How is the generic type getting inferred here?

Question

public static void main(String[] args) {
    Map>> map = getHashMap();
}

static  Map getHashM         


        

Answer 1

The getHashMap function does not have to infer the types. It's at the call site that javac is required by the Java Language Spec to infer that the types agree (15.12.2.7 Inferring Type Arguments Based on Actual Arguments).

I believe the current plan is (still) for JDK7 to support the diamond operator, so this sort of thing will work with new too, although with a bit of apparently pointless syntax.

Map>> map = new HashMap<>();
                                                      ^^diamond