Guava Study notes: multimaps

Guava Study notes: multimaps

Sometimes we need this data type Map<string,collection<string>>,guava in Multimap is to solve this kind of problem.

The realization of Multimap

Multimap provides a rich implementation, so you can use it to replace the map<k in the program, COLLECTION<V>>, the specific implementation is as follows:

Realize	Key implementation	Value implementation
Arraylistmultimap	HashMap	ArrayList
Hashmultimap	HashMap	HashSet
Linkedlistmultimap	Linkedhashmap	LinkedList
Linkedhashmultimap	Linkedhashmap	Linkedhashset
Treemultimap	TreeMap	TreeSet
Immutablelistmultimap	Immutablemap	Immutablelist
Immutablesetmultimap	Immutablemap	Immutableset

We use an example to understand how multimap is used:

Public Class Mutlimaptest {Public Static voidMain(String...Args) {Multimap<String, String>Mymultimap= Arraylistmultimap.Create();To add a key-value pairMymultimap.Put("Fruits", "Bannana");Add another element to the fruits elementMymultimap.Put("Fruits", "Apple");Mymultimap.Put("Fruits", "Pear");Mymultimap.Put("Vegetables", "Carrot");Get the size of MultimapIntSize=Mymultimap.Size();System.Out.println(Size);4Get all values corresponding to the fruitsCollection<string>Fruits=Mymultimap.Get("Fruits");System.Out.println(Fruits); [Bannana, Apple, Pear]Collection<string>Vegetables=Mymultimap.Get("Vegetables");System.Out.println(Vegetables); [Carrot]Traverse MutlimapFor(StringValue:Mymultimap.Values()) {System.Out.println(Value); }Removing a single valueMymultimap.Remove("Fruits","Pear");System.Out.println(Mymultimap.Get("Fruits")); //[Bannana, Pear]        //Remove all values for a key    mymultimap. Removeall "Fruits"     system.. Println (mymultimap. "Fruits" //[] (Empty collection!)  }  < Span class= "pun" >}             

Guava Learning Note: multimaps