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  • Ways to ensure unique instances of a class?

    - by Peanut
    I'm looking for different ways to ensure that each instance of a given class is a uniquely identifiable instance. For example, I have a Name class with the field name. Once I have a Name object with name initialised to John Smith I don't want to be able to instantiate a different Name object also with the name as John Smith, or if instantiation does take place I want a reference to the orginal object to be passed back rather than a new object. I'm aware that one way of doing this is to have a static factory that holds a Map of all the current Name objects and the factory checks that an object with John Smith as the name doesn't already exist before passing back a reference to a Name object. Another way I could think of off the top of my head is having a static Map in the Name class and when the constructor is called throwing an exception if the value passed in for name is already in use in another object, however I'm aware throwing exceptions in a constructor is generally a bad idea. Are there other ways of achieving this?

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  • What is the effect of this order_by clause?

    - by bread
    I don't understand what this order_by clause is doing and whether I need it or not: select c.customerid, c.firstname, c.lastname, i.order_date, i.item, i.price from items_ordered i, customers c where i.customerid = c.customerid group by c.customerid, i.item, i.order_date order by i.order_date desc; This produces this data: 10330 Shawn Dalton 30-Jun-1999 Pogo stick 28.00 10101 John Gray 30-Jun-1999 Raft 58.00 10410 Mary Ann Howell 30-Jan-2000 Unicycle 192.50 10101 John Gray 30-Dec-1999 Hoola Hoop 14.75 10449 Isabela Moore 29-Feb-2000 Flashlight 4.50 10410 Mary Ann Howell 28-Oct-1999 Sleeping Bag 89.22 10339 Anthony Sanchez 27-Jul-1999 Umbrella 4.50 10449 Isabela Moore 22-Dec-1999 Canoe 280.00 10298 Leroy Brown 19-Sep-1999 Lantern 29.00 10449 Isabela Moore 19-Mar-2000 Canoe paddle 40.00 10413 Donald Davids 19-Jan-2000 Lawnchair 32.00 10330 Shawn Dalton 19-Apr-2000 Shovel 16.75 10439 Conrad Giles 18-Sep-1999 Tent 88.00 10298 Leroy Brown 18-Mar-2000 Pocket Knife 22.38 10299 Elroy Keller 18-Jan-2000 Inflatable Mattress 38.00 10438 Kevin Smith 18-Jan-2000 Tent 79.99 10101 John Gray 18-Aug-1999 Rain Coat 18.30 10449 Isabela Moore 15-Dec-1999 Bicycle 380.50 10439 Conrad Giles 14-Aug-1999 Ski Poles 25.50 10449 Isabela Moore 13-Aug-1999 Unicycle 180.79 10101 John Gray 08-Mar-2000 Sleeping Bag 88.70 10299 Elroy Keller 06-Jul-1999 Parachute 1250.00 10438 Kevin Smith 02-Nov-1999 Pillow 8.50 10101 John Gray 02-Jan-2000 Lantern 16.00 10315 Lisa Jones 02-Feb-2000 Compass 8.00 10449 Isabela Moore 01-Sep-1999 Snow Shoes 45.00 10438 Kevin Smith 01-Nov-1999 Umbrella 6.75 10298 Leroy Brown 01-Jul-1999 Skateboard 33.00 10101 John Gray 01-Jul-1999 Life Vest 125.00 10330 Shawn Dalton 01-Jan-2000 Flashlight 28.00 10298 Leroy Brown 01-Dec-1999 Helmet 22.00 10298 Leroy Brown 01-Apr-2000 Ear Muffs 12.50 While if I remove the order_by clause completely, as in this query: select c.customerid, c.firstname, c.lastname, i.order_date, i.item, i.price from items_ordered i, customers c where i.customerid = c.customerid group by c.customerid, i.item, i.order_date; I get these results: 10101 John Gray 30-Dec-1999 Hoola Hoop 14.75 10101 John Gray 02-Jan-2000 Lantern 16.00 10101 John Gray 01-Jul-1999 Life Vest 125.00 10101 John Gray 30-Jun-1999 Raft 58.00 10101 John Gray 18-Aug-1999 Rain Coat 18.30 10101 John Gray 08-Mar-2000 Sleeping Bag 88.70 10298 Leroy Brown 01-Apr-2000 Ear Muffs 12.50 10298 Leroy Brown 01-Dec-1999 Helmet 22.00 10298 Leroy Brown 19-Sep-1999 Lantern 29.00 10298 Leroy Brown 18-Mar-2000 Pocket Knife 22.38 10298 Leroy Brown 01-Jul-1999 Skateboard 33.00 10299 Elroy Keller 18-Jan-2000 Inflatable Mattress 38.00 10299 Elroy Keller 06-Jul-1999 Parachute 1250.00 10315 Lisa Jones 02-Feb-2000 Compass 8.00 10330 Shawn Dalton 01-Jan-2000 Flashlight 28.00 10330 Shawn Dalton 30-Jun-1999 Pogo stick 28.00 10330 Shawn Dalton 19-Apr-2000 Shovel 16.75 10339 Anthony Sanchez 27-Jul-1999 Umbrella 4.50 10410 Mary Ann Howell 28-Oct-1999 Sleeping Bag 89.22 10410 Mary Ann Howell 30-Jan-2000 Unicycle 192.50 10413 Donald Davids 19-Jan-2000 Lawnchair 32.00 10438 Kevin Smith 02-Nov-1999 Pillow 8.50 10438 Kevin Smith 18-Jan-2000 Tent 79.99 10438 Kevin Smith 01-Nov-1999 Umbrella 6.75 10439 Conrad Giles 14-Aug-1999 Ski Poles 25.50 10439 Conrad Giles 18-Sep-1999 Tent 88.00 10449 Isabela Moore 15-Dec-1999 Bicycle 380.50 10449 Isabela Moore 22-Dec-1999 Canoe 280.00 10449 Isabela Moore 19-Mar-2000 Canoe paddle 40.00 10449 Isabela Moore 29-Feb-2000 Flashlight 4.50 10449 Isabela Moore 01-Sep-1999 Snow Shoes 45.00 10449 Isabela Moore 13-Aug-1999 Unicycle 180.79 I'm not sure what the order_by is doing here and if it's having the intended effects.

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  • Tricky SQL query involving consecutive values

    - by Gabriel
    I need to perform a relatively easy to explain but (given my somewhat limited skills) hard to write SQL query. Assume we have a table similar to this one: exam_no | name | surname | result | date ---------+------+---------+--------+------------ 1 | John | Doe | PASS | 2012-01-01 1 | Ryan | Smith | FAIL | 2012-01-02 <-- 1 | Ann | Evans | PASS | 2012-01-03 1 | Mary | Lee | FAIL | 2012-01-04 ... | ... | ... | ... | ... 2 | John | Doe | FAIL | 2012-02-01 <-- 2 | Ryan | Smith | FAIL | 2012-02-02 2 | Ann | Evans | FAIL | 2012-02-03 2 | Mary | Lee | PASS | 2012-02-04 ... | ... | ... | ... | ... 3 | John | Doe | FAIL | 2012-03-01 3 | Ryan | Smith | FAIL | 2012-03-02 3 | Ann | Evans | PASS | 2012-03-03 3 | Mary | Lee | FAIL | 2012-03-04 <-- Note that exam_no and date aren't necessarily related as one might expect from the kind of example I chose. Now, the query that I need to do is as follows: From the latest exam (exam_no = 3) find all the students that have failed (John Doe, Ryan Smith and Mary Lee). For each of these students find the date of the first of the batch of consecutively failing exams. Another way to put it would be: for each of these students find the date of the first failing exam that comes after their last passing exam. (Look at the arrows in the table). The resulting table should be something like this: name | surname | date_since_failing ------+---------+-------------------- John | Doe | 2012-02-01 Ryan | Smith | 2012-01-02 Mary | Lee | 2012-01-04 Ann | Evans | 2012-02-03 How can I perform such a query? Thank you for your time.

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  • Odd SQL Results

    - by Ryan Burnham
    So i have the following query Select id, [First], [Last] , [Business] as contactbusiness, (Case When ([Business] != '' or [Business] is not null) Then [Business] Else 'No Phone Number' END) from contacts The results look like id First Last contactbusiness (No column name) 2 John Smith 3 Sarah Jane 0411 111 222 0411 111 222 6 John Smith 0411 111 111 0411 111 111 8 NULL No Phone Number 11 Ryan B 08 9999 9999 08 9999 9999 14 David F NULL No Phone Number I'd expect record 2 to also show No Phone Number If i change the "[Business] is not null" to [Business] != null then i get the correct results id First Last contactbusiness (No column name) 2 John Smith No Phone Number 3 Sarah Jane 0411 111 222 0411 111 222 6 John Smith 0411 111 111 0411 111 111 8 NULL No Phone Number 11 Ryan B 08 9999 9999 08 9999 9999 14 David F NULL No Phone Number Normally you need to use is not null rather than != null. whats going on here?

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  • Creating an excel macro to sum lines with duplicate values

    - by john
    I need a macro to look at the list of data below, provide a number of instances it appears and sum the value of each of them. I know a pivot table or series of forumlas could work but i'm doing this for a coworker and it has to be a 'one click here' kinda deal. The data is as follows. A B Smith 200.00 Dean 100.00 Smith 100.00 Smith 50.00 Wilson 25.00 Dean 25.00 Barry 100.00 The end result would look like this Smith 3 350.00 Dean 2 125.00 Wilson 1 25.00 Barry 1 100.00 Thanks in advance for any help you can offer!

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  • Simple Select Statement on MySQL Database Hanging

    - by AlishahNovin
    I have a very simple sql select statement on a very large table, that is non-normalized. (Not my design at all, I'm just trying to optimize while simultaneously trying to convince the owners of a redesign) Basically, the statement is like this: SELECT FirstName, LastName, FullName, State FROM Activity Where (FirstName=@name OR LastName=@name OR FullName=@name) AND State=@state; Now, FirstName, LastName, FullName and State are all indexed as BTrees, but without prefix - the whole column is indexed. State column is a 2 letter state code. What I'm finding is this: When @name = 'John Smith', and @state = '%' the search is really fast and yields results immediately. When @name = 'John Smith', and @state = 'FL' the search takes 5 minutes (and usually this means the web service times out...) When I remove the FirstName and LastName comparisons, and only use the FullName and State, both cases above work very quickly. When I replace FirstName, LastName, FullName, and State searches, but use LIKE for each search, it works fast for @name='John Smith%' and @state='%', but slow for @name='John Smith%' and @state='FL' When I search against 'John Sm%' and @state='FL' the search finds results immediately When I search against 'John Smi%' and @state='FL' the search takes 5 minutes. Now, just to reiterate - the table is not normalized. The John Smith appears many many times, as do many other users, because there is no reference to some form of users/people table. I'm not sure how many times a single user may appear, but the table itself has 90 Million records. Again, not my design... What I'm wondering is - though there are many many problems with this design, what is causing this specific problem. My guess is that the index trees are just too large that it just takes a very long time traversing the them. (FirstName, LastName, FullName) Anyway, I appreciate anyone's help with this. Like I said, I'm working on convincing them of a redesign, but in the meantime, if I someone could help me figure out what the exact problem is, that'd be fantastic.

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  • Is it possible to use ContainsTable to get results for more than one column?

    - by LockeCJ
    Consider the following table: People FirstName nvarchar(50) LastName nvarchar(50) Let's assume for the moment that this table has a full-text index on it for both columns. Let's suppose that I wanted to find all of the people named "John Smith" in this table. The following query seems like a perfectly rational way to accomplish this: SELECT * from People p INNER JOIN CONTAINSTABLE(People,*,'"John*" AND "Smith*"') Unfortunately, this will return no results, assuming that there is no record in the People table that contains both "John" and "Smith" in either the FirstName or LastName columns. It will not match a record with "John" in the FirstName column, and "Smith" in the LastName column, or vice-versa. My question is this: How does one accomplish what I'm trying to do above? Please consider that the example above is simplified. The real table I'm working with has ten columns and the input I'm receiving is a single string which is split up based on standard word breakers (space, dash, etc.)

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  • Parsing complex string using regex

    - by wojtek_z
    My regex skills are not very good and recently a new data element has thrown my parser into a loop Take the following string "+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write" Previously I had the following for my regex : [+\\-/] Which would turn the result into USER=Bob Smith GROUP=Admin FUNCTION=Read FUNCTION=Write FUNCTION=Read But now I have values with dashes in them which is causing bad output New string looks like "+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write/FUNCTION=Read-Write" Which gives me the following result , and breaks the key = value structure. USER=Bob Smith GROUP=Admin FUNCTION=Read FUNCTION=Write FUNCTION=Read Write Can someone help me formulate a valid regex for handling this or point me to some key / value examples. Basically I need to be able to handle + - / signs in order to get combinations.

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  • Are there any well known algorithms to detect the presence of names?

    - by Rhubarb
    For example, given a string: "Bob went fishing with his friend Jim Smith." Bob and Jim Smith are both names, but bob and smith are both words. Weren't for them being uppercase, there would be less indication of this outside of our knowledge of the sentence. Without doing grammar analysis, are there any well known algorithms for detecting the presence of names, at least Western names?

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  • Need help joining tables...

    - by yuudachi
    I am a MySQL newbie, so sorry if this is a dumb question.. These are my tables. student table: SID (primary) student_name advisor (foreign key to faculty.facultyID) requested_advisor (foreign key to faculty.facultyID) faculty table: facultyID (primary key) advisor_name I want to query a table that shows everything in the student table, but I want advisor and requested_advisor to show up as names, not the ID numbers. so like it displays like this on the webpage: Student Name: Jane Smith SID: 860123456 Current Advisor: John Smith Requested advisor: James Smith not like this Student Name: Jane Smith SID: 860123456 Current Advisor: 1 Requested advisor: 2 SELECT student.student_name, SID, student_email, faculty.advisor_name FROM student INNER JOIN faculty ON student.advisor = faculty.facultyID; this comes out close, but I don't know how to get the requested_advisor to show up as a name.

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  • Setting variables in shell script by running commands

    - by rajya vardhan
    >cat /tmp/list1 john jack >cat /tmp/list2 smith taylor It is guaranteed that list1 and list2 will have equal number of lines. f(){ i=1 while read line do var1 = `sed -n '$ip' /tmp/list1` var2 = `sed -n '$ip' /tmp/list2` echo $i,$var1,$var2 i=`expr $i+1` echo $i,$var1,$var2 done < $INFILE } So output of f() should be: 1,john,smith 2,jack,taylor But getting 1,p,p 1+1,p,p If i replace following: var1 = `sed -n '$ip' /tmp/list1` var2 = `sed -n '$ip' /tmp/list2` with this: var1=`head -$i /tmp/vip_list|tail -1` var2=`head -$i /tmp/lb_list|tail -1` Then output: 1,john,smith 1,john,smith Not an expert of shell, so please excuse if sounds childish :)

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  • Creating one row of information in excel using a unique value

    - by user1426513
    This is my first post. I am currently working on a project at work which requires that I work with several different worksheets in order to create one mail master worksheet, as it were, in order to do a mail merge. The worksheet contains information regarding different purchases, and each purchaser is identified with their own ID number. Below is an example of what my spreadsheet looks like now (however I do have more columns): ID Salutation Address ID Name Donation ID Name Tickets 9 Mr. John Doe 123 12 Ms. Jane Smith 100.00 12 Ms.Jane Smith 300.00 12 Ms. Jane Smith 456 22 Mr. Mike Man 500.00 84 Ms. Jo Smith 300.00 What I would like to do is somehow sort my data so that everythign with the same unique identifier (ID) lines up on the same row. For example ID 12 Jane Smith - all the information for her will show up under her name matched by her ID number, and ID 22 will match up with 22 etc... When I merged all of my spreadsheets together, I sorted them all by ID number, however my problem is, not everyone who made a donation bought a ticket or some people just bought tickets and nothing us, so sorting doesn't work. Hopefully this makes sense. Thanks in advance.

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  • Android ActiveSync/Outlook Error

    - by Kyle B.
    Getting the following error when attempt to press "Refresh" inside the Mail app for an exchange server account. Using an Android 2.1 device (Evo). "Exchange email synchronization is disabled". I can send outbound messages, but new emails are not coming in. Anyone know what would cause this error? Thanks, Kyle

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  • Sirius Satellite Radio Streaming via XBOX 360

    - by Kyle B.
    Anyone have any luck with this? I've found a number of articles which point to an application uSirius which is apparently discontinued (bought out by Apple or something it looks like) but it is nowhere I have found. Basically I know media center has some baked in functionality for XM radio streaming, but nothing for Sirius radio. Anyone have any luck with this? Thanks, Kyle

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  • Run script after switching user account "to the same account"

    - by Peter Sivák
    In Ubuntu, when I click on Switch User Account... and then choose the same account to log in (for example if my name is John Smith, I click on switch user account and then log into the John Smith account again), how can I run a script after that? (I know, that I can run a script after "first" login by putting it in /etc/profile file, but this script is not executed again when I choose switch user account and then immediately log in back to the same account.)

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  • GDL Presents: Women Techmakers with JESS3

    GDL Presents: Women Techmakers with JESS3 Join Leslie, COO and Co-founder of JESS3, in conversation with Megan Smith and Betsy Masiello, as they discuss Leslie's experience growing a design business from two employees to a transnational operation. Hosts: Megan Smith - Vice President, Google [x] | Betsy Masiello - Policy Manager Guest: Leslie Bradshaw - President, COO and Co-founder, JESS3 From: GoogleDevelopers Views: 0 3 ratings Time: 01:00:00 More in Science & Technology

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  • How to count the most recent value based on multiple criteria?

    - by Andrew
    I keep a log of phone calls like the following where the F column is LVM = Left Voice Mail, U = Unsuccessful, S = Successful. A1 1 B1 Smith C1 John D1 11/21/2012 E1 8:00 AM F1 LVM A2 2 B2 Smith C2 John D2 11/22/2012 E1 8:15 AM F2 U A3 3 B3 Harvey C3 Luke D3 11/22/2012 E1 8:30 AM F3 S A4 4 B4 Smith C4 John D4 11/22/2012 E1 9:00 AM F4 S A5 5 B5 Smith C5 John D5 11/23/2012 E5 8:00 AM F5 LVM This is a small sample. I actually have over 700 entries. In my line of work, it is important to know how many unsuccessful (LVM or U) calls I have made since the last Successful one (S). Since values in the F column can repeat, I need to take into consideration both the B and C column. Also, since I can make a successful call with a client and then be trying to contact them again, I need to be able to count from the last successful call. My G column is completely open which is where I would like to put a running total for each client (G5 would = 1 ideally while G4 = 0, G3 = 0, G2 = 2, G1 = 1 but I want these values calculated automatically so that I do not have scroll through 700 names).

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  • MS Word 2010: Hide citation title when 2 publications by same first author from different years are in one citation block

    - by srunni
    I'm trying to hide the display of the titles for two publications by the same first author from different years that are in the same citation block. By default, the title is shown in citations when there are two publications by the same author in a given document. The easiest way to get around this is to right click on the citation, click "Edit Citation", and then suppress the title. However, the issue with this is that if there are 2 citations in 1 citation block (i.e., "(Smith, J., et al. 2010, Smith, J., et al. 2011)" rather than "(Smith, J., et al. 2010) (Smith, J., et al. 2011)"), then using that suppress option only suppresses the title for the first citation (in this case, the 2010 publication). OTOH, if I try to initially insert the publications in separate citation blocks, I can suppress the title in both citations, but I can't cut and paste one into the other's citation block. I can click "Cut" and the citation that was just cut disappears, but the "Paste" option is not available when my cursor is in the second citation block. Any ideas? Thanks!

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  • WebCenter Content (WCC) Trace Sections

    - by Kevin Smith
    Kyle has a good post on how to modify the size and number of WebCenter Content (WCC) trace files. His post reminded me I have been meaning to write a post on WCC trace sections for a while. searchcache - Tells you if you query was found in the WCC search cache. searchquery - Shows the processing of the query as it is converted form what the user submitted to the end query that will be sent to the database. Shows conversion from the universal query syntax to the syntax specific to the search solution WCC is configured to use. services (verbose) - Lists the filters that are called for each service. This will let you know what filters are available for each service and will also tell you what filters are used by WCC add-on components and any custom components you have installed. The How To Component Sample has a list of filters, but it has not been updated since 7.5, so it is a little outdated now. With each new release WCC adds more filters. If you have a filter that has no code attached to it you will see output like this: services/6    09.25 06:40:26.270    IdcServer-423    Called filter event computeDocName with no filter plugins registered When a WCC add-on or custom component uses a filter you will see trace output like this: services/6    09.25 06:40:26.275    IdcServer-423    Calling filter event postValidateCheckinData on class collections.CollectionValidateCheckinData with parameter postValidateCheckinDataservices/6    09.25 06:40:26.275    IdcServer-423    Calling filter event postValidateCheckinData on class collections.CollectionFilters with parameter postValidateCheckinData As you can see from this sample output it is possible to have multiple code points using the same filter. systemdatabase - Dumps the database call AFTER it executes. This can be somewhat troublesome if you are trying to track down some weird database problems. We had a problem where WCC was getting into a deadlock situation. We turned on the systemdatabase trace section and thought we had the problem database call, but it turned out since it printed out the database call after it was executed we were looking at the database call BEFORE the one causing the deadlock. We ended up having to turn on tracing at the database level to see the database call WCC was making that was causing the deadlock. socketrequests (verbose) - dumps the actual messages received and sent over the socket connection by WCC for a service. If you have gzip enabled you will see junk on the response coming back from WCC. For debugging disable the gzip of the WCC response.Here is an example of the dump of the request for a GET_SEARCH_RESULTS service call. socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: REMOTE_USER=sysadmin.USER-AGENT=Java;.Stel socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: lent.CIS.11g.CONTENT_TYPE=text/html.HEADER socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: _ENCODING=UTF-8.REQUEST_METHOD=POST.CONTEN socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: T_LENGTH=270.HTTP_HOST=CIS.$$$$.NoHttpHead socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: ers=0.IsJava=1.IdcService=GET_SEARCH_RESUL socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: [email protected] socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: calData.SortField=dDocName.ClientEncoding= socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: UTF-8.IdcService=GET_SEARCH_RESULTS.UserTi socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: meZone=UTC.UserDateFormat=iso8601.SortDesc socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: =ASC.QueryText=dDocType..matches..`Documen socketrequests/6 09.25 06:46:02.501 IdcServer-6 request: t`.@end. userstorage, jps - Provides trace details for user authentication and authorization. Includes information on the determination of what roles and accounts a user has access to. In 11g a new trace section, jps, was added with the addition of the JpsUserProvider to communicate with WebLogic Server. The WCC developers decide when to use the verbose option for their trace output, so sometime you need to try verbose to see what different information you get. One of the things I would always have liked to see if the ability to turn on verbose output selectively for individual trace sections. When you turn on verbose output you get it for all trace sections you have enabled. This can quickly fill up your trace files with a lot of information if you have the socket trace section turned on.

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  • To ref or not to ref

    - by nmarun
    So the question is what is the point of passing a reference type along with the ref keyword? I have an Employee class as below: 1: public class Employee 2: { 3: public string FirstName { get; set; } 4: public string LastName { get; set; } 5:  6: public override string ToString() 7: { 8: return string.Format("{0}-{1}", FirstName, LastName); 9: } 10: } In my calling class, I say: 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: }   After having a look at the code, you’ll probably say, Well, an instance of a class gets passed as a reference, so any changes to the instance inside the CallSomeMethod, actually modifies the original object. Hence the output will be ‘John-Doe’ on the first call and ‘Smith-Doe’ on the second. And you’re right: So the question is what’s the use of passing this Employee parameter as a ref? 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: } The output is still the same: Ok, so is there really a need to pass a reference type using the ref keyword? I’ll remove the ‘ref’ keyword and make one more change to the CallSomeMethod method. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } In line 17 you’ll see I’ve ‘new’d up the incoming Employee parameter and then set its properties to new values. The output tells me that the original instance of the Employee class does not change. Huh? But an instance of a class gets passed by reference, so why did the values not change on the original instance or how do I keep the two instances in-sync all the times? Aah, now here’s the answer. In order to keep the objects in sync, you pass them using the ‘ref’ keyword. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } Viola! Now, to prove it beyond doubt, I said, let me try with another reference type: string. 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(ref name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(ref string name) 12: { 13: name = "def"; 14: } 15: } The output was as expected, first ‘abc’ and then ‘def’ - proves the 'ref' keyword works here as well. Now, what if I remove the ‘ref’ keyword? The output should still be the same as the above right, since string is a reference type? 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(string name) 12: { 13: name = "def"; 14: } 15: } Wrong, the output shows ‘abc’ printed twice. Wait a minute… now how could this be? This is because string is an immutable type. This means that any time you modify an instance of string, new memory address is allocated to the instance. The effect is similar to ‘new’ing up the Employee instance inside the CallSomeMethod in the absence of the ‘ref’ keyword. Verdict: ref key came to the rescue and saved the planet… again!

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  • Trouble using remote desktop when connected via Cisco VPN

    - by Kyle B.
    I just setup my Cisco VPN and everything appears to be working fine. I opened the 'remote desktop' application and am unable to connect to my work desktop machine. When I disable Windows Firewall, I am able to connect, but not when Firewall is enabled. Is there a specific settings inside Windows 7 Firewall that should I be enabling or disabling for this to work without having to shut down the entire system? I can post this in superuser.com instead if you feel it belongs there, but posted here due to it being related to VPN and Firewall. Thanks, Kyle

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