Using a map operation to transform values

The following lines declare a new getGameNamesTransformedToUpperCase method for our previously coded MemoryMobileGameRepository class. The new method performs one of the simplest map operations. The call to the map method transforms a Stream<MobileGame> into a Stream<String>.The lambda expression passed as an argument to the map method generates a Function<MobileGame, String>, that is, it receives a MobileGame argument and returns a String. The call to the collect method generates a List<String> from the Stream<String> returned by the map method.

The code file for the sample is included in the java_9_oop_chapter_12_01 folder, in the example12_10.java file.

public List<String> getGameNamesTransformedToUpperCase() {
    return getAll().stream()
        .map(game -> game.name.toUpperCase())
        .collect(Collectors.toList());
}

The getGameNamesTransformedToUpperCase method returns a List<String>. The map...