是否 大于date2 * @param date1 * @param date2 * @param format * @return */ public static boolean date1DYdate2NY(String date1, String date2, String format){ DateTimeFormatter dtf = DateTimeFormatter.ofPattern(format,Locale.CHINA); LocalDate dt1 = LocalDate.parse(date1,dtf); LocalDate dt2 = LocalDate.parse(date2,dtf); return dt1.isAfter(dt2); } public static String getTimeYYYYMMDD() { DateTimeFormatter sdf = DateTimeFormatter.ofPattern("yyyyMMdd",Locale.CHINA); return LocalDate.now().format(sdf); } public static String getTimeHHmmss() { DateTimeFormatter sdf = DateTimeFormatter.ofPattern("HHmmss",Locale.CHINA); return LocalTime.now().format(sdf); } public static String getTimeHHmmss000() { DateTimeFormatter sdf = DateTimeFormatter.ofPattern("HHmmss000",Locale.CHINA); return LocalTime.now().format(sdf); } public static LocalDateTime changeMonth(LocalDateTime date, int i) { return date.minusMonths(i); } public static String changeMonth(int month, String format) { LocalDateTime dateTime = changeMonth(LocalDateTime.now(),month); return dateToString(getFirstDayOfMonth(dateTime.toLocalDate()), format); } private static String dateToString(LocalDate date, String format) { DateTimeFormatter dtf = DateTimeFormatter.ofPattern(format,Locale.CHINA); return date.format(dtf); } /** * 获取上年第一天 * @param format * @param year * @return */ public static String getFirstDayOfPastYear(String format, int year) { LocalDateTime dateTime = LocalDateTime.now().minusYears(year); DateTimeFormatter dtf = DateTimeFormatter.ofPattern(format,Locale.CHINA); String sdate = dateTime.with(TemporalAdjusters.firstDayOfYear()).format(dtf) ; return sdate; } public static String getFirstDayOfLastYear(String format) { return getFirstDayOfPastYear(format, 1); } /** * 获取上x年的的最后一天 * @param format * @param year * @return */ public static String getLastDayOfPastYear(String format, int year) { LocalDateTime dateTime = LocalDateTime.now().minusYears(year); DateTimeFormatter dtf = DateTimeFormatter.ofPattern(format,Locale.CHINA); String sdate = dateTime.with(TemporalAdjusters.lastDayOfYear()).format(dtf) ; return sdate; } /** * 获取上1年的的最后一天 * @param format * @return */ public static String getLastDayOfLastYear(String format) { return getLastDayOfPastYear(format, 1); } /** * 当前月 + month 的第一天 * @param month * @return */ public static String getFirstDayOfMonth(int month) { LocalDate localDate = LocalDate.now().minusMonths(-month); LocalDate day = localDate.with(TemporalAdjusters.firstDayOfMonth()); return dateToString(getFirstDayOfMonth(day), "yyyy-MM-dd"); } /** * 当前年+year , 月 + month 的第一天 * @param month * @return */ public static String getFirstDayOfMonth(int month, int year) { LocalDate localDate = LocalDate.now().minusYears(-year).minusMonths(-month); LocalDate day = localDate.with(TemporalAdjusters.firstDayOfMonth()); return dateToString(getFirstDayOfMonth(day), "yyyy-MM-dd"); } public static boolean isMonthEnd(LocalDate date){ LocalDate day = date.with(TemporalAdjusters.lastDayOfMonth()); if(date.equals(day)){ return true; } return false; } public static boolean isFirstDayOfMonth(String date){ LocalDate dt = convertStringToDate("yyyy-MM-dd",date); return Strings.isNullOrEmpty(date) ? false : dt.equals(dt.with(TemporalAdjusters.firstDayOfMonth())); } public static LocalDate getFirstDayOfWeek(LocalDate date){ TemporalField fieldISO = WeekFields.ISO.dayOfWeek(); return date.with(fieldISO,1); }}
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