[JAVA] How to use Calendar Class

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The Calendar class is one of the most popular items for Java developers.

Calendar is a feature included in java's util and is a built-in offering on Java-based platforms.

Java Platform SE 7

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EXAMPLE

The source below is the one that extracts the date this Saturday of last year as of today.
For SimpleDateFormat
You can check it in the link below.

2024.02.10 - [개발 창고/Java] - [JAVA] How to use SimpleDateFormat Class

[JAVA] How to use SimpleDateFormat Class

SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd E");

Calendar cal = Calendar.getInstance();                  // Calendar Declaration
// Calendar cal = Calendar.getInstance(Locale.KOREA);   // Tip. If Locale is not included, the Default value is applied (based on installed environment)
// cal.setTime(new Date());                             // Tip. If you do not specify a specific date, the date will be applied as Default
System. out.println(fmt.format(cal.getTime()));         // 2024-02-11 Sun

int year = cal.get(Calendar.YEAR);                      // Return this year as of today
int week = cal.get(Calendar.WEEK_OF_YEAR);              // Return week of year as of today
cal.set(Calendar. YEAR, year-1);                        // As of today - 1 year applied
cal.set(Calendar. WEEK_OF_YEAR, week);                  // As of today week of year applied
cal.set(Calendar. DAY_OF_WEEK, Calendar.MONDAY);        // As of today monday applied
System. out.println(fmt.format(cal.getTime()));         // 2023-02-13 Mon

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FIELD AND DESCRIPTION

FIELD	DESCRIPTION
YEAR	Field number for get and set indicating the year.
MONTH	Field number for get and set indicating the month. (Returns January to 0 and December to 11. +1 for actual marking)
DATE	Field number for get and set indicating the day of the month.
HOUR	Field number for get and set indicating the hour of the morning or afternoon. (AM/PM BASED. 0~11)
HOUR_OF_DAY	Field number for get and set indicating the hour of the day. (24HOURE BASED. 0~23)
MINUTE	Field number for get and set indicating the minute within the hour.
SECOND	Field number for get and set indicating the second within the minute.
MILLISECOND	Field number for get and set indicating the millisecond within the second. (All milliseconds use cal.getTimeInMillis())
DAY_OF_YEAR	Field number for get and set indicating the day number within the current year.
WEEK_OF_MONTH	Field number for get and set indicating the week number within the current month. (1~5)
WEEK_OF_YEAR	Field number for get and set indicating the week number within the current year. (1~53)

 

You can check the test source by attaching the source below to the source above.

SimpleDateFormat fmt02 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss D E W w");
System. out.println(fmt02.format(cal.getTime()));
System.out.println("YEAR\t" + cal.get(Calendar.YEAR));
System.out.println("MONTH\t" + cal.get(Calendar.MONTH));
System.out.println("DATE\t" + cal.get(Calendar.DATE));
System.out.println("HOUR\t" + cal.get(Calendar.HOUR));
System.out.println("HOUR_OF_DAY\t" + cal.get(Calendar.HOUR_OF_DAY));
System.out.println("MINUTE\t" + cal.get(Calendar.MINUTE));
System.out.println("SECOND\t" + cal.get(Calendar.SECOND));
System.out.println("MILLISECOND\t" + cal.get(Calendar.MILLISECOND));
System.out.println("DAY_OF_YEAR\t" + cal.get(Calendar.DAY_OF_YEAR));
System.out.println("WEEK_OF_MONTH\t" + cal.get(Calendar.WEEK_OF_MONTH));
System.out.println("WEEK_OF_YEAR\t" + cal.get(Calendar.WEEK_OF_YEAR));

Execution result

 

 It has been returned to 2019 because the existing source has been doing -1 year and it is as below the first line of the result.

 

RESULT	DESCRIPTION
2023	Year
1	Month
13	Date
2	Hour (24 hours based)
17	Minutes
53	Seconds
44	Day 44 as of January 1st
3	Week 3 as of this month
7	7th week as of this year

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More details can be found at the link below.

https://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html

Calendar (Java Platform SE 7 )

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Full Source

import java.util.Calendar;
import java.text.SimpleDateFormat;

class Main {
	public static void main(String[] args) {
		SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd E");
		
		Calendar cal = Calendar.getInstance();                  // Calendar Declaration
		// Calendar cal = Calendar.getInstance(Locale.KOREA);   // Tip. If Locale is not included, the Default value is applied (based on installed environment)
		// cal.setTime(new Date());                             // Tip. If you do not specify a specific date, the date will be applied as Default
		System. out.println(fmt.format(cal.getTime()));         // 2024-02-11 Sun
		
		int year = cal.get(Calendar.YEAR);                      // Return this year as of today
		int week = cal.get(Calendar.WEEK_OF_YEAR);              // Return week of year as of today
		cal.set(Calendar. YEAR, year-1);                        // As of today - 1 year applied
		cal.set(Calendar. WEEK_OF_YEAR, week);                  // As of today week of year applied
		cal.set(Calendar. DAY_OF_WEEK, Calendar.MONDAY);        // As of today monday applied
		System. out.println(fmt.format(cal.getTime()));         // 2023-02-13 Mon

		SimpleDateFormat fmt02 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss D E W w");
		System. out.println(fmt02.format(cal.getTime()));
		System.out.println("YEAR\t" + cal.get(Calendar.YEAR));
		System.out.println("MONTH\t" + cal.get(Calendar.MONTH));
		System.out.println("DATE\t" + cal.get(Calendar.DATE));
		System.out.println("HOUR\t" + cal.get(Calendar.HOUR));
		System.out.println("HOUR_OF_DAY\t" + cal.get(Calendar.HOUR_OF_DAY));
		System.out.println("MINUTE\t" + cal.get(Calendar.MINUTE));
		System.out.println("SECOND\t" + cal.get(Calendar.SECOND));
		System.out.println("MILLISECOND\t" + cal.get(Calendar.MILLISECOND));
		System.out.println("DAY_OF_YEAR\t" + cal.get(Calendar.DAY_OF_YEAR));
		System.out.println("WEEK_OF_MONTH\t" + cal.get(Calendar.WEEK_OF_MONTH));
		System.out.println("WEEK_OF_YEAR\t" + cal.get(Calendar.WEEK_OF_YEAR));
	}
}

Execution result

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[JAVA] Calendar Class 사용하기

🇰🇷 Korean

2020.07.23 - [개발 창고/Java] - [JAVA] Calendar Class 사용하기

[JAVA] Calendar Class 사용하기