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Diagram

Candy Kata

Learning through exercises

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Candy Kata domain

  • A Bag of randomized instances of type Candy is generated by invoking SchoolGroup.trickOrTreat()

Diagram

Candy Kata Test

  • down: New concepts for Candy Kata Test
  • right: Candy Kata Test solutions

Top/Bottom Occurrences

  • Belong to the set of methods of the Bag interface
  • topOccurrences(int count) returns the count most frequently occuring items (e.g. topOccurrences(2) returns the top 2 most reoccuring items inside the bag).
  • Similarly, bottomOccurrences(int count) returns the count least frequently occuring items.
  • If there is a tie among the items which qualify, the logic is inclusive and will include all items whose occurrences match the occurrences of the last item.

Top Occurrences

MutableBag<Candy> bag =
       Bags.mutable.with(Candy.CRUNCH, Candy.HERSHEYS, Candy.HERSHEYS,
               Candy.HERSHEYS, Candy.MOUNDS, Candy.CRUNCH);

ImmutableList<ObjectIntPair<Candy>> expectedNoTies =
       Lists.immutable.with(PrimitiveTuples.pair(Candy.HERSHEYS, 3),
               PrimitiveTuples.pair(Candy.CRUNCH, 2));
Assertions.assertEquals(expectedNoTies, bag.topOccurrences(2));

bag.add(Candy.MOUNDS);

// The top 2 occurrences actually now includes 3 since there was a tie
// The expected output is converted to a Set to ignore ordering
Set<ObjectIntPair<Candy>> expectedTie = expectedNoTies.toSet()
       .with(PrimitiveTuples.pair(Candy.MOUNDS, 2));
Assertions.assertEquals(expectedTie, bag.topOccurrences(2).toSet());

Candy Kata Test

  • Fix CandyKataTest; there are failing tests.
  • Use topOccurrences()

Candy Kata Test solutions

  • down: Exercise solutions

Get Top Most Occurred Candy

@Test
public void topCandy()
{
    MutableList<Bag<Candy>> bagsOfCandy = this.collectBagsOfCandy();

    Bag<Candy> bigBagOfCandy =
            bagsOfCandy.flatCollect(bag -> bag).toBag();

    MutableSet<Candy> mostCommon =
            bigBagOfCandy.topOccurrences(1)
                    .collect(ObjectIntPair::getOne)
                    .toSet();

    var expectedSet = Sets.mutable.with(Candy.REESES_PIECES);
    Assert.assertEquals(expectedSet, mostCommon);
}

Get Common Candies in Top 10

@Test
public void commonInTop10()
{
    MutableList<Bag<Candy>> bagsOfCandy = this.collectBagsOfCandy();

    MutableSet<Candy> commonInTop10 =
            bagsOfCandy.collect(
                    bag -> bag.topOccurrences(10)
                            .collect(ObjectIntPair::getOne)
                            .toSet())
                    .reduce(MutableSet::intersect)
                    .get();

    var expectedSet = Sets.mutable.with(Candy.REESES_PIECES, Candy.CRUNCH);
    Assert.assertEquals(expectedSet, commonInTop10);
}

Congratulations!

You have completed the Candy Kata!

Enjoy happy Java development with Eclipse Collections!