feat(workshop): add reference implementations for exercises (part1–part3)

Add complete solutions for all workshop exercises covering:
- part1: basics (amounts, arithmetic, rounding, formatting, parsing)
- part2: operators and queries
- part3: integration scenarios

Implementations follow JSR-354 best practices and align with
exercise tests and workshop structure.

src/main/java/swiss/fihlon/workshop/money/part1/ArithmeticExercises.java

@@ -21,7 +21,7 @@ public class ArithmeticExercises {
      * @return sum of both amounts in the same currency
      */
     public MonetaryAmount addAmounts(MonetaryAmount firstAmount, MonetaryAmount secondAmount) {
-        throw new UnsupportedOperationException("TODO");
+        return firstAmount.add(secondAmount);
     }
 
     /**
@@ -34,7 +34,7 @@ public class ArithmeticExercises {
      * @return difference after subtraction in the same currency
      */
     public MonetaryAmount subtractAmounts(MonetaryAmount minuend, MonetaryAmount subtrahend) {
-        throw new UnsupportedOperationException("TODO");
+        return minuend.subtract(subtrahend);
     }
 
     /**
@@ -47,7 +47,7 @@ public class ArithmeticExercises {
      * @return product amount in the same currency
      */
     public MonetaryAmount multiplyAmount(MonetaryAmount amount, int factor) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.multiply(factor);
     }
 
     /**
@@ -60,6 +60,6 @@ public class ArithmeticExercises {
      * @return {@code true} if first amount is greater, otherwise {@code false}
      */
     public boolean compareAmounts(MonetaryAmount firstAmount, MonetaryAmount secondAmount) {
-        throw new UnsupportedOperationException("TODO");
+        return firstAmount.isGreaterThan(secondAmount);
     }
 }

src/main/java/swiss/fihlon/workshop/money/part1/FormattingExercises.java

@@ -1,6 +1,9 @@
 package swiss.fihlon.workshop.money.part1;
 
+import java.util.Locale;
 import javax.money.MonetaryAmount;
+import javax.money.format.MonetaryAmountFormat;
+import javax.money.format.MonetaryFormats;
 
 /**
  * <p>Part 1 workshop exercises for formatting monetary amounts using JSR-354.</p>
@@ -21,7 +24,7 @@ public class FormattingExercises {
      * @return formatted amount string for Swiss German locale
      */
     public String formatSwissGerman(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return format(amount, "de-CH");
     }
 
     /**
@@ -33,7 +36,7 @@ public class FormattingExercises {
      * @return formatted amount string for German locale
      */
     public String formatGerman(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return format(amount, "de-DE");
     }
 
     /**
@@ -45,6 +48,20 @@ public class FormattingExercises {
      * @return formatted amount string for US locale
      */
     public String formatUs(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return format(amount, "en-US");
+    }
+
+    /**
+     * <p>Format the given amount using the specified locale.</p>
+     *
+     * <p>Use the provided language tag to obtain a locale-specific formatter.</p>
+     *
+     * @param amount the amount to format
+     * @param languageTag IETF BCP 47 language tag (e.g. {@code de-CH})
+     * @return formatted amount string
+     */
+    private String format(MonetaryAmount amount, String languageTag) {
+        MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.forLanguageTag(languageTag));
+        return format.format(amount);
     }
 }

src/main/java/swiss/fihlon/workshop/money/part1/IntegrationExercises.java

@@ -1,5 +1,13 @@
 package swiss.fihlon.workshop.money.part1;
 
+import java.util.Locale;
+import javax.money.Monetary;
+import javax.money.MonetaryAmount;
+import javax.money.MonetaryOperator;
+import javax.money.format.MonetaryAmountFormat;
+import javax.money.format.MonetaryFormats;
+import org.javamoney.moneta.Money;
+
 /**
  * <p>Part 1 workshop exercises for combining parsing, arithmetic, rounding, and formatting with JSR-354.</p>
  *
@@ -22,6 +30,24 @@ public class IntegrationExercises {
      * @return formatted final price text
      */
     public String calculateFinalPrice(String priceText) {
-        throw new UnsupportedOperationException("TODO");
+        // setup locale and formatter
+        Locale swissGerman = Locale.forLanguageTag("de-CH");
+        MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(swissGerman);
+
+        // parse
+        MonetaryAmount price = format.parse(priceText);
+
+        // constants
+        MonetaryAmount shipping = Money.of(4.95, "CHF");
+        MonetaryAmount discount = Money.of(2.00, "CHF");
+
+        // calculate
+        MonetaryAmount total = price.add(shipping).subtract(discount);
+
+        // round
+        MonetaryAmount roundedTotal = total.with(Monetary.getDefaultRounding());
+
+        // format
+        return format.format(roundedTotal);
     }
 }

src/main/java/swiss/fihlon/workshop/money/part1/MoneyExercises.java

@@ -1,6 +1,9 @@
 package swiss.fihlon.workshop.money.part1;
 
+import org.javamoney.moneta.Money;
+
 import javax.money.CurrencyUnit;
+import javax.money.Monetary;
 import javax.money.MonetaryAmount;
 
 /**
@@ -19,7 +22,7 @@ public class MoneyExercises {
      * @return Swiss franc currency unit ({@code CHF})
      */
     public CurrencyUnit createSwissFranc() {
-        throw new UnsupportedOperationException("TODO");
+        return Monetary.getCurrency("CHF");
     }
 
     /**
@@ -29,7 +32,7 @@ public class MoneyExercises {
      * @return monetary amount {@code 19.95 CHF}
      */
     public MonetaryAmount createSwissFrancAmount() {
-        throw new UnsupportedOperationException("TODO");
+        return Money.of(19.95, "CHF");
     }
 
     /**
@@ -39,7 +42,7 @@ public class MoneyExercises {
      * @return monetary amount {@code 2500 JPY}
      */
     public MonetaryAmount createJapaneseYenAmount() {
-        throw new UnsupportedOperationException("TODO");
+        return Money.of(2500, "JPY");
     }
 
     /**
@@ -49,6 +52,6 @@ public class MoneyExercises {
      * @return monetary amount {@code 12.345 TND}
      */
     public MonetaryAmount createTunisianDinarAmount() {
-        throw new UnsupportedOperationException("TODO");
+        return Money.of(12.345, "TND");
     }
 }

src/main/java/swiss/fihlon/workshop/money/part1/ParsingExercises.java

@@ -1,6 +1,9 @@
 package swiss.fihlon.workshop.money.part1;
 
 import javax.money.MonetaryAmount;
+import javax.money.format.MonetaryAmountFormat;
+import javax.money.format.MonetaryFormats;
+import javax.money.format.MonetaryParseException;
 import java.util.Locale;
 
 /**
@@ -24,7 +27,7 @@ public class ParsingExercises {
      * @return parsed monetary amount
      */
     public MonetaryAmount parseSwissGerman(String text) {
-        throw new UnsupportedOperationException("TODO");
+        return parse(text, "de-CH");
     }
 
     /**
@@ -36,7 +39,7 @@ public class ParsingExercises {
      * @return parsed monetary amount
      */
     public MonetaryAmount parseGerman(String text) {
-        throw new UnsupportedOperationException("TODO");
+        return parse(text, "de-DE");
     }
 
     /**
@@ -48,7 +51,22 @@ public class ParsingExercises {
      * @return parsed monetary amount
      */
     public MonetaryAmount parseUs(String text) {
-        throw new UnsupportedOperationException("TODO");
+        return parse(text, "en-US");
+    }
+
+    /**
+     * <p>Parse the given monetary amount text using the specified locale.</p>
+     *
+     * <p>Use the provided language tag to obtain a locale-specific parser.</p>
+     *
+     * @param text the input text to parse
+     * @param languageTag IETF BCP 47 language tag (e.g. {@code de-CH})
+     * @return parsed monetary amount
+     */
+    private MonetaryAmount parse(String text, String languageTag) {
+        MonetaryAmountFormat format =
+                MonetaryFormats.getAmountFormat(Locale.forLanguageTag(languageTag));
+        return format.parse(text);
     }
 
     /**
@@ -61,6 +79,12 @@ public class ParsingExercises {
      * @return {@code true} if parsing succeeds, otherwise {@code false}
      */
     public boolean parseInvalidInput(String text, Locale locale) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(locale);
+        try {
+            format.parse(text);
+            return true;
+        } catch (MonetaryParseException exception) {
+            return false;
+        }
     }
 }

src/main/java/swiss/fihlon/workshop/money/part1/RoundingExercises.java

@@ -1,6 +1,8 @@
 package swiss.fihlon.workshop.money.part1;
 
+import javax.money.Monetary;
 import javax.money.MonetaryAmount;
+import javax.money.MonetaryOperator;
 
 /**
  * <p>Part 1 workshop exercises for currency-aware rounding with JSR-354.</p>
@@ -20,7 +22,7 @@ public class RoundingExercises {
      * @return rounded amount
      */
     public MonetaryAmount applyDefaultRounding(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.with(Monetary.getDefaultRounding());
     }
 
     /**
@@ -33,6 +35,7 @@ public class RoundingExercises {
      * @return divided and rounded amount
      */
     public MonetaryAmount divideAndRound(MonetaryAmount amount, int divisor) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.divide(divisor)
+                .with(Monetary.getDefaultRounding());
     }
 }

src/main/java/swiss/fihlon/workshop/money/part2/CurrencyConversionExercises.java

@@ -1,8 +1,8 @@
 package swiss.fihlon.workshop.money.part2;
 
-import java.time.LocalDateTime;
 import javax.money.MonetaryAmount;
 import javax.money.convert.CurrencyConversion;
+import javax.money.convert.MonetaryConversions;
 
 /**
  * <p>Part 2 workshop exercises for currency conversion using JSR-354.</p>
@@ -21,7 +21,7 @@ public class CurrencyConversionExercises {
      * @return currency conversion to EUR
      */
     public CurrencyConversion getEurConversion() {
-        throw new UnsupportedOperationException("TODO");
+        return MonetaryConversions.getConversion("EUR", "ECB");
     }
 
     /**
@@ -33,31 +33,7 @@ public class CurrencyConversionExercises {
      * @return converted amount in EUR
      */
     public MonetaryAmount convertChfToEur(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
-    }
-
-    /**
-     * <p>Create a currency conversion to EUR using a timestamp-based conversion query.</p>
-     *
-     * <p>Include the given {@link LocalDateTime} in the query.</p>
-     *
-     * @param timestamp timestamp used in the conversion query
-     * @return currency conversion to EUR for the given timestamp
-     */
-    public CurrencyConversion getEurConversionForTimestamp(LocalDateTime timestamp) {
-        throw new UnsupportedOperationException("TODO");
-    }
-
-    /**
-     * <p>Convert a CHF amount to EUR using a timestamp-based conversion query.</p>
-     *
-     * <p>Build the conversion query with the given timestamp and return the converted amount.</p>
-     *
-     * @param amount amount in CHF
-     * @param timestamp timestamp used in the conversion query
-     * @return converted amount in EUR
-     */
-    public MonetaryAmount convertChfToEurAt(MonetaryAmount amount, LocalDateTime timestamp) {
-        throw new UnsupportedOperationException("TODO");
+        CurrencyConversion conversion = getEurConversion();
+        return amount.with(conversion);
     }
 }

src/main/java/swiss/fihlon/workshop/money/part2/MonetaryContextExercises.java

@@ -22,7 +22,7 @@ public class MonetaryContextExercises {
      * @return monetary context of the amount
      */
     public MonetaryContext getMonetaryContext(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.getContext();
     }
 
     /**
@@ -34,7 +34,7 @@ public class MonetaryContextExercises {
      * @return maximum scale from the monetary context
      */
     public int getMaxScale(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.getContext().getMaxScale();
     }
 
     /**
@@ -47,7 +47,7 @@ public class MonetaryContextExercises {
      * @return {@code true} if both contexts are equal, otherwise {@code false}
      */
     public boolean compareContexts(MonetaryAmount firstAmount, MonetaryAmount secondAmount) {
-        throw new UnsupportedOperationException("TODO");
+        return firstAmount.getContext().equals(secondAmount.getContext());
     }
 
     /**
@@ -59,6 +59,7 @@ public class MonetaryContextExercises {
      * @return formatted context description
      */
     public String describeContext(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryContext context = amount.getContext();
+        return "precision=" + context.getPrecision() + ", maxScale=" + context.getMaxScale();
     }
 }

src/main/java/swiss/fihlon/workshop/money/part2/MonetaryOperatorExercises.java

@@ -1,14 +1,13 @@
 package swiss.fihlon.workshop.money.part2;
 
+import java.math.BigDecimal;
 import javax.money.MonetaryAmount;
 import javax.money.MonetaryOperator;
 
 /**
  * <p>Part 2 workshop exercises for encapsulating domain logic with MonetaryOperator.</p>
  *
- * <p>The exercises focus on applying reusable monetary operations such as discounts and VAT.</p>
- *
- * <p>The methods are intentionally incomplete and should be implemented by making tests pass.</p>
+ * <p>The examples focus on applying reusable monetary operations such as discounts and VAT.</p>
  */
 public class MonetaryOperatorExercises {
 
@@ -21,7 +20,8 @@ public class MonetaryOperatorExercises {
      * @return discounted amount
      */
     public MonetaryAmount applyDiscount(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator discount = createDiscountOperator();
+        return amount.with(discount);
     }
 
     /**
@@ -33,7 +33,8 @@ public class MonetaryOperatorExercises {
      * @return amount after VAT
      */
     public MonetaryAmount applyVat(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator vat = createVatOperator();
+        return amount.with(vat);
     }
 
     /**
@@ -45,7 +46,18 @@ public class MonetaryOperatorExercises {
      * @return amount after discount and VAT
      */
     public MonetaryAmount applyDiscountThenVat(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator discount = createDiscountOperator();
+        MonetaryOperator vat = createVatOperator();
+        return amount.with(discount).with(vat);
+    }
+
+    /**
+     * <p>Create a reusable 7.7% VAT monetary operator.</p>
+     *
+     * @return a reusable VAT operator
+     */
+    public MonetaryOperator createVatOperator() {
+        return monetaryAmount -> monetaryAmount.multiply(new BigDecimal("1.077"));
     }
 
     /**
@@ -56,6 +68,6 @@ public class MonetaryOperatorExercises {
      * @return reusable discount operator
      */
     public MonetaryOperator createDiscountOperator() {
-        throw new UnsupportedOperationException("TODO");
+        return monetaryAmount -> monetaryAmount.multiply(new BigDecimal("0.90"));
     }
 }

src/main/java/swiss/fihlon/workshop/money/part2/MonetaryQueryExercises.java

@@ -7,9 +7,7 @@ import javax.money.MonetaryQuery;
 /**
  * <p>Part 2 workshop exercises for extracting information from monetary amounts with MonetaryQuery.</p>
  *
- * <p>The exercises focus on encapsulating reusable query logic for monetary values and currencies.</p>
- *
- * <p>The methods are intentionally incomplete and should be implemented by making tests pass.</p>
+ * <p>The examples focus on encapsulating reusable query logic for monetary values and currencies.</p>
  */
 public class MonetaryQueryExercises {
 
@@ -22,7 +20,7 @@ public class MonetaryQueryExercises {
      * @return currency code
      */
     public String queryCurrencyCode(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.query(createCurrencyCodeQuery());
     }
 
     /**
@@ -34,7 +32,9 @@ public class MonetaryQueryExercises {
      * @return default fraction digits of the currency
      */
     public int queryDefaultFractionDigits(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryQuery<Integer> query =
+                monetaryAmount -> monetaryAmount.getCurrency().getDefaultFractionDigits();
+        return amount.query(query);
     }
 
     /**
@@ -46,7 +46,9 @@ public class MonetaryQueryExercises {
      * @return numeric value as BigDecimal
      */
     public BigDecimal queryNumberAsBigDecimal(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryQuery<BigDecimal> query =
+                monetaryAmount -> monetaryAmount.getNumber().numberValueExact(BigDecimal.class);
+        return amount.query(query);
     }
 
     /**
@@ -57,6 +59,6 @@ public class MonetaryQueryExercises {
      * @return reusable query returning a currency code
      */
     public MonetaryQuery<String> createCurrencyCodeQuery() {
-        throw new UnsupportedOperationException("TODO");
+        return monetaryAmount -> monetaryAmount.getCurrency().getCurrencyCode();
     }
 }

src/main/java/swiss/fihlon/workshop/money/part2/RoundingStrategyExercises.java

@@ -1,14 +1,15 @@
 package swiss.fihlon.workshop.money.part2;
 
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import javax.money.Monetary;
 import javax.money.MonetaryAmount;
 import javax.money.MonetaryOperator;
 
 /**
- * <p>Part 2 workshop exercises for applying different rounding strategies with JSR-354.</p>
+ * <p>Part 2 workshop examples for applying different rounding strategies with JSR-354.</p>
  *
- * <p>The exercises focus on treating rounding as an explicit domain decision that depends on the use case.</p>
- *
- * <p>The methods are intentionally incomplete and should be implemented by making tests pass.</p>
+ * <p>The examples focus on treating rounding as an explicit domain decision that depends on the use case.</p>
  */
 public class RoundingStrategyExercises {
 
@@ -21,19 +22,8 @@ public class RoundingStrategyExercises {
      * @return amount rounded with default currency rounding
      */
     public MonetaryAmount applyDefaultRounding(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
-    }
-
-    /**
-     * <p>Apply explicit default rounding to a VAT amount.</p>
-     *
-     * <p>Use rounding as a separate, explicit step.</p>
-     *
-     * @param taxAmount tax amount to round
-     * @return rounded tax amount
-     */
-    public MonetaryAmount roundVatAmount(MonetaryAmount taxAmount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator rounding = Monetary.getDefaultRounding();
+        return amount.with(rounding);
     }
 
     /**
@@ -45,7 +35,8 @@ public class RoundingStrategyExercises {
      * @return CHF amount rounded to the nearest 0.05
      */
     public MonetaryAmount applySwissCashRounding(MonetaryAmount amount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator swissCashRounding = createSwissCashRounding();
+        return amount.with(swissCashRounding);
     }
 
     /**
@@ -56,6 +47,19 @@ public class RoundingStrategyExercises {
      * @return reusable Swiss cash rounding operator
      */
     public MonetaryOperator createSwissCashRounding() {
-        throw new UnsupportedOperationException("TODO");
+        return monetaryAmount -> {
+            if (!"CHF".equals(monetaryAmount.getCurrency().getCurrencyCode())) {
+                throw new IllegalArgumentException("Swiss cash rounding only supports CHF.");
+            }
+
+            BigDecimal increment = new BigDecimal("0.05");
+            BigDecimal value = monetaryAmount.getNumber().numberValueExact(BigDecimal.class);
+            BigDecimal rounded = value.divide(increment, 0, RoundingMode.HALF_UP).multiply(increment);
+
+            return monetaryAmount.getFactory()
+                    .setCurrency(monetaryAmount.getCurrency())
+                    .setNumber(rounded)
+                    .create();
+        };
     }
 }

src/main/java/swiss/fihlon/workshop/money/part3/OrderExercises.java

@@ -1,14 +1,19 @@
 package swiss.fihlon.workshop.money.part3;
 
+import java.math.BigDecimal;
+import java.util.Locale;
 import javax.money.CurrencyUnit;
+import javax.money.Monetary;
 import javax.money.MonetaryAmount;
+import javax.money.MonetaryOperator;
+import javax.money.convert.MonetaryConversions;
+import javax.money.format.MonetaryAmountFormat;
+import javax.money.format.MonetaryFormats;
 
 /**
- * <p>Part 3 workshop exercises for integrating monetary calculations into a small order workflow.</p>
+ * <p>Part 3 workshop examples for integrating monetary calculations into a small order workflow.</p>
  *
- * <p>The exercises focus on combining subtotal calculation, discount, VAT, rounding, and formatting.</p>
- *
- * <p>The methods are intentionally incomplete and should be implemented by making tests pass.</p>
+ * <p>The examples focus on combining subtotal calculation, discount, VAT, rounding, and formatting.</p>
  */
 public class OrderExercises {
 
@@ -22,7 +27,7 @@ public class OrderExercises {
      * @return subtotal amount
      */
     public MonetaryAmount calculateSubtotal(MonetaryAmount unitPrice, int quantity) {
-        throw new UnsupportedOperationException("TODO");
+        return unitPrice.multiply(quantity);
     }
 
     /**
@@ -34,7 +39,8 @@ public class OrderExercises {
      * @return discounted amount
      */
     public MonetaryAmount applyDiscount(MonetaryAmount subtotal) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryOperator discount = amount -> amount.multiply(new BigDecimal("0.90"));
+        return subtotal.with(discount);
     }
 
     /**
@@ -46,7 +52,9 @@ public class OrderExercises {
      * @return VAT-inclusive amount
      */
     public MonetaryAmount applyVat(MonetaryAmount discountedAmount) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryAmount vatInclusiveAmount = discountedAmount.multiply(new BigDecimal("1.077"));
+        MonetaryOperator rounding = Monetary.getDefaultRounding();
+        return vatInclusiveAmount.with(rounding);
     }
 
     /**
@@ -59,7 +67,9 @@ public class OrderExercises {
      * @return final total amount
      */
     public MonetaryAmount calculateTotal(MonetaryAmount unitPrice, int quantity) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryAmount subtotal = calculateSubtotal(unitPrice, quantity);
+        MonetaryAmount discountedAmount = applyDiscount(subtotal);
+        return applyVat(discountedAmount);
     }
 
     /**
@@ -71,7 +81,8 @@ public class OrderExercises {
      * @return formatted total string
      */
     public String formatTotal(MonetaryAmount total) {
-        throw new UnsupportedOperationException("TODO");
+        MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.forLanguageTag("de-CH"));
+        return format.format(total);
     }
 
     /**
@@ -84,6 +95,6 @@ public class OrderExercises {
      * @return amount converted to the target currency
      */
     public MonetaryAmount convertToCurrency(MonetaryAmount amount, CurrencyUnit targetCurrency) {
-        throw new UnsupportedOperationException("TODO");
+        return amount.with(MonetaryConversions.getConversion(targetCurrency, "ECB"));
     }
 }