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  • add database Tablenames to the JList in java

    - by Litecia
    // Declare JList private JList jlstTab, jlstCol; . . . DefaultListModel dlmTables = new DefaultListModel(); DefaultListModel dlmCol = new DefaultListModel(); // Instantiate dlmTables.addElement("kl"); jlstTab= new JList(dlmTables); jlstTab.setSelectedIndex(0); jlstTab.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); . . . . Connect to the database public static void main(String args[]) { DBToolSwing cs = new DBToolSwing("DB Tool Swing"); try DBAccessObject dbAccess1 = new DBAccessObject("jdbc:odbc:JavaClassDSN"); DBAccessObject dbAccess2 = new DBAccessObject(); ResultSet rsTables = dbAccess1.getDatabaseTableNames(); while (rsTables.next()) System.out.println(rsTables.getString("TABLE_NAME")); I need to get the table names from the database, the output shouldn't be printed on the screen, instead I need the output added to the JlstTab so dlmTables.addElement("TABLE_NAME"); Please if someone can help I would appreciate it. Thanks in advance.

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  • Java consistent synchronization

    - by ring0
    We are facing the following problem in a Spring service, in a multi-threaded environment: three lists are freely and independently accessed for Read once in a while (every 5 minutes), they are all updated to new values. There are some dependencies between the lists, making that, for instance, the third one should not be read while the second one is being updated and the first one already has new values ; that would break the three lists consistency. My initial idea is to make a container object having the three lists as properties. Then the synchronization would be first on that object, then one by one on each of the three lists. Some code is worth a thousands words... so here is a draft private class Sync { final List<Something> a = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> b = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> c = Collections.synchronizedList(new ArrayList<Something>()); } private Sync _sync = new Sync(); ... void updateRunOnceEveryFiveMinutes() { final List<Something> newa = new ArrayList<Something>(); final List<Something> newb = new ArrayList<Something>(); final List<Something> newc = new ArrayList<Something>(); ...building newa, newb and newc... synchronized(_sync) { synchronized(_sync.a) { _synch.a.clear(); _synch.a.addAll(newa); } synchronized(_sync.b) { ...same with newb... } synchronized(_sync.c) { ...same with newc... } } // Next is accessed by clients public List<Something> getListA() { return _sync.a; } public List<Something> getListB() { ...same with b... } public List<Something> getListC() { ...same with c... } The question would be, is this draft safe (no deadlock, data consistency)? would you have a better implementation suggestion for that specific problem? update Changed the order of _sync synchronization and newa... building. Thanks

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  • Java, Massive message processing with queue manager (trading)

    - by Ronny
    Hello, I would like to design a simple application (without j2ee and jms) that can process massive amount of messages (like in trading systems) I have created a service that can receive messages and place them in a queue to so that the system won't stuck when overloaded. Then I created a service (QueueService) that wraps the queue and has a pop method that pops out a message from the queue and if there is no messages returns null, this method is marked as "synchronized" for the next step. I have created a class that knows how process the message (MessageHandler) and another class that can "listen" for messages in a new thread (MessageListener). The thread has a "while(true)" and all the time tries to pop a message. If a message was returned, the thread calls the MessageHandler class and when it's done, he will ask for another message. Now, I have configured the application to open 10 MessageListener to allow multi message processing. I have now 10 threads that all time are in a loop. Is that a good design?? Can anyone reference me to some books or sites how to handle such scenario?? Thanks, Ronny

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  • JAVA-I don't want clicking on my app make other apps lose focus

    - by Auxiliary
    Wow, what a stupid question you might say. But is it possible? I have a mouse move event in a Jpanel and it works even when the application is not in focus, now can I have something like that for the clicking event or something similar. And most importantly I don't want other apps (even something like the main menu) to lose focus when i click on my app. I was the system's event queue but i'm not sure where that would lead me to. Thanks in advance.

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  • Android / Java rare and seemingly impossible exception causing force close

    - by Guzba
    Hello all, I have an interesting problem being reported to me from an android application I have published. I have a two-dimensional array that I am iterating through using two for loops like so: for (int i = 0; i < arr.length; ++i) { for (int j = 0; j < arr[i].length; ++j) { if (arr[i][j] != 0) // does stuff } } The problem is, somehow arr[i][j] != 0 is throwing an ArrayIndexOutOfBoundsException. But very rarely. I have thousands of people use the app on a daily basis and get maybe twenty force close reports. Is this something I can't avoid, maybe a problem with the phones memory, etc. or is there something I can do that I haven't thought of yet? Thanks.

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  • How to delete duplicate/aggregate rows faster in a file using Java (no DB)

    - by S. Singh
    I have a 2GB big text file, it has 5 columns delimited by tab. A row will be called duplicate only if 4 out of 5 columns matches. Right now, I am doing dduping by first loading each coloumn in separate List , then iterating through lists, deleting the duplicate rows as it encountered and aggregating. The problem: it is taking more than 20 hours to process one file. I have 25 such files to process. Can anyone please share their experience, how they would go about doing such dduping? This dduping will be a throw away code. So, I was looking for some quick/dirty solution, to get job done as soon as possible. Here is my pseudo code (roughly) Iterate over the rows i=current_row_no. Iterate over the row no. i+1 to last_row if(col1 matches //find duplicate && col2 matches && col3 matches && col4 matches) { col5List.set(i,get col5); //aggregate } Duplicate example A and B will be duplicate A=(1,1,1,1,1), B=(1,1,1,1,2), C=(2,1,1,1,1) and output would be A=(1,1,1,1,1+2) C=(2,1,1,1,1) [notice that B has been kicked out]

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  • Please clarify a few points concerning Java Servlets

    - by EugeneP
    suppose, I use Tomcat as a web container. Is it true that once all the servlets found in a web-app/WEBAPPNAME are init(IALIZED) then every change of a Servlet's property will be seen to every session. So session 1 changes a property userName of a Servlet1 from "user1" to "user2" session 1 is closed. session 2 starts. It will see "user2" as the only value of Servlet1.userName property?? Any change of a Servlet's field will be seen to all subsequent sessions? Are servlets singletons, aren't they?

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  • Changing Color with LinearLayout and TextView in Java (Android)

    - by Rob S.
    I'm a relatively new Android developer and I noticed what seems like an oddity to me that I'm hoping someone can explain. I have LinearLayout ll. This line of code fails for me when executed: ll.setBackgroundColor(R.color.white); However this line of code works: ll.setBackgroundResource(R.color.white); I assume its simply because I have white defined in my resources. However, I've also tried passing 0xFFFFFF in setBackgroundColor() and that doesn't work either. Similarly with my TextView text this line of code fails when executed: text.setTextColor(R.color.white); I can see my TextView so I know I initialized it correctly (like my LinearLayout which I can also see). So I guess my question boils down to: How do I properly use LinearLayout.setBackgroundColor() and TextView.setTextColor() ? Thanks a ton in advance. I've read through the docs and tried to find information online via googling and haven't come up with anything.

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  • Adding file names to an array list in java

    - by Chris G
    Hi I am currently needing to load the contents of a folders filenames to an arraylist I have but I am unsure as how to do this. To put it into perspective I have a folder with One.txt, Two.txt, Three.txt etc. I want to be able to load this list into an arraylist so that if I was to check the arraylist its contents would be : arraylist[0] = One arraylist[1] = Two arraylist[3] = Three If anyone could give me any insight into this it would be much appreciated.

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  • object construct a class of objects in java

    - by Mgccl
    There is a super class, A, and there are many subclasses, B,C,D... people can write more subclasses. Each of the class have the method dostuff(), each is different in some way. I want an object that constructs any object that belong to A or any of it's subclass. For example I can pass the name of the subclass, or a object of that class, and it will construct another object of the class. Of course I can write A construct(A var){ stuff = var.dostuff(); domorestuff(stuff) return new A(stuff); } B construct(B var){ stuff = var.dostuff(); domorestuff(stuff) return new B(stuff); } C construct(C var){ stuff = var.dostuff(); domorestuff(stuff) return new C(stuff); } but this is not efficient. I have to write a few new lines every time I make a new subclass. It seems I can't use generics either. Because I can't use dostuff() on objects not in any of the subclass of A. What should I do in this situation?

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  • Clone List Elements in Java

    - by Amir Rachum
    Hi all, I have a variable of type List<RelationHeader>. Now I want to copy all the elements in this list to a new list, but I want to actually copy all the members by value (clone them). Is there a quick command to do this, or do I need to iterate over the list and copy them one at a time?

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  • How to end a thread in java?

    - by beagleguy
    hi all, I have 2 pools of threads ioThreads = (ThreadPoolExecutor)Executors.newCachedThreadPool(); cpuThreads = (ThreadPoolExecutor)Executors.newFixedThreadPool(numCpus); I have a simple web crawler that I want to create an iothread, pass it a url, it will then fetch the url and pass the contents over to a cpuThread to be processed and the ioThread will then fetch another url, etc... At some point the IO thread will not have any new pages to crawl and I want to update my database that this session is complete. How can I best tell when the threads are all done processing and the program can be ended?

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  • Java BufferedReader behavior in CSV vs TXT file

    - by Gabriel
    If i try to read a CSV file called csv_file.csv. The problem is that when i read lines with BufferedReader.readLine() it skips the first line with months. But when i rename the file to csv_file.txt it reads it allright and it's not skipping the first line. Is there an undocumented "feature" of BufferedReader that i'm not aware? Example of file: Months, SEP2010, OCT2010, NOV2010 col1, col2, col3, col4, col5 aaa,,sdf,"12,456",bla bla bla, xsaffadfafda and so on, and so on, "10,00", xxx, xxx The code: FileInputStream stream = new FileInputStream(UploadSupport.TEMPORARY_FILES_PATH+fileName); BufferedReader br = new BufferedReader(new InputStreamReader(stream, "UTF-8")); String line = br.readLine(); String months[] = line.split(","); while ((line=br.readLine())!=null) { /*parse other lines*/ }

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  • Android Java writing text file to sd card

    - by Paul
    I have a strange problem I've come across. My app can write a simple textfile to SD card and sometimes it works for some people but not for others and I have no idea why. Some people it force closes if they put some characters like "..." in it and such. I cannot seem to reproduce it as I've had no troubles but this is the code that handles it. Can anyone think of something that may lead to problems or a better to way to do it? public void generateNoteOnSD(String sFileName, String sBody){ try { File root = new File(Environment.getExternalStorageDirectory(), "Notes"); if (!root.exists()) { root.mkdirs(); } File gpxfile = new File(root, sFileName); FileWriter writer = new FileWriter(gpxfile); writer.append(sBody); writer.flush(); writer.close(); Toast.makeText(this, "Saved", Toast.LENGTH_SHORT).show(); } catch(IOException e) { e.printStackTrace(); importError = e.getMessage(); iError(); } }

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  • java increase xmx dynamically at runtime

    - by Tomer
    Hi, I have a jvm server in my machine, now I want to have 2 apservers of mine sitting in same machine, however I want the standby one to have a really low amount of memory allocated with xmx because its passive, one the main server (active) goes down I want to allocate more memory to my passive server which is already up without restarting it (I have have them both having too much xmx - note they would consume memory at startup and I cant allow possibility of outOfMemory). So I want passive - low xmx once active goes down I want my passive to receive much more xmx. is there a way for me to achieve that. Thanks

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  • Java generics question with wildcards

    - by Sean
    Just came across a place where I'd like to use generics and I'm not sure how to make it work the way I want. I have a method in my data layer that does a query and returns a list of objects. Here's the signature. public List getList(Class cls, Map query) This is what I'd like the calling code to look like. List<Whatever> list = getList(WhateverImpl.class, query); I'd like to make it so that I don't have to cast this to a List coming out, which leads me to this. public <T> List<T> getList(Class<T> cls, Map query) But now I have the problem that what I get out is always the concrete List<WhateverImpl> passed in whereas I'd like it to be the Whatever interface. I tried to use the super keyword but couldn't figure it out. Any generics gurus out there know how this can be done?

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  • java detect clicked buttons

    - by user253530
    I have multiple panels on a JFrame window. I am going to populate each panel differently every time. For example: i start the GUI: (image center panel, right panel, bottom panel). Center panel is populated with 20 buttons, right panel with 10 buttons and bottom panel with 3. second start of the GUI (same gui). Center panel has 50 buttons, right panel has 12 buttons, bottom has 3. So everytime there is a random number of buttons, impossible to be all uniquely named. Given the fact that I don't have a unique name for each button (just a list) I would like to know which buttons were clicked according to the panel they belong to. is that possible?

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  • Java Swing popup visibility

    - by Octavio
    Why a popup created like this is shown in front of all windows applications with JRE 1.6.0_18 but it doesn't using 1.6.0_03 ? PopupFactory popupFactory = new PopupFactory(); Popup popup= popupFactory.getPopup(null,new JPanel(),200,200); popup.show();

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  • How to access java classes in a subfolder.

    - by Jacob
    Hi all. I'm trying to make a program that can load an unknown set of plugins from a sub-folder, "Plugins". All of these plugins implement the same interface. What I need to know is how do I find all of the classes in this folder so that I can instantiate and use them?

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  • Java URL Connection Time Out

    - by webren
    Hello, I am attempting to connect to a website where I'd like to extract its HTML contents. My application will never connect to the site - only time out. Here is my code: URL url = new URL("www.website.com"); URLConnection connection = url.openConnection(); connection.setConnectTimeout(2000); connection.setReadTimeOut(2000); BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()); String line; while ((line = reader.readLine()) != null) { // do stuff with line } reader.close(); Any ideas would be greatly appreciated. Thanks!

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