I have just added support for concrete collections to
J15:  use Ctrl-1 on the creation of a concrete collection and J15 will add the
correct Generic parameters.

Before:

List l2 = new ArrayList();
Float n2 = new Float(42);
l2.add(n2);

After:

ArrayList<Float> l2 = new ArrayList<Float>();
Float n2 = new Float(42);
l2.add(n2);

Before:

Map m = new HashMap();
m.put(new Integer(42), "Cedric");

After:

HashMap<Integer, String> m = new HashMap<Integer, String>();
m.put(new Integer(42), "Cedric");

Let me know if you can think of other conversions that this plug-in could make
for you.