Using Optional as a better alternative to null - Java 8 in Action: Lambdas, Streams, and Functional-Style Programming - page 293

Table 10.1. The methods of the Optional class

Method Description

empty Returns an empty Optional instance

filter If the value is present and matches the given predicate, returns this Optional; otherwise

returns the empty one

flatMap If a value is present, returns the Optional resulting from the application of the provided

mapping function to it; otherwise returns the empty Optional

get Returns the value wrapped by this Optional if present; otherwise throws a

NoSuchElementException

ifPresent If a value is present, invokes the specified consumer with the value; otherwise does nothing

isPresent Returns true if there is a value present; otherwise false

map If a value is present, applies the provided mapping function to it

of Returns an Optional wrapping the given value or throws a NullPointerException if this value

is null

ofNullable Returns an Optional wrapping the given value or the empty Optional if this value is null

orElse Returns the value if present or the given default value otherwise

orElseGet Returns the value if present or the one provided by the given Supplier otherwise

orElseThrow Returns the value if present or throws the exception created by the given Supplier otherwise

10.4. Practical examples of using Optional

As you've learned, effective use of the new Optional class implies a complete rethink of how you
deal with potentially missing values. This rethink involves not only the code you write but,
possibly even more important, how you interact with native Java APIs.