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.

Main.java

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.

Main.java

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.

Main.java

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.

Main.java

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.

Main.java

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.

Main.java

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.

Author

My name is Jan Bodnar, and I am a dedicated programmer with many years of experience in the field. I began writing programming articles in 2007 and have since authored over 1,400 articles and eight e-books. With more than eight years of teaching experience, I am committed to sharing my knowledge and helping others master programming concepts.

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