1.1 --- a/task1/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Sun Sep 28 14:12:38 2008 +0200
     1.2 +++ b/task1/solution06/src/org/apidesign/apifest08/currency/Convertor.java	Tue Sep 30 12:24:45 2008 +0200
     1.3 @@ -1,23 +1,30 @@
     1.4  package org.apidesign.apifest08.currency;
     1.5  
     1.6 +import static org.apidesign.apifest08.currency.Assert.notNull;
     1.7 +
     1.8  import java.math.BigDecimal;
     1.9 +import java.math.RoundingMode;
    1.10  import java.util.Currency;
    1.11  
    1.12 -public abstract class Convertor {
    1.13 -    
    1.14 -   /**
    1.15 -    * Converts an amount to another amount according to a given currency.
    1.16 -    *  
    1.17 -	* @param from a source 
    1.18 -	* @param toCurrency a target currency
    1.19 -	* @return a converted amount
    1.20 -	* @throws ConversionException if the conversion fails
    1.21 -	* @throws UnsupportedConversionException if the conversion between a given currencies is not supported.
    1.22 -	*/
    1.23 -	public abstract Amount convert(Amount from, Currency toCurrency) throws ConversionException, UnsupportedConversionException;
    1.24 +public final class Convertor {
    1.25  	
    1.26 +	private final Currency first;
    1.27 +	private final Currency second;
    1.28 +	private final BigDecimal rateValue; // a rate between the first currency and the second currency
    1.29 +	public static final BigDecimal one = new BigDecimal(1);	
    1.30 +	
    1.31 +	public Convertor(BigDecimal rateValue, Currency currencyFirst, Currency currencySecond) {
    1.32 +		notNull(currencyFirst, "currencyFirst");
    1.33 +		notNull(currencySecond, "currencySecond");		
    1.34 +		notNull(rateValue, "rateValue");
    1.35 +		
    1.36 +		this.rateValue = rateValue;
    1.37 +		this.first = currencyFirst;
    1.38 +		this.second = currencySecond;
    1.39 +	}
    1.40 +    	
    1.41  	/**
    1.42 -	 * Converts an amount value between two currencies.
    1.43 +	 * Converts an amount value between the two currencies of this converter.
    1.44  	 *  
    1.45  	 * @param amount an amount
    1.46  	 * @param fromCurrency an amount currency
    1.47 @@ -27,6 +34,31 @@
    1.48  	 * @throws ConversionException if the conversion fails
    1.49  	 * @throws UnsupportedConversionException if the conversion between a given currencies is not supported.
    1.50  	 */
    1.51 -	public abstract Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException, UnsupportedConversionException;
    1.52 +	public Amount convert(BigDecimal amount, Currency fromCurrency, Currency toCurrency) throws ConversionException {
    1.53 +		notNull(amount, "amount");
    1.54 +		notNull(fromCurrency, "fromCurrency");
    1.55 +		notNull(toCurrency, "toCurrency");
    1.56 +		
    1.57 +		if((fromCurrency != first && fromCurrency != second) || (toCurrency != first && toCurrency != second)) {
    1.58 +			throw new UnsupportedConversionException(fromCurrency, toCurrency);
    1.59 +		}		
    1.60  
    1.61 +		BigDecimal rateValue = getRateValue(fromCurrency, toCurrency);
    1.62 +		BigDecimal result = rateValue.multiply(amount);			
    1.63 +		return new Amount(result, toCurrency);	
    1.64 +	}
    1.65 +	
    1.66 +	private BigDecimal getRateValue(Currency fromCurrency, Currency toCurrency) {		
    1.67 +		
    1.68 +		BigDecimal retVal;
    1.69 +		
    1.70 +		if(first == fromCurrency) {
    1.71 +			retVal = rateValue;
    1.72 +		} else {	
    1.73 +			//reverse rate	
    1.74 +			retVal = one.divide(rateValue, 10 ,RoundingMode.HALF_UP);
    1.75 +		}
    1.76 +		
    1.77 +		return retVal;
    1.78 +	}
    1.79  }