Java Optional | How and When to use it

How to use Optional

How to create an Optional

• Use Optional.of(value) when you are certain that the value is non-null.

• Use Optional.ofNullable(value) when the value might be null.

String nonNullValue = "Hello";
Optional String optional1 = Optional.of(nonNullValue);

String nullableValue = null;
Optional<String> optional2 = Optional.ofNullable(nullableValue);

How to access the value of an Optional

• Use get() cautiously; it throws NoSuchElementException if the value is not present.

• Prefer orElse(defaultValue) or orElseGet(() -> defaultValue) to provide a default value when the original value is not present.

Optional<String> optional = // ...

// Avoid using get() without checking isPresent()
String value = optional.orElse("Default");

How to avoid null checks with optional

Use ifPresent(Consumer<? super T> consumer) to perform an action only when the value is present, which eliminates the need for explicit null checks.

Optional<String> optional = // ...

optional.ifPresent(val -> System.out.println("Value: " + val));

Best Practices

Avoid using Optional for method parameters

While using Optional for method return types is acceptable, it’s generally not recommended for method parameters. It can make the code less readable and complicate the method signature.

Use Optional in Stream API

Optional integrates well with the Stream API. For example, you can use Optional in combination with filter, map, and other stream operations.

List<String> strings = // ...
Optional<String> result = strings.stream()
                                .filter(s -> s.startsWith("A"))
                                .findFirst();

Consider alternative approaches

In some cases, using Optional might be unnecessary, and a simple null check or default value assignment could be more readable and straightforward.

When to use and not to use Optional

Use Optional when:

• You want to make it explicit that a value might be absent.
• You want to take advantage of the functional programming features in the Stream API.
• You want to enforce explicit handling of absent values.

Avoid Optional when:

• Dealing with method parameters; it’s generally not recommended.
• It doesn’t improve the code readability or when simpler alternatives suffice.

Optional is a powerful tool for expressing optional values more clearly and avoiding null pointer exceptions.
However, it should be used judiciously, and developers should be mindful of its appropriate application to avoid unnecessary complexity in the code.

References

Tired of Null Pointer Exceptions? Consider Using Java SE 8’s Optional!

Chapter 10. Using Optional as a better alternative to null · Java 8 in Action: Lambdas, streams, and functional-style programming

The difference between Map and FlatMap methods in Java Stream API