Lambda-Enabled Concurrency - Java 8 Lambdas - page 168

. count ();

}

}

The first part of this exercise is to refactor the blocking return code to use a callback inter-
face. In this case, we'll be using a Consumer<Boolean> . Remember that Consumer is a func-
tional interface that ships with the JVM that accepts a value and returns void . Your mission,
should you choose to accept it, is to alter BlockingArtistAnalyzer so that it implements
ArtistAnalyzer ( Example 9-19 ) .

Example 9-19. The ArtistAnalyzer that you need to make BlockingArtistAnalyzer implement
public public interface interface ArtistAnalyzer ArtistAnalyzer {

public public void void isLargerGroup ( String artistName ,

String otherArtistName ,
Consumer < Boolean > handler );

}

Now that we have an API that fits into the callback model, we can remove the need for both
of the blocking lookups to happen at the same time. You should refactor the isLargerGroup
method so that they can operate concurrently using the CompletableFuture class.