How do I access nested HashMaps in Java?

Question

I have a HashMap in Java, the contents of which (as you all probably know) can be accessed by

HashMap.get(\"keyname\");

If a have a HashMap

Answer 1

I prefer creating a custom map that extends HashMap. Then just override get() to add extra logic so that if the map doesnt contain your key. It will a create a new instance of the nested map, add it, then return it.

public class KMap extends HashMap {

    public KMap() {
        super();
    }

    @Override
    public V get(Object key) {
        if (this.containsKey(key)) {
            return super.get(key);
        } else {
            Map value = new KMap();
            super.put((K)key, (V)value);
            return (V)value;
        }
    }
}

Now you can use it like so:

Map>> nestedMap = new KMap>>();

Map map = (Map) nestedMap.get(1).get(2);
Object obj= new Object();
map.put(someKey, obj);