Is there a best practice for writing maps literal style in Java?

Question

In short, if you want to write a map of e.g. constants in Java, which in e.g. Python and Javascript you would write as a literal,

T<String,String> CONSTANTS = {     "CONSTANT_NAME_0": CONSTANT_VALUE_0 ,     "CONSTANT_NAME_1": CONSTANT_VALUE_1 ,     "CONSTANT_NAME_2": CONSTANT_VALUE_2 ,     //... } ; 

is there a Class or any preset Object that you can use for writing a data structure like that?

Answer 1

I like to do it this way:

Map map = new HashMap() {{     put("foo", "bar");     put(123, 456); }}; 

The double {{ }} are an instance initialization block. They are a bit unusual but they are useful. No need for libraries or helpers.

Answer 2

No, Java doesn't have a map literal. The closest you'll come to this is using Google Collections' ImmutableMap:

Map<K,V> CONSTANTS = ImmutableMap.of(     NAME_1, VALUE_1,     NAME_2, VALUE_2     //etc.   );