Alternative Collections in Java Tutorial With Examples 2023

Multimap in Guava, Apache and Eclipse Collections

This multimap allows duplicate key-value pairs. JDK analogs are HashMap, HashMap and so on.

Examples using Multimap

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)

MultiValueMap from Apache

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

     // 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 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

    String INPUT_TEXT = "Hello World! Hello All! Hi World!";
    // Parse text to words and index
    List words = Arrays.asList(INPUT_TEXT.split(" "));
    // Create Multimap
    Multimap 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

More examples:

I. Apache Collection:

MultiValueMap
MultiValueMapLinked
MultiValueMapTree

II. GS / Eclipse Collection

FastListMultimap
HashBagMultimap
TreeSortedSetMultimap
UnifiedSetMultimap

III. Guava

HashMultiMap
LinkedHashMultimap
LinkedListMultimap
TreeMultimap
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, when values is count of copies this key.

Examples:

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

Using TreeBag from Eclipse(GC):

// Parse text to separate words
String INPUT_TEXT = "Hello World! Hello All! Hi World!";
// Create Multiset
MutableSortedBag 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

Using LinkedHashMultiset from Guava:

// Parse text to separate words
String INPUT_TEXT = "Hello World! Hello All! Hi World!";
// Create Multiset
Multiset 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:

HashBag – order not defined
SynchronizedBag – concurrent and order not defined
SynchronizedSortedBag – – concurrent and sorted order
TreeBag – sorted order

II. GS / Eclipse Collection

MutableBag – order not defined
MutableSortedBag – sorted order

III. Guava

HashMultiset – order not defined
TreeMultiset – sorted order
LinkedHashMultiset – insertion order
ConcurrentHashMultiset – concurrent and order not defined

Compare operation with collections – Create collections

Create List

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 emptyGuava = Lists.newArrayList(); // using guava
   List emptyJDK = new ArrayList<>(); // using JDK
   MutableList emptyGS = FastList.newList(); // using gs

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

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

   // Create list with some elements
   List withElements = Lists.newArrayList("alpha", "beta", "gamma"); // using guava
   List withElementsJDK = Arrays.asList("alpha", "beta", "gamma"); // using JDK
   MutableList 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 collection = new HashSet<>(3);
   collection.add("1");
   collection.add("2");
   collection.add("3");

   List fromIterable = Lists.newArrayList(collection); // using  guava
   List fromIterableJDK = new ArrayList<>(collection); // using JDK
   MutableList 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 iterator = collection.iterator();
   List fromIterator = Lists.newArrayList(iterator); // using guava
   System.out.println(fromIterator);

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

   System.out.println(fromArray);
   System.out.println(fromArrayJDK);
   System.out.println(fromArrayGS);

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

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

2 Create Set

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 emptyGuava = Sets.newHashSet(); // using guava
     Set emptyJDK = new HashSet<>(); // using JDK
     Set emptyGS = UnifiedSet.newSet(); // using gs

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

     // Create set from some elements
     Set withElements = Sets.newHashSet("alpha", "beta", "gamma"); // using guava
     Set withElementsJDK = new HashSet<>(Arrays.asList("alpha", "beta", "gamma")); // using JDK
     Set 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 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 iterator = collection.iterator();
    Set fromIterator = Sets.newHashSet(iterator); // using guava
    System.out.println(fromIterator);

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

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

3 Create Map

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 emptyGuava = Maps.newHashMap(); // using guava
   Map emptyJDK = new HashMap<>(); // using JDK
   Map emptyGS = UnifiedMap.newMap(); // using gs

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

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

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

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

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

More examples: CreateCollectionTest

CollectionCompare
CollectionSearch
JavaTransform

Apache HashBag, Guava HashMultiset and Eclipse HashBag

Compare operation with collections – Create collections

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