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 CON         


        

Answer 1

You can write yourself a quick helper function:

@SuppressWarnings("unchecked")
public static  Map ImmutableMap(Object... keyValPair){
    Map map = new HashMap();

    if(keyValPair.length % 2 != 0){
        throw new IllegalArgumentException("Keys and values must be pairs.");
    }

    for(int i = 0; i < keyValPair.length; i += 2){
        map.put((K) keyValPair[i], (V) keyValPair[i+1]);
    }

    return Collections.unmodifiableMap(map);
}

Note the code above isn't going to stop you from overwriting constants of the same name, using CONST_1 multiple places in your list will result in the final CONST_1's value appearing.

Usage is something like:

Map constants = ImmutableMap(
    "CONST_0", 1.0,
    "CONST_1", 2.0
);