[Java] chap12: 기본 API - Calendar

• Calendar 클래스

Calendar 클래스
   추상클래스임.  
     1. 추상메서드를 멤버로 가질수있다.
     2. 객체화 불가. new Calendar() 오류.
         => 상속을 통해서 자손클래스의 객체화를 통해 객체화 가능.
     3. abstract 예약어로 구현함.
   getInstance() static 메서드를 통해서 객체 전달   

 

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package chap12;

import java.util.Calendar;

public class CalendarEx1 {
	public static void main(String[] args) {
		Calendar now = Calendar.getInstance();
		System.out.println(now);
		//get(상수값) : 지정된 상수값에 맞는 값을 리턴
		System.out.println("년도:" + now.get(Calendar.YEAR));
		System.out.println("월(0 ~ 11):" + (now.get(Calendar.MONTH) + 1));
		System.out.println("일:" + now.get(Calendar.DATE));
		System.out.println("일:" + now.get(Calendar.DAY_OF_MONTH));
		System.out.println("년도기준일자:" + now.get(Calendar.DAY_OF_YEAR));
		System.out.println("요일(1:일~7:토):" + now.get(Calendar.DAY_OF_WEEK));
		System.out.println("월기준 몇째주:" + now.get(Calendar.WEEK_OF_MONTH));
		System.out.println("년기준 몇째주:" + now.get(Calendar.WEEK_OF_YEAR));
		System.out.println("월기준 몇째요일:" + now.get(Calendar.DAY_OF_WEEK_IN_MONTH));
		System.out.println("오전0/오후1:" + now.get(Calendar.AM_PM));
		System.out.println("시간(0~11):" + now.get(Calendar.HOUR));
		System.out.println("시간(0~23):" + now.get(Calendar.HOUR_OF_DAY));
		System.out.println("분(0~59):" + now.get(Calendar.MINUTE));
		System.out.println("초(0~59):" + now.get(Calendar.SECOND));
		System.out.println("밀리초(0~999):" + now.get(Calendar.MILLISECOND));
		System.out.println("TimeZone(밀리초):" + now.get(Calendar.ZONE_OFFSET));
		System.out.println("TimeZone(시간):" + (now.get(Calendar.ZONE_OFFSET))/(1000*60*60)); //시간대 
		System.out.println("이번달의 마지막일자:" + now.getActualMaximum(Calendar.DATE));
		
	}
}

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• Calander.getlnstance()

                      : 현재 일시

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package chap12;

import java.util.Calendar;

/*
 * Calendar 객체로 날짜 설정하기
 */
public class CalendarEx2 {
	public static void main(String[] args) {
		Calendar cal = Calendar.getInstance(); //현재일시
		//2022년 12월 31로 설정
		cal.set(2022,(12-1),31); //날짜 설정. set(년도, 월(0~11), 일)
		System.out.println("날짜:"+cal.get(Calendar.YEAR)+"년"+
		                         (cal.get(Calendar.MONTH)+1)+"월"+
				                  cal.get(Calendar.DATE)+ "일");
		//cal 요일 출력하기
		String week = "일월화수목금토일";
		System.out.println(week.charAt(cal.get(Calendar.DAY_OF_WEEK)-1)+"요일");
	}
}

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package chap12;

import java.util.Calendar;
import java.util.Date;

public class CalendarEx3 {
	public static void main(String[] args) {
		Calendar cal = Calendar.getInstance();
		Date now = new Date();
		now.setTime(now.getTime()+(1000*60*60*24));
		cal.setTime(now);
		System.out.println("날짜:"+cal.get(Calendar.YEAR)+"년"+
                (cal.get(Calendar.MONTH)+1)+"월"+
                 cal.get(Calendar.DATE)+ "일");
		Date day = new Date();
	    day.setTime(cal.getTimeInMillis());
	    System.out.println(day);
	}
}