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  • disposing a class loader

    - by java_geek
    I am using a custom class loader which extends URLClassLoader. I load some classes into my custom class loader and perform some task. Once the task is completed i want to dispose of the class loader. I tried doing that by setting the reference to null. But this does not garbage collect the class loader. Is there a way that can help what i want to achieve?

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  • Is there any appreciable difference between if and if-else?

    - by Drew
    Given the following code snippets, is there any appreciable difference? public boolean foo(int input) { if(input > 10) { doStuff(); return true; } if(input == 0) { doOtherStuff(); return true; } return false; } vs. public boolean foo(int input) { if(input > 10) { doStuff(); return true; } else if(input == 0) { doOtherStuff(); return true; } else { return false; } } Or would the single exit principle be better here with this piece of code... public boolean foo(int input) { boolean toBeReturned = false; if(input > 10) { doStuff(); toBeReturned = true; } else if(input == 0) { doOtherStuff(); toBeReturned = true; } return toBeReturned; } Is there any perceptible performance difference? Do you feel one is more or less maintainable/readable than the others?

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  • Can I get a table name from a join select resultset metadata

    - by Matt
    Below is my code trying to retrieve table name form Resultset ResultSet rs = stmt.executeQuery("select * from product"); ResultSetMetaData meta = rs.getMetaData(); int count = meta.getColumnCount(); for (int i=0; i<count; i++) { System.out.println(meta.getTableName(i)); } But it returns empty, no mention it is a join select resultset. Is there any other approaches to retrieve table name from reusltset metadata?

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  • best practice for passing many arguments to method ?

    - by Tony
    Occasionally , we have to write methods that receive many many arguments , for example : public void doSomething(Object objA , Object objectB ,Date date1 ,Date date2 ,String str1 ,String str2 ) { } When I encounter this kind of problem , I often encapsulate arguments into a map. Map<Object,Object> params = new HashMap<Object,Object>(); params.put("objA",ObjA) ; ...... public void doSomething(Map<Object,Object> params) { // extracting params Object objA = (Object)params.get("objA"); ...... } This is not a good practice , encapsulate params into a map is totally a waste of efficiency. The good thing is , the clean signature , easy to add other params with fewest modification . what's the best practice for this kind of problem ?

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  • how to put jcheckbox to table cell?

    - by joseph
    Hello, I cannot put jChceckBox to jTable cell. More likely I can put checkBox to table, but when I run module with that table, the cell where should be checkBox shows text "true" or "false". The behaviors of that cell are the same like checkbox, but it shows text value instead of checkbox. Here is the code. DefaultTableModel dm = new DefaultTableModel(); dm.setDataVector(new Object[][]{{"dd", "Edit", "Delete"}, {"dd","Edit", "Delete"}}, new Object[]{"Include","Component", "Ekvi"}); jTable1 = new javax.swing.JTable(); jTable1.setModel(dm); JCheckBox chBox=new JCheckBox(); jTable1.getColumn("Include").setCellEditor(new DefaultCellEditor(chBox)); jScrollPane1.setViewportView(jTable1);

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  • Extracting rightmost N bits of an integer

    - by srandpersonia
    In the yester Code Jam Qualification round http://code.google.com/codejam/contest/dashboard?c=433101#s=a&a=0 , there was a problem called Snapper Chain. From the contest analysis I came to know the problem requires bit twiddling stuff like extracting the rightmost N bits of an integer and checking if they all are 1. I saw a contestant's(Eireksten) code which performed the said operation like below: (((K&(1<<N)-1))==(1<<N)-1) I couldn't understand how this works. What is the use of -1 there in the comparison?. If somebody can explain this, it would be very much useful for us rookies. Also, Any tips on identifying this sort of problems would be much appreciated. I used a naive algorithm to solve this problem and ended up solving only the smaller data set.(It took heck of a time to compile the larger data set which is required to be submitted within 8 minutes.). Thanks in advance.

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  • Need help with writing test

    - by London
    I'm trying to write a test for this class its called Receiver : public void get(People person) { if(null != person) { LOG.info("Person with ID " + person.getId() + " received"); processor.process(person); }else{ LOG.info("Person not received abort!"); } } Here is the test : @Test public void testReceivePerson(){ context.checking(new Expectations() {{ receiver.get(person); atLeast(1).of(person).getId(); will(returnValue(String.class)); }}); } Note: receiver is the instance of Receiver class(real not mock), processor is the instance of Processor class(real not mock) which processes the person(mock object of People class). GetId is a String not int method that is not mistake. Test fails : unexpected invocation of person.getId() I'm using jMock any help would be appreciated. As I understood when I call this get method to execute it properly I need to mock person.getId() , and I've been sniping around in circles for a while now any help would be appreciated.

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  • JAXB adding namespace to parent but not to the child elements contained

    - by Nishant
    I put together an XSD and used JAXB to generate classes out of it. Here are my XSDs- myDoc.xsd : <?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns="http://www.mydoc.org" targetNamespace="http://www.mydoc.org" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:mtp="http://www.mytypes.com" elementFormDefault="qualified"> <xs:import namespace="http://www.mytypes.com" schemaLocation="mytypes.xsd" /> <xs:element name="myDoc"> <xs:complexType> <xs:sequence> <xs:element name="crap" type="xs:string"/> <xs:element ref="mtp:foo"/> <xs:element ref="mtp:bar"/> </xs:sequence> </xs:complexType> </xs:element> mytypes.xsd <?xml version="1.0" encoding="UTF-8"?> <xs:schema targetNamespace="http://www.mytypes.com" xmlns="http://www.mytypes.com" xmlns:tns="http://www.mytypes.com" xmlns:xs="http://www.w3.org/2001/XMLSchema" attributeFormDefault="qualified" elementFormDefault="qualified"> <xs:element name="foo" type="tns:Foo"/> <xs:element name="bar" type="tns:Bar"/> <xs:element name="spam" type="tns:Spam"/> <xs:simpleType name="Foo"> <xs:restriction base="xs:string"></xs:restriction> </xs:simpleType> <xs:complexType name="Bar"> <xs:sequence> <xs:element ref="spam"/> </xs:sequence> </xs:complexType> <xs:simpleType name="Spam"> <xs:restriction base="xs:string" /> </xs:simpleType> </xs:schema> The document marshalled is- <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <myDoc xmlns:ns2="http://www.mytypes.com"> <crap>real crap</crap> <ns2:foo>bleh</ns2:foo> <ns2:bar> <spam>blah</spam> </ns2:bar> </myDoc> Note that the <spam> element uses the default namespace. I would like it to use the ns2 namespace. The schema (mytypes.xsd) expresses the fact that <spam> is contained within <bar> which in the XML instance is bound to the ns2 namespace. I've broken my head over this for over a week and I would like ns2 prefix to appear in <spam>. What should I do? Required : <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <myDoc xmlns:ns2="http://www.mytypes.com"> <crap>real crap</crap> <ns2:foo>bleh</ns2:foo> <ns2:bar> <ns2:spam>blah</ns2:spam><!--NS NS NS--> </ns2:bar> </myDoc>

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  • Allow for modular development while still running in same JVM?

    - by Marcus
    Our current app runs in a single JVM. We are now splitting up the app into separate logical services where each service runs in its own JVM. The split is being done to allow a single service to be modified and deployed without impacting the entire system. This reduces the need to QA the entire system - just need to QA the interaction with the service being changed. For inter service communication we use a combination of REST, an MQ system bus, and database views. What I don't like about this: REST means we have to marshal data to/from XML DB views couple the systems together which defeats the whole concept of separate services MQ / system bus is added complexity There is inevitably some code duplication between services You have set up n JBoss server configurations, we have to do n number of deployments, n number of set up scripts, etc, etc. Is there a better way to structure an internal application to allow modular development and deployment while allowing the app to run in a single JVM (and achieving the associated benefits)?

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  • how to handle result set data

    - by ashwani66476
    Hello All I am getting lacks of records in my Result Set. My concerns are : How Result Set handle these records internally? and How a programmer can handle those records in batches So that memory problem would not occur.? waiting for your answers .. Many Thanks

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  • JDBC call not executing

    - by dbyrne
    I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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  • Are entities cached in jpa by default ?

    - by Nitesh Panchal
    Hello, I add entity to my database and it works fine. But when i retrieve the List, i get the old entity, the new entities i add are not shown until i undeploy the application and redeploy it again. This means are my entities cached by default? But, I haven't made any settings for caching entities in my persistence.xml or any such file. I have even tried calling flush(), refresh() and merge(). But still it shows the old entities only. Am i missing something? Please help me.

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  • What is Problem in Runtime.getruntime which does not open notepad.exe

    - by magh
    when try to execute the servlet containing following code Runtime rt = Runtime.getRuntime(); Process p = rt.exec("notepad.exe"); It doesn't launch the application in the environment windows server 2003 and Tomcat 5 but a process is being created as notepad.exe in the windows task manager. In windows xp and tomcat 6 environment launches the notepad i need to work on the windows server 2003 and tomcat 5 Thanks in advance

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  • How to find which file is open in eclipse editor without using IEditorPart?

    - by Destructor
    I want to know which file (or even project is enough) is opened in eclipse editor? I know we can do this once we get IEditorPart from doSetInput method, IFile file = ((IFileEditorInput) iEditorPart).getFile(); But I want the name of file without using IEditorPart, how can I do the same? Checking which is the selected file in project explorer is not of much help because, user can select multiple files at once and open all simultaneously and I did not way to distinguish which file opened at what time. Adding more info: I have an editor specified for a particular type of file, now every time it opens, during intializing editor I have some operation to do based on project properties. While initializing editor, I need the file handle (of the one which user opened/double clicked) or the corresponding project handle. I have my editor something this way: public class MyEditor extends TextEditor{ @Override protected void initializeEditor() { setSourceViewerConfiguration(new MySourceViewerConfiguration( CDTUITools.getColorManager(), store, "MyPartitions", this)); } //other required methods @Override protected void doSetInput(IEditorInput input) throws CoreException { if(input instanceof IFileEditorInput) { IFile file = ((IFileEditorInput) input).getFile(); } } } as I have done in the doSetInput() method , I want the file handle(even project handle is sufficient). But the problem is in initializeEditor() function there is no reference to editorInput, hence I am unable to get the file handle. In the source viewer configuration file, I set the code scanners and this needs some project specific information that will set the corresponding rules.

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  • Is it possible to open and edit 2 or more RecordStores at the same time in j2me?

    - by me123
    Hi, I was wondering if it is possible in j2me to have 2 or more recordStores open at the same time. I basically want to be able to add/remove records from 2 different recordStores in the same execution of the code. Is this possible? If so, how would you do it? At the top of the class, you do something like 'private RecordStore rs;' would you need to have two instances of this to make it work or could you do it with the one declaration? Thanks in advance.

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  • Why is my panel not positioned correctly even after setting the boundaries?

    - by nutellafella
    I'm trying to make a simple GUI with radio buttons and I grouped them into one panel. I wanted it positioned on the leftmost side so I used the setBounds method. Whatever numbers I put on the parameters, the panel won't move. Are panels not affected by the setBounds method? Or is there another way to position my panel. Here's the snippet of my code: JPanel radioPanel = new JPanel(); radioPanel.setLayout(new GridLayout(3,1)); JRadioButton Rbutton1 = new JRadioButton("Credit Card"); JRadioButton Rbutton2 = new JRadioButton("E-Funds"); JRadioButton Rbutton3 = new JRadioButton("Check"); Rbutton3.setSelected(true); ButtonGroup Bgroup = new ButtonGroup(); Bgroup.add(Rbutton1); Bgroup.add(Rbutton2); Bgroup.add(Rbutton3); radioPanel.add(Rbutton1); radioPanel.add(Rbutton2); radioPanel.add(Rbutton3); radioPanel.setBounds(10,50,50,40); //this is where I'm trying to position the panel with the radio buttons paymentPanel.add(radioPanel); contentPane.add(paymentPanel); //contentPane is the frame contentPane.setVisible(true);

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  • How to draw on JPanel on fixed position?

    - by kovike
    I have JPanel wrapped in JScrollPane and I want the rectangle to be drawn always on the same position = moving with scrollbars wont affect the visibility of the rectangle. I tried following code: public void paintComponent(Graphics g) { g.setColor(Color.red); g.drawRect(50, (int)getVisibleRect().getY(), 20 , 20); } but it only repaints the rectangle when size of whole JPanel is changed.

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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • Hibernate updating records and implementing listeners : getting only required attribute values for event.getOldState()

    - by Narendra
    Hi All, I am using Hibernate 3 as my persistence framework. Below is the sample hbm file I am using. <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.test.User" table="user"> <meta attribute="implements">com.test.dao.interfaces.IEntity</meta> <id name="key" type="long" column="user_key"> <generator class="increment" /> </id> <property name="userName" column="user_name" not-null="true" type="string" /> <property name="password" column="password" not-null="true" type="string" /> <property name="firstName" column="first_name" not-null="true" type="string" /> <property name="lastName" column="last_name" not-null="true" type="string" /> <property name="createdDate" column="created_date" not-null="true" type="timestamp" insert="false" update="false" /> <property name="createdBy" column="created_by" not-null="true" type="string" update="false" /> </class> </hibernate-mapping> I am added a post-update listener. What it will do is if there any updations perfomed on User then it will be invoked and cahnges will be inserted to audit table. Below is the sample implementation for postupdate event. public void onPostUpdate(PostUpdateEvent event) { LogHelper.info(logger, "Begin - onPostUpdate " + event.getEntity().getClass().getSimpleName()); if (!this.checkForAudit(event.getEntity().getClass().getSimpleName())) { // check do we need to audit it. } // Get Attribute Names String[] attrNames = event.getPersister().getEntityMetamodel() .getPropertyNames(); Object[] oldobjectValue = c Object[] newObjectValue = event.getState(); this.auditDetailsEvent(attrNames, oldobjectValue, newObjectValue); LogHelper.info(logger, "End - onPostUpdate"); // return false; } Here is my requirement. event.getPersister().getEntityMetamodel() .getPropertyNames(); or event.getOldState(); or event.getState(); must return attribute names or value which i can update or insert. Is there any way to control the return values of above one's. Pleas help me on this regard. Thanks, Narendra

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  • how to return a list using SwingWorker

    - by Ender
    I have an assignment where i have to create an Image Gallery which uses a SwingWorker to load the images froma a file, once the image is load you can flip threw the image and have a slideshow play. I am having trouble getting the list of loaded images using SwingWorker. This is what happens in the background it just publishes the results to a TextArea // In a thread @Override public List<Image> doInBackground() { List<Image> images = new ArrayList<Image>(); for (File filename : filenames) { try { //File file = new File(filename); System.out.println("Attempting to add: " + filename.getAbsolutePath()); images.add(ImageIO.read(filename)); publish("Loaded " + filename); System.out.println("Added file" + filename.getAbsolutePath()); } catch (IOException ioe) { publish("Error loading " + filename); } } return images; } } when it is done I just insert the images in a List<Image> and that is all it does. // In the EDT @Override protected void done() { try { for (Image image : get()) { list.add(image); } } catch (Exception e) { } } Also I created an method that returns the list called getImages() what I need to get is the list from getImages() but doesn't seam to work when I call execute() for example MySwingWorkerClass swingworker = new MySwingWorkerClass(log,list,filenames); swingworker.execute(); imageList = swingworker.getImage() Once it reaches the imageList it doesn't return anything the only way I was able to get the list was when i used the run() instead of the execute() is there another way to get the list or is the run() method the only way?. or perhaps i am not understanding the Swing Worker Class.

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  • Understanding max JVM heap size

    - by Marcus
    I've read the max heap size on 32bit Windows is ~1.5GB which is due to the fact that the JVM requires contiguous memory. Can someone explain the concept of "contiguous memory" and why you only have max 1.5GB on Windows? Secondly, what then is the max heap size on 64 bit Windows and why is this different than what's available on 32 bit?

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