Java constructs map and initializes map

First method: Static block initialization

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2. Public class demo{
4. private Static final map<string, string> MyMap;
6. Static
8. {
10. MyMap = new hashmap<string, string> ();
12. Mymap.put ("A", "B");
14. Mymap.put ("C", "D");
16. }
18. }

Second method: Double-brace initialization (anonymous inner class)

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1. Hashmap<string, String > H = new hashmap<string, string> () {{
2. Put ("a","B");
3. }};

Caution, non-static inner class/Anonymous inner class contains a reference to a perimeter instance, and if you have a longer life cycle than the external class, there is a third method of memory leak: Guava

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1. Map<string, integer> left = Immutablemap.of ("A", 1, "B", 2, "C", 3);
2. Or
3. map<string, string> test = immutablemap.<string, String>builder ()
4. . put ("K1", "v1")
5. . put ("K2", "v2")
6. ...
7. . build ();

Java constructs map and initializes map