currency.java

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/*
 * @(#)Currency.java	1.4 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util;

import java.io.Serializable;
import java.security.AccessController;
import java.security.PrivilegedAction;
import sun.text.resources.LocaleData;


/**
 * Represents a currency. Currencies are identified by their ISO 4217 currency
 * codes. See the
 * <a href="http://www.bsi-global.com/iso4217currency">
 * ISO 4217 maintenance agency</a> for more information, including a table of
 * currency codes.
 * <p>
 * The class is designed so that there's never more than one
 * <code>Currency</code> instance for any given currency. Therefore, there's
 * no public constructor. You obtain a <code>Currency</code> instance using
 * the <code>getInstance</code> methods.
 *
 * @version 1.4, 01/23/03
 * @since 1.4
 */
public final class Currency implements Serializable {
    
    /**
     * ISO 4217 currency code for this currency.
     *
     * @serial
     */
    private String currencyCode;
    
    /**
     * Default fraction digits for this currency.
     * Set from currency data tables.
     */
    transient private int defaultFractionDigits;


    // class data: instance map

    private static HashMap instances = new HashMap(7);

    
    // Class data: currency data obtained from java.util.CurrencyData.
    // Purpose:
    // - determine valid country codes
    // - determine valid currency codes
    // - map country codes to currency codes
    // - obtain default fraction digits for currency codes
    //
    // sc = special case; dfd = default fraction digits
    // Simple countries are those where the country code is a prefix of the
    // currency code, and there are no known plans to change the currency.
    //
    // table formats:
    // - mainTable:
    //   - maps country code to 8-bit char
    //   - 26*26 entries, corresponding to [A-Z]*[A-Z]
    //   - \u007F -> not valid country
    //   - bit 7 - 1: special case, bits 0-4 indicate which one
    //             0: simple country, bits 0-4 indicate final char of currency code
    //   - bits 5-6: fraction digits for simple countries, 0 for special cases
    //   - bits 0-4: final char for currency code for simple country, or ID of special case
    // - special case IDs:
    //   - 0: country has no currency
    //   - other: index into sc* arrays + 1
    // - scCutOverTimes: cut-over time in millis as returned by
    //   System.currentTimeMillis for special case countries that are changing
    //   currencies; Long.MAX_VALUE for countries that are not changing currencies
    // - scOldCurrencies: old currencies for special case countries
    // - scNewCurrencies: new currencies for special case countries that are
    //   changing currencies; null for others
    // - scOldCurrenciesDFD: default fraction digits for old currencies
    // - scNewCurrenciesDFD: default fraction digits for new currencies, 0 for
    //   countries that are not changing currencies
    // - otherCurrencies: concatenation of all currency codes that are not the
    //   main currency of a simple country, separated by "-"
    // - otherCurrenciesDFD: decimal format digits for currencies in otherCurrencies, same order

    static String mainTable;
    static long[] scCutOverTimes;
    static String[] scOldCurrencies;
    static String[] scNewCurrencies;
    static int[] scOldCurrenciesDFD;
    static int[] scNewCurrenciesDFD;
    static String otherCurrencies;
    static int[] otherCurrenciesDFD;

    // handy constants - must match definitions in GenerateCurrencyData
    // number of characters from A to Z
    private static final int A_TO_Z = ('Z' - 'A') + 1;
    // entry for invalid country codes
    private static final int INVALID_COUNTRY_ENTRY = 0x007F;
    // entry for countries without currency
    private static final int COUNTRY_WITHOUT_CURRENCY_ENTRY = 0x0080;
    // mask for simple case country entries
    private static final int SIMPLE_CASE_COUNTRY_MASK = 0x0000;
    // mask for simple case country entry final character
    private static final int SIMPLE_CASE_COUNTRY_FINAL_CHAR_MASK = 0x001F;
    // mask for simple case country entry default currency digits
    private static final int SIMPLE_CASE_COUNTRY_DEFAULT_DIGITS_MASK = 0x0060;
    // shift count for simple case country entry default currency digits
    private static final int SIMPLE_CASE_COUNTRY_DEFAULT_DIGITS_SHIFT = 5;
    // mask for special case country entries
    private static final int SPECIAL_CASE_COUNTRY_MASK = 0x0080;
    // mask for special case country index
    private static final int SPECIAL_CASE_COUNTRY_INDEX_MASK = 0x001F;
    // delta from entry index component in main table to index into special case tables
    private static final int SPECIAL_CASE_COUNTRY_INDEX_DELTA = 1;
    // mask for distinguishing simple and special case countries
    private static final int COUNTRY_TYPE_MASK = SIMPLE_CASE_COUNTRY_MASK | SPECIAL_CASE_COUNTRY_MASK;

    static {
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                try {
                    Class data = Class.forName("java.util.CurrencyData");
                    mainTable = (String) data.getDeclaredField("mainTable").get(data);
                    scCutOverTimes = (long[]) data.getDeclaredField("scCutOverTimes").get(data);
                    scOldCurrencies = (String[]) data.getDeclaredField("scOldCurrencies").get(data);
                    scNewCurrencies = (String[]) data.getDeclaredField("scNewCurrencies").get(data);
                    scOldCurrenciesDFD = (int[]) data.getDeclaredField("scOldCurrenciesDFD").get(data);
                    scNewCurrenciesDFD = (int[]) data.getDeclaredField("scNewCurrenciesDFD").get(data);
                    otherCurrencies = (String) data.getDeclaredField("otherCurrencies").get(data);
                    otherCurrenciesDFD = (int[]) data.getDeclaredField("otherCurrenciesDFD").get(data);
                } catch (ClassNotFoundException e) {
                    throw new InternalError();
                } catch (NoSuchFieldException e) {
                    throw new InternalError();
                } catch (IllegalAccessException e) {
                    throw new InternalError();
                }
                return null;
            }
        });
    }
    

    /**
     * Constructs a <code>Currency</code> instance. The constructor is private
     * so that we can insure that there's never more than one instance for a
     * given currency.
     */
    private Currency(String currencyCode, int defaultFractionDigits) {
        this.currencyCode = currencyCode;
        this.defaultFractionDigits = defaultFractionDigits;
    }
    
    /**
     * Returns the <code>Currency</code> instance for the given currency code.
     *
     * @param currencyCode the ISO 4217 code of the currency
     * @return the <code>Currency</code> instance for the given currency code
     * @exception NullPointerException if <code>currencyCode</code> is null
     * @exception IllegalArgumentException if <code>currencyCode</code> is not
     * a supported ISO 4217 code.
     */
    public static Currency getInstance(String currencyCode) {
        return getInstance(currencyCode, Integer.MIN_VALUE);
    }
    
    private static Currency getInstance(String currencyCode, int defaultFractionDigits) {
        synchronized (instances) {
            // Try to look up the currency code in the instances table.
            // This does the null pointer check as a side effect.
            // Also, if there already is an entry, the currencyCode must be valid.
            Currency instance = (Currency) instances.get(currencyCode);
            if (instance != null) {
                return instance;
            }
        
            if (defaultFractionDigits == Integer.MIN_VALUE) {
                // Currency code not internally generated, need to verify first
                // A currency code must have 3 characters and exist in the main table
                // or in the list of other currencies.