Prashant Soood wrote:But I can write public static final String abc="Hello"; in an interface
True enough. I guess 'field' is kind of ambiguous. What the writer means to say is interfaces cannot have variables. The only fields allowed in an interface are constant (final) fields. Some would classify "field" as a variable, some would also call constants "fields". It's a matter of interpretation.
Mind: interface constants are NOT inherently immutable. So while you cannot reassign final references, you can reassign the properties (if any) of the object a final reference is pointing to, unless that object is immutable.