31 implement factory for creation of transactions

src/main/java/millions/calculators/TransactionCalculatorFactory.java

@@ -0,0 +1,16 @@
+package millions.calculators;
+
+import millions.Share;
+
+public class TransactionCalculatorFactory {
+
+  private TransactionCalculatorFactory() {}
+
+  public TransactionCalculator createPurchaseCalculator(Share share) {
+    return new PurchaseCalculator(share);
+  }
+
+  public TransactionCalculator createSaleCalculator(Share share) {
+    return new SaleCalculator(share);
+  }
+}