diff -r f6073056b9fe -r 80f2d8751f35 task2/solution12/src/org/apidesign/apifest08/currency/Convertor.java
--- a/task2/solution12/src/org/apidesign/apifest08/currency/Convertor.java	Wed Oct 01 10:43:05 2008 +0200
+++ b/task2/solution12/src/org/apidesign/apifest08/currency/Convertor.java	Tue Oct 07 00:17:07 2008 +0200
@@ -1,7 +1,9 @@
 package org.apidesign.apifest08.currency;
 
+import java.util.ArrayList;
 import java.util.Currency;
 import java.util.Hashtable;
+import java.util.List;
 
 import org.apidesign.apifest08.currency.exceptions.ConvertorException;
 import org.apidesign.apifest08.currency.exceptions.InvalidCurrencyException;
@@ -18,20 +20,19 @@
 
   private static Hashtable<String, ExchangeRate> exchangeRates;
 
-  private ExchangeRate exchangeRate12;
-  private ExchangeRate exchangeRate21;
+  private Hashtable<String, ExchangeRate> convertorInstanceExchangeRates; 
 
-  private Convertor(Currency currency1, Currency currency2) throws UnknownConvertorException {
-    String key12 = currency1.getCurrencyCode() + currency2.getCurrencyCode();
-    String key21 = currency2.getCurrencyCode() + currency1.getCurrencyCode();
-
-    if (!(exchangeRates.containsKey(key12) && exchangeRates.containsKey(key21))) {
-      throw new UnknownConvertorException("Selected convertor (" + currency1.getCurrencyCode() + "->"
-          + currency2.getCurrencyCode() + ") has not defined any rates!!!");
-    }
-
-    this.exchangeRate12 = exchangeRates.get(key12);
-    this.exchangeRate21 = exchangeRates.get(key21);
+  private Convertor(List<Currency> currencies) throws UnknownConvertorException {
+	  convertorInstanceExchangeRates = new Hashtable<String, ExchangeRate>();
+	  for (Currency currency1 : currencies) {
+		for (Currency currency2 : currencies) {
+			if(!currency1.getCurrencyCode().equals(currency2.getCurrencyCode())) {
+				String key = currency1.getCurrencyCode() + currency2.getCurrencyCode();
+				ExchangeRate exchangeRate = exchangeRates.get(key);
+				convertorInstanceExchangeRates.put(key, exchangeRate);
+			}
+		}
+	}
   }
 
   /**
@@ -67,6 +68,18 @@
     exchangeRates.put(key21, new ExchangeRate(currency2, currency1, recountedRate, unit));
 
   }
+  
+  /**
+   * Merge exchange rates of actual convertor with exchange rates from selected 
+   * convertor. If there are same currencies in both convertors, these from selected
+   * convertor rewrites these in actual convertor.
+   * @param convertor convertor to merge with actual one
+   * @return convertor with merged exchange rates 
+   */
+  public Convertor merge(Convertor convertor) {
+	  convertorInstanceExchangeRates.putAll(convertor.getInstanceExchangeRates());
+	  return this;
+  }
 
   /**
    * Creates new instance of convertor.
@@ -78,11 +91,33 @@
    * @throws UnknownConvertorException
    *           thrown if convertor for selected currencies has not been defined
    */
-  public static Convertor getConvertorInstance(Currency currency1, Currency currency2) throws UnknownConvertorException {
-    if (currency1 == null || currency2 == null) {
-      throw new ConvertorException("None of the currencies should be null!!!");
-    }
-    return new Convertor(currency1, currency2);
+  public static Convertor getConvertorInstance(Currency... currencies) throws UnknownConvertorException {
+   	List<Currency> currencyList = new ArrayList<Currency>();
+   	
+   	if(currencies.length < 2) {
+   		throw new ConvertorException("To get convertor instance, you have to select at least two currencies!!!");
+   	}
+
+   	for (Currency currency1 : currencies) {
+   		for (Currency currency2 : currencies) {
+   	   		if(currency1 == null || currency2 == null) {
+   	   			throw new ConvertorException("None of the currencies should be null!!!");
+   	   		}
+   	   		
+   			if(!currency1.getCurrencyCode().equals(currency2.getCurrencyCode())) {
+   				String key12 = currency1.getCurrencyCode() + currency2.getCurrencyCode();
+   				String key21 = currency2.getCurrencyCode() + currency1.getCurrencyCode();
+   				if (!(exchangeRates.containsKey(key12) && exchangeRates.containsKey(key21))) {
+   					throw new UnknownConvertorException("Selected convertor (" + currency1.getCurrencyCode() + "<->"
+   		    			+ currency2.getCurrencyCode() + ") has not defined exchange rates!!!");
+   				}
+   			}
+		}
+   		
+   		currencyList.add(currency1);
+	}
+    
+    return new Convertor(currencyList);
   }
 
   /**
@@ -125,25 +160,25 @@
    */
   private ExchangeRate getExchangeRate(Currency originalCurrency, Currency newCurrency) throws InvalidCurrencyException {
     ExchangeRate actualyUsedExchangeRate = null;
+    
+    String key = originalCurrency.getCurrencyCode() + newCurrency.getCurrencyCode();
 
-    if (originalCurrency.getCurrencyCode().equals(exchangeRate12.getOriginalCurrency().getCurrencyCode())
-        && newCurrency.getCurrencyCode().equals(exchangeRate12.getNewCurrency().getCurrencyCode())) {
-      actualyUsedExchangeRate = exchangeRate12;
-    } else if (originalCurrency.getCurrencyCode().equals(exchangeRate21.getOriginalCurrency().getCurrencyCode())
-        && newCurrency.getCurrencyCode().equals(exchangeRate21.getNewCurrency().getCurrencyCode())) {
-      actualyUsedExchangeRate = exchangeRate21;
+    if(convertorInstanceExchangeRates.containsKey(key)) {
+      actualyUsedExchangeRate = convertorInstanceExchangeRates.get(key);
     } else {
-      throw new InvalidCurrencyException("This convertor " + this
-          + " could not be used for converting selected currencies (" + originalCurrency.getCurrencyCode() + "->"
+      throw new InvalidCurrencyException("This convertor could not be used for converting selected currencies (" + originalCurrency.getCurrencyCode() + "->"
           + newCurrency.getCurrencyCode() + ") !!!");
     }
 
     return actualyUsedExchangeRate;
   }
-
-  public String toString() {
-    String currency1Code = exchangeRate12.getOriginalCurrency().getCurrencyCode();
-    String currency2Code = exchangeRate12.getNewCurrency().getCurrencyCode();
-    return "Converter [" + currency1Code + "->" + currency2Code + ", " + currency2Code + "->" + currency1Code + "]";
+  
+  /**
+   * Returns exchange rates for actual instance of convertor.
+   * @return exchange rates for actual instance of convertor
+   */
+  Hashtable<String, ExchangeRate> getInstanceExchangeRates() {
+	  return convertorInstanceExchangeRates;
   }
+  
 }