Doh! Of course, you are right about the private static declaration. Why is non-static wrong "conceptually"? It seems that what you are asking for, is something that changes per-instance, because the instances may be of different subclasses. That's exactly what a non-static variable is for.
In fact, making it static is downright wrong, because all instances of A (regardless of which subclass) see the same static variable. If your logger reference must be static then you must put it individually into every subclass. In the case where it's an instance variable in the superclass, you aren't looking up a reference to the logger every time you log, only once per object creation. And of course you aren't creating multiple logger instances, only one per class. This is only a potential performance problem if you are logging within objects that are frequently created. Keith -----Original Message----- From: wleana [mailto:[EMAIL PROTECTED] Sent: 03 April 2003 23:04 To: [EMAIL PROTECTED] Subject: Re: static/inherit problem It doesn't make the difference...:-( Of course, make it non-static will work technically, but conceptually it is not correct, and performance-wise not right either... This should be a very common problem, how does everyone handling this? --- In [EMAIL PROTECTED], "Keith Hatton" <[EMAIL PROTECTED]> wrote: > Perhaps something like this: > > class A { > private static MyLog mLog; > protected myId; > A(){ > this("A"); > } > > protected A(String id) { > myId = id; > init myLog with myId... > } > > public void doSth(String aMsg){ > mLog.debug(aMsg); > } > } > > class B extends A{ > B(){ > super("B"); > } > } > > > Keith > > > -----Original Message----- > From: wleana [mailto:[EMAIL PROTECTED] > Sent: 03 April 2003 10:05 > To: [EMAIL PROTECTED] > Subject: static/inherit problem > > > Hi, I have a design issue related to the fact that the Logger needs > to be static. And suppose I have A and its subclass B. > > I have a wrapper MyLog that wraps around Logger and a myId field of > each class, in which, the log message always print out myId of its > caller. > > class A { > private static MyLog mLog; > protected myId; > A(){ > myId = "A"; > init myLog with myId... > } > > public void doSth(String aMsg){ > mLog.debug(aMsg); > } > } > > class B extends A{ > B(){ > myId = "B"; > super() > } > } > > When I do this: > B b=new B(); > b.doSth("blah"); > > The log will actually show the caller's myId is "A", instead of "B". > (you see I even make the myId field non-static because of the same > issue, but actually I would like it to be static conceptually) > > I have tried different ways, it only works if mLog is not static, the > within doSth from class A, it will actually dynamically use object of > type B's mLog...But we want the Logger class (or its wrapper class) > to belong to class not to an object...how should we solve this? What > should be the right design of this? Please share your thoughts. > > Thanks a lot. > -wleana > > > -------------------------------------------------------------------- - > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > > -------------------------------------------------------------------- - > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
