[Java]文字列と日時の変換 (ZonedDateTime, LocalDateTime)

文字列を日時(ZonedDateTime)に変換する

package com.example;

import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class Example {

    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ssZ");
        ZonedDateTime zonedDateTime = ZonedDateTime.parse("2020-01-01 00:00:00+0900", formatter);
        System.out.println(zonedDateTime);
    }

}

実行結果:

2020-01-01T00:00+09:00

文字列を日時(LocalDateTime)に変換する

package com.example;

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

public class Example {

    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime localDateTime = LocalDateTime.parse("2020-01-01 00:00:00", formatter);
        System.out.println(localDateTime);
    }

}

実行結果:

2020-01-01T00:00+09:00

日時を文字列に変換・フォーマットする

package com.example;

import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class Example {

    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ssZ");
        ZonedDateTime zonedDateTime = ZonedDateTime.of(2020, 1, 1, 0, 0, 0, 0, ZoneId.systemDefault());

        System.out.println(formatter.format(zonedDateTime));
        System.out.println(zonedDateTime.format(formatter));
    }

}

実行結果:

2020-01-01 00:00:00+0900
2020-01-01 00:00:00+0900