added solution with tariff options as enum and map

src/main/java/com/pfefferminzia/petinsurance/Main.java

@@ -2,14 +2,12 @@ package com.pfefferminzia.petinsurance;
 
 import java.time.LocalDate;
 import com.pfefferminzia.petinsurance.animals.Dog;
-import com.pfefferminzia.petinsurance.calculations.Calculations;
+import com.pfefferminzia.petinsurance.calculations.InsuranceContract;
 import com.pfefferminzia.petinsurance.tariffs.Tariff;
 
 public class Main {
     public static void main(String[] args) {
-        Dog dog = new Dog(LocalDate.of(2020, 4, 14), "Husky");
-        Calculations calc = new Calculations();
-        System.out.println(calc.calculateInsuranceSum(dog, Tariff.OPTIMAL, LocalDate.of(2026, 1, 2)));
-        
+        System.out.println(new InsuranceContract(new Dog(LocalDate.of(2025, 1, 1), "Dackel"),
+                LocalDate.of(2026, 1, 1), Tariff.OPTIMAL));
     }
 }

src/main/java/com/pfefferminzia/petinsurance/animals/Animal.java

@@ -4,7 +4,12 @@ import java.math.BigDecimal;
 import java.time.LocalDate;
 
 public sealed interface Animal permits Dog, Cat, SmallAnimal {
-    
+
     LocalDate birthday();
+
     BigDecimal getBaseInsuranceSum();
+
+    default BigDecimal getPremiumAdjustment() {
+        return BigDecimal.ZERO;
+    }
 }

src/main/java/com/pfefferminzia/petinsurance/animals/Dog.java

@@ -2,6 +2,7 @@ package com.pfefferminzia.petinsurance.animals;
 
 import java.math.BigDecimal;
 import java.time.LocalDate;
+import com.pfefferminzia.petinsurance.tariffs.BreedPremiumAdjustment;
 
 public final record Dog(LocalDate birthday, String breed) implements Animal {
 
@@ -9,4 +10,9 @@ public final record Dog(LocalDate birthday, String breed) implements Animal {
     public BigDecimal getBaseInsuranceSum() {
         return BigDecimal.valueOf(2500.0);
     }
+
+    @Override
+    public BigDecimal getPremiumAdjustment() {
+        return BreedPremiumAdjustment.forBreed(breed);
+    }
 }

src/main/java/com/pfefferminzia/petinsurance/calculations/CalculationResult.java

@@ -0,0 +1,5 @@
+package com.pfefferminzia.petinsurance.calculations;
+
+import java.math.BigDecimal;
+
+public record CalculationResult(BigDecimal insuranceSum, BigDecimal yearlyPremium) {}

src/main/java/com/pfefferminzia/petinsurance/calculations/Calculations.java

@@ -2,18 +2,43 @@ package com.pfefferminzia.petinsurance.calculations;
 
 import java.math.BigDecimal;
 import java.time.LocalDate;
-import com.pfefferminzia.petinsurance.animals.Animal;
+import java.time.temporal.ChronoUnit;
+import com.pfefferminzia.petinsurance.tariffs.AgeTariff;
 import com.pfefferminzia.petinsurance.tariffs.Tariff;
 
 public class Calculations {
 
-    public BigDecimal calculateInsuranceSum(Animal animal, Tariff tariff,
-            LocalDate insuranceStartDate) {
+    public CalculationResult result(InsuranceContract contract) {
 
-        TariffValidator validator = new TariffValidator(insuranceStartDate);
-        validator.checkTariffAvailability(tariff);
-        
-        BigDecimal insuranceBaseSum = animal.getBaseInsuranceSum();
-        return insuranceBaseSum.multiply(tariff.getRate());
+        Tariff tariff = contract.tariff();
+
+        BigDecimal insuranceSum =
+                getInsuranceSum(contract.animal().getBaseInsuranceSum(), tariff.getRate());
+
+        BigDecimal ageFactor =
+                ageFactorLookup(contract.animal().birthday(), contract.insuranceStartDate());
+
+
+        BigDecimal breedPremiumAdjustment = contract.animal().getPremiumAdjustment();
+
+        BigDecimal yearlyPremium = insuranceSum.multiply(ageFactor)
+                .multiply(BigDecimal.ONE.add(breedPremiumAdjustment));
+
+        return new CalculationResult(insuranceSum, yearlyPremium);
+    }
+
+    BigDecimal getInsuranceSum(BigDecimal baseInsuranceSum, BigDecimal tariffRate) {
+        return baseInsuranceSum.multiply(tariffRate);
+    }
+
+    BigDecimal ageFactorLookup(LocalDate birthday, LocalDate insuranceStartDate) {
+        if (insuranceStartDate.isBefore(birthday)) {
+            throw new IllegalArgumentException(
+                    "Start der Versicherung kann nicht vor dem Geburtstag sein.");
+        }
+
+        long exactYears = ChronoUnit.YEARS.between(birthday, insuranceStartDate);
+
+        return AgeTariff.getFactorForAge(Math.toIntExact(exactYears));
     }
 }

src/main/java/com/pfefferminzia/petinsurance/calculations/InsuranceContract.java

@@ -0,0 +1,29 @@
+package com.pfefferminzia.petinsurance.calculations;
+
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.List;
+import com.pfefferminzia.petinsurance.animals.Animal;
+import com.pfefferminzia.petinsurance.exception.InvalidInsuranceContractException;
+import com.pfefferminzia.petinsurance.tariffs.Tariff;
+
+public record InsuranceContract(Animal animal, LocalDate insuranceStartDate, Tariff tariff) {
+
+    private static final LocalDate PREMIUM_AVAILABLE_FROM = LocalDate.of(2026, 7, 1);
+
+    public InsuranceContract {
+        List<String> violations = new ArrayList<>();
+
+        if (animal.birthday().isAfter(insuranceStartDate)) {
+            violations.add("Start der Versicherung kann nicht vor dem Geburtstag sein.");
+        }
+
+        if (insuranceStartDate.isBefore(PREMIUM_AVAILABLE_FROM) && tariff == Tariff.PREMIUM) {
+            violations.add("Die Premium Tarifvariante ist nicht vor dem 1. Juli 2026 verfügbar.");
+        }
+
+        if (!violations.isEmpty()) {
+            throw new InvalidInsuranceContractException(violations);
+        }
+    }
+}

src/main/java/com/pfefferminzia/petinsurance/calculations/TariffValidator.java

@@ -1,21 +0,0 @@
-package com.pfefferminzia.petinsurance.calculations;
-
-import java.time.LocalDate;
-import com.pfefferminzia.petinsurance.exception.TariffNotAvailableException;
-import com.pfefferminzia.petinsurance.tariffs.Tariff;
-
-public class TariffValidator {
-    private LocalDate insuranceStartDate;
-
-    public TariffValidator(LocalDate insuranceStartDate) {
-        this.insuranceStartDate = insuranceStartDate;
-    }
-
-    public boolean checkTariffAvailability(Tariff tariff) {
-        if (insuranceStartDate.isBefore(LocalDate.of(2026, 7, 1)) && tariff == Tariff.PREMIUM) {
-            throw new TariffNotAvailableException(
-                    "Die Premium Tarifvariante ist nicht vor dem 1. Juli 2026 verfügbar.");
-        }
-        return true;
-    }
-}

src/main/java/com/pfefferminzia/petinsurance/exception/InvalidInsuranceContractException.java

@@ -0,0 +1,17 @@
+package com.pfefferminzia.petinsurance.exception;
+
+import java.util.List;
+
+public class InvalidInsuranceContractException extends RuntimeException {
+
+    private final List<String> violations;
+
+    public InvalidInsuranceContractException(List<String> violations) {
+        super(String.join("\n", violations));
+        this.violations = List.copyOf(violations);
+    }
+
+    public List<String> getViolations() {
+        return violations;
+    }
+}

src/main/java/com/pfefferminzia/petinsurance/exception/TariffNotAvailableException.java

@@ -1,8 +0,0 @@
-package com.pfefferminzia.petinsurance.exception;
-
-public class TariffNotAvailableException extends RuntimeException {
-
-    public TariffNotAvailableException(String message) {
-        super(message);
-    }
-}

src/main/java/com/pfefferminzia/petinsurance/tariffs/AgeTariff.java

@@ -0,0 +1,27 @@
+package com.pfefferminzia.petinsurance.tariffs;
+
+import java.math.BigDecimal;
+
+public enum AgeTariff {
+    UP_TO_TWO(2, new BigDecimal("0.2")), UP_TO_FIVE(5, new BigDecimal("0.25")), UP_TO_SEVEN(7,
+            new BigDecimal("0.28")), OVER_SEVEN(Integer.MAX_VALUE, new BigDecimal("0.3"));
+
+    private final int maxAge;
+
+    private final BigDecimal factor;
+
+    private AgeTariff(int maxAge, BigDecimal factor) {
+        this.maxAge = maxAge;
+        this.factor = factor;
+    }
+
+    public static BigDecimal getFactorForAge(int age) {
+        for (AgeTariff rate : values()) {
+            if (age <= rate.maxAge) {
+                return rate.factor;
+            }
+        }
+        throw new AssertionError("Unexpected age: " + age);
+    }
+
+}

src/main/java/com/pfefferminzia/petinsurance/tariffs/BreedPremiumAdjustment.java

@@ -0,0 +1,18 @@
+package com.pfefferminzia.petinsurance.tariffs;
+
+import java.math.BigDecimal;
+import java.util.Map;
+
+public final class BreedPremiumAdjustment {
+    
+    private static final Map<String, BigDecimal> ADJUSTMENTS = Map.of(
+        "Dackel", new BigDecimal("-0.1"),
+        "Bernhardiner", new BigDecimal("0.1")
+    );
+
+    public static BigDecimal forBreed(String breed) {
+        return ADJUSTMENTS.getOrDefault(breed, BigDecimal.ZERO);
+    }
+
+    private BreedPremiumAdjustment() {}
+}

src/main/java/com/pfefferminzia/petinsurance/tariffs/Tariff.java

@@ -3,7 +3,7 @@ package com.pfefferminzia.petinsurance.tariffs;
 import java.math.BigDecimal;
 
 public enum Tariff {
-    KOMPAKT(BigDecimal.ONE), OPTIMAL(BigDecimal.valueOf(1.2)), PREMIUM(BigDecimal.valueOf(1.4));
+    KOMPAKT(BigDecimal.ONE), OPTIMAL(new BigDecimal("1.2")), PREMIUM(new BigDecimal("1.4"));
 
     private final BigDecimal rate;