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

As others have said you can do this but you should define the map with generics like so:

Map> map = new HashMap>();

However, if you just blindly run the following:

map.get("keyname").get("nestedkeyname");

you will get a null pointer exception whenever keyname is not in the map and your program will crash. You really should add the following check:

String valueFromMap = null;
if(map.containsKey("keyname")){
  valueFromMap = map.get("keyname").get("nestedkeyname");
}