如何確定ZonedDateTime是否爲「今天」？

Question

我認爲這已經被問過了，但我找不到anything。

使用java.time確定給定的ZonedDateTime是否爲「今天」的最佳方法是什麼？

我已經想出了至少兩種可能的解決方案。我不確定這些方法是否存在漏洞或陷阱。基本想法是讓java.time數字出來，並沒有做任何的數學自己：

/** 
* @param zonedDateTime a zoned date time to compare with "now". 
* @return true if zonedDateTime is "today". 
* Where today is defined as year, month, and day of month being equal. 
*/ 
public static boolean isZonedDateTimeToday1(ZonedDateTime zonedDateTime) { 
    ZonedDateTime now = ZonedDateTime.now(); 

    return now.getYear() == zonedDateTime.getYear() 
      && now.getMonth() == zonedDateTime.getMonth() 
      && now.getDayOfMonth() == zonedDateTime.getDayOfMonth(); 
} 


/** 
* @param zonedDateTime a zoned date time to compare with "now". 
* @return true if zonedDateTime is "today". 
* Where today is defined as atStartOfDay() being equal. 
*/ 
public static boolean isZoneDateTimeToday2(ZonedDateTime zonedDateTime) { 
    ZonedDateTime now = ZonedDateTime.now(); 
    LocalDateTime atStartOfToday = now.toLocalDate().atStartOfDay(); 

    LocalDateTime atStartOfDay = zonedDateTime.toLocalDate().atStartOfDay(); 

    return atStartOfDay == atStartOfToday; 
} 

Answer 1

如果你指的是在缺省時區的今天：

return zonedDateTime.toLocalDate().equals(LocalDate.now()); 

//you may want to clarify your intent by explicitly setting the time zone: 
return zonedDateTime.toLocalDate().equals(LocalDate.now(ZoneId.systemDefault())); 

如果你在同一個時區的意思今天ZonedDateTime：

return zonedDateTime.toLocalDate().equals(LocalDate.now(zonedDateTime.getZone()));