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Laura Williamson

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since Apr 28, 2004
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Recent posts by Laura Williamson

Hi - I have a simple applet that reads in from a text file and displays the values to the screen. Has anyone done this, but reading in from Excel file instead? Thanks
16 years ago
hurrah - thanks guys this site was invaluable. took me forever as was busy at work but got there in the end...onto SCEA...L
17 years ago
Hi - need a bit of advice. I have a program that moves files from one directory to another (and then does some stuff...). The program has multiple threads running e.g.

//in main
XmlCompare xc = new XmlCompare();
Thread t1 = new Thread(xc);

XmlCompare xc2 = new XmlCompare();
Thread t2 = new Thread(xc2);

The problem is that while one thread is moving a file from dir1 to dir2, no other thread should be able to move a file. But I don't think I can sychronize because I have multiple objects? Or can I? I thought about using some kind of lock, so the first thread sets lockCookie to "locked" and while lockCookie.equals("locked") the second thread cannot move the file. But if I have two XmlCompare objects, and lockCookie is a variable within the XmlCompare class, then each object will have its own instance of lockCookie. So was thinking could write a cookie to a file, delete when done - i.e. external to the actual program, but seems kind of clumsy. Any suggestions on best way to do this?

Also - two more questions - why are threads spawned one per object? i.e. why not have:

XmlCompare xc = new XmlCompare();
Thread t1 = new Thread(xc);
Thread t2 = new Thread(xc);

Also, I am setting the name using Thread.setName in main, but in run the name always comes out as -1, or -3 or whatever. Why is this?

All advice appreciated.


Is there anything specific i need to revise for the exam - or just go back over assignment notes, etc...

Doing B&S (...still...) just wondering can I tweak DBAccess interface to implement RMI?


hmm thanks for your replies. i am still a bit confused. i am doing boggit and scraper..i have coded my GUI and database access code, works fine as standalone. then i have coded a simple RMI program separately. Unsure how to integrate them...should there not just be one GUI? Does the RMI code not just call networked data code?

all advice appreciated


Ok so I am good with passing in an arg at the command line - but does the program itself need to start the rmiregistry and server, or would the user do that manually?
rmiregistry &
java HelloServer &

I assume that the user at the server end would start these manually, so we are not expected to code them?

Unsure on the following:

"The operating mode is selected using the single command line argument that is permitted."

How does this work? java GUI is the command that kicks off my program - can this take an additional argument?
Thanks for yr help.
I should add that all is well when I compile with:

javac -d . suncertify\db\*java

But when I try to run a class within the package (e.g.
I get 'Exception in thread "main" java.lang.NoClassDefFoundError: MyTest

I have been working on something else for a while and have foolishly forgotten how to set up classpath/package structure properly as am getting class not found errors. I am on Windows NT.

I have altered autoexec.bat to include: set CLASSPATH = C:suncertify\db
The files I am trying to execute are located at: C:\suncertify\db
The package statement at the top of each file reads package suncertify.db;

Do I have to add another PATH or CLASSPATH statement to autoexec?
along the lines of: set PATH =j2sdk1.4_01\bin;

Thanks - sorry for the thick question but have been doing non-Java stuff for 5 months and forgotten this rudimentary thing.
re Record v String []
-- ok, i got it.

re: time

I think I am pretty much an average programmer - in terms of the programmers who would be sitting this cert. I have an MSc Comp Sci and about 1 year commercial experience (but not in Java). Working with other programmers, I would normally be about maybe 3rd or 4th in a team of 10 - (based on speed, ease of solving problems, code actually working and passing testing, etc, etc) I'm not brilliant, but I can work it out (usually). I got 73% in the SJPC - again, about average. I think the assignment would take me between 100-200 hours. Maybe closer to 200 by the time I test and document it all. But I am not working on it solidly, as I work full-time. I just happen to be on 'training' this week...
no probs, i got it now, thanks very much.

i read somewhere (on Sun site?) that a decent programmer would finish this assignment in 20 hours!! which makes me think that I must be really crap. o well, perseverance conquers all, i mean, most things...

one more question
any preference on storing record as a string [] of data
as opposed to
creating a Record object (i.e. having a record class, with the data as the fields?)
just wondering..........i've gone for string [] data, but maybe a Record would be more OO
1) OK I assume where you put "ANY" you mean "NULL" ??

Case 0:

Criteria[0] = "Pete"
Criteria[1] = "ANY"
Criteria[2] = "ANY"

2) Match on fields makes sense to me. criteria [n] must match field [n] not just any field.
// Returns an array of record numbers that match the specified
// criteria. Field n in the database file is described by
// criteria[n]. A null value in criteria[n] matches any field
// value. A non-null value in criteria[n] matches any field
// value that begins with criteria[n]. (For example, "Fred"
// matches "Fred" or "Freddy".)

-- this is (perhaps intentionally) unclear.
-- do I have to match on posn. within the array or just on the search term?
e.g. if Fred is in the criteria array, at the posn. for owner, should i also return Fred's Frog Legs if that is the company name? or only searching for matches at posn[n]. Does that make sense? Is the match on any value in any field? or any value in a specific field?

--null in any of the criteria elements will return all records, no?