Question

I have a HashMap<String, Object> that looks like this when I call .toString() on it:

{somekey=false, anotherKey=someString, thirdKey={nestedKey=hello, nestedKey2=world,etc=etcetcetc}}

At a certain point in my script, I would like to iterate over the “thirdKey” set as its own map. Is there a common convention used to isolate a “nested” HashMap and use it as its own one-dimensional map?

Answer 1

Here’s my code for recursively extracting all values from the map (and the maps within these map).

public List<Object> getValues(Map<String, Object> map) {

    List<Object> retVal = new ArrayList<Object>();

    for (Map.Entry<String, Object> entry : map.entrySet()) {
        Object value = entry.getValue();

        if (value instanceof Map) {
            retVal.addAll(getValues((Map) value));
        } else {
            retVal.add(value);
        }
    }

    return retVal;
}

As Vikdor already said, I don’t think there is a real convention for this.

Edit:
You could, of course, also write the keys and values into a new Map (“flattening” it). I just added the values to a List, because this way you don’t run into problems when one of the nested maps uses an already present key.