DevTut

# Alternative Collections

# Multimap in Guava, Apache and Eclipse Collections

This multimap allows duplicate key-value pairs. JDK analogs are HashMap<K, List>, HashMap<K, Set> and so on.

Key's order Value's order Duplicate Analog key Analog value Guava Apache Eclipse (GS) Collections JDK
not defined Insertion-order yes HashMap (opens new window) ArrayList (opens new window) ArrayListMultimap (opens new window) MultiValueMap FastListMultimap HashMap<K, ArrayList<V>>
not defined not defined no HashMap (opens new window) HashSet (opens new window) HashMultimap (opens new window) MultiValueMap. multiValueMap( new HashMap<K, Set>(), HashSet.class); UnifiedSetMultimap HashMap<K, HashSet<V>>
not defined sorted no HashMap (opens new window) TreeSet (opens new window) Multimaps. newMultimap( HashMap, Supplier <TreeSet>) MultiValueMap.multiValueMap( new HashMap<K, Set>(), TreeSet.class) TreeSortedSet- Multimap HashMap<K, TreeSet<V>>
Insertion-order Insertion-order yes LinkedHashMap (opens new window) ArrayList (opens new window) LinkedListMultimap (opens new window) MultiValueMap. multiValueMap(new LinkedHashMap<K, List>(), ArrayList.class); LinkedHashMap< K, ArrayList>
Insertion-order Insertion-order no LinkedHashMap (opens new window) LinkedHashSet (opens new window) LinkedHashMultimap (opens new window) MultiValueMap. multiValueMap(new LinkedHashMap<K, Set>(), LinkedHashSet.class) LinkedHashMap<K, LinkedHashSet<V>>
sorted sorted no TreeMap (opens new window) TreeSet (opens new window) TreeMultimap (opens new window) MultiValueMap. multiValueMap( new TreeMap<K, Set>(),TreeSet.class) TreeMap<K, TreeSet<V>>

Task: Parse "Hello World! Hello All! Hi World!" string to separate words and print all indexes of every word using MultiMap (for example, Hello=[0, 2], World!=[1, 5] and so on)

1. MultiValueMap from Apache


   String INPUT_TEXT = "Hello World! Hello All! Hi World!";
    // Parse text to words and index
    List<String> words = Arrays.asList(INPUT_TEXT.split(" "));
    // Create Multimap
    MultiMap<String, Integer> multiMap = new MultiValueMap<String, Integer>();


    // Fill Multimap
    int i = 0;
    for(String word: words) {
        multiMap.put(word, i);
        i++;
    }

    // Print all words
    System.out.println(multiMap); // print {Hi=[4], Hello=[0, 2], World!=[1, 5], All!=[3]} - in random orders
    // Print all unique words
    System.out.println(multiMap.keySet());    // print [Hi, Hello, World!, All!] - in random orders

    // Print all indexes
    System.out.println("Hello = " + multiMap.get("Hello"));    // print [0, 2]
    System.out.println("World = " + multiMap.get("World!"));    // print [1, 5]
    System.out.println("All = " + multiMap.get("All!"));    // print [3]
    System.out.println("Hi = " + multiMap.get("Hi"));    // print [4]
    System.out.println("Empty = " + multiMap.get("Empty"));    // print null

    // Print count unique words
    System.out.println(multiMap.keySet().size());    //print 4

2. HashBiMap from GS / Eclipse Collection


   String[] englishWords = {"one", "two", "three","ball","snow"};
    String[] russianWords = {"jeden", "dwa", "trzy", "kula", "snieg"};

    // Create Multiset
    MutableBiMap<String, String> biMap = new HashBiMap(englishWords.length);
    // Create English-Polish dictionary
    int i = 0;
    for(String englishWord: englishWords) {
        biMap.put(englishWord, russianWords[i]);
        i++;
    }

    // Print count words
    System.out.println(biMap); // print {two=dwa, ball=kula, one=jeden, snow=snieg, three=trzy} - in random orders
    // Print all unique words
    System.out.println(biMap.keySet());    // print [snow, two, one, three, ball] - in random orders
    System.out.println(biMap.values());    // print [dwa, kula, jeden, snieg, trzy] - in random orders

    // Print translate by words
    System.out.println("one = " + biMap.get("one"));    // print one = jeden
    System.out.println("two = " + biMap.get("two"));    // print two = dwa
    System.out.println("kula = " + biMap.inverse().get("kula"));    // print kula = ball
    System.out.println("snieg = " + biMap.inverse().get("snieg"));    // print snieg = snow
    System.out.println("empty = " + biMap.get("empty"));    // print empty = null

    // Print count word's pair
    System.out.println(biMap.size());    //print 5
  • HashMultiMap from Guava 
     String INPUT_TEXT = "Hello World! Hello All! Hi World!";
 // Parse text to words and index
 List<String> words = Arrays.asList(INPUT_TEXT.split(" "));
 // Create Multimap
 Multimap<String, Integer> multiMap = HashMultimap.create();

 // Fill Multimap
 int i = 0;
 for(String word: words) {
     multiMap.put(word, i);
     i++;
 }

 // Print all words
 System.out.println(multiMap); // print {Hi=[4], Hello=[0, 2], World!=[1, 5], All!=[3]} - keys and values in random orders
 // Print all unique words
 System.out.println(multiMap.keySet());    // print [Hi, Hello, World!, All!] - in random orders

 // Print all indexes
 System.out.println("Hello = " + multiMap.get("Hello"));    // print [0, 2]
 System.out.println("World = " + multiMap.get("World!"));    // print [1, 5]
 System.out.println("All = " + multiMap.get("All!"));    // print [3]
 System.out.println("Hi = " + multiMap.get("Hi"));    // print [4]
 System.out.println("Empty = " + multiMap.get("Empty"));    // print []

 // Print count all words
 System.out.println(multiMap.size());    //print 6

 // Print count unique words
 System.out.println(multiMap.keySet().size());    //print 4

    • # Nore examples:

    I. Apache Collection:

    1. MultiValueMap (opens new window)
    2. MultiValueMapLinked (opens new window)
    3. MultiValueMapTree (opens new window)

    II. GS / Eclipse Collection

    1. FastListMultimap (opens new window)
    2. HashBagMultimap (opens new window)
    3. TreeSortedSetMultimap (opens new window)
    4. UnifiedSetMultimap (opens new window)

    III. Guava

    1. HashMultiMap (opens new window)
    2. LinkedHashMultimap (opens new window)
    3. LinkedListMultimap (opens new window)
    4. TreeMultimap (opens new window)
    5. ArrayListMultimap (opens new window)

    # Apache HashBag, Guava HashMultiset and Eclipse HashBag

    A Bag/ultiset stores each object in the collection together with a count of occurrences. Extra methods on the interface allow multiple copies of an object to be added or removed at once. JDK analog is HashMap<T, Integer>, when values is count of copies this key.

    Type Guava Apache Commons Collections GS Collections JDK
    Order not defined HashMultiset (opens new window) HashBag (opens new window) HashBag (opens new window) HashMap (opens new window)
    Sorted TreeMultiset (opens new window) TreeBag (opens new window) TreeBag (opens new window) TreeMap (opens new window)
    Insertion-order LinkedHashMultiset (opens new window) - - LinkedHashMap (opens new window)
    Concurrent variant ConcurrentHashMultiset (opens new window) SynchronizedBag (opens new window) SynchronizedBag (opens new window) Collections.synchronizedMap(HashMap<String, Integer>)
    Concurrent and sorted - SynchronizedSortedBag (opens new window) SynchronizedSortedBag (opens new window) Collections.synchronizedSortedMap(TreeMap<String,Integer>)
    Immutable collection ImmutableMultiset (opens new window) UnmodifiableBag (opens new window) UnmodifiableBag (opens new window) Collections.unmodifiableMap(HashMap<String, Integer)]
    Immutable and sorted ImmutableSortedMultiset (opens new window) UnmodifiableSortedBag (opens new window) UnmodifiableSortedBag Collections.unmodifiableSortedMap(TreeMap<String, Integer>)

    Examples:

    # 1. Using SynchronizedSortedBag from Apache (opens new window):

    
   // Parse text to separate words
    String INPUT_TEXT = "Hello World! Hello All! Hi World!";
    // Create Multiset
    Bag bag = SynchronizedSortedBag.synchronizedBag(new TreeBag(Arrays.asList(INPUT_TEXT.split(" "))));

    // Print count words
    System.out.println(bag); // print [1:All!,2:Hello,1:Hi,2:World!]- in natural (alphabet) order
    // Print all unique words
    System.out.println(bag.uniqueSet());    // print [All!, Hello, Hi, World!]- in natural (alphabet) order


    // Print count occurrences of words
    System.out.println("Hello = " + bag.getCount("Hello"));    // print 2
    System.out.println("World = " + bag.getCount("World!"));    // print 2
    System.out.println("All = " + bag.getCount("All!"));    // print 1
    System.out.println("Hi = " + bag.getCount("Hi"));    // print 1
    System.out.println("Empty = " + bag.getCount("Empty"));    // print 0

    // Print count all words
    System.out.println(bag.size());    //print 6

    // Print count unique words
    System.out.println(bag.uniqueSet().size());    //print 4

    # 2. Using TreeBag from Eclipse(GC) (opens new window):

    
   // Parse text to separate words
    String INPUT_TEXT = "Hello World! Hello All! Hi World!";
    // Create Multiset
    MutableSortedBag<String> bag =  TreeBag.newBag(Arrays.asList(INPUT_TEXT.split(" ")));

    // Print count words
    System.out.println(bag); // print [All!, Hello, Hello, Hi, World!, World!]- in natural order
    // Print all unique words
    System.out.println(bag.toSortedSet());    // print [All!, Hello, Hi, World!]- in natural order

    // Print count occurrences of words
    System.out.println("Hello = " + bag.occurrencesOf("Hello"));    // print 2
    System.out.println("World = " + bag.occurrencesOf("World!"));    // print 2
    System.out.println("All = " + bag.occurrencesOf("All!"));    // print 1
    System.out.println("Hi = " + bag.occurrencesOf("Hi"));    // print 1
    System.out.println("Empty = " + bag.occurrencesOf("Empty"));    // print 0

    // Print count all words
    System.out.println(bag.size());    //print 6

    // Print count unique words
    System.out.println(bag.toSet().size());    //print 4

    # 3. Using LinkedHashMultiset from Guava (opens new window):

    
   // Parse text to separate words
    String INPUT_TEXT = "Hello World! Hello All! Hi World!";
    // Create Multiset
    Multiset<String> multiset = LinkedHashMultiset.create(Arrays.asList(INPUT_TEXT.split(" ")));

    // Print count words
    System.out.println(multiset); // print [Hello x 2, World! x 2, All!, Hi]- in predictable iteration order
    // Print all unique words
    System.out.println(multiset.elementSet());    // print [Hello, World!, All!, Hi] - in predictable iteration order

    // Print count occurrences of words
    System.out.println("Hello = " + multiset.count("Hello"));    // print 2
    System.out.println("World = " + multiset.count("World!"));    // print 2
    System.out.println("All = " + multiset.count("All!"));    // print 1
    System.out.println("Hi = " + multiset.count("Hi"));    // print 1
    System.out.println("Empty = " + multiset.count("Empty"));    // print 0

    // Print count all words
    System.out.println(multiset.size());    //print 6

    // Print count unique words
    System.out.println(multiset.elementSet().size());    //print 4

    # More examples:

    I. Apache Collection:

    1. HashBag (opens new window) - order not defined
    2. SynchronizedBag (opens new window) - concurrent and order not defined
    3. SynchronizedSortedBag (opens new window) - - concurrent and sorted order
    4. TreeBag (opens new window) - sorted order

    II. GS / Eclipse Collection

    1. MutableBag (opens new window) - order not defined
    2. MutableSortedBag (opens new window) - sorted order

    III. Guava

    1. HashMultiset (opens new window) - order not defined
    2. TreeMultiset (opens new window) - sorted order
    3. LinkedHashMultiset (opens new window) - insertion order
    4. ConcurrentHashMultiset (opens new window) - concurrent and order not defined

    # Compare operation with collections - Create collections

    # Compare operation with collections - Create collections

    Description JDK guava gs-collections
    Create empty list new ArrayList<>() Lists.newArrayList() FastList.newList()
    Create list from values Arrays.asList("1", "2", "3") Lists.newArrayList("1", "2", "3") FastList.newListWith("1", "2", "3")
    Create list with capacity = 100 new ArrayList<>(100) Lists.newArrayListWithCapacity(100) FastList.newList(100)
    Create list from any collectin new ArrayList<>(collection) Lists.newArrayList(collection) FastList.newList(collection)
    Create list from any Iterable - Lists.newArrayList(iterable) FastList.newList(iterable)
    Create list from Iterator - Lists.newArrayList(iterator) -
    Create list from array Arrays.asList(array) Lists.newArrayList(array) FastList.newListWith(array)
    Create list using factory - - FastList.newWithNValues(10, () -> "1")

    Examples:

    
   System.out.println("createArrayList start");
    // Create empty list
    List<String> emptyGuava = Lists.newArrayList(); // using guava
    List<String> emptyJDK = new ArrayList<>(); // using JDK
    MutableList<String>  emptyGS = FastList.newList(); // using gs

    // Create list with 100 element
    List < String > exactly100 = Lists.newArrayListWithCapacity(100); // using guava
    List<String> exactly100JDK = new ArrayList<>(100); // using JDK
    MutableList<String>  empty100GS = FastList.newList(100); // using gs

    // Create list with about 100 element
    List<String> approx100 = Lists.newArrayListWithExpectedSize(100); // using guava
    List<String> approx100JDK = new ArrayList<>(115); // using JDK
    MutableList<String>  approx100GS = FastList.newList(115); // using gs

    // Create list with some elements
    List<String> withElements = Lists.newArrayList("alpha", "beta", "gamma"); // using guava
    List<String> withElementsJDK = Arrays.asList("alpha", "beta", "gamma"); // using JDK
    MutableList<String>  withElementsGS = FastList.newListWith("alpha", "beta", "gamma"); // using gs

    System.out.println(withElements);
    System.out.println(withElementsJDK);
    System.out.println(withElementsGS);

    // Create list from any Iterable interface (any collection)
    Collection<String> collection = new HashSet<>(3);
    collection.add("1");
    collection.add("2");
    collection.add("3");

    List<String> fromIterable = Lists.newArrayList(collection); // using guava
    List<String> fromIterableJDK = new ArrayList<>(collection); // using JDK
    MutableList<String>  fromIterableGS = FastList.newList(collection); // using gs

    System.out.println(fromIterable);
    System.out.println(fromIterableJDK);
    System.out.println(fromIterableGS);
    /* Attention: JDK create list only from Collection, but guava and gs can create list from Iterable and Collection */

    // Create list from any Iterator
    Iterator<String> iterator = collection.iterator();
    List<String> fromIterator = Lists.newArrayList(iterator); // using guava
    System.out.println(fromIterator);

    // Create list from any array
    String[] array = {"4", "5", "6"};
    List<String> fromArray = Lists.newArrayList(array); // using guava
    List<String> fromArrayJDK = Arrays.asList(array); // using JDK
    MutableList<String>  fromArrayGS = FastList.newListWith(array); // using gs
    System.out.println(fromArray);
    System.out.println(fromArrayJDK);
    System.out.println(fromArrayGS);

    // Create list using fabric
    MutableList<String>  fromFabricGS = FastList.newWithNValues(10, () -> String.valueOf(Math.random())); // using gs
    System.out.println(fromFabricGS);

    System.out.println("createArrayList end");
    Description JDK guava gs-collections
    Create empty set new HashSet<>() Sets.newHashSet() UnifiedSet.newSet()
    Creatre set from values new HashSet<>(Arrays.asList("alpha", "beta", "gamma")) Sets.newHashSet("alpha", "beta", "gamma") UnifiedSet.newSetWith("alpha", "beta", "gamma")
    Create set from any collections new HashSet<>(collection) Sets.newHashSet(collection) UnifiedSet.newSet(collection)
    Create set from any Iterable - Sets.newHashSet(iterable) UnifiedSet.newSet(iterable)
    Create set from any Iterator - Sets.newHashSet(iterator) -
    Create set from Array new HashSet<>(Arrays.asList(array)) Sets.newHashSet(array) UnifiedSet.newSetWith(array)

    Examples:

    
   System.out.println("createHashSet start");
    // Create empty set
    Set<String> emptyGuava = Sets.newHashSet(); // using guava
    Set<String> emptyJDK = new HashSet<>(); // using JDK
    Set<String> emptyGS = UnifiedSet.newSet(); // using gs

    // Create set with 100 element
    Set<String> approx100 = Sets.newHashSetWithExpectedSize(100); // using guava
    Set<String> approx100JDK = new HashSet<>(130); // using JDK
    Set<String> approx100GS = UnifiedSet.newSet(130); // using gs

    // Create set from some elements
    Set<String> withElements =  Sets.newHashSet("alpha", "beta", "gamma"); // using guava
    Set<String> withElementsJDK = new HashSet<>(Arrays.asList("alpha", "beta", "gamma")); // using JDK
    Set<String> withElementsGS  = UnifiedSet.newSetWith("alpha", "beta", "gamma"); // using gs

    System.out.println(withElements);
    System.out.println(withElementsJDK);
    System.out.println(withElementsGS);

    // Create set from any Iterable interface (any collection)
    Collection<String> collection = new ArrayList<>(3);
    collection.add("1");
    collection.add("2");
    collection.add("3");

    Set<String> fromIterable = Sets.newHashSet(collection); // using guava
    Set<String> fromIterableJDK = new HashSet<>(collection); // using JDK
    Set<String> fromIterableGS  = UnifiedSet.newSet(collection); // using gs

    System.out.println(fromIterable);
    System.out.println(fromIterableJDK);
    System.out.println(fromIterableGS);
    /* Attention: JDK create set only from Collection, but guava and gs can create set from Iterable and Collection */

    // Create set from any Iterator
    Iterator<String> iterator = collection.iterator();
    Set<String> fromIterator = Sets.newHashSet(iterator); // using guava
    System.out.println(fromIterator);

    // Create set from any array
    String[] array = {"4", "5", "6"};
    Set<String> fromArray = Sets.newHashSet(array); // using guava
    Set<String> fromArrayJDK = new HashSet<>(Arrays.asList(array)); // using JDK
    Set<String> fromArrayGS  = UnifiedSet.newSetWith(array); // using gs
    System.out.println(fromArray);
    System.out.println(fromArrayJDK);
    System.out.println(fromArrayGS);

    System.out.println("createHashSet end");
    Description JDK guava gs-collections
    Create empty map new HashMap<>() Maps.newHashMap() UnifiedMap.newMap()
    Create map with capacity = 130 new HashMap<>(130) Maps.newHashMapWithExpectedSize(100) UnifiedMap.newMap(130)
    Create map from other map new HashMap<>(map) Maps.newHashMap(map) UnifiedMap.newMap(map)
    Create map from keys - - UnifiedMap.newWithKeysValues("1", "a", "2", "b")

    Examples:

    
   System.out.println("createHashMap start");
    // Create empty map
    Map<String, String> emptyGuava = Maps.newHashMap(); // using guava
    Map<String, String> emptyJDK = new HashMap<>(); // using JDK
    Map<String, String> emptyGS = UnifiedMap.newMap(); // using gs

    // Create map with about 100 element
    Map<String, String> approx100 = Maps.newHashMapWithExpectedSize(100); // using guava
    Map<String, String> approx100JDK = new HashMap<>(130); // using JDK
    Map<String, String> approx100GS = UnifiedMap.newMap(130); // using gs

    // Create map from another map
    Map<String, String> map = new HashMap<>(3);
    map.put("k1","v1");
    map.put("k2","v2");
    Map<String, String> withMap =  Maps.newHashMap(map); // using guava
    Map<String, String> withMapJDK = new HashMap<>(map); // using JDK
    Map<String, String> withMapGS = UnifiedMap.newMap(map); // using gs

    System.out.println(withMap);
    System.out.println(withMapJDK);
    System.out.println(withMapGS);

    // Create map from keys
    Map<String, String> withKeys =  UnifiedMap.newWithKeysValues("1", "a", "2", "b");
    System.out.println(withKeys);

    System.out.println("createHashMap end");

    More examples: CreateCollectionTest (opens new window)

    1. CollectionCompare (opens new window)
    2. CollectionSearch (opens new window)
    3. JavaTransform (opens new window)

    # Remarks

    This topic about Java collections from guava, apache, eclipse: Multiset, Bag, Multimap, utils function from this lib and so on.

    ← Concurrent Collections →