getInstance() methods rather than by using
* a constructor.
*
* @see java.util.Locale
* @author Guilhem Lavaux (guilhem.lavaux@free.fr)
* @author Dalibor Topic (robilad@kaffe.org)
* @author Bryce McKinlay (mckinlay@redhat.com)
* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
* @since 1.4
*/
public final class Currency
implements Serializable
{
/**
* For compatability with Sun's JDK
*/
static final long serialVersionUID = -158308464356906721L;
/**
* The set of properties which map a currency to
* the currency information such as the ISO 4217
* currency code and the number of decimal points.
*
* @see #getCurrencyCode()
* @serial ignored.
*/
private static transient Properties properties;
/**
* The ISO 4217 currency code associated with this
* particular instance.
*
* @see #getCurrencyCode()
* @serial the ISO 4217 currency code
*/
private String currencyCode;
/**
* The number of fraction digits associated with this
* particular instance.
*
* @see #getDefaultFractionDigits()
* @serial the number of fraction digits
*/
private transient int fractionDigits;
/**
* A cached map of country codes
* instances to international currency code
* Strings. Seperating this
* from the Currency instances
* ensures we have a common lookup between
* the two getInstance() methods.
*
* @see #getInstance(java.util.Locale)
* @serial ignored.
*/
private static transient Map countryMap;
/**
* A cache of Currency instances to
* ensure the singleton nature of this class. The key
* is the international currency code.
*
* @see #getInstance(java.util.Locale)
* @see #getInstance(java.lang.String)
* @see #readResolve()
* @serial ignored.
*/
private static transient Map cache;
/**
* Instantiates the cache and reads in the properties.
*/
static
{
/* Create a hash map for the locale mappings */
countryMap = new HashMap();
/* Create a hash map for the cache */
cache = new HashMap();
/* Create the properties object */
properties = new Properties();
/* Try and load the properties from our iso4217.properties resource */
try
{
properties.load(Currency.class.getResourceAsStream("iso4217.properties"));
}
catch (IOException exception)
{
throw new InternalError("Failed to load currency resource: " + exception);
}
}
/**
* Default constructor for deserialization
*/
private Currency()
{
}
/**
* Constructor to create a Currency object
* for a particular Locale.
* All components of the given locale, other than the
* country code, are ignored. The results of calling this
* method may vary over time, as the currency associated with
* a particular country changes. For countries without
* a given currency (e.g. Antarctica), the result is null.
*
* @param loc the locale for the new currency, or null if
* there is no country code specified or a currency
* for this country.
*/
private Currency(Locale loc)
{
String countryCode;
String currencyKey;
String fractionDigitsKey;
int commaPosition;
/* Retrieve the country code from the locale */
countryCode = loc.getCountry();
/* If there is no country code, return */
if (countryCode.equals(""))
{
throw new
IllegalArgumentException("Invalid (empty) country code for locale:"
+ loc);
}
/* Construct the key for the currency */
currencyKey = countryCode + ".currency";
/* Construct the key for the fraction digits */
fractionDigitsKey = countryCode + ".fractionDigits";
/* Retrieve the currency */
currencyCode = properties.getProperty(currencyKey);
/* Return if the currency code is null */
if (currencyCode == null)
{
return;
}
/* Split off the first currency code (we only use the first for now) */
commaPosition = currencyCode.indexOf(",");
if (commaPosition != -1)
{
currencyCode = currencyCode.substring(0, commaPosition);
}
/* Retrieve the fraction digits */
fractionDigits = Integer.parseInt(properties.getProperty(fractionDigitsKey));
}
/**
* Constructor for the "XXX" special case. This allows
* a Currency to be constructed from an assumed good
* currency code.
*
* @param code the code to use.
*/
private Currency(String code)
{
currencyCode = code;
fractionDigits = -1; /* Pseudo currency */
}
/**
* Returns the ISO4217 currency code of this currency.
*
* @return a String containing currency code.
*/
public String getCurrencyCode()
{
return currencyCode;
}
/**
* Returns the number of digits which occur after the decimal point
* for this particular currency. For example, currencies such
* as the U.S. dollar, the Euro and the Great British pound have two
* digits following the decimal point to indicate the value which exists
* in the associated lower-valued coinage (cents in the case of the first
* two, pennies in the latter). Some currencies such as the Japanese
* Yen have no digits after the decimal point. In the case of pseudo
* currencies, such as IMF Special Drawing Rights, -1 is returned.
*
* @return the number of digits after the decimal separator for this currency.
*/
public int getDefaultFractionDigits()
{
return fractionDigits;
}
/**
* Builds a new currency instance for this locale.
* All components of the given locale, other than the
* country code, are ignored. The results of calling this
* method may vary over time, as the currency associated with
* a particular country changes. For countries without
* a given currency (e.g. Antarctica), the result is null.
*
* @param locale a Locale instance.
* @return a new Currency instance.
* @throws NullPointerException if the locale or its
* country code is null.
* @throws IllegalArgumentException if the country of
* the given locale is not a supported ISO3166 code.
*/
public static Currency getInstance(Locale locale)
{
/**
* The new instance must be the only available instance
* for the currency it supports. We ensure this happens,
* while maintaining a suitable performance level, by
* creating the appropriate object on the first call to
* this method, and returning the cached instance on
* later calls.
*/
Currency newCurrency;
String country = locale.getCountry();
if (locale == null || country == null)
{
throw new
NullPointerException("The locale or its country is null.");
}
/* Check that country of locale given is valid. */
if (country.length() != 2)
throw new IllegalArgumentException();
/* Attempt to get the currency from the cache */
String code = (String) countryMap.get(country);
if (code == null)
{
/* Create the currency for this locale */
newCurrency = new Currency(locale);
/*
* If the currency code is null, then creation failed
* and we return null.
*/
code = newCurrency.getCurrencyCode();
if (code == null)
{
return null;
}
else
{
/* Cache it */
countryMap.put(country, code);
cache.put(code, newCurrency);
}
}
else
{
newCurrency = (Currency) cache.get(code);
}
/* Return the instance */
return newCurrency;
}
/**
* Builds the currency corresponding to the specified currency code.
*
* @param currencyCode a string representing a currency code.
* @return a new Currency instance.
* @throws NullPointerException if currencyCode is null.
* @throws IllegalArgumentException if the supplied currency code
* is not a supported ISO 4217 code.
*/
public static Currency getInstance(String currencyCode)
{
Locale[] allLocales;
/*
* Throw a null pointer exception explicitly if currencyCode is null.
* One is not thrown otherwise. It results in an
* IllegalArgumentException.
*/
if (currencyCode == null)
{
throw new NullPointerException("The supplied currency code is null.");
}
/* Nasty special case to allow an erroneous currency... blame Sun */
if (currencyCode.equals("XXX"))
return new Currency("XXX");
Currency newCurrency = (Currency) cache.get(currencyCode);
if (newCurrency == null)
{
/* Get all locales */
allLocales = Locale.getAvailableLocales();
/* Loop through each locale, looking for the code */
for (int i = 0;i < allLocales.length; i++)
{
try
{
Currency testCurrency = getInstance (allLocales[i]);
if (testCurrency != null &&
testCurrency.getCurrencyCode().equals(currencyCode))
{
return testCurrency;
}
}
catch (IllegalArgumentException exception)
{
/* Ignore locales without valid countries */
}
}
/*
* If we get this far, the code is not supported by any of
* our locales.
*/
throw new IllegalArgumentException("The currency code, " + currencyCode +
", is not supported.");
}
else
{
return newCurrency;
}
}
/**
* This method returns the symbol which precedes or follows a
* value in this particular currency in the default locale.
* In cases where there is no such symbol for the currency,
* the ISO 4217 currency code is returned.
*
* @return the currency symbol, or the ISO 4217 currency code if
* one doesn't exist.
*/
public String getSymbol()
{
return getSymbol(Locale.getDefault());
}
/**
* * This method returns the symbol which precedes or follows a * value in this particular currency. The returned value is * the symbol used to denote the currency in the specified locale. *
*
* For example, a supplied locale may specify a different symbol
* for the currency, due to conflicts with its own currency.
* This would be the case with the American currency, the dollar.
* Locales that also use a dollar-based currency (e.g. Canada, Australia)
* need to differentiate the American dollar using 'US$' rather than '$'.
* So, supplying one of these locales to getSymbol() would
* return this value, rather than the standard '$'.
*
* In cases where there is no such symbol for a particular currency, * the ISO 4217 currency code is returned. *
* * @param locale the locale to express the symbol in. * @return the currency symbol, or the ISO 4217 currency code if * one doesn't exist. * @throws NullPointerException if the locale is null. */ public String getSymbol(Locale locale) { String property = "currenciesSymbol." + currencyCode; try { return ResourceBundle.getBundle("gnu.java.locale.LocaleInformation", locale).getString(property); } catch (MissingResourceException exception) { /* This means runtime support for the locale * is not available, so we check providers. */ } for (CurrencyNameProvider p : ServiceLoader.load(CurrencyNameProvider.class)) { for (Locale loc : p.getAvailableLocales()) { if (loc.equals(locale)) { String localizedString = p.getSymbol(currencyCode, locale); if (localizedString != null) return localizedString; break; } } } if (locale.equals(Locale.ROOT)) // Base case return currencyCode; return getSymbol(LocaleHelper.getFallbackLocale(locale)); } /** * Returns the international ISO4217 currency code of this currency. * * @return aString containing the ISO4217 currency code.
*/
public String toString()
{
return getCurrencyCode();
}
/**
* Resolves the deserialized object to the singleton instance for its
* particular currency. The currency code of the deserialized instance
* is used to return the correct instance.
*
* @return the singleton instance for the currency specified by the
* currency code of the deserialized object. This replaces
* the deserialized object as the returned object from
* deserialization.
* @throws ObjectStreamException if a problem occurs with deserializing
* the object.
*/
private Object readResolve()
throws ObjectStreamException
{
return getInstance(currencyCode);
}
}