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  • Keeping a large volume of data in Session - Suggestions / alternatives?

    - by Fishcake
    I'm developing a web app for which the client wants us to query their data as little as possible. The data will be coming from a Microsoft CRM instance. So we've agreed that data will only be queried as and when it is needed, therefore if a web user wants to see a list of contacts (for example) that list is fetched into a local DataTable. Then if a new contact is created on the website the new contact is sent to CRM and added to the local DataTable at the same time. Likewise for edits. If the user then looks at their contacts again the data will just come from the local DataTable. At the moment local data is being kept in Session but my concern is that too much memory will start being used up. However traffic is expected to be pretty small, perhaps no more than 20 concurrent users so am I worrying about nothing or is there a better way you can suggest to handle this?

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  • How to structure an index for type ahead for extremely large dataset using Lucene or similar?

    - by Pete
    I have a dataset of 200million+ records and am looking to build a dedicated backend to power a type ahead solution. Lucene is of interest given its popularity and license type, but I'm open to other open source suggestions as well. I am looking for advice, tales from the trenches, or even better direct instruction on what I will need as far as amount of hardware and structure of software. Requirements: Must have: The ability to do starts with substring matching (I type in 'st' and it should match 'Stephen') The ability to return results very quickly, I'd say 500ms is an upper bound. Nice to have: The ability to feed relevance information into the indexing process, so that, for example, more popular terms would be returned ahead of others and not just alphabetical, aka Google style. In-word substring matching, so for example ('st' would match 'bestseller') Note: This index will purely be used for type ahead, and does not need to serve standard search queries. I am not worried about getting advice on how to set up the front end or AJAX, as long as the index can be queried as a service or directly via Java code. Up votes for any useful information that allows me to get closer to an enterprise level type ahead solution

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  • How can I optimize retrieving lowest edit distance from a large table in SQL?

    - by Matt
    Hey, I'm having troubles optimizing this Levenshtein Distance calculation I'm doing. I need to do the following: Get the record with the minimum distance for the source string as well as a trimmed version of the source string Pick the record with the minimum distance If the min distances are equal (original vs trimmed), choose the trimmed one with the lowest distance If there are still multiple records that fall under the above two categories, pick the one with the highest frequency Here's my working version: DECLARE @Results TABLE ( ID int, [Name] nvarchar(200), Distance int, Frequency int, Trimmed bit ) INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@Source, [Name])) As Distance, Frequency, 'False' As Trimmed FROM MyTable INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@SourceTrimmed, [Name])) As Distance, Frequency, 'True' As Trimmed FROM MyTable SET @ResultID = (SELECT TOP 1 ID FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @Result = (SELECT TOP 1 [Name] FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultDist = (SELECT TOP 1 Distance FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultTrimmed = (SELECT TOP 1 Trimmed FROM @Results ORDER BY Distance, Trimmed, Frequency) I believe what I need to do here is to.. Not dumb the results to a temporary table Do only 1 select from `MyTable` Setting the results right in the select from the initial select statement. (Since select will set variables and you can set multiple variables in one select statement) I know there has to be a good implementation to this but I can't figure it out... this is as far as I got: SELECT top 1 @ResultID = ID, @Result = [Name], (dbo.Levenshtein(@Source, [Name])) As distOrig, (dbo.Levenshtein(@SourceTrimmed, [Name])) As distTrimmed, Frequency FROM MyTable WHERE /* ... yeah I'm lost */ ORDER BY distOrig, distTrimmed, Frequency Any ideas?

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  • Qt Creator draws up build issue: "target pattern contains no %. Stop."

    - by Louis93
    The compile output says no% in line 240 of the makefile. Here is an extract of that portion in the Makefile: debug/lv.simplon.class.o: c:/SimplonQt/include/lv.simplon.class.cpp $(CXX) -c $(CXXFLAGS) $(INCPATH) -o debug/lv.simplon.class.o c:/SimplonQt/include/lv.simplon.class.cpp I'm loading a project I have saved in my C drive in Windows, but I am not sure what exactly is the cause of the problem. Thanks in advance!

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  • MVC2 IModelBinder and parsing a string to an object - How do I do it?

    - by burnt_hand
    I have an object called Time public class Time{ public int Hour {get;set;} public int Minute {get;set;} public static Time Parse(string timeString){ //reads the ToString()'s previous output and returns a Time object } override protected string ToString(){ //puts out something like 14:50 (as in 2:50PM) } } So what I want is for the automatic model binding on the Edit or Create action to set this Time instance up from a string (i.e. feed the Parse method with the string and return the result). The reason I am doing this is that I will have a DropDownList with selectable times. The value of each option will be the parser readable string. Can anyone provide an example BindModel method from the IModelBinder interface?

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  • Which design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English. EDITED - Asking for multiple patterns.

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  • [Python] How can I speed up unpickling large objects if I have plenty of RAM?

    - by conradlee
    It's taking me up to an hour to read a 1-gigabyte NetworkX graph data structure using cPickle (its 1-GB when stored on disk as a binary pickle file). Note that the file quickly loads into memory. In other words, if I run: import cPickle as pickle f = open("bigNetworkXGraph.pickle","rb") binary_data = f.read() # This part doesn't take long graph = pickle.loads(binary_data) # This takes ages How can I speed this last operation up? Note that I have tried pickling the data both in using both binary protocols (1 and 2), and it doesn't seem to make much difference which protocol I use. Also note that although I am using the "loads" (meaning "load string") function above, it is loading binary data, not ascii-data. I have 128gb of RAM on the system I'm using, so I'm hoping that somebody will tell me how to increase some read buffer buried in the pickle implementation.

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  • How to make TwoWay binding on properties of ObservableCollection of custom class using mvvm pattern?

    - by mill
    I have the following class: public class UserGroup { public string GroupName { get; set; } public bool IsIntheGroup{ get; set; } } I want to bind an ObservableCollection of UserGroup items to listbox containing checkbox’s for each item in the collection and the checkbox is cheked based on the IsIntheGroup property of the UserGroup. In my ViewModel I made an ObservableCollection of the UserGroup class: public ObservableCollection Groups { get; set; } and loaded its contents (instances of UserGroup) from my database model I used the following code in my view: ListBox ItemsSource="{Binding Groups, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" ListBox.ItemTemplate DataTemplate StackPanel Orientation="Horizontal" CheckBox IsChecked="{Binding IsIntheGroup, Mode=TwoWay}"/ TextBlock Text="{Binding GroupName}" / /StackPanel /DataTemplate /ListBox.ItemTemplate /ListBox The problem is I am not notified when the user checks/unchecks a check box in the list so my two way binding failed… How do I do a two way binding in such a case?

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  • Ruby: Why is Array.sort slow for large objects?

    - by David Waller
    A colleague needed to sort an array of ActiveRecord objects in a Rails app. He tried the obvious Array.sort! but it seemed surprisingly slow, taking 32s for an array of 3700 objects. So just in case it was these big fat objects slowing things down, he reimplemented the sort by sorting an array of small objects, then reordering the original array of ActiveRecord objects to match - as shown in the code below. Tada! The sort now takes 700ms. That really surprised me. Does Ruby's sort method end up copying objects about the place rather than just references? He's using Ruby 1.8.6/7. def self.sort_events(events) event_sorters = Array.new(events.length) {|i| EventSorter.new(i, events[i])} event_sorters.sort! event_sorters.collect {|es| events[es.index]} end private # Class used by sort_events class EventSorter attr_reader :sqn attr_reader :time attr_reader :index def initialize(index, event) @index = index @sqn = event.sqn @time = event.time end def <=>(b) @time != b.time ? @time <=> b.time : @sqn <=> b.sqn end end

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  • How should I delete a child object from within a parent's slot? Possibly boost::asio specific.

    - by kaliatech
    I have written a network server class that maintains a std::set of network clients. The network clients emit a signal to the network server on disconnect (via boost::bind). When a network client disconnects, the client instance needs to be removed from the Set and eventually deleted. I would think this is a common pattern, but I am having problems that might, or might not, be specific to ASIO. I've tried to trim down to just the relevant code: /** NetworkServer.hpp **/ class NetworkServices : private boost::noncopyable { public: NetworkServices(void); ~NetworkServices(void); private: void run(); void onNetworkClientEvent(NetworkClientEvent&); private: std::set<boost::shared_ptr<const NetworkClient>> clients; }; /** NetworkClient.cpp **/ void NetworkServices::run() { running = true; boost::asio::io_service::work work(io_service); //keeps service running even if no operations // This creates just one thread for the boost::asio async network services boost::thread iot(boost::bind(&NetworkServices::run_io_service, this)); while (running) { boost::system::error_code err; try { tcp::socket* socket = new tcp::socket(io_service); acceptor->accept(*socket, err); if (!err) { NetworkClient* networkClient = new NetworkClient(io_service, boost::shared_ptr<tcp::socket>(socket)); networkClient->networkClientEventSignal.connect(boost::bind(&NetworkServices::onNetworkClientEvent, this, _1)); clients.insert(boost::shared_ptr<NetworkClient>(networkClient)); networkClient->init(); //kicks off 1st asynch_read call } } // etc... } } void NetworkServices::onNetworkClientEvent(NetworkClientEvent& evt) { switch(evt.getType()) { case NetworkClientEvent::CLIENT_ERROR : { boost::shared_ptr<const NetworkClient> clientPtr = evt.getClient().getSharedPtr(); // ------ THIS IS THE MAGIC LINE ----- // If I keep this, the io_service hangs. If I comment it out, // everything works fine (but I never delete the disconnected NetworkClient). // If actually deleted the client here I might expect problems because it is the caller // of this method via boost::signal and bind. However, The clientPtr is a shared ptr, and a // reference is being kept in the client itself while signaling, so // I would the object is not going to be deleted from the heap here. That seems to be the case. // Never-the-less, this line makes all the difference, most likely because it controls whether or not the NetworkClient ever gets deleted. clients.erase(clientPtr); //I should probably put this socket clean-up in NetworkClient destructor. Regardless by doing this, // I would expect the ASIO socket stuff to be adequately cleaned-up after this. tcp::socket& socket = clientPtr->getSocket(); try { socket.shutdown(boost::asio::socket_base::shutdown_both); socket.close(); } catch(...) { CommServerContext::error("Error while shutting down and closing socket."); } break; } default : { break; } } } /** NetworkClient.hpp **/ class NetworkClient : public boost::enable_shared_from_this<NetworkClient>, Client { NetworkClient(boost::asio::io_service& io_service, boost::shared_ptr<tcp::socket> socket); virtual ~NetworkClient(void); inline boost::shared_ptr<const NetworkClient> getSharedPtr() const { return shared_from_this(); }; boost::signal <void (NetworkClientEvent&)> networkClientEventSignal; void onAsyncReadHeader(const boost::system::error_code& error, size_t bytes_transferred); }; /** NetworkClient.cpp - onAsyncReadHeader method called from io_service.run() thread as result of an async_read operation. Error condition usually result of an unexpected client disconnect.**/ void NetworkClient::onAsyncReadHeader( const boost::system::error_code& error, size_t bytes_transferred) { if (error) { //Make sure this instance doesn't get deleted from parent/slot deferencing //Alternatively, somehow schedule for future delete? boost::shared_ptr<const NetworkClient> clientPtr = getSharedPtr(); //Signal to service that this client is disconnecting NetworkClientEvent evt(*this, NetworkClientEvent::CLIENT_ERROR); networkClientEventSignal(evt); networkClientEventSignal.disconnect_all_slots(); return; } I believe it's not safe to delete the client from within the slot handler because the function return would be ... undefined? (Interestingly, it doesn't seem to blow up on me though.) So I've used boost:shared_ptr along with shared_from_this to make sure the client doesn't get deleted until all slots have been signaled. It doesn't seem to really matter though. I believe this question is not specific to ASIO, but the problem manifests in a peculiar way when using ASIO. I have one thread executing io_service.run(). All ASIO read/write operations are performed asynchronously. Everything works fine with multiple clients connecting/disconnecting UNLESS I delete my client object from the Set per the code above. If I delete my client object, the io_service seemingly deadlocks internally and no further asynchronous operations are performed unless I start another thread. I have try/catches around the io_service.run() call and have not been able to detect any errors. Questions: Are there best practices for deleting child objects, that are also signal emitters, from within parent slots? Any ideas as to why the io_service is hanging when I delete my network client object?

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  • Beginner Question: For extract a large subset of a table from MySQL, how does Indexing, order of tab

    - by chongman
    Sorry if this is too simple, but thanks in advance for helping. This is for MySQL but might be relevant for other RDMBSs tblA has 4 columns: colA, colB, colC, mydata, A_id It has about 10^9 records, with 10^3 distinct values for colA, colB, colC. tblB has 3 columns: colA, colB, B_id It has about 10^4 records. I want all the records from tblA (except the A_id) that have a match in tblB. In other words, I want to use tblB to describe the subset that I want to extract and then extract those records from tblA. Namely: SELECT a.colA, a.colB, a.colC, a.mydata FROM tblA as a INNER JOIN tblB as b ON a.colA=b.colA a.colB=b.colB ; It's taking a really long time (more than an hour) on a newish computer (4GB, Core2Quad, ubuntu), and I just want to check my understanding of the following optimization steps. ** Suppose this is the only query I will ever run on these tables. So ignore the need to run other queries. Now my questions: 1) What indexes should I create to optimize this query? I think I just need a multiple index on (colA, colB) for both tables. I don't think I need separate indexes for colA and colB. Another stack overflow article (that I can't find) mentioned that when adding new indexes, it is slower when there are existing indexes, so that might be a reason to use the multiple index. 2) Is INNER JOIN correct? I just want results where a match is found. 3) Is it faster if I join (tblA to tblB) or the other way around, (tblB to tblA)? This previous answer says that the optimizer should take care of that. 4) Does the order of the part after ON matter? This previous answer say that the optimizer also takes care of the execution order.

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  • Android: howto parse String with spaces to URI object?

    - by Mannaz
    I have a string representing an URL containing spaces and want to convert it to an URI object. If is simple try to do String myString = "http://myhost.com/media/mp3s/9/Agenda of swine - 13. Persecution Ascension_ leave nothing standing.mp3"; URI myUri = new URI(myString); it gives me java.net.URISyntaxException: Illegal character in path at index X where index X is the position of the first space in the URL string. How can i parse myStringinto a URI object?

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  • What OOP pattern to use when only adding new methods, not data?

    - by Jonathon Reinhart
    Hello eveyone... In my app, I have deal with several different "parameters", which derive from IParameter interface, and also ParamBase abstract base class. I currently have two different parameter types, call them FooParameter and BarParameter, which both derive from ParamBase. Obviously, I can treat them both as IParameters when I need to deal with them generically, or detect their specific type when I need to handle their specific functionality. My question lies in specific FooParameters. I currently have a few specific ones with their own classes which derive from FooParameter, we'll call them FP12, FP13, FP14, etc. These all have certain characteristics, which make me treat them differently in the UI. (Most have names associated with the individual bits, or ranges of bits). Note that these specific, derived FP's have no additional data associated with them, only properties (which refer to the same data in different ways) or methods. Now, I'd like to keep all of these parameters in a Dictionary<String, IParameter> for easy generic access. The problem is, if I want to refer to a specific one with the special GUI functions, I can't write: FP12 fp12 = (FP12)paramList["FP12"] because you can't downcast to a derived type (rightfully so). But in my case, I didn't add any data, so the cast would theoretically work. What type of programming model should I be using instead? Thanks!

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  • How can I capture a multiline pattern using a regular expressions in java?

    - by lampShade
    I have a text file that I need to parse using regular expressions. The text that I need to capture is in multiline groups like this: truck zDoug Doug's house (123) 456-7890 [email protected] 30 61234.56 8/10/2003 vehicle eRob Rob's house (987) 654-3210 [email protected] For this example I need to capture truck followed by the next seven lines.In other words, in this "block" I have 8 groups. This is what I've tried but it will not capture the next line: (truck)\n(\w). NOTE: I'm using the program RegExr to test my regex before I port it to Java.

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  • Best way to keep a large number of hobby projects alive; open sourcing?

    - by Daan van Yperen
    Because my time is limited I can usually only focus on one or two of my hobby projects, while the others sit there wasting away. I am looking for a solution that would allow me to divide my time better. is open sourcing where I take the role of guiding the project realistic, or are there better solutions? In my case, one project has a reasonably sized community of users going for it but is currently closed source. There have been requests to open source it.

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  • Google App Engine update an object from servlet not working ?

    - by Frank
    I use the following code to update an object from servlet in Google App Engine : String Time_Stamp=Get_Date_Format(6),query="select from "+Contact_Info_Entry.class.getName()+" where Contact_Id == '"+Contact_Id+"' order by Contact_Id desc"; PersistenceManager pm=null; try { pm=PMF.get().getPersistenceManager(); // note that this returns a list, there could be multiple, DataStore does not ensure uniqueness for non-primary key fields List<Contact_Info_Entry> results=(List<Contact_Info_Entry>)pm.newQuery(query).execute(); Contact_Info_Entry A_Contact_Entry=results.get(0); A_Contact_Entry.Extra_10=Time_Stamp; pm.makePersistent(A_Contact_Entry); } catch (Exception e) { Send_Email(Email_From,Email_To,"Check_License_Servlet Error [ "+Time_Stamp+" ]",new Text(e.toString()+"\n"+Get_Stack_Trace(e)),null); } finally { pm.close(); } The value "[ 2010-05-13 Thu 15:58:31 ]" was in A_Contact_Entry.Extra_10, but it seems "pm.makePersistent(A_Contact_Entry);" was not executed. The object was not updated and there was no error message, why ? How to fix it ?

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  • Which type of design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English. EDITED: Asking for multiple patterns.

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  • How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

    - by BillyONeal
    Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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  • How to obtain specific Excel object library without the corresponding Office version installed.

    - by james-h-l
    I am developing a Excel automation app that read and write to Excel spreadsheet. I have Office 2007 installed on my machine. I therefore can reference the Excel 12.0 Object Library and the Excel 5.0 Object Library. I don't want to use Excel 5.0 because it's really quite old and poorly documented. Therefore I'm referencing Excel 12.0. However the target machine have Office 2003 installed and therefore only have Excel 11.0. So when I compile my program it crashes on the target machine since the referenced library are different. I was wondering is there a way I could obtain the Excel 11.0 without installing Office 03? I tried to find answers from msdn and microsoft support page but couldn't find anything? This is quite strange since it could also happen in the future where developers has newer editions of Office than clients?

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  • Databinding in windows forms on an object graph with possible null properties?

    - by Fredrik
    If I have an object graph like this: class Company { public Address MainAddress {...} } class Address { public string City { ... } } Company c = new Company(); c.MainAddress = new Address(); c.MainAddress.City = "Stockholm"; and databind to a control using: textBox1.DataBinding.Add( "Text", c, "MainAddress.City" ); Everything is fine, but If I bind to: Company c2 = new Company(); c2 using the same syntax it crashes since the MainAddress property is null. I wonder if there is a custom Binding class that can set up listeners for all the possible paths here and bind to the actual object dynamically when/if I sometime later in the application set the MainAddress property.

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  • Why an object declared in method is subject to garbage collection before the method returns?

    - by SiLent SoNG
    Consider an object declared in a method: public void foo() { final Object obj = new Object(); // A long run job that consumes tons of memory and // triggers garbage collection } Will obj be subject to garbage collection before foo() returns? UPDATE: Previously I thought obj is not subject to garbage collection until foo() returns. However, today I find myself wrong. I have spend several hours in fixing a bug and finally found the problem is caused by obj garbage collected! Can anyone explain why this happens? And if I want obj to be pinned how to achieve it? Here is the code that has problem. public class Program { public static void main(String[] args) throws Exception { String connectionString = "jdbc:mysql://<whatever>"; // I find wrap is gc-ed somewhere SqlConnection wrap = new SqlConnection(connectionString); Connection con = wrap.currentConnection(); Statement stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY); stmt.setFetchSize(Integer.MIN_VALUE); ResultSet rs = stmt.executeQuery("select instance_id, doc_id from crawler_archive.documents"); while (rs.next()) { int instanceID = rs.getInt(1); int docID = rs.getInt(2); if (docID % 1000 == 0) { System.out.println(docID); } } rs.close(); //wrap.close(); } } After running the Java program, it will print the following message before it crashes: 161000 161000 ******************************** Finalizer CALLED!! ******************************** ******************************** Close CALLED!! ******************************** 162000 Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: And here is the code of class SqlConnection: class SqlConnection { private final String connectionString; private Connection connection; public SqlConnection(String connectionString) { this.connectionString = connectionString; } public synchronized Connection currentConnection() throws SQLException { if (this.connection == null || this.connection.isClosed()) { this.closeConnection(); this.connection = DriverManager.getConnection(connectionString); } return this.connection; } protected void finalize() throws Throwable { try { System.out.println("********************************"); System.out.println("Finalizer CALLED!!"); System.out.println("********************************"); this.close(); } finally { super.finalize(); } } public void close() { System.out.println("********************************"); System.out.println("Close CALLED!!"); System.out.println("********************************"); this.closeConnection(); } protected void closeConnection() { if (this.connection != null) { try { connection.close(); } catch (Throwable e) { } finally { this.connection = null; } } } }

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