Java Reference
In-Depth Information
The overriding methods have their own access specifiers. A subclass can
change the access of a superclass's methods, but only to provide more
access. A method declared
protected
in the superclass can be redeclared
protected
(the usual thing to do) or declared
public
, but it cannot be de-
clared
private
or have package access. Making a method less accessible
than it was in a superclass would violate the contract of the superclass,
because an instance of the subclass would not be usable in place of a
superclass instance.
The overriding method is also allowed to change other method modifi-
ers. The
synchronized
,
native
, and
strictfp
modifiers can be freely varied
because they are implementation concerns, as are any annotationssee
od it is overriding cannotsee "
Marking Methods and Classes final
"
on
not have the same signature as an inherited static method, and vice
versa. The overriding method can, however, be made
abstract
, even
though the superclass method was notsee "
Abstract Classes and Meth-
A subclass can change whether a parameter in an overriding method is
final
; a
final
modifier for a parameter is not part of the method signa-
tureit is an implementation detail. Also, the overriding method's
throws
clause can be different from that of the superclass method's as long as
every exception type listed in the overriding method is the same as or
a subtype of the exceptions listed in the superclass's method. That is,
each type in the overriding method's
tHRows
clause must be polymorph-
ically compatible with at least one of the types listed in the
throws
clause
of the supertype's method. This means that the
throws
clause of an over-
riding method can have fewer types listed than the method in the super-
class, or more specific types, or both. The overriding method can even
have no
tHRows
clause, which means that it results in no checked excep-
