FWIW This will raise a warning in my dev environment as I have declared in my pom file that I use JDK 8. Also I'd consider it better style to only specify the

FWIW This will raise a warning in my dev environment as I have declared in my pom file that I use JDK 8. Also I'd consider it better style to only specify the interface on the left hand side, something like this should work: private final Map<String, Map<String, Record>> searchTree = new TreeMap<>(); Edit: if you use Netbeans with maven it will automatically pick up correct settings from the pom and autocomplete with a shorter version like the one I suggested.