Java 11 の新しい DateTimeFormatter クラスと TemporalAccessor インターフェイスを使用して日付と時刻を解析およびフォーマットする

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

public class DateTimeFormatterExample {
    public static void main(String[] args) {
        LocalDateTime dateTime = LocalDateTime.now();

        // 格式化为字符串
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formattedDateTime = dateTime.format(formatter);
        System.out.println("Formatted Date and Time: " + formattedDateTime);

        // 解析字符串为日期和时间
        String dateTimeString = "2022-01-01 12:00:00";
        LocalDateTime parsedDateTime = LocalDateTime.parse(dateTimeString, formatter);
        System.out.println("Parsed Date and Time: " + parsedDateTime);
    }
}

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

public class CustomDateTimeFormatterExample {
    public static void main(String[] args) {
        LocalDate date = LocalDate.now();

        DateTimeFormatter formatter = new DateTimeFormatterBuilder()
                .appendLiteral("Today is ")
                .appendValue(DateTimeFormatter.ISO_LOCAL_DATE)
                .appendLiteral(".")
                .toFormatter();
        String formattedDate = date.format(formatter);
        System.out.println(formattedDate);
    }
}

import java.time.LocalDateTime;
import java.time.temporal.ChronoField;

public class TemporalAccessorExample {
    public static void main(String[] args) {
        LocalDateTime dateTime = LocalDateTime.now();

        int year = dateTime.get(ChronoField.YEAR);
        int month = dateTime.get(ChronoField.MONTH_OF_YEAR);
        int day = dateTime.get(ChronoField.DAY_OF_MONTH);
        int hour = dateTime.get(ChronoField.HOUR_OF_DAY);
        int minute = dateTime.get(ChronoField.MINUTE_OF_HOUR);
        int second = dateTime.get(ChronoField.SECOND_OF_MINUTE);

        System.out.println("Current Date: " + year + "-" + month + "-" + day);
        System.out.println("Current Time: " + hour + ":" + minute + ":" + second);
    }
}