Java MinguoDate Class
Last modified: April 16, 2025
The java.time.chrono.MinguoDate class represents a date in the
Minguo calendar system. This calendar is primarily used in Taiwan, where
years are counted from 1912 (the founding of the Republic of China).
MinguoDate is immutable and thread-safe. It follows the same
design principles as other Java time classes. The Minguo calendar is a
solar calendar with the same month structure as the Gregorian calendar.
MinguoDate Class Overview
MinguoDate provides methods to create, manipulate, and format
dates in the Minguo system. Key operations include date arithmetic, field
access, and conversion to other calendar systems. The class handles dates
from year 1 onwards.
public final class MinguoDate implements ChronoLocalDate, Serializable {
public static MinguoDate now();
public static MinguoDate now(ZoneId zone);
public static MinguoDate now(Clock clock);
public static MinguoDate of(int prolepticYear, int month, int dayOfMonth);
public static MinguoDate from(TemporalAccessor temporal);
public static MinguoDate parse(CharSequence text);
public int getChronology();
public int getEra();
public int getYear();
public int getMonthValue();
public int getDayOfMonth();
}
The code above shows key methods provided by MinguoDate. These
methods allow creating, accessing fields, and converting between calendar
systems. The class integrates with Java's standard date-time API.
Creating MinguoDate Objects
MinguoDate objects can be created in several ways. The most common methods
are now for current date and factory methods for specific dates.
Parsing from strings is also supported.
package com.zetcode;
import java.time.chrono.MinguoDate;
import java.time.ZoneId;
public class Main {
public static void main(String[] args) {
// Current date
MinguoDate today = MinguoDate.now();
System.out.println("Today in Minguo: " + today);
// Specific date
MinguoDate founding = MinguoDate.of(1, 1, 1);
System.out.println("Republic founding: " + founding);
// From system clock with zone
MinguoDate nowInTokyo = MinguoDate.now(ZoneId.of("Asia/Tokyo"));
System.out.println("Now in Tokyo: " + nowInTokyo);
// From string
MinguoDate parsed = MinguoDate.parse("Minguo 112-04-16");
System.out.println("Parsed date: " + parsed);
}
}
This example demonstrates different ways to create MinguoDate objects. The output shows dates in Minguo calendar format. Note that year 1 in Minguo corresponds to 1912 in Gregorian calendar.
Accessing Date Components
A MinguoDate can be decomposed into its year, month, and day components. These values represent the date in the Minguo calendar system. The methods are similar to other Java date classes.
package com.zetcode;
import java.time.chrono.MinguoDate;
import java.time.chrono.MinguoEra;
public class Main {
public static void main(String[] args) {
MinguoDate date = MinguoDate.now();
// Get year (Minguo era)
int year = date.getYear();
System.out.println("Minguo year: " + year);
// Get month (1-12)
int month = date.getMonthValue();
System.out.println("Month: " + month);
// Get day of month
int day = date.getDayOfMonth();
System.out.println("Day: " + day);
// Get era (BEFORE_ROC or ROC)
MinguoEra era = date.getEra();
System.out.println("Era: " + era);
}
}
This example shows how to extract components from a MinguoDate. The era can be either ROC (Republic of China) or BEFORE_ROC. Most dates will be in the ROC era starting from year 1.
Converting Between Calendars
MinguoDate can be converted to and from other calendar systems like Gregorian. These conversions are essential when working with multiple calendar systems in an application.
package com.zetcode;
import java.time.LocalDate;
import java.time.chrono.MinguoDate;
public class Main {
public static void main(String[] args) {
MinguoDate minguoToday = MinguoDate.now();
// Convert to LocalDate (Gregorian)
LocalDate gregorianDate = LocalDate.from(minguoToday);
System.out.println("Gregorian date: " + gregorianDate);
// Convert back to MinguoDate
MinguoDate backToMinguo = MinguoDate.from(gregorianDate);
System.out.println("Back to Minguo: " + backToMinguo);
// Specific conversion example
MinguoDate minguoNewYear = MinguoDate.of(112, 1, 1);
LocalDate gregorianNewYear = LocalDate.from(minguoNewYear);
System.out.println("Minguo 112 New Year: " + gregorianNewYear);
}
}
This example demonstrates conversions between MinguoDate and Gregorian calendar dates. The conversion preserves the same absolute date while changing the calendar system representation.
Date Arithmetic
MinguoDate supports date arithmetic through plus and
minus methods. These operations are useful for calculating
future or past dates. The class handles month and year boundaries correctly.
package com.zetcode;
import java.time.chrono.MinguoDate;
import java.time.temporal.ChronoUnit;
public class Main {
public static void main(String[] args) {
MinguoDate today = MinguoDate.now();
// Add 1 week
MinguoDate nextWeek = today.plus(1, ChronoUnit.WEEKS);
System.out.println("Next week: " + nextWeek);
// Subtract 3 months
MinguoDate threeMonthsAgo = today.minus(3, ChronoUnit.MONTHS);
System.out.println("Three months ago: " + threeMonthsAgo);
// Add 2 years
MinguoDate inTwoYears = today.plus(2, ChronoUnit.YEARS);
System.out.println("In two years: " + inTwoYears);
// Mixed operations
MinguoDate complex = today.plus(1, ChronoUnit.MONTHS)
.minus(10, ChronoUnit.DAYS);
System.out.println("Complex operation result: " + complex);
}
}
This example shows various ways to perform date arithmetic with MinguoDate. Operations can use ChronoUnit constants for different time units. All calculations respect the calendar rules.
Comparing Dates
MinguoDate objects can be compared to determine chronological order. The
class provides isBefore, isAfter, and
compareTo methods. These comparisons work the same as other
Java date classes.
package com.zetcode;
import java.time.chrono.MinguoDate;
import java.time.temporal.ChronoUnit;
public class Main {
public static void main(String[] args) {
MinguoDate today = MinguoDate.now();
MinguoDate tomorrow = today.plus(1, ChronoUnit.DAYS);
MinguoDate yesterday = today.minus(1, ChronoUnit.DAYS);
System.out.println("Today is before tomorrow: " + today.isBefore(tomorrow));
System.out.println("Today is after yesterday: " + today.isAfter(yesterday));
System.out.println("Comparison result: " + today.compareTo(tomorrow));
// Equality check
MinguoDate sameDate = MinguoDate.of(today.getYear(),
today.getMonthValue(), today.getDayOfMonth());
System.out.println("Today equals sameDate: " + today.equals(sameDate));
}
}
This example demonstrates various ways to compare MinguoDate objects. The comparison methods consider the complete date value. Note that equality requires all date components to match exactly.
Formatting Minguo Dates
MinguoDate can be formatted using DateTimeFormatter. Special pattern letters are available for Minguo-specific fields like era and year. Formatting follows the same principles as other Java date classes.
package com.zetcode;
import java.time.chrono.MinguoDate;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
MinguoDate date = MinguoDate.now();
// Default format
String defaultFormat = date.toString();
System.out.println("Default format: " + defaultFormat);
// Custom format
DateTimeFormatter formatter = DateTimeFormatter
.ofPattern("GGGG y年M月d日", Locale.TAIWAN);
String customFormat = date.format(formatter);
System.out.println("Custom format: " + customFormat);
// Alternative format
DateTimeFormatter altFormatter = DateTimeFormatter
.ofPattern("'民國' y年 MM月 dd日");
String altFormat = date.format(altFormatter);
System.out.println("Alternative format: " + altFormat);
// ISO format
String isoFormat = date.format(DateTimeFormatter.ISO_DATE);
System.out.println("ISO format: " + isoFormat);
}
}
This example shows different ways to format MinguoDate objects. The formatters can use locale-specific patterns and text. Special pattern letters handle Minguo calendar specifics.
Source
Java MinguoDate Class Documentation
In this article, we've covered the essential methods and features of the Java MinguoDate class. Understanding these concepts is crucial for working with dates in Taiwan's official calendar system.
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