具体代码详见：https://github.com/LynHB/ProjectA/blob/master/src/main/java/study/date/LocalDateTimeTest.java
相比于SimpleDateFormat，线程安全。
1. LocalDate日期类
LocalDate JDK新增日期类
System.out.println("LocalDate演示：");
LocalDate localDate = LocalDate.now();
System.out.println("LocalDate打印:"+localDate);
System.out.println("LocalDate获取年:"+localDate.getYear());
System.out.println("LocalDate获取月："+localDate.getMonthValue());
System.out.println("LocalDate获取日："+localDate.getDayOfMonth());
System.out.println("LocalDate获取周几："+localDate.getDayOfWeek().getValue());
System.out.println("LocalDate获取周（英文）："+localDate.getDayOfWeek().name());
2.LocalTime时间类
System.out.println("LocalTime演示：");
LocalTime localTime = LocalTime.now();
System.out.println("LocalTime获取小时："+localTime.getHour());
System.out.println("LocalTime获取分钟："+localTime.getMinute());
System.out.println("LocalTime获取秒："+localTime.getSecond());
3 LocalDateTime日期时间类
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println("LocalDateTime演示：");
System.out.println("LocalDateTime获取年："+localDateTime.getYear());
System.out.println("LocalDateTime获取月："+localDateTime.getMonthValue());
System.out.println("LocalDateTime获取日："+localDateTime.getDayOfMonth());
System.out.println("LocalDateTime获取周几："+localDateTime.getDayOfWeek().getValue());
System.out.println("LocalDateTime获取周（英文）："+localDateTime.getDayOfWeek().name());
System.out.println("LocalDateTime获取小时："+localDateTime.getHour());
System.out.println("LocalDateTime获取分钟："+localDateTime.getMinute());
System.out.println("LocalDateTime获取秒："+localDateTime.getSecond());
4 Instant实例类
Instant instant = Instant.now();
System.out.println("Instant演示：");
System.out.println("Instant获取秒数："+instant.getEpochSecond());
System.out.println("Instant获取毫秒数："+instant.toEpochMilli());
5 LocalDateTime深入
LocalDate和LocalTime同理。
5.1 修改LocalDateTime具体时间
LocalDateTime localDateTime1 = LocalDateTime.now();
System.out.println("针对LocalDateTime进行修改转换：");
System.out.println("LocalDateTime减少一年："+localDateTime1.minus(1, ChronoUnit.YEARS));
System.out.println("LocalDateTime增加一月："+localDateTime1.plusMonths(1));
System.out.println("LocalDateTime修改成固定年2011："+localDateTime1.withYear(2011));
5.2 字符串转换LocalDateTime
String dateStr = "2020-01-02 11:11:11";
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
localDateTime = LocalDateTime.parse(dateStr,dtf);
5.3 LocalDateTime转字符串
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
String dateStr = localDateTime.format(dtf);
5.4 LocalDateTime转Date
localDateTime = LocalDateTime.now();
Date date = Date.from(localDateTime.atZone(ZoneOffset.ofHours(8)).toInstant());
5.5 localDateTime转时间戳
localDateTime = LocalDateTime.now();
long timestamp = localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant().toEpochMilli();
5.6 时间戳转LocalDateTime
timestamp = System.currentTimeMillis();
localDate = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDate();
localDateTime = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDateTime();
5.7 LocalDate转LocalDateTime
localDateTime = LocalDateTime.of(localDate,LocalTime.MIN);
5.8 LocalDate转时间戳
localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant().toEpochMilli();
