ThaiBuddhistEra.java

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 * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
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package java.time.chrono;

import static java.time.temporal.ChronoField.ERA;

import java.time.DateTimeException;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.TextStyle;
import java.util.Locale;

/**
 * An era in the Thai Buddhist calendar system.
 * <p>
 * The Thai Buddhist calendar system has two eras.
 * The current era, for years from 1 onwards, is known as the 'Buddhist' era.
 * All previous years, zero or earlier in the proleptic count or one and greater
 * in the year-of-era count, are part of the 'Before Buddhist' era.
 *
 * <table class="striped" style="text-align:left">
 * <caption style="display:none">Buddhist years and eras</caption>
 * <thead>
 * <tr>
 * <th scope="col">year-of-era</th>
 * <th scope="col">era</th>
 * <th scope="col">proleptic-year</th>
 * <th scope="col">ISO proleptic-year</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr>
 * <td>2</td><td>BE</td><th scope="row">2</th><td>-542</td>
 * </tr>
 * <tr>
 * <td>1</td><td>BE</td><th scope="row">1</th><td>-543</td>
 * </tr>
 * <tr>
 * <td>1</td><td>BEFORE_BE</td><th scope="row">0</th><td>-544</td>
 * </tr>
 * <tr>
 * <td>2</td><td>BEFORE_BE</td><th scope="row">-1</th><td>-545</td>
 * </tr>
 * </tbody>
 * </table>
 * <p>
 * <b>Do not use {@code ordinal()} to obtain the numeric representation of {@code ThaiBuddhistEra}.
 * Use {@code getValue()} instead.</b>
 *
 * @implSpec
 * This is an immutable and thread-safe enum.
 *
 * @since 1.8
 */
public enum ThaiBuddhistEra implements Era {

    /**
     * The singleton instance for the era before the current one, 'Before Buddhist Era',
     * which has the numeric value 0.
     */
    BEFORE_BE,
    /**
     * The singleton instance for the current era, 'Buddhist Era',
     * which has the numeric value 1.
     */
    BE;

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ThaiBuddhistEra} from an {@code int} value.
     * <p>
     * {@code ThaiBuddhistEra} is an enum representing the Thai Buddhist eras of BEFORE_BE/BE.
     * This factory allows the enum to be obtained from the {@code int} value.
     *
     * @param thaiBuddhistEra  the era to represent, from 0 to 1
     * @return the BuddhistEra singleton, never null
     * @throws DateTimeException if the era is invalid
     */
    public static ThaiBuddhistEra of(int thaiBuddhistEra) {
        switch (thaiBuddhistEra) {
            case 0:
                return BEFORE_BE;
            case 1:
                return BE;
            default:
                throw new DateTimeException("Invalid era: " + thaiBuddhistEra);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the numeric era {@code int} value.
     * <p>
     * The era BEFORE_BE has the value 0, while the era BE has the value 1.
     *
     * @return the era value, from 0 (BEFORE_BE) to 1 (BE)
     */
    @Override
    public int getValue() {
        return ordinal();
    }

    /**
     * {@inheritDoc}
     *
     * @param style {@inheritDoc}
     * @param locale {@inheritDoc}
     */
    @Override
    public String getDisplayName(TextStyle style, Locale locale) {
        return new DateTimeFormatterBuilder()
            .appendText(ERA, style)
            .toFormatter(locale)
            .withChronology(ThaiBuddhistChronology.INSTANCE)
            .format(this == BE ? ThaiBuddhistDate.of(1, 1, 1) : ThaiBuddhistDate.of(0, 1, 1));
    }

}