Esempi con gli Optional

modern-java/src/main/java/org/gym/fp/moderjava/OptionalTest.java

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+package org.gym.fp.moderjava;
+
+import org.gym.fp.moderjava.optional.Car;
+import org.gym.fp.moderjava.optional.Insurance;
+import org.gym.fp.moderjava.optional.Person;
+
+import java.util.Optional;
+
+import static java.lang.System.out;
+
+public class OptionalTest {
+
+    public static void main(String[] args) {
+        Insurance myInsurance1 = new Insurance("Allianz");
+        Car myCar1 = new Car(Optional.of(myInsurance1));
+        Person person1 = new Person(Optional.of(myCar1));
+        out.println("My insurance's name is " + getCarInsuranceName(Optional.ofNullable(person1)));
+        out.println("----------------------------------------");
+        Car myCar2 = new Car(Optional.ofNullable(null));
+        Person person2 = new Person(Optional.ofNullable(myCar2));
+        out.println("My insurance's name is " + getCarInsuranceName(Optional.ofNullable(person2)));
+        out.println("----------------------------------------");
+    }
+
+    static String getCarInsuranceName(Optional<Person> maybePerson) {
+        return maybePerson
+                .flatMap(Person::getCar)
+                .flatMap(Car::getInsurance)
+                .map(Insurance::getName)
+                .orElse("Unknown");
+    }
+
+}

modern-java/src/main/java/org/gym/fp/moderjava/optional/Car.java

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+package org.gym.fp.moderjava.optional;
+
+import lombok.Getter;
+import lombok.ToString;
+
+import java.util.Optional;
+
+@ToString
+public class Car {
+
+    @Getter
+    private Optional<Insurance> insurance;
+
+    public Car(Optional<Insurance> insurance) {
+        this.insurance = insurance;
+    }
+}

modern-java/src/main/java/org/gym/fp/moderjava/optional/Insurance.java

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+package org.gym.fp.moderjava.optional;
+
+import lombok.Getter;
+import lombok.ToString;
+
+@ToString
+public class Insurance {
+
+    @Getter
+    private String name;
+
+    public Insurance(String name) {
+        this.name = name;
+    }
+
+}

modern-java/src/main/java/org/gym/fp/moderjava/optional/Person.java

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+package org.gym.fp.moderjava.optional;
+
+import lombok.Getter;
+import lombok.ToString;
+
+import java.util.Optional;
+
+@ToString
+public class Person {
+
+    @Getter
+    private Optional<Car> car;
+
+    public Person(Optional<Car> car) {
+        this.car = car;
+    }
+
+}