Libraries - Java 8 Lambdas - page 61

Exercises

1. Given the Performance interface in Example 4-25 , add a method called
getAllMusicians that returns a Stream of the artists performing and, in the case of
groups, any musicians who are members of those groups. For example, if getMusi-
cians returns The Beatles , then you should return The Beatles along with Lennon,
McCartney, and so on.

Example 4-25. An interface denoting the concept of a musical performance
/** A Performance by some musicians - e.g., an Album or Gig. */
public public interface interface Performance Performance {

public public String getName ();

public public Stream < Artist > getMusicians ();

}

2. Based on the resolution rules described earlier, can you ever override equals or
hashCode in a default method?

3. Take a look at the Artists domain class in Example 4-26 , which represents a group
of artists. Your assignment is to refactor the getArtist method in order to return an
Optional<Artist> . It contains an element if the index is within range and is an
empty Optional otherwise. Remember that you also need to refactor the
getArtistName method, and it should retain the same behavior.

Example 4-26. The Artists domain class, which represents more than one Artist
public public class class Artists Artists {

private private List < Artist > artists ;

public public Artists ( List < Artist > artists ) {

this

this . artists = artists ;

}

public public Artist getArtist ( int int index ) {

iif ( index < 0 || index >= artists . size ()) {
indexException ( index );

}
return

return artists . get ( index );

}