no.finn.lambdacompanion

Class Optionals

java.lang.Object

no.finn.lambdacompanion.Optionals

public final class Optionals
extends Object

Method Summary

Modifier and Type	Method and Description
static <T> Optional<T>	filter(Optional<?> opt, Class<T> cls) Convenience method to filter an optional based on its class and cast it at the same time
static <T> Optional<T>	firstOf(Supplier<Optional<T>>... suppliers) Out of a list of suppliers of optional values, returns the first one that is present without unnecessary evaluating the next suppliers.
static Optional<String>	ofBlankable(String blankable) Convenience method to build and Optional out of a String that can be null or blank
static <T> Stream<T>	stream(Optional<T> optional) Convenience method to turn an Optional into a Stream, due to the lack Optional#stream() method...

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

firstOf

public static <T> Optional<T> firstOf(Supplier<Optional<T>>... suppliers)

Out of a list of suppliers of optional values, returns the first one that is present without unnecessary evaluating the next suppliers. Ex:

 
     Optional first = Optionals.firstOf(() -> firstCostyOperation()
                                        () -> secondCostlyOperation()
                                        () -> thirdCostlyOperation());
 
 

In case firstCostyOperation() returns an Optional.empty(), then secondCostlyOperation() will be invoked. If secondCostlyOperation() returns a present Optional, then thirdCostlyOperation() won't be invoked.

Type Parameters:

T - t

Parameters:

suppliers - for methods that need to be conditionnally invoked

Returns:

the first supplied Optional that is present

stream

public static <T> Stream<T> stream(Optional<T> optional)

Convenience method to turn an Optional into a Stream, due to the lack Optional#stream() method...

 
     List<Optional<String>> listOfOptionals = //...
     List<String> strings = list.stream().flatMap(Optionals::stream).collect(toList());
 
 

Type Parameters:

T - t

Parameters:

optional - optional

Returns:

a Stream of 1 element or an empty Stream

filter

public static <T> Optional<T> filter(Optional<?> opt,
                                     Class<T> cls)

Convenience method to filter an optional based on its class and cast it at the same time

Type Parameters:

T - T

Parameters:

opt - opt

cls - cls

Returns:

a present Optional casted to T if present and matching filtering class, else Optional#empty()

ofBlankable

public static Optional<String> ofBlankable(String blankable)

Convenience method to build and Optional out of a String that can be null or blank

Parameters:

blankable - blankable

Returns:

a present Optional of the string if not null and not blank, else Optional#empty()