SilverioMG

	@Test
	public void getStateField_with_StateNull() {
		Person personWithStateNull = personRepository.getPersonWithStateNull();
		
		//Se lanza una Exception ya que 'personWithStateNull.getAdress().getState()' vale 'null'.
		assertThrows(NullPointerException.class,
				() -> {
					String stateNameFails = personWithStateNull.getAddress().getState().getName();
				});
		

SilverioMG

	@Test
	public void getAddressField_with_AddressNotNull() {
		Person personWithAddress = personRepository.getPersonTest();
		String street = personWithAddress.getAddress().getStreet();
		assertTrue(street != null);
				
		//En este caso se utiliza 'MethodReference' en el método 'map()' en vez de expresiones lambda pero el resultado es el mismo.
		String streetOptional = Optional.ofNullable(personWithAddress)
				.map(Person::getAddress) //Es equivalente a '.map(person -> person.getAddress())'
				.map(Address::getStreet)

SilverioMG

	@Test
	public void getAddressField_with_AddressNull() {
		Person personWithAddressNull = personRepository.getPersonWithAddressNull();
		
		//Se lanza una Exception ya que 'personWithAddressNull.address' vale 'null'.
		assertThrows(NullPointerException.class,
				() -> {
					String streetFails = personWithAddressNull.getAddress().getStreet();
				});
		

SilverioMG

package net.atopecode.optionals.repository;

import net.atopecode.optionals.model.Address;
import net.atopecode.optionals.model.Person;
import net.atopecode.optionals.model.State;

public class PersonRepository {

	private State getState() {
		return new State("State1", 12345);

SilverioMG

	public String getStateName(Person person){
		  string stateName = person?.address?.state?.getName();
		  return stateName;
	}

SilverioMG

	public String getStateName(Person person){
		  String stateName = null;  
		  
		  if(person != null){
		      Address address = person.getAddress();
		      if(address != null){
		        State state = address.getState();
		        if(state != null){
		          stateName = state.getName(); 
		        }

SilverioMG

	@Test
	public void safeGetFromOptional_with_orElseGet_ExecuteFunction_onlyWhen_emptyOptional() {
		Person person = personRepository.getPersonTest();

		//Declaro la expresión Lambda en una variable para poder reutilizarla en ambos casos.
		String modifiedName = "Modified Name";
		Supplier<String> supplierLambda = () -> {
			person.setName(modifiedName);
			System.out.println("LambdaModifiedPersonName() executed!"); //Nunca se va a ejecutar esta función lambda.
			return person.getName();

SilverioMG

	@Test
	public void safeGetFromOptional_with_orElse_alwaysExecuteFunction() {
		Person person = personRepository.getPersonTest();
		String notEmptyValue = "NotEmptyOptional";
		Optional<String> optional = Optional.ofNullable(notEmptyValue);
		
		//El objeto 'optional' no está vacío, pero al utilizar 'orElse()' para recuperar su valor, se ejecutará de todas forma la función enviada como parámetro 'getPersonName()'.
		//Para evitar que esto suceda es mejor utilizar siempre 'orElseGet()', o si se utiliza 'orElse()' indicar siempre un valor directamente en vez de una función.
		String modifiedName = "Modified Name";
		String value = optional.orElse(getModifiedPersonName(person, modifiedName));

SilverioMG

	@Test
	public void checkingOptionalValue() {
		Optional<String> emptyOptional = Optional.ofNullable(null);
		boolean isEmpty = emptyOptional.isEmpty();
		assertTrue(isEmpty);
		
		Optional<String> notEmptyOptional = Optional.ofNullable("Valor1");
		isEmpty = notEmptyOptional.isEmpty();
		assertFalse(isEmpty);
	}

SilverioMG

	@Test
	public void whenCreateFrom_NullValue_then_NullPointerException() {
		Exception ex = assertThrows(NullPointerException.class,
				() -> {
					Person person = null;
					Optional<Person> personOpt = Optional.of(person);
				});			
	}
	
	@Test