diff -r 251d0ed461fb -r 58ec6da75f6f task4/solution07/src/org/apidesign/apifest08/currency/TableConvertor.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/task4/solution07/src/org/apidesign/apifest08/currency/TableConvertor.java	Sat Oct 11 23:38:46 2008 +0200
@@ -0,0 +1,71 @@
+package org.apidesign.apifest08.currency;
+
+import java.util.Currency;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A {@link Convertor} that works from a pre-set conversion table.
+ * First use {@link #putIntoTable(org.apidesign.apifest08.currency.ConversionRate)} to set the conversion table.
+ * Then invoke the {@link #convert(org.apidesign.apifest08.currency.Convertor.ConversionRequest)} method as many times as you wish.
+ * @author jdvorak
+ */
+public class TableConvertor implements Convertor {
+
+    private final Map<Currency, Map<Currency, ConversionRate>> conversionTable = new HashMap<Currency, Map<Currency, ConversionRate>>();
+    
+    public TableConvertor() {
+    }
+
+    /**
+     * Puts a rate into the table.
+     * @param rate
+     */
+    public void putIntoTable( final ConversionRate rate ) {
+        final Currency srcCurrency = rate.getSrcUnitAmount().getCurrency();
+        final Currency tgtCurrency = rate.getTgtUnitAmount().getCurrency();
+        synchronized ( conversionTable ) {
+            Map<Currency, ConversionRate> targetTable = conversionTable.get( srcCurrency );
+            if ( targetTable == null ) {
+                targetTable = new HashMap<Currency, ConversionRate>();
+                conversionTable.put( srcCurrency, targetTable );
+            }
+            targetTable.put( tgtCurrency, rate );
+        }
+    }
+    
+    /**
+     * Carries out the conversion.
+     * If the table does not contain a conversion from the source currency to the target one,
+     * a {@link ConversionResult} is returned that has null netAmount.
+     * This implementation works with any {@link ConversionRequest}, it won't throw {@link IllegalRequestSubtypeException}.
+     * @param req the conversion request
+     * @return the conversion result
+     */
+    public ConversionResult convert( final ConversionRequest req ) {
+        final Currency srcCurrency = req.getSrcAmount().getCurrency();
+        final Currency tgtCurrency = req.getTgtCurrency();
+        final ConversionRate rate = findConversionRate( srcCurrency, tgtCurrency );
+        if ( rate != null ) {
+            final MonetaryAmount tgtAmount = rate.convert( req.getSrcAmount() );
+            return new ConversionResult( tgtAmount );
+        } else {
+            return new ConversionResult( null );    // did not find the pair of currencies in the table
+        }
+    }
+
+    /**
+     * Looks up the conversion between the given currencies in the table.
+     * @param srcCurrency the source currency
+     * @param tgtCurrency the target currency
+     * @return the conversion rate; null means no conversion between the currencies was found in the table
+     */
+    protected ConversionRate findConversionRate( final Currency srcCurrency, final Currency tgtCurrency ) {
+        synchronized ( conversionTable ) {
+            final Map<Currency, ConversionRate> targetTable = conversionTable.get(srcCurrency);
+            final ConversionRate rate = (targetTable != null) ? targetTable.get(tgtCurrency) : null;
+            return rate;
+        }
+    }
+
+}