All you can do is send a message (AYCDISAM) = Actors model - there is no direct manipulation of objects, only communication with (or invocation of) them. The presence of fields in Java violates this.
from what I understand in Java... there are some variables on classes (class instances) that are only acessible through methods and for those the "only send message" paradigm holds but there are also fields which are like attributes in python which you can change directly