Java 8 - StringをLocalDateに変換する方法

いくつかのJavaの例では、Stringを新しいJava 8のDate APIに変換する方法を示します。 - java.time.LocalDate

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/MM/yyyy");

    String date = "16/08/2016";

   //convert String to LocalDate
    LocalDate localDate = LocalDate.parse(date, formatter);

1. String = 2016-08-16

文字列がhttps://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html#ISO LOCAL DATE[ISO LOCAL DATE]のようにフォーマットされている場合、変換は不要で、文字列を直接解析できます。

TestNewDate1.java

package com.mkyong.java8.date;

import java.time.LocalDate;

public class TestNewDate1 {

    public static void main(String[]argv) {

        String date = "2016-08-16";

       //default, ISO__LOCAL__DATE
        LocalDate localDate = LocalDate.parse(date);

        System.out.println(localDate);

    }

}

出力

2016-08-16

2. String = 16-Aug-2016

TestNewDate2.java

package com.mkyong.java8.date;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class TestNewDate2 {

    public static void main(String[]argv) {

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d-MMM-yyyy");

        String date = "16-Aug-2016";

        LocalDate localDate = LocalDate.parse(date, formatter);

        System.out.println(localDate); //default, print ISO__LOCAL__DATE

        System.out.println(formatter.format(localDate));

    }

}

出力

2016-08-16
16-Aug-2016

3. String = 16/08/2016

TestNewDate3.java

package com.mkyong.java8.date;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class TestNewDate3 {

    public static void main(String[]argv) {

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/MM/yyyy");

        String date = "16/08/2016";

        LocalDate localDate = LocalDate.parse(date, formatter);

        System.out.println(localDate);

        System.out.println(formatter.format(localDate));

    }

}

出力

2016-08-16
16/08/2016

4. String = Tue、Aug 16 1616

TestNewDate4.java

package com.mkyong.java8.date;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class TestNewDate4 {

    public static void main(String[]argv) {

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("E, MMM d yyyy");

        String date = "Tue, Aug 16 2016";

        LocalDate localDate = LocalDate.parse(date, formatter);

        System.out.println(localDate);

        System.out.println(formatter.format(localDate));

    }

}

出力

2016-08-16
Tue, Aug 16 2016

5. String = 2016年8月16日12:10:56 PM

この例では、Stringを `java.time.LocalDateTime`に変換します。

TestNewDate5.java

package com.mkyong.java8.date;

package com.mkyong.pageview;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class TestNewDate5 {

    public static void main(String[]argv) {

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEEE, MMM d, yyyy HH:mm:ss a");

        String date = "Tuesday, Aug 16, 2016 12:10:56 PM";

        LocalDateTime localDateTime = LocalDateTime.parse(date, formatter);

        System.out.println(localDateTime);

        System.out.println(formatter.format(localDateTime));

    }

}

出力

2016-08-16T12:10:56
Tuesday, Aug 16, 2016 12:10:56 PM

6. String = 2016-08-16T15:23:01Z

'Z’接尾辞はUTCを意味し、 `java.time.instant`に直接変換してタイムゾーンで表示することができます。

TestNewDate6.java

package com.mkyong.java8.date;

import java.time.** ;

public class TestNewDate6 {

    public static void main(String[]argv) {

        String dateInString = "2016-08-16T15:23:01Z";

        Instant instant = Instant.parse(dateInString);

        System.out.println("Instant : " + instant);

       //get date time only
        LocalDateTime result = LocalDateTime.ofInstant(instant, ZoneId.of(ZoneOffset.UTC.getId()));

       //get localdate
        System.out.println("LocalDate : " + result.toLocalDate());

       //get date time + timezone
        ZonedDateTime zonedDateTime = instant.atZone(ZoneId.of("Asia/Tokyo"));
        System.out.println(zonedDateTime);

       //get date time + timezone
        ZonedDateTime zonedDateTime2 = instant.atZone(ZoneId.of("Europe/Athens"));
        System.out.println(zonedDateTime2);

    }

}

出力

Instant : 2016-08-16T15:23:01Z
LocalDate : 2016-08-16
2016-08-17T00:23:01+09:00[Asia/Tokyo]2016-08-16T18:23:01+03:00[Europe/Athens]....

===  7. String = 2016-08-16T10:15:30 08:00

文字列 - > ZonedDateTime  - > LocalDate

TestNewDate7.java

package com.mkyong.java8.date;

import java.time.** ; import java.time.format.DateTimeFormatter;

public class TestNewDate7 {

public static void main(String[]argv) {
String date = "2016-08-16T10:15:30+08:00";
ZonedDateTime result = ZonedDateTime.parse(date, DateTimeFormatter.ISO__DATE__TIME);
System.out.println("ZonedDateTime : " + result);
System.out.println("TimeZone : " + result.getZone());
LocalDate localDate = result.toLocalDate();
System.out.println("LocalDate : " + localDate);
}

}

出力

ZonedDateTime : 2016-08-16T10:15:30+08:00 TimeZone : +08:00 LocalDate : 2016-08-16

=== 参考文献

.  https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html[DateTimeFormatter

JavaDoc]。 http://docs.oracle.com/javase/8/docs/api/java/text/SimpleDateFormat.html[Classic

SimpleDateFormat JavaDoc]。リンク://java/how-to-convert-string-to-date-java/[Java  - 変換方法

文字列を日付]。 http://stackoverflow.com/questions/2580925/simpledateformat-parsing-date-with-z-literal[Stackoverflow

: simpledateformat parsing date with ‘Z’ literal]. https://en.wikipedia.org/wiki/ISO__8601[Wikipedia : ISO 8601]

.  http://www.diffen.com/difference/GMT__vs__UTC[GMT VS UTC]

.  http://www.timeanddate.com/time/what-is-a-time-zone.html[Whatとは

タイムゾーン?]

リンク://タグ/変換/[変換]リンク://タグ/日付/[日付]link://タグ/日付形式/[日付形式]link://タグ/java8/[java8]link://tag/localdate/[localdate]link://タグ/タイムゾーン/[timezone]
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