Henry Zhang

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since Jan 16, 2001
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Recent posts by Henry Zhang

It seems JCert is a new path for Java certification but
there are not many people seeking this way. Sun's certification
is well-known and it's enough to be good reference when you
seek Java jobs. I think JCert will be the future way for Java
certification. Actually you only need to get through IBM's UML
test and plus sun'd SCJD then you can get VCSD and VCED.
So go ahead for Sun's certifications.
If my understanding is correct, you may type
prompt>jar tvf jarfile.jar
to list the path of the files in JAR file.
Hope this clears up a little bit.

[This message has been edited by Henry Zhang (edited February 28, 2001).]
Good morning, Jenny-
Except the suggestions from kiran kumarb, I want to
mention that in UNIX, "/" represents root directory,
but for Java Web Server 2.0, the default servlets directory
should be /absolutePathofJavaWebServerInstallation/servlets
instead of "/servlets".
In order to catch the error messages, you can put
catch (Exception e){
out.println("Exception: "+e.getMessage());
after the try{} block or put out.println("label1,2...")
before or after the code you think it has problem. "out" is
defined by "PrintWriter out = response.getWriter();".
Hope it helps you.
21 years ago
Thank you very much for your help. I'll buy the book you wrote. BTW, your Java 2 Exam Cram did help me a lot to pass the SCPJ2.
Thank you for your consistent contribution for this forum.
21 years ago
I am struggling for this over ten days. Please help me.(^_^)
Everything else is fine, except for the java runtime part (towards the end of the file). The purpose of GQL.java is to take user input from the web interface and query the Oracle DB in my account, then save the SQL query result into a text file called "foo.txt" into my public_html directory; then I need to call a Perl script "newfup.cgi" which resides under the same path as GQL.java, to take the file "foo.txt" as input and generate a GIF file called "plotfile.gif" and put this GIF file to my public_html directory so that the user can see this image file as the final query result.
There must be something wrong with the runtime call. I could execuate the Perl script on the command line by "/usr/bin/perl newfup.cgi". I could get the image file plotfile.gif generated and saved under my public_html directory this way. But it just wouldn't work out from execuating the servlet code.
import java.net.*;
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import oracle.jdbc.driver.*;
public class GQL extends HttpServlet
public void init(ServletConfig config) throws ServletException
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
String cmd = "/usr/bin/perl newfup.cgi";
Runtime r = Runtime.getRuntime();
Process p = r.exec(cmd);
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String tmp = new String();
while (tmp != null)
tmp = in.readLine();
out.println("<img src=\"http://...myAccount.../plotfile.gif\">");
out.println("<img src=\"http://...myAccount.../bully.gif\">");

catch (Exception e)
[This message has been edited by Henry Zhang (edited February 24, 2001).]
21 years ago
Thanks for your reply! I am working on the Developer Certificate. I believe hard working can lead to success.
Happy Valentine!
Dear Adrian-
It seems that I got a similar assignment as yours. It involved
a Flying Booking system which should work locally and remotely.
I was mandatorilly required to use either serialized socket connection or RMI. I decided to use RMI which I never know. And
also must use Swing components(JTable) to build the GUI.
I wonder what books you are reading? And what is your recommendation? I want to know every unfamiliar concept before I start the design.
As for the design, did you use any particular method like UML?
There is another track to get Java developer certification. See my post about that topic Here or you visit www.jcert.com .
Thanks for your reply in advance.
Thanks Neeraj Vasudeva-
Your detail story about Java inventors enlarged my visions. It seems that people's thought is related to their life and environment they are with.
Long live inventions!
21 years ago
Thanks Meadowlark-
You were recalling the mathematics function definition in your dream, weren't you? Could you specify "one-on-one relationship" in more detail? I feel Vendor's Java Developer Certification is harder than SCJD since you have to pass IBM's UML Exam plus any
other company's Java platform implementation.
There are many "programmers" who know writing code but don't know how to design according to customer's specifications. I think UML is a very good standard and tool to set up a bridge between spec and implementation. Passing the SCJD + IBM UML test, you'll get
Vendor's Certified Solution Developer certificate.
I read many Java Senior developers' ads., many requires UML knowledge which I think it's correct because as a Java developer, you should master basic knowledge about software engineering. You should know the whole cycle of project(spec->design->implementation->testing->maintenance). Many projects failed or partially failed because of the step from spec to design.
This is my two cents.
I think the Java Coffee gives them the refreshing idea.
21 years ago
I was wondering who knows the story why SUN people called it
"Java" which is an island name in Indonesia. Java was initially
called "Oak". Why they changes the name because they went to
Java island for a vacation and change their mind?
Who knows the story behind this?
21 years ago
Nobody has the answer? I think this is very important for future
Java certifications. If you work so hard on some under obsolete
Java certification process, the IT industry does not widely accept it. That's sad, isn't it?
I think you passed IBM OOAD with UML test, isn't it? It is very useful for you to pass VCSD(Vendor Certified Solution Developer)
since UML test is a prerequisite for that VCSD test.
See www.jcert.com

Originally posted by Rahul123 Khanna:

Ques 1) It is written in JLS that NaN is unordered. So comparing it with another NaN always results in False.
However look at this code:
class t {
public static void main(String args[]){
Double a = new Double(Double.NaN);
Double b = new Double(Double.NaN);
It produces output TRUE. How is this possible . We know that equals compare the contents of Objects meaning here it should check for the Values of a & b, but as they are unordered therefore it should return false.

NaN is non-ordinal for comparison BUT equals method on wrapper object with a NaN value compares NaN's correctly.
Q2: okButton is put in a "pool" the first time, the second time
JVM will look for the pool, if there is one there, JVM will regard them the same. So there is ONLY one button appears. Rememmber the borderlayout default is CENTER.
Q3: same reason as Q2, 3 okButton only shows one plus another two
newly created buttons - the total is 3 buttons.
hope this helps you.
Hi, All Gurus-
I am thinking to get SCJD(Sun Certified Java Developer) after I got my SCJP. One of my friends told me that there is another way to get Java certifications(see www.jcert.com). I read this forum but don't see many posts talking about their pros/cons. I wonder which is better(say more widely accepted by industries), SCJD(Sun Certified Java Developer)/SCEA(Sun Certified Enterprise Architect) or VCSD(Vendor Certified Solution Developer)/VCED(Vendor Certified Enterprise Developers)?
I read through www.jcert.com, and feel there are more tests needs to be done before you take VCSD, such as "Object-Oriented Analysis and Design with UML test" and a company specific tool test. Is there anyone knew the difficulties of taking those exams? I personally feel the jcert lacks of standards for those tests, but jcert includes some J2EE stuff in their VCED test.
How useful is it to get jcert? Is that more popular than Sun Java certifications? Hope gurus can teach me on these issues.
Thanks in advance.