# 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 ArrayList ArrayListMultimap MultiValueMap FastListMultimap HashMap<K, ArrayList<V>>
not defined not defined no HashMap HashSet HashMultimap MultiValueMap. multiValueMap( new HashMap<K, Set>(), HashSet.class); UnifiedSetMultimap HashMap<K, HashSet<V>>
not defined sorted no HashMap TreeSet 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 ArrayList LinkedListMultimap MultiValueMap. multiValueMap(new LinkedHashMap<K, List>(), ArrayList.class); LinkedHashMap< K, ArrayList>
Insertion-order Insertion-order no LinkedHashMap LinkedHashSet LinkedHashMultimap MultiValueMap. multiValueMap(new LinkedHashMap<K, Set>(), LinkedHashSet.class) LinkedHashMap<K, LinkedHashSet<V>>
sorted sorted no TreeMap TreeSet TreeMultimap 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
    2. MultiValueMapLinked
    3. MultiValueMapTree

    II. GS / Eclipse Collection

    1. FastListMultimap
    2. HashBagMultimap
    3. TreeSortedSetMultimap
    4. UnifiedSetMultimap

    III. Guava

    1. HashMultiMap
    2. LinkedHashMultimap
    3. LinkedListMultimap
    4. TreeMultimap
    5. ArrayListMultimap

    # 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 HashBag HashBag HashMap
    Sorted TreeMultiset TreeBag TreeBag TreeMap
    Insertion-order LinkedHashMultiset - - LinkedHashMap
    Concurrent variant ConcurrentHashMultiset SynchronizedBag SynchronizedBag Collections.synchronizedMap(HashMap<String, Integer>)
    Concurrent and sorted - SynchronizedSortedBag SynchronizedSortedBag Collections.synchronizedSortedMap(TreeMap<String,Integer>)
    Immutable collection ImmutableMultiset UnmodifiableBag UnmodifiableBag Collections.unmodifiableMap(HashMap<String, Integer)]
    Immutable and sorted ImmutableSortedMultiset UnmodifiableSortedBag UnmodifiableSortedBag Collections.unmodifiableSortedMap(TreeMap<String, Integer>)

    Examples:

    # 1. Using SynchronizedSortedBag from Apache:

    
       // 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):

    
       // 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:

    
       // 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 - order not defined
    2. SynchronizedBag - concurrent and order not defined
    3. SynchronizedSortedBag - - concurrent and sorted order
    4. TreeBag - sorted order

    II. GS / Eclipse Collection

    1. MutableBag - order not defined
    2. MutableSortedBag - sorted order

    III. Guava

    1. HashMultiset - order not defined
    2. TreeMultiset - sorted order
    3. LinkedHashMultiset - insertion order
    4. ConcurrentHashMultiset - 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

    1. CollectionCompare
    2. CollectionSearch
    3. JavaTransform

    # Remarks

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