Alternative Collections
Remarks#
This topic about Java collections from guava, apache, eclipse: Multiset, Bag, Multimap, utils function from this lib and so on.
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:
- 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
Multimap in Guava, Apache and Eclipse Collections
This multimap allows duplicate key-value pairs. JDK analogs are HashMap<K, List
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>> |
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)
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:
II. GS / Eclipse Collection
III. Guava
Compare operation with collections - Create collections
Compare operation with collections - Create collections
1. 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<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");
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<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");
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<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