Guava Multimap – TreeMultimap Implementation Example – Developers Corner

Guava Multimap – TreeMultimap Implementation

The TreeMultimap is a variation of a Map in which multiple values or objects are associated with a single key but it will return a sorted list of objects according to their natural ordering without any duplicate key/value pairs. In this example, you will notice that the values are all sorted in order and Amaury Valdes appears only once in the Multimap element with a key of 777. Notice how duplicates are not allowed and silently fail to be added.

Methods available to TreeMultimap

@GwtCompatible(serializable=true, emulated=true)
public class TreeMultimap<K,V>>
extends Object

#	Method and Description
1	NavigableMap<K,Collection<V>> asMap() Returns a map view that associates each key with the corresponding values in the multimap.
2	void clear() Removes all key-value pairs from the multimap, leaving it empty.
3	boolean containsEntry(Object key, Object value) Returns true if this multimap contains at least one key-value pair with the key key and the value value.
4	boolean containsKey(Object keyName) Returns true if this multimap contains at least one key-value pair with the key keyName.
5	boolean containsValue(Object valueName) Returns true if this multimap contains at least one key-value pair with the value valueName.
6	static <K extends Comparable,V extends Comparable> TreeMultimap<K,V> create() Creates an empty TreeMultimap ordered by the natural ordering of its keys and values.
7	static <K,V> TreeMultimap<K,V> create(Comparator<? super K> keyComparator, Comparator<? super V> valueComparator) Creates an empty TreeMultimap instance using explicit comparators.
8	static <K extends Comparable,V extends Comparable> TreeMultimap<K,V> create(Multimap<? extends K,? extends V> multimap) Constructs a TreeMultimap, ordered by the natural ordering of its keys and values, with the same mappings as the specified multimap.
9	Set<Map.Entry<K,V>> entries() Returns a view collection of all key-value pairs contained in this multimap, as Map.Entry instances.
10	boolean equals(Object obj) Compares the specified object with this multimap for equality.
11	NavigableSet<V> get(K key) Returns a collection view of all values associated with a key.
12	int hashCode() Returns the hash code for this multimap.
13	boolean isEmpty() Returns true if this multimap contains no key-value pairs.
14	Comparator<? super K> keyComparator() Returns the comparator that orders the multimap keys.
15	Multiset<K> keys() Returns a view collection containing the key from each key-value pair in this multimap, without collapsing duplicates.
16	NavigableSet<K> keySet() Returns a view collection of all distinct keys contained in this multimap.
17	boolean put(K key, V value) Stores a key-value pair in this multimap.
18	boolean putAll(K key, Iterable<? extends V> values) Stores a key-value pair in this multimap for each of values, all using the same key, key.
19	boolean putAll(Multimap<? extends K,? extends V> multimap) Stores all key-value pairs of multimap in this multimap, in the order returned by multimap.entries().
20	boolean remove(Object key, Object value) Removes a single key-value pair with the key key and the value value from this multimap, if such exists.
21	SortedSet<V> removeAll(Object key) Removes all values associated with the key keyName.
22	SortedSet<V> replaceValues(K key, Iterable<? extends V> values) Stores a collection of values with the same key, replacing any existing values for that key.
23	int size() Returns the number of key-value pairs in this multimap.
24	int size() Returns the number of key-value pairs in this multimap.
25	String toString() Returns a string representation of the multimap, generated by calling toString on the map returned by Multimap.asMap().
26	Comparator<? super V> valueComparator() Returns the comparator that orders the multimap values, with null indicating that natural ordering is used.
27	Collection<V> values() Returns a view collection containing the value from each key-value pair contained in this multimap, without collapsing duplicates (so values().size() == size()).

Java TreeMultimap Example of Guava Multimap

package com.avaldes;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Multimap;
import com.google.common.collect.SortedSetMultimap;
import com.google.common.collect.TreeMultimap;

public class GuavaSetMultiMapExample {
  
  public static void main(String[] args) {
    Logger logger = LoggerFactory.getLogger(GuavaSetMultiMapExample.class);

    logger.info("myTreeMultimap: " + myArrayListMultimap);
    logger.info("No duplicates allowed, Sorted Set...");
    SortedSetMultimap<String,String> myTreeMultimap = TreeMultimap.create();
    myTreeMultimap.put("777", "Amaury Valdes");
    myTreeMultimap.put("777", "Walter White");
    myTreeMultimap.put("777", "Eric Hamlin");
    myTreeMultimap.put("777", "John Smith");
    myTreeMultimap.put("777", "Eric Hamlin");
    
    logger.info("myTreeMultimap: " + myTreeMultimap);
  }
}

Output

22:02:31.310 [main] INFO  com.avaldes.GuavaSetMultiMapExample - ---myTreeMultimap----------
22:02:31.314 [main] INFO  com.avaldes.GuavaSetMultiMapExample - No duplicates allowed, Sorted Set...
22:02:31.329 [main] INFO  com.avaldes.GuavaSetMultiMapExample - myTreeMultimap: {777=[Amaury Valdes, Eric Hamlin, John Smith, Walter White]}

That’s It!

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GuavaTreeMultimap

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Guava Multimap - HashMultimap Implementation Example
In this tutorial we will cover implementing an HashMultimap which does not allow duplicate key/value pairs, using HashMultimap.
Guava Multimap - TreeMultimap Implementation Example
In this tutorial we will cover a implementing an TreeMultimap which performs Sorting according to natural order and does not allow duplicate key/value pairs.
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