Hexagonal Architecture in Java

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/ConstantTaxRateRepository.java

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+package com.baeldung.hexagon;
+
+public class ConstantTaxRateRepository implements TaxRateRepository{
+
+	private static final double TAX_RATE = 0.13d;
+	
+	@Override
+	public double getRate() {
+		return TAX_RATE;
+	}
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/TaxCalculator.java

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+package com.baeldung.hexagon;
+
+public class TaxCalculator implements TaxService {
+
+	private TaxRateRepository taxRateRepository;
+
+	public TaxCalculator(TaxRateRepository repository) {
+		super();
+		taxRateRepository = repository;
+	}
+
+	@Override
+	public double calculateTax(Double amount) {
+		return amount * taxRateRepository.getRate();
+	}
+	
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/TaxFactory.java

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+package com.baeldung.hexagon;
+
+public class TaxFactory {
+	
+	public static TaxService getTaxService() {
+		return new TaxCalculator(getTaxRepository());
+	}
+	
+	public static TaxRateRepository getTaxRepository() {
+		return new ConstantTaxRateRepository();
+	}
+
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/TaxRateRepository.java

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+package com.baeldung.hexagon;
+
+public interface TaxRateRepository {
+
+	public double getRate();
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/TaxService.java

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+package com.baeldung.hexagon;
+
+public interface TaxService {
+
+	public double calculateTax(Double amount);
+	
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hexagon/TestTaxUser.java

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+package com.baeldung.hexagon;
+
+public class TestTaxUser {
+
+	public double calculateTax(Double amount) {
+		return TaxFactory.getTaxService().calculateTax(amount);
+	}
+
+}