简单整理时间处理问题

日期 LocalDate：

// 查看当天 年月日
LocalDate date= LocalDate.now();  // 2021-06-30

	//格式化：转为String
	String str2 = date.format(DateTimeFormatter.ISO_LOCAL_DATE); //  2021-06-30
	
	String str1 = date.format(DateTimeFormatter.BASIC_ISO_DATE); //  20210630
	DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
	String str5 = date.format(dtf); // 2021-06-30
	LocalDate date13 = LocalDate.parse(str5, dtf); // 2021-06-30

字符串：LocalDate date = LocalDate.parse(" 2021-06-30");

LocalDate date = LocalDate.parse("2021-06-30");

时间戳：LocalDate–> long

 long todayTime = LocalDateTime.of(LocalDate.now(), LocalTime.MIN).atZone(ZoneId.systemDefault())
                .toInstant().toEpochMilli();
                
//时间戳，增加80天，再转乘时间戳
long newTime = Instant.ofEpochMilli(info.getExpireTime()).plus(80, ChronoUnit.DAYS)
        .toEpochMilli();  

//Instant 
Instant instant = Instant.ofEpochMilli(123123123132L);  
instant.plus(80, ChronoUnit.DAYS).toEpochMilli();             

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Period
Period用于计算两个LocalDate之间的时长。举些例子：

LocalDate date2 = LocalDate.of(2021, 5, 29);
Period period = Period.between(date2, date);
int monthsBetween = period.getMonths(); // 1
int daysBetween = period.getDays(); // 1

比较两个时间的先后

	LocalDate date15 = LocalDate.of((2021, 5, 29);
	date.isEqual(date15); // false
	date.isAfter(date15); // false
	date.isBefore(date15); // true

添加天数：

LocalDateTime todayStartTime = LocalDateTime.of(LocalDate.now(), LocalTime.MIN).plusDays(3);
long now = todayStartTime.atZone(ZoneId.systemDefault()).toInstant().ofEpochMilli(123123123132L);