1.1 --- a/task3/solution04/src/org/apidesign/apifest08/currency/ConverterImpl.java	Tue Oct 07 11:05:34 2008 +0200
     1.2 +++ b/task3/solution04/src/org/apidesign/apifest08/currency/ConverterImpl.java	Fri Oct 10 22:05:15 2008 +0200
     1.3 @@ -20,12 +20,12 @@
     1.4      implements Convertor
     1.5  {
     1.6      /**
     1.7 -     * The currency to cvonvert from.
     1.8 +     * The currency to convert from.
     1.9       */
    1.10      private final Currency currencyA;
    1.11  
    1.12      /**
    1.13 -     * The currency to cvonvert from.
    1.14 +     * The currency to convert to.
    1.15       */
    1.16      private final Currency currencyB;
    1.17  
    1.18 @@ -142,9 +142,20 @@
    1.19       * @param from the currency to convert from.
    1.20       * @param to the currency to convert to.
    1.21       * @return true if the conversion is possible.
    1.22 +     * @throws IllegalArgumentException if either from or to are null.
    1.23       */
    1.24      public boolean canConvert(final Currency from, final Currency to)
    1.25      {
    1.26 +        if(from == null)
    1.27 +        {
    1.28 +            throw new IllegalArgumentException("from cannot be null");
    1.29 +        }
    1.30 +        
    1.31 +        if(to == null)
    1.32 +        {
    1.33 +            throw new IllegalArgumentException("to cannot be null");
    1.34 +        }
    1.35 +        
    1.36          return ((from.equals(currencyA) || from.equals(currencyB)) &&
    1.37                  (to.equals(currencyA)   || to.equals(currencyB)));
    1.38      }
    1.39 @@ -172,12 +183,23 @@
    1.40       * @param to the currency to convert to.
    1.41       * @return the conversion rate between the two currencies.
    1.42       * @throws InvalidConversionException if canConvert would return false.
    1.43 +     * @throws IllegalArgumentException if either from or to are null.
    1.44       */
    1.45      public BigDecimal getConversionRate(final Currency from, 
    1.46                                          final Currency to)
    1.47          throws InvalidConversionException
    1.48 -    {
    1.49 +    {                
    1.50          final BigDecimal rate;
    1.51 +        
    1.52 +        if(from == null)
    1.53 +        {
    1.54 +            throw new IllegalArgumentException("from cannot be null");
    1.55 +        }
    1.56 +        
    1.57 +        if(to == null)
    1.58 +        {
    1.59 +            throw new IllegalArgumentException("to cannot be null");
    1.60 +        }
    1.61  
    1.62          if(from.equals(to))
    1.63          {