AccountingEra.java

/*
 * Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
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package org.threeten.extra.chrono;

import java.time.DateTimeException;
import java.time.chrono.Era;

/**
 * An era in the Accounting calendar system.
 * <p>
 * The Accounting calendar system has two eras.
 * The current era, for years from 1 onwards, is known as the 'Current 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 Current Era' era.
 * <p>
 * The start of accounting epochs {@code 0001-01-01 (Accounting)} will vary against the ISO calendar.
 * Depending on options chosen, it can start as early as {@code 0000-01-26 (ISO)} or as late as {@code 0001-01-04 (ISO)}.
 * <p>
 * <b>Do not use {@code ordinal()} to obtain the numeric representation of {@code AccountingEra}.
 * Use {@code getValue()} instead.</b>
 *
 * <h3>Implementation Requirements:</h3>
 * This is an immutable and thread-safe enum.
 */
public enum AccountingEra implements Era {

    /**
     * The singleton instance for the era before the current one, 'Before Current Era',
     * which has the numeric value 0.
     */
    BCE,
    /**
     * The singleton instance for the current era, 'Current Era',
     * which has the numeric value 1.
     */
    CE;

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code AccountingEra} from an {@code int} value.
     * <p>
     * {@code AccountingEra} is an enum representing the Accounting eras of BCE/CE.
     * This factory allows the enum to be obtained from the {@code int} value.
     *
     * @param era  the BCE/CE value to represent, from 0 (BCE) to 1 (CE)
     * @return the era singleton, not null
     * @throws DateTimeException if the value is invalid
     */
    public static AccountingEra of(int era) {
        switch (era) {
            case 0:
                return BCE;
            case 1:
                return CE;
            default:
                throw new DateTimeException("Invalid era: " + era);
        }
    }

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

}