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package org.apidesign.apifest08.currency;
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import java.math.BigDecimal;
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import java.math.MathContext;
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import java.math.RoundingMode;
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import java.util.Collections;
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import java.util.Currency;
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import java.util.HashSet;
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import java.util.Set;
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/**
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* Convert between two currencies.
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*
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* @author D'Arcy Smith
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* @version 1.0
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*/
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final class ConvertorImpl
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implements Convertor
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{
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/**
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* The currency to cvonvert from.
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*/
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private final Currency currencyA;
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/**
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* The currency to cvonvert from.
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*/
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private final Currency currencyB;
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/**
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* The echange rate between a and b.
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*/
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private final BigDecimal currencyARate;
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/**
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* The echange rate between b and a.
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*/
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private final BigDecimal currencyBRate;
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/**
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* Constructs a convertor with the specified currencies.
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*
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* @param a the currency to convert from.
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* @param aRate the exchage rage between from and to.
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* @param b the currency to convert to.
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* @param bRate the exchage rage between to and from.
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* @throws IllegalArgumentException if either any of the arguments are null or if either rate <= 0.
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*/
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public ConvertorImpl(final Currency a,
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final BigDecimal aRate,
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final Currency b,
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final BigDecimal bRate)
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{
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if(a == null)
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{
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throw new IllegalArgumentException("a cannot be null");
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}
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if(b == null)
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{
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throw new IllegalArgumentException("b cannot be null");
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}
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if(aRate == null)
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{
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throw new IllegalArgumentException("aRate cannot be null");
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}
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if(bRate == null)
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{
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throw new IllegalArgumentException("bRate cannot be null");
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}
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if(aRate.compareTo(BigDecimal.ZERO) <= 0)
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{
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throw new IllegalArgumentException("aRate must be > 0, was: " + aRate);
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}
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if(bRate.compareTo(BigDecimal.ZERO) <= 0)
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{
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throw new IllegalArgumentException("bRate must be > 0, was: " + bRate);
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}
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currencyA = a;
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currencyB = b;
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currencyARate = aRate;
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currencyBRate = bRate;
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}
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/**
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* Convert an amount from one currency to another.
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*
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* @param from the currency to convert from.
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* @param to the currency to convert to.
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* @param amount the amount to convert.
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* @return the converted amount.
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* @throws IllegalArgumentException if any of the arguments are null.
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* @throws InvalidConversionException if either from or to are not equal to the currencies passed to the constructor.
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*/
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public BigDecimal convert(final Currency from,
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final Currency to,
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final BigDecimal amount)
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throws InvalidConversionException
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{
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final BigDecimal result;
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if(amount == null)
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{
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throw new IllegalArgumentException("amount cannot be null");
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}
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if(from == null)
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{
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throw new IllegalArgumentException("from cannot be null");
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}
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if(to == null)
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{
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throw new IllegalArgumentException("to cannot be null");
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}
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if(!(from.equals(currencyA)) && (!(from.equals(currencyB))))
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{
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throw new InvalidConversionException("cannot convert from: " + from.getCurrencyCode(), from, currencyA, currencyB);
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}
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if(!(to.equals(currencyA)) && (!(to.equals(currencyB))))
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{
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throw new InvalidConversionException("cannot convert to: " + to.getCurrencyCode(), to, currencyA, currencyB);
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}
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result = amount.multiply(getConversionRate(from, to));
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return (result.setScale(2, RoundingMode.HALF_DOWN));
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}
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/**
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* Check to see if converting between the two currencies is possible.
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*
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* @param from the currency to convert from.
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* @param to the currency to convert to.
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* @return true if the conversion is possible.
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*/
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public boolean canConvert(final Currency from, final Currency to)
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{
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return ((from.equals(currencyA) || from.equals(currencyB)) &&
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(to.equals(currencyA) || to.equals(currencyB)));
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}
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/**
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* Get the currencies that the convertor supports.
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*
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* @return the supported currencies.
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*/
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public Set<Currency> getCurrencies()
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{
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final Set<Currency> currencies;
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currencies = new HashSet<Currency>();
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currencies.add(currencyA);
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currencies.add(currencyB);
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return (Collections.unmodifiableSet(currencies));
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}
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/**
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* Get the conversion rate between two currencies.
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*
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* @param from the currency to convert from.
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* @param to the currency to convert to.
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* @return the conversion rate between the two currencies.
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* @throws InvalidConversionException if canConvert would return false.
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*/
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public BigDecimal getConversionRate(final Currency from,
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final Currency to)
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throws InvalidConversionException
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{
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final BigDecimal rate;
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if(from.equals(to))
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{
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rate = BigDecimal.ONE;
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}
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else
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{
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final BigDecimal rateX;
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final BigDecimal rateY;
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final BigDecimal temp;
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if(from.equals(currencyA))
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{
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rateX = currencyARate;
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rateY = currencyBRate;
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}
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else
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{
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rateX = currencyBRate;
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rateY = currencyARate;
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}
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temp = BigDecimal.ONE.divide(rateX, MathContext.DECIMAL64);
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rate = temp.multiply(rateY);
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}
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return (rate.setScale(20, RoundingMode.HALF_EVEN));
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}
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/**
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* Check to see if two ConvertorImpls are equal.
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*
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* @param obj the object to check
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* @return if the ConvertorImpls are not the same (cuyrrencies and rates).
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*/
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@Override
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public boolean equals(Object obj)
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{
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if (obj == null)
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{
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return false;
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}
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if (getClass() != obj.getClass())
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{
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return false;
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}
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final ConvertorImpl other = (ConvertorImpl) obj;
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// it would be nice if NetBeans could chck to see if the variable is final and guaranteed not to be null... but that
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// would likely be tricky... but in a NetBeans engineer reads that see if you can do it :-)
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if (this.currencyA != other.currencyA && (this.currencyA == null || !this.currencyA.equals(other.currencyA)))
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{
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return false;
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}
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if (this.currencyB != other.currencyB && (this.currencyB == null || !this.currencyB.equals(other.currencyB)))
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{
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return false;
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}
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if (this.currencyARate != other.currencyARate && (this.currencyARate == null || !this.currencyARate.equals(other.currencyARate)))
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{
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return false;
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}
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if (this.currencyBRate != other.currencyBRate && (this.currencyBRate == null || !this.currencyBRate.equals(other.currencyBRate)))
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{
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return false;
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}
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return true;
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}
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/**
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* Get the hashCode of the Convertor.
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*
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* @return the hashCode of the convertor.
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*/
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@Override
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public int hashCode()
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{
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int hash = 7;
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hash = 37 * hash + (this.currencyA != null ? this.currencyA.hashCode() : 0);
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hash = 37 * hash + (this.currencyB != null ? this.currencyB.hashCode() : 0);
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hash = 37 * hash + (this.currencyARate != null ? this.currencyARate.hashCode() : 0);
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hash = 37 * hash + (this.currencyBRate != null ? this.currencyBRate.hashCode() : 0);
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return hash;
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}
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/**
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* Get the currencyCode of both currencies.
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*
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* @return the currency codes of both currencies.
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*/
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@Override
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public String toString()
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{
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return (currencyA.getCurrencyCode() + " to " + currencyB.getCurrencyCode());
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}
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}
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