Henry Zheng

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since Jan 24, 2004
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Recent posts by Henry Zheng

if you cannot receive it, you can send a request to Prometric for follow-up purposes.

Hi Nick,

To whom do we send this request?


Hi all,

I am doing the URLyBird assignment and having some troubles with the records in the db file.

My question is: Since the only field matters in the logic of the application is the date field (thanks to the 48 hour rule) and all other fields are never evaluated or modified, I am not about to parse the record and leave the fields all as Strings. In this way, all I need to do is to parse the Date field once and decide whether to display it or not.

Is it OK? I need your opinions.

Another question is regarding to data validation. I'm not doing any validation at server side, but will check the user input at client side(the owner field). Do I need to take extra attention at server side, and is it necessary to validate the data read from the db file?

Hi all,

As one candidate can only get upto 3 vouchers, my question is, may I apply for another prometric ID and thus become eligible for another 3 vouchers?

Well, a dirty thought though...
Hi all,

I have some questions regarding to enums, please shed some light

1) In the API document, the java.lang.Enum was declared as Class Enum<E extends Enum<E>>, but isn't it a recursive declaration? what does it mean then? "The type parameter should be a type extends Enum<E> in which E is itself?" -- just too complicated for me.

2) Where is the static values() method declared? I didn't find it in the Enum class, however.


(SCJP 5 prefix added to topic title)
[ January 12, 2005: Message edited by: Barry Gaunt ]

1] If I clear beta then will I get dummy cirtificate or anything else ... Because exam it self is not real ...

You will get a full-fledged certificate which is exactly the same as those for a nomal exam.

2] what topics are different in Java 1.5 & Java 1.4 .

You can refer to a spec or a book. Generally speaking, Tiger is quite a different creature

3] if a person is sure that he will clear beta ( with passing marks ) as well as SCJP 1.4 ( with good marks ) then what should be his decision ... he just want any one to give ...

I just agree with Nick, it depends on your point of view. What I know is that many people who have already obtained a SCJP 1.4 are still gonna take the Tiger beta. So am I.
Thanks for your reply

Did you email Evelyn to tell her that you completed the survey right after taking it like she asked? If not, that could be the reason - but I'm not sure.

I did send a confirmation right after finishing the survey.

I sent a mail to Evelyn several days ago but got no reply yet. What could be wrong out there?
Hi all,

Have all survey takers received all their vouchers??

Anyway, I haven't

Just wanna make sure whether all survey takers are eligible for a voucher...
Still waiting for the voucher here...

Hope I can find it in my emails when back from X'mas

I'm currently working with my assignment, and I got a problem regarding to the format of the text fields in the db file.

My assignment mandates all text fields be "null terminated if less than the maximum length for the field"(directly quoted from instructions).

But when I checked the original db file comes along with the assignment, I found that text fields are padded by spaces.

So should I pad the empty bytes with 0 or with white spaces? And do I need to consider the whitespace padding in the original records part of the fields(which is not sensible) or just rip them off?

My choice is P: The Biker Couple

The reason is that the couple in the photo reminds of one of those patterns: the decorator pattern -- The outside one holds the inner one on arms, just like one class decorates another.

Remember the figure that demonstrates the decorator pattern in the GoF book? It's exactly the same
15 years ago
Hey guys,

I read the "Effective Java" the other day and got quite confused with the threading section.

The author wrote that without synchronization, change on a variable made by one thread is not guaranteed to be visible to other threads, even they made their accesses after the change had token place.

How come this could happen? The threads access a variable might not get the most recent version of it without synchronization?

Really hope someone could shed some light.

Thanks Andrew

For question 2, I wanna know whether we could use collection.synchronizedMap() to create a synchronized map instead of synchronize the access to the map manually?

Hey guys, I've been working with my URLyBird assignment for a while, and I got some question regarding to server design. Hope someone could help

1. Are we allowed to implement the locking logic in a custom LockManager class, but leave the lock/unlock method in the Data class empty?

2. Would it be fine if I create a WeakHashMap as synchronized instead of manually synchronize accesses to the map in methods?

3. I suggest that the Data class is the class accessing the DB File on server side, is that right? But I read in some thread that every client would have its Data instance? Anyone can clarify on this?

4. How do we track client connections? Do we need to assign a session ID to every client connection? And how do we maintain those IDs? In another WeakHashMap?

Nick, me too need your help