• Map.getOrDefault method could be used to replace the code like this:

        aValue = map.get(aKey);
        if (aValue == null) {
          aValue = "none";
        }
      

• Map.computeIfAbsent method could be used to replace the code like this:

        List<String> list = map.get(key);
        if (list == null) {
          list = new ArrayList<>();
          map.put(key, list);
        }
      

• Map.putIfAbsent method could be used to replace the code like this:

        String val = map.get(key);
        if (val == null) {
          map.put(key, newVal);
        }
      

• Map.merge method could be used to replace the code like this:

        Integer val = map.get(key);
        if (val == null) {
          map.put(key, 1);
        } else {
          map.put(key, val + 1);
        }
      

This inspection is available since Java 8 only.