How to directly initialize a HashMap (in a literal way)?

Question

Is there some way of initializing a Java HashMap like this?:

Map test = 
    new HashMap{\"test\":\"test\",\"test\         


        

Answer 1

You could possibly make your own Map.of (which is only available in Java 9 and higher) method easily in 2 easy ways

Make it with a set amount of parameters

Example

public  Map mapOf(K k1, V v1, K k2, V v2 /* perhaps more parameters */) {
    return new HashMap() {{
      put(k1, v1);
      put(k2,  v2);
      // etc...
    }};
}

Make it using a List

You can also make this using a list, instead of making a lot of methods for a certain set of parameters.

Example

public  Map mapOf(List keys, List values) {
   if(keys.size() != values.size()) {
        throw new IndexOutOfBoundsException("amount of keys and values is not equal");
    }

    return new HashMap() {{
        IntStream.range(0, keys.size()).forEach(index -> put(keys.get(index), values.get(index)));
    }};
}

Note It is not recommended to use this for everything as this makes an anonymous class every time you use this.