I have implemented a HashMap in the following way:
HashMap<Long,ArrayList<MouseEnterListener>> map = new HashMap<>();
map.put( id,new ArrayList<MouseEnterListener>());
When trying to access the map, I get a NullPointerException:
for( MouseEnterListener mouseEnterListener: map.get( id ) ) // Exception here
mouseEnterListener.invoke( entered );
What I’ve debugged sofar:
- “id” is correct and the HashMap contains an entry for this id
- the size of the “map” is 1, while the ArrayList is empty
What’s going wrong here?