Literal declaration of HashMap in Java [duplicate]

Question

In JavaScript, you can declare all the keys and value combinations for a JSON object in one go as follows...

var myJSON = {
    'key1' : 'value 1',
    'key2' : 'value 2',
    'key3' : 'value 3',
    'key4' : 'value 4',
    'key5' : 'value 5',
    'key6' : 'value 6'
};

I was wondering whether we can do something similar in Java for HashMaps.

HashMap<String, String> map = new HashMap<String, String>(
    "Key 1", "Value 1",
    "Key 2", "Value 2",
    "Key 3", "Value 3"
);

Basically, I need this as a one time read only thing as Config for the other parts of my code. I searched and tried a few solutions, but was not able to make them work. Or is there a better approach that I can do?

Answer 1

Though {{ (double brace) is an anti pattern, something like this you can write

HashMap<String, String> map = new HashMap<String, String>(){{
put("Key 1", "Value 1");
put("Key 2", "Value 2");
put("Key 3", "Value 3");    
}};

Edit :

If you are looking for a better way to put elements, iterate over your json and put key values in a loop.

Answer 2

There is no concept of map literals in Java but you can easily write a utility method to achieve something similar. See this implementation for example. You can then initialise a map (using static imports):

Map<String, String> map = map("k1", "v1", "k2", "v2");

An alternative is to use the "double brace initialisation" syntax but it creates an anonymous inner class which is not necessarily a good idea.