Product Version = NetBeans IDE 7.3 (Build 201302132200)
Operating System = Linux version 3.2.0-44-generic running on amd64
Java; VM; Vendor = 1.7.0_11
Runtime = Java HotSpot(TM) 64-Bit Server VM 23.6-b04

The suggestion for "Unnecessary test for null" is incorrect.  I have something like:
public class NewClass {
    public static void main( String[] args ) {
        HashMap<String,String> m= new HashMap();
        String alpha= m.get("alpha");
        if ( alpha==null && m.containsKey("alphanumeric") ) {
            alpha= "T";
        }
        if ( alpha==null ) {
            System.err.println( "alpha is null" );
        }
    }
}

 and I'm getting the suggestion on the "alpha==null" test.