What is a MultiValueMap?
A MultiValueMap decorates another map, allowing it to have more than one value for a key. A MultiMap is a Map with slightly different semantics. Putting a value into the map will add the value to a Collection at that key. Getting a value will return a Collection, holding all the values put to that key.
Is MultiKeyMap thread safe?
Note that MultiKeyMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. This class may throw exceptions when accessed by concurrent threads without synchronization.
What is a MultiMap Java?
A Multimap is a new collection type that is found in Google’s Guava library for Java. A Multimap can store more than one value against a key. Both the keys and the values are stored in a collection, and considered to be alternates for Map> or Map> (standard JDK Collections Framework).
What is MultiKeyMap?
A Map implementation that uses multiple keys to map the value. This class is the most efficient way to uses multiple keys to map to a value.
What is the difference between MAP and MultiValueMap?
A map cannot contain duplicate keys; each key can map to at most one value. So in a MultivaluedMap you can insert 0, 1, 2, 3 or more objects related to the same key. In a Map you can insert exactly 1 object related to a key.
Is MultiValuedMap thread-safe?
Now, it’s worth noting that this class is not thread-safe. Therefore, if we want to use this map from multiple threads, we must be sure to use proper synchronization.
Is ConcurrentHashMap slower than HashMap?
Only modifying operations on ConcurrentHashMap are synchronized. Hence, add or remove operations on ConcurrentHashMap are slower than on HashMap . The read operations on both, ConcurrentHashMap and HashMap , give same performance as read operations on both maps are not synchronized.
Why do we need ConcurrentHashMap?
You should use ConcurrentHashMap when you need very high concurrency in your project. It is thread safe without synchronizing the whole map . Reads can happen very fast while write is done with a lock. There is no locking at the object level.
What is the difference between a map and a multimap?
The map and the multimap are both containers that manage key/value pairs as single components. The essential difference between the two is that in a map the keys must be unique, while a multimap permits duplicate keys.
What is a MultiMap C++?
Multimaps are part of the C++ STL (Standard Template Library). Multimaps are the associative containers like map that stores sorted key-value pair, but unlike maps which store only unique keys, multimap can have duplicate keys. By default it uses < operator to compare the keys.
Can HashMap have two keys?
Or in general, multiple keys: Map<((key1, key2,..,keyN), Value) in a way that I can access the element with using get(key1,key2,… keyN). I came across another way for NxN matrix . A simple solution is to mapping one key in other hashmap.