As usual, but the original code to be refactored was just too evil and had to be fixed.
package chapter11;
import org.junit.jupiter.api.Test;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toSet;
import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;
public class DataGroupingOperationsTest {
interface Scores {
Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores);
}
public static class ScoresBefore implements Scores {
public Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores) {
final Map<Integer, Set<String>> result = new HashMap<>();
for (Map.Entry<String, Integer> entry : scores.entrySet()) {
final String name = entry.getKey();
final Integer score = entry.getValue();
if (!result.containsKey(score)) {
result.put(score, new HashSet<>());
}
result.get(score).add(name);
}
return result;
}
}
public static class ScoresAfter implements Scores {
public Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores) {
return scores.keySet().stream()
.collect(groupingBy(scores::get, toSet()));
}
}
private static void commonNamesForScoresTests(final Scores scores) {
assertAll(
() -> assertEquals(Map.of(), scores.namesForScores(Map.of())),
() -> assertEquals(
Map.of(1, Set.of("Jill")), scores.namesForScores(Map.of("Jill", 1))),
() -> assertEquals(
Map.of(1, Set.of("Jill"), 2, Set.of("Paul")),
scores.namesForScores(Map.of("Jill", 1, "Paul", 2))),
() -> assertEquals(
Map.of(1, Set.of("Jill", "Kate"), 2, Set.of("Paul")),
scores.namesForScores(Map.of("Jill", 1, "Paul", 2, "Kate", 1)))
);
}
@Test
void scoresBefore() {
commonNamesForScoresTests(new ScoresBefore());
}
@Test
void scoresAfter() {
commonNamesForScoresTests(new ScoresAfter());
}
}