diff -r 09d690bb97f6 -r 58ec6da75f6f task4/solution11/src/org/apidesign/apifest08/currency/Computer.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/task4/solution11/src/org/apidesign/apifest08/currency/Computer.java	Sat Oct 11 23:38:46 2008 +0200
@@ -0,0 +1,61 @@
+package org.apidesign.apifest08.currency;
+
+/**
+ * Interface declaring method for computing conversion.
+ * 
+ * Because of a vague definition of currency amount's type,
+ * the interface has a generic type.
+ * 
+ * @author ked
+ * @see http://wiki.apidesign.org/wiki/APIDesignPatterns:ResponseReply
+ */
+interface Computer<AmountType> {
+
+    void compute(ComputerRequest<AmountType> request, ComputerResponse<AmountType> response);
+
+    final class ComputerRequest<AmountType> {
+
+        private AmountType input;
+        private AmountType inputCurrencyRatio;
+        private AmountType outputCurrencyRatio;
+
+        AmountType getInput() {
+            return input;
+        }
+
+        void setInput(AmountType input) {
+            this.input = input;
+        }
+
+        AmountType getInputCurrencyRatio() {
+            return inputCurrencyRatio;
+        }
+
+        void setInputCurrencyRatio(AmountType inputCurrencyRatio) {
+            this.inputCurrencyRatio = inputCurrencyRatio;
+        }
+
+        AmountType getOutputCurrencyRatio() {
+            return outputCurrencyRatio;
+        }
+
+        void setOutputCurrencyRatio(AmountType outputCurrencyRatio) {
+            this.outputCurrencyRatio = outputCurrencyRatio;
+        }
+    }
+
+    final class ComputerResponse<AmountType> {
+
+        private AmountType result;
+
+        AmountType getResult() {
+            return result;
+        }
+
+        void setResult(AmountType result) {
+            this.result = result;
+        }
+    }
+    
+    
+}
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