japod@37: package org.apidesign.apifest08.currency;
japod@37: 
japod@37: import java.io.Serializable;
japod@37: 
japod@37: /**
japod@37:  * Value class, holding an exchange rate between two currencies.
japod@37:  * Designed to be an immutable.
japod@37:  * 
japod@37:  * @author ked
japod@37:  */
japod@37: public final class ExchangeRateValue<AmountType, IdentifierType> implements Serializable {
japod@37: 
japod@37:     private final CurrencyValue<AmountType, IdentifierType> currencyA;
japod@37:     private final CurrencyValue<AmountType, IdentifierType> currencyB;
japod@37: 
japod@37:     private ExchangeRateValue(
japod@37:             CurrencyValue<AmountType, IdentifierType> currencyA,
japod@37:             CurrencyValue<AmountType, IdentifierType> currencyB) {
japod@37:         if (currencyA.getIdentifier() == null ||
japod@37:             currencyB.getIdentifier() == null ||
japod@37:             currencyA.getIdentifier().equals(currencyB)) {
japod@37:                 throw new IllegalArgumentException("Inappropriate exchange rates' identifiers!");
japod@37:         }
japod@37: 
japod@37:         this.currencyA = currencyA;
japod@37:         this.currencyB = currencyB;
japod@37:     }
japod@37: 
japod@37:     public CurrencyValue<AmountType, IdentifierType> getCurrencyA() {
japod@37:         return currencyA;
japod@37:     }
japod@37: 
japod@37:     public CurrencyValue<AmountType, IdentifierType> getCurrencyB() {
japod@37:         return currencyB;
japod@37:     }
japod@37: 
japod@37:     @Override
japod@37:     public boolean equals(Object obj) {
japod@37:         if (obj == null) {
japod@37:             return false;
japod@37:         }
japod@37:         if (getClass() != obj.getClass()) {
japod@37:             return false;
japod@37:         }
japod@37:         final ExchangeRateValue other = (ExchangeRateValue) obj;
japod@37:         if (this.currencyA != other.currencyA && (this.currencyA == null || !this.currencyA.equals(other.currencyA))) {
japod@37:             return false;
japod@37:         }
japod@37:         if (this.currencyB != other.currencyB && (this.currencyB == null || !this.currencyB.equals(other.currencyB))) {
japod@37:             return false;
japod@37:         }
japod@37:         return true;
japod@37:     }
japod@37: 
japod@37:     @Override
japod@37:     public int hashCode() {
japod@37:         int hash = 3;
japod@37:         hash = 71 * hash + (this.currencyA != null ? this.currencyA.hashCode() : 0);
japod@37:         hash = 71 * hash + (this.currencyB != null ? this.currencyB.hashCode() : 0);
japod@37:         return hash;
japod@37:     }
japod@37: 
japod@37:     /**
japod@37:      * Creates new instance.
japod@37:      * Generic types of the new instance are derived from types of the parameters.
japod@37:      * 
japod@37:      * @param <AmountType> type of the currency amount
japod@37:      * @param <IdentifierType> type of the currency identifier
japod@37:      * @param currencyA one currency of the exchange rate
japod@37:      * @param currencyB another currency of the exchange rate
japod@37:      * @return new instance
japod@37:      */
japod@37:     public static <AmountType, IdentifierType> ExchangeRateValue<AmountType, IdentifierType> getExchangeRate(
japod@37:             CurrencyValue<AmountType, IdentifierType> currencyA,
japod@37:             CurrencyValue<AmountType, IdentifierType> currencyB) {
japod@37:         return new ExchangeRateValue<AmountType, IdentifierType>(currencyA, currencyB);
japod@37:     }
japod@37: }