|
Provides support for monetary quantities and their currencies.
Conversions between quantities stated in different currencies is possible
if the exchange rates for the currencies have been set (otherwise
ConversionException is thrown).
Monetary quantities support the dynamic changes of the currencies exchange
rates as illustrated in the following example:[code]
import static javax.measure.units.SI.*;
import static javax.measure.units.NonSI.*;
import static org.jscience.economics.money.Currency.*;
///////////////////////////////////////////////////////////////////////
// Calculates the cost of a car trip in Europe for an American tourist.
///////////////////////////////////////////////////////////////////////
// Use currency symbols instead of ISO-4217 codes.
UnitFormat.getStandardInstance().label(USD, "$"); // Use "$" symbol instead of currency code ("USD")
UnitFormat.getStandardInstance().label(EUR, "€"); // Use "€" symbol instead of currency code ("EUR")
// Sets exchange rates.
Currency.setReferenceCurrency(USD);
EUR.setExchangeRate(1.17); // 1.0 € = 1.17 $
// Calculates trip cost.
Amount carMileage = Amount.valueOf(20, MILE.divide(GALLON_LIQUID_US)); // 20 mi/gal.
Amount gazPrice = Amount.valueOf(1.2, EUR.divide(LITER)); // 1.2 €/L
Amount tripDistance = Amount.valueOf(400, KILO(METRE)); // 400 km
Amount tripCost = tripDistance.divide(carMileage).times(gazPrice).to(USD);
// Displays cost.
System.out.println("Trip cost = " + tripCost + " (" + tripCost.to(EUR) + ")");
> Trip cost = 66.05 $ (56.45 €)
[/code]
The exchange rates between {@link org.jscience.economics.money.Currency currencies}
is {@link javolution.context.LocalContext context local}.
Application may use different sets of exchange rates concurrently (e.g. rates for buying and
rates for selling). For example:[code]
LocalContext.enter();
try {
EUR.setExchangeRate(1.22); // Buying rate.
Amount price = Amount.valueOf(9.99, EUR);
System.out.println("Price: " + price.to(USD);
} finally {
LocalContext.exit();
}
...
LocalContext.enter();
try {
EUR.setExchangeRate(1.18); // Selling rate.
Amount price = Amount.valueOf(14.99, USD);
System.out.println("Price: " + price.to(EUR);
} finally {
LocalContext.exit();
}[/code]
Like any {@link org.jscience.physics.amount.Amount amount},
money quantities can be exact or approximate (with an error known
and guaranteed).
[code]
Unit CENTS = Currency.USD.times(100);
Amount exactPrice = Amount.valueOf(1499, CENTS); // Integer value.
Amount apprxPrice = Amount.valueOf(14.99, USD); // Floating-Point IEEE 754 accuracy.
[/code]
|