자바 - 날짜와 시간

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Period;
import java.time.format.DateTimeFormatter;
import java.time.format.FormatStyle;

public class Main {
    public static void main(String[] args) {
        // 현재 시간
        System.out.println("now usages");
        LocalDate date = LocalDate.now();
        LocalTime time = LocalTime.now();
        LocalDateTime dateTIme = LocalDateTime.now();
        System.out.println(date);
        System.out.println(time);
        System.out.println(dateTIme);

        // 특정 시간
        System.out.println("\nof() usage");
        LocalDate dateOf = LocalDate.of(1993, 5, 3);
        LocalTime timeOf = LocalTime.of(14, 5, 30);
        System.out.println(dateOf);
        System.out.println(timeOf);

        // 등록된 날짜와 시간 형식 중 선택 지정
        DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT);
        String shortFormat = formatter.format(LocalTime.now());
        System.out.println(shortFormat);

        // 날찌와 시간 형식 정의
        // https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
        DateTimeFormatter myFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd");
        String myDate = myFormatter.format(LocalDate.now());
        System.out.println(myDate);

        // 날짜와 시간 차이 계산
        LocalDate today = LocalDate.now();
        LocalDate birthday = LocalDate.of(2023, 5, 3);
        Period period = Period.between(today, birthday);
        System.out.println(period.getMonths());
        System.out.println(period.getDays());
        
        // 응용
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd hh:mm:ss");
        String now = dateTimeFormatter.format(LocalDateTime.now());
        System.out.println("current time: " + now);
    }
}