#author("2021-06-23T17:44:29+09:00","","")
[[Java]]
#author("2021-06-24T15:53:20+09:00","","")
[[ソフトウェア開発>SoftwareEngineering]] / [[Java>../]] / [[Java API>./]]

* Java API [#u935f976]
#contents

* java.time [#eb43be4e]
** LocalDateTime [#oe53feb8]
*** truncatedTo メソッド [#xf0c12e8]
- example
#highlightjs([java])
 LocalDateTime localDateTime = LocalDateTime.now();
 
 System.out.println("localDateTime                                :" + localDateTime);
 System.out.println("localDateTime.truncatedTo(ChronoUnit.DAYS)   :" + localDateTime.truncatedTo(ChronoUnit.DAYS));
 System.out.println("localDateTime.truncatedTo(ChronoUnit.HOURS)  :" + localDateTime.truncatedTo(ChronoUnit.HOURS));
 System.out.println("localDateTime.truncatedTo(ChronoUnit.MINUTES):" + localDateTime.truncatedTo(ChronoUnit.MINUTES));
 System.out.println("localDateTime.truncatedTo(ChronoUnit.SECONDS):" + localDateTime.truncatedTo(ChronoUnit.SECONDS));
 System.out.println("localDateTime.truncatedTo(ChronoUnit.MILLIS) :" + localDateTime.truncatedTo(ChronoUnit.MILLIS));

- result
 localDateTime                                :2019-06-15T17:35:16.723566900
 localDateTime.truncatedTo(ChronoUnit.DAYS)   :2019-06-15T00:00
 localDateTime.truncatedTo(ChronoUnit.HOURS)  :2019-06-15T17:00
 localDateTime.truncatedTo(ChronoUnit.MINUTES):2019-06-15T17:35
 localDateTime.truncatedTo(ChronoUnit.SECONDS):2019-06-15T17:35:16
 localDateTime.truncatedTo(ChronoUnit.MILLIS) :2019-06-15T17:35:16.723

** 型変換 [#l58e529b]
*** Date => LocalDateTime [#d5531a10]
- example
#highlightjs([java])
 Date date = new Date();
 LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
 
 System.out.println("date         :" + date);
 System.out.println("localDateTime:" + localDateTime);

- result
 date         :Sat Jun 15 17:51:36 JST 2019
 localDateTime:2019-06-15T17:51:36.151

*** Date => LocalDate [#m8e96391]
- example
#highlightjs([java])
 Date date = new Date();
 LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
 LocalDate localDate = localDateTime.toLocalDate();
 
 System.out.println("date         :" + date);
 System.out.println("localDateTime:" + localDateTime);
 System.out.println("localDate    :" + localDate);

- result
 date         :Sat Jun 15 23:08:37 JST 2019
 localDateTime:2019-06-15T23:08:37.014
 localDate    :2019-06-15

*** LocalDateTime => LocalDate [#q6f34f5a]
- example
#highlightjs([java])
 LocalDateTime localDateTime = LocalDateTime.now();
 LocalDate localDate = localDateTime.toLocalDate();
 
 System.out.println("localDateTime:" + localDateTime);
 System.out.println("localDate    :" + localDate);

- result
 localDateTime:2019-06-15T17:51:36.193991600
 localDate    :2019-06-15

*** LocalDateTime => Date [#j2d54ba6]
- example
#highlightjs([java])
 LocalDateTime localDateTime = LocalDateTime.now();
 Date date = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
 
 System.out.println("localDateTime:" + localDateTime);
 System.out.println("date         :" + date);

- result
 localDateTime:2019-06-15T23:08:37.015564600
 date         :Sat Jun 15 23:08:37 JST 2019

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