Looking at the Reflection API I'd say you missed the parameterTypes
. I'd assume it to be:
Object obj2 = coll.getClass().getMethod("find", new Class[]{})
.invoke(coll, new Object[]{});
or
Object obj2 = coll.getClass().getMethod("find",null)
.invoke(coll, new Object[]{});
Look at this example as well.