japod@6
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package org.apidesign.apifest08.currency;
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japod@6
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japod@21
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import static org.apidesign.apifest08.currency.Assert.notNull;
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japod@21
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japod@6
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import java.math.BigDecimal;
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japod@21
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import java.math.RoundingMode;
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japod@38
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import java.util.ArrayList;
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japod@6
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import java.util.Currency;
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japod@38
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import java.util.List;
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japod@6
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japod@52
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/**
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japod@52
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* Currency covertor.
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japod@52
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*/
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japod@21
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public final class Convertor {
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japod@6
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japod@38
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private List<ConvertorDelegate> convertorDelegates = new ArrayList<ConvertorDelegate>();
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japod@21
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japod@38
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japod@38
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/**
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japod@38
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* Create new instance of the converter for the given currencies and its rate.
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japod@38
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*
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japod@38
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* @param rateValue the rate between the first and the second currency
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japod@38
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* @param currencyFirst the first currency
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japod@38
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* @param currencySecond the second currency
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japod@38
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*/
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japod@21
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public Convertor(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
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japod@21
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notNull(currencyFirst, "currencyFirst");
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japod@21
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notNull(currencySecond, "currencySecond");
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japod@38
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notNull(rateValue, "rateValue");
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convertorDelegates.add(new ConvertorDelegate(new StaticRateProvider(rateValue), currencyFirst, currencySecond));
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japod@52
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}
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japod@52
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japod@52
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/**
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japod@52
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* Create new instance of the converter for the given currencies and its rate.
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japod@52
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* A rate value is provided by {@link RateProvider}.
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japod@52
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*
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* @param rateProvider the rate provider
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* @param currencyFirst the first currency
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* @param currencySecond the second currency
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japod@52
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*/
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japod@52
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public Convertor(RateProvider rateProvider, Currency currencyFirst, Currency currencySecond) {
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japod@52
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notNull(currencyFirst, "currencyFirst");
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japod@52
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notNull(currencySecond, "currencySecond");
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notNull(rateProvider, "rateProvider");
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convertorDelegates.add(new ConvertorDelegate(rateProvider, currencyFirst, currencySecond));
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japod@38
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}
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japod@38
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japod@38
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/**
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japod@38
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* Create new instance of the convertor from the given convertors.
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japod@38
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* @param convertors the convertors
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japod@38
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*/
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japod@38
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public Convertor(Convertor... convertors) {
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japod@38
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notNull(convertors, "convertors");
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japod@38
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if(convertors.length == 0) {
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throw new IllegalArgumentException("There must be at least one converter.");
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japod@38
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}
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japod@21
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japod@38
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for(Convertor convertor: convertors) {
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japod@38
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if(convertor != null) {
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japod@38
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convertorDelegates.addAll(convertor.convertorDelegates);
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japod@38
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}
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}
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japod@21
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}
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japod@21
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japod@6
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/**
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* Converts an amount value between the two currencies of this converter.
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*
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* @param amount an amount
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japod@6
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* @param fromCurrency an amount currency
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japod@6
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* @param toCurrency to a target currency
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* @return a converted amount value
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*
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* @throws ConversionException if the conversion fails
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* @throws UnsupportedConversionException if the conversion between a given currencies is not supported.
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*/
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public Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException {
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japod@21
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notNull(amount, "amount");
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notNull(fromCurrency, "fromCurrency");
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notNull(toCurrency, "toCurrency");
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ConvertorDelegate appropriateDelegate = null;
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//try find an appropriate delegate for conversion
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for(ConvertorDelegate delegate : convertorDelegates) {
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if(delegate.isConversionSupported(fromCurrency, toCurrency)) {
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appropriateDelegate = delegate;
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break;
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japod@38
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}
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japod@38
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}
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japod@38
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if(appropriateDelegate == null) {
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throw new UnsupportedConversionException(fromCurrency, toCurrency);
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}
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return appropriateDelegate.convert(amount, fromCurrency, toCurrency);
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}
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japod@21
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/**
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japod@38
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* Internal delegate implements a logic for conversion between two currencies
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japod@38
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* and vice versa.
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* @see #isConversionSupported(Currency, Currency)
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japod@38
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*/
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japod@38
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private static class ConvertorDelegate {
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japod@38
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private final Currency first;
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japod@38
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private final Currency second;
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private final RateProvider rateProvider;
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japod@38
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public static final BigDecimal one = new BigDecimal(1);
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private ConvertorDelegate(RateProvider rateProvider, Currency currencyFirst, Currency currencySecond) {
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this.rateProvider = rateProvider;
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this.first = currencyFirst;
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this.second = currencySecond;
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}
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japod@21
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japod@38
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private Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException {
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japod@38
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BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
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japod@38
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BigDecimal result = rateValue.multiply(amount);
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japod@38
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return new Amount(result, toCurrency);
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japod@38
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}
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japod@38
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japod@38
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private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {
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japod@38
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japod@38
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BigDecimal retVal;
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japod@38
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if(first == fromCurrency) {
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japod@52
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BigDecimal rateValue = rateProvider.getRate();
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if(rateValue == null) {
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throw new NullPointerException("Rate cannot be null!");
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}
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retVal = rateValue;
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} else {
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japod@52
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BigDecimal rateValue = rateProvider.getRate();
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if(rateValue == null) {
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throw new NullPointerException("Rate cannot be null!");
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}
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japod@38
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//reverse rate
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retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
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}
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japod@38
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return retVal;
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japod@38
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}
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japod@38
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japod@38
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/**
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japod@38
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* @return <code>true</code> if the delegate is able to convert from the given currency
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japod@38
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* to the given currency and vice versa otherwise <code>false</code>.
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*/
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private boolean isConversionSupported(Currency fromCurrency, Currency toCurrency) {
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return ((fromCurrency == first || fromCurrency == second) && (toCurrency == first || toCurrency == second));
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}
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}
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japod@52
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japod@52
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/**
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japod@52
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* A rate provider. This class represents a way how could be "static" convertor
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japod@52
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* extended in order converts according to current rate.
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japod@52
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*/
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japod@52
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public static abstract class RateProvider {
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/**
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* @return a rate between the from currency and the to currency associated with
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japod@52
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* a given convertor.
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*/
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public abstract BigDecimal getRate();
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japod@52
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}
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japod@52
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japod@52
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private static class StaticRateProvider extends RateProvider{
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japod@52
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private final BigDecimal rateValue;
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private StaticRateProvider(BigDecimal rateValue){
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japod@52
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this.rateValue = rateValue;
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}
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public BigDecimal getRate() {
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japod@52
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return this.rateValue;
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japod@52
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}
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japod@52
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}
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japod@6
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}
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