Person.java

package com.tomaszpolanski.androidsandbox.models;

import com.tomaszpolanski.androidsandbox.utils.option.Option;

public class Person {

    public final String Name;

    private Person(String name) {
        Name = name;
    }

    public static Option<Person> create(final String name) {
        return Option.asOption(name)
                     .filter(personName -> personName.length() != 0)
                     .filter(personName -> personName.length() < 20)
                     .map(personName -> new Person(personName));
    }
}

PersonDetails.java

package com.tomaszpolanski.androidsandbox.models;

import com.tomaszpolanski.androidsandbox.utils.option.Option;

public class PersonDetails {
    public final String FirstName;
    public final String LastName;
    public final Option<PersonDetails> Boss;

    private PersonDetails(final String firstName,
                          final String lastName,
                          final Option<PersonDetails> boss) {
        FirstName = firstName;
        LastName = lastName;
        Boss = boss;
    }

    public static Option<PersonDetails> create(final String firstName,
                                               final String lastName,
                                               final Option<PersonDetails> significantOther) {
        return Option.asOption(firstName)
                     .flatMap(first -> Option.asOption(lastName)
                                             .map(last -> new PersonDetails(first, last, significantOther)));
    }

    public static Option<PersonDetails> createCEO(final String firstName,
                                                  final String lastName) {
        return create(firstName, lastName, Option.NONE);
    }
}

TestPerson.java

package com.tomaszpolanski.androidsandbox;

import com.tomaszpolanski.androidsandbox.models.Person;
import com.tomaszpolanski.androidsandbox.models.PersonDetails;
import com.tomaszpolanski.androidsandbox.utils.option.Option;

public class TestPerson {

    private static void print(final String message, final Person person) {
        System.console().printf(message + person.Name);
    }

    private static void printPerson(final String name) {
        Option<Person> personOption = Person.create(name);

        if (personOption != Option.NONE) {
            Person person = personOption.get();
            print("Person exits: ", person);
        } else {
            System.console().printf("Was not able to create person with name: " + name);
        }
    }


    private static void printPersonIfJohn(final String name) {
        Option<Person> johnOption = Person.create(name)
                                          .filter(personName -> personName.equals("John"));

        if (johnOption != Option.NONE) {
            Person person = johnOption.get();
            print("Hi John! ", person);
        } else {
            System.console().printf("That's not John: " + name);
        }
    }


    // Pattern matching

    private static void betterPrintPerson(final String name) {
        Person.create(name)
              .match(
                      person -> print("Person exits: ", person),
                      () -> System.console().printf("Was not able to create person with name: " + name));
    }


    // More advance


    private static void printPersonDetails(final String first, final String last) {
        PersonDetails.createCEO(first, last)
                     .map(details -> "First name: " + details.FirstName + ", last name: " + details.LastName)
                     .iter(formattedDetails -> System.console().printf(formattedDetails));
    }

    private static String getBoss(Option<PersonDetails> firstPersonOption) {
        return firstPersonOption.flatMap(firstPerson -> firstPerson.Boss
                .map(secondPerson -> "Boss: " + secondPerson.FirstName + ", " + secondPerson.LastName))
                                .orDefault(() -> "No one here");
    }


    public static void main() {
        printPerson("Kevin"); // valid
        printPerson(""); //too short
        printPerson(null); // null
        printPerson("kalsdjfkljqewkfjadslkjfkleqjwjkdlsjflkasdjfkldjsaklfjadslkfjasdklfjasdlfjksd"); // too long

        printPersonIfJohn("Mike");
        printPersonIfJohn("John");

        betterPrintPerson("Tomek");
        betterPrintPerson("");
        betterPrintPerson(null);

        printPersonDetails("John", "Doe");
        printPersonDetails("John", null);

        Option<PersonDetails> boss = PersonDetails.createCEO("Bill", "Gates");
        Option<PersonDetails> john = PersonDetails.create("John", "Doe", boss);

        System.console().printf(getBoss(john));
        System.console().printf(getBoss(boss));
    }

}