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  • Compare class objects

    - by reto
    I have to compare a class object against a list of pre defined classes. Is it safe to use == or should I use equals()? if (klass == KlassA.class) { } else if (klass == KlassB.class) { } else if (klass == KlassC.class) { } else { } Note: I cannot use instanceof, I don't have an object, I just have the class object. I (mis)use it like an enum in this situation! Thanks!

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  • Refining Solr searches, getting exact matches?

    - by thebluefox
    Afternoon chaps, Right, I'm constructing a fairly complex (to me anyway) search system for a website using Solr, although this question is quite simple I think... I have two search criteria, location and type. I want to return results that are exact matches to type (letter to letter, no exceptions), and like location. My current search query is as follows ../select/?q=location:N1 type:blue&rows=100&fl=*,score&debugQuery=true This firstly returns all the type blue's that match N1, but then returns any type that matches N1, which is opposite to what I'm after. Both fields are set as textgen in the Solr schema. Any pointers? Cheers gang

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  • When to use @Singleton in a Jersey resource

    - by dexter
    I have a Jersey resource that access the database. Basically it opens a database connection in the initialization of the resource. Performs queries on the resource's methods. I have observed that when I do not use @Singleton, the database is being open at each request. And we know opening a connection is really expensive right? So my question is, should I specify that the resource be singleton or is it really better to keep it at per request especially when the resource is connecting to the database? My resource code looks like this: //Use @Singleton here or not? @Path(/myservice/) public class MyResource { private ResponseGenerator responser; private Log logger = LogFactory.getLog(MyResource.class); public MyResource() { responser = new ResponseGenerator(); } @GET @Path("/clients") public String getClients() { logger.info("GETTING LIST OF CLIENTS"); return responser.returnClients(); } ... // some more methods ... } And I connect to the database using a code similar to this: public class ResponseGenerator { private Connection conn; private PreparedStatement prepStmt; private ResultSet rs; public ResponseGenerator(){ Class.forName("org.h2.Driver"); conn = DriverManager.getConnection("jdbc:h2:testdb"); } public String returnClients(){ String result; try{ prepStmt = conn.prepareStatement("SELECT * FROM hosts"); rs = prepStmt.executeQuery(); ... //do some processing here ... } catch (SQLException se){ logger.warn("Some message"); } finally { rs.close(); prepStmt.close(); // should I also close the connection here (in every method) if I stick to per request // and add getting of connection at the start of every method // conn.close(); } return result } ... // some more methods ... } Some comments on best practices for the code will also be helpful.

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  • Get a value from hashtable by a part of its key

    - by htf
    Hi. Say I have a Hashtable<String, Object> with such keys and values: apple => 1 orange => 2 mossberg => 3 I can use the standard get method to get 1 by "apple", but what I want is getting the same value (or a list of values) by a part of the key, for example "ppl". Of course it may yield several results, in this case I want to be able to process each key-value pair. So basically similar to the LIKE '%ppl%' SQL statement, but I don't want to use a (in-memory) database just because I don't want to add unnecessary complexity. What would you recommend?

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  • What is the most efficient way to list all of the files in a directory (including sub-directories)?

    - by prometheus
    I am writing a servlet which will examine a directory on the server (external to the web container), and recursively search for certain files (by certain files, I mean files that are of a certain extension as well as a certain naming convention). Once these files are found, the servlet responds with a long list of all of the found files (including the full path to the files). My problem is that there are so many files and directories that my servlet goes extremely slow. I was wondering if there was a best practice or existing servlet for this type of problem? Would it be more efficient to simply compile the entire list of files and do the filtering via js/jquery on the client side?

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  • Tuning garbage collections for low latency

    - by elec
    I'm looking for arguments as to how best to size the young generation (with respect to the old generation) in an environment where low latency is critical. My own testing tends to show that latency is lowest when the young generation is fairly large (eg. -XX:NewRatio <3), however I cannot reconcile this with the intuition that the larger the young generation the more time it should take to garbage collect. The application runs on linux, jdk 6 before update 14, i.e G1 not available.

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  • Finding the digit root of a number

    - by Jessica M.
    Study question is to find the digit root of a already provided number. The teacher provides us with the number 2638. In order to find the digit root you have to add each digit separately 2 + 6 + 3 + 8 = 19. Then you take the result 19 and add those two digits together 1 + 9 = 10. Do the same thing again 1 + 0 = 1. The digit root is 1. My first step was to use the variable total to add up the number 2638 to find the total of 19. Then I tried to use the second while loop to separate the two digits by using the % I have to try and solve the problem by using basic integer arithmetic (+, -, *, /). 1.Is it necessary and or possible to solve the problem using nested while loops? 2.Is my math correct? 3. As I wrote it here it does not run in Eclipse. Am I using the while loops correctly? import acm.program.*; public class Ch4Q7 extends ConsoleProgram { public void run(){ println("This program attempts to find the digit root of your number: "); int n = readInt("Please enter your number: "); int total = 0; int root = total; while (n > 0 ){ total = total + (n %10); n = (n / 10); } while ( total > 0 ){ root = total; total = ((total % 10) + total / 10); } println("your root should be " + root); } }

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  • Please help me to allow my `JTable` to search the text even the table is in editable mode on key-press

    - by Ashish Pancholi
    If user starts pressing keys using keyboards then JTable is supposed to be searched the matching text for him and if user double clicks on cell then Table should allow him to edit the text. And the issue is - Table is only searching text when the table is in non-editable mode and if Table is editable and user starts typing the text-using keyboard, cell is allowing him to edit the cell rather then search. Mr mKorbel has just solved my issue to allow edit only if double click on Table cell. Please help me to allow my JTable to search the text even the table is in editable mode on key-press.

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  • Is it possible to use instanceof when passing objects between Threads?

    - by Risser
    I've run into an issue where instanceof works, and then it doesn't. Going into details is difficult, but I think this might be the problem: Reading this: http://www.theserverside.com/news/thread.tss?thread_id=40229 (search for Thread.currentThread), it seems to imply that, even if the two objects are the same class, if you pass them between threads with different class loaders, instanceof (and isAssignableFrom) might still fail. This certainly would explain the behavior I'm having, but I was wondering if anyone could verify it? (I wish the article linked at the beginning of the discussion was still available, but it doesn't seem like it is.) Thanks, Peter

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  • ActiveMq integration with Spring 2.5

    - by Tony
    I am using ActiveMq 5.32 with Spring 2.5.5. I use pretty generic configuration, as long as I include the jmsTransactionManager in DefaultMessageListenerContainer, Spring throw an error on start up: "Error creating bean with name 'org.springframework.jms.listener.DefaultMessageListenerContainer#0'" Without the transactionManager attribute , this works fine, but when I add 10 messages to the message queue, a transaction exception will occur. Part of my configurations : <bean class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory" /> <property name="destination" ref="emailDestination" /> <property name="messageListener" ref="emailServiceMDP" /> <property name="transactionManager" ref="jmsTransactionManager" /> </bean> <bean id="jmsTransactionManager" class="org.springframework.jms.connection.JmsTransactionManager"> <property name="connectionFactory" ref="connectionFactory" /> </bean> Does this version of Spring and Activemq has some know issues in integration ? Or do I need additional libs to get jmsTransactionManager to work ?

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  • Is there any point in using a volatile long?

    - by Adamski
    I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

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  • JSF h:outputStylesheet doesn't work everywhere

    - by s3rius
    I'm currently learning Icefaces, now I'm trying to integrate a css file via h:OutputStylesheet into my code. I have a main page and a second page. Using outputStylesheet in my main page works well (and then I can also access the css in the second page, which I guess is intended). But when I try to integrate it in my second page it doesn't work at all. The code for both pages is basically identical. main page: <h:head></h:head> <h:body> <!-- this line works --> <h:outputStylesheet library="css" name="style.css" /> <!-- this line is only shown in red if the outputStylesheet from above is there --> <div class="red">This is red color in main page</div> </h:body> second page: <h:head></h:head> <h:body> <!-- this line doesn't work --> <h:outputStylesheet library="css" name="style.css" /> <!-- this line is only shown in red if the outputStylesheet in main page is there --> <div class="red">This is red color in second page</div> </h:body> I've made sure that I have h:body and h:head tags in both files. There's nothing more in the html pages except the standard doctype and xml version declarations. I've tried packing everything into h:forms, but that doesn't change anything. Can anyone explain to me what's going on?

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  • Connection Pooling in J2SE?

    - by Zombies
    It is hard to find a resource on this without finding J2EE, but here is what I am looking for: All I have is a standard J2SE app, it makes a lot of DB connections. I simply need to make use of a connection pool. Any suggestions?

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  • Hibernate database connection configuration

    - by Alvin
    We have 2 different server environments using the same Hibernate configuration. One server has JNDI support for datasource, but the other does not. Currently the Hibernate configuration is configured to use JNDI, which is causing problem on the server that does not support JNDI. I have also tried to put the direct JDBC configuration together with JNDI configuration into the configuration file, but it looks like hibernate always favors JNDI over direct JDBC configuration if both exist. My question is, will it be the same if both JNDI and connection_provider configuration both exists? Will Hibernate still use JNDI over connection_provider? Or is there any way to change the precedence of the database connection property? I do not have access to the server all the time, so I thought I do ask the question before my window of the sever time. Thanks in advance.

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  • InputVerifier don't display each component icon(lable)

    - by Sajjad
    I have a form that set a input verifier to it. I want when a user type a correct value for a text field and want to go to other text field, a check icon should be display besides of text field. But now in my code, when user type a correct value on first text field an go to other, Two icons displayed together! public class UserDialog extends JDialog { JButton cancelBtn, okBtn; JTextField fNameTf, lNameTf; JRadioButton maleRb, femaleRb; ButtonGroup group; JLabel fNameLbl, fNamePicLbl, lNameLbl, lNamePicLbl, genderLbl, tempBtn, temp3; public UserDialog() { add(createForm(), BorderLayout.CENTER); setDefaultCloseOperation(DISPOSE_ON_CLOSE); setLocation(400, 100); pack(); setVisible(true); } public JPanel createForm() { JPanel panel = new JPanel(); ImageIcon image = new ImageIcon("Check.png"); okBtn = new JButton("Ok"); cancelBtn = new JButton("Cancel"); tempBtn = new JLabel(); fNameLbl = new JLabel("First Name"); fNamePicLbl = new JLabel(image); fNamePicLbl.setVisible(false); lNameLbl = new JLabel("Last Name"); lNamePicLbl = new JLabel(image); lNamePicLbl.setVisible(false); genderLbl = new JLabel("Gender"); maleRb = new JRadioButton("Male"); femaleRb = new JRadioButton("Female"); temp3 = new JLabel(); group = new ButtonGroup(); group.add(maleRb); group.add(femaleRb); fNameTf = new JTextField(10); fNameTf.setName("FnTF"); fNameTf.setInputVerifier(new MyVerifier(new JComponent[]{maleRb, femaleRb, okBtn})); lNameTf = new JTextField(10); lNameTf.setName("LnTF"); lNameTf.setInputVerifier(new MyVerifier(new JComponent[]{maleRb, femaleRb, okBtn})); panel.add(fNameLbl); panel.add(fNameTf); panel.add(fNamePicLbl); panel.add(lNameLbl); panel.add(lNameTf); panel.add(lNamePicLbl); panel.add(genderLbl); JPanel radioPanel = new JPanel(new FlowLayout(FlowLayout.LEFT)); radioPanel.add(maleRb); radioPanel.add(femaleRb); panel.add(radioPanel); panel.add(temp3); panel.add(okBtn); panel.add(cancelBtn); panel.add(tempBtn); panel.setLayout(new SpringLayout()); SpringUtilities.makeCompactGrid(panel, 4, 3, 50, 10, 80, 60); return panel; } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { new UserDialog(); } }); } public class MyVerifier extends InputVerifier { private JComponent[] component; public MyVerifier(JComponent[] components) { component = components; } @Override public boolean verify(JComponent input) { String name = input.getName(); if (name.equals("FnTF")) { String text = ((JTextField) input).getText().trim(); if (text.matches(".*\\d.*") || text.length() == 0) { //disable dependent components for (JComponent r : component) { r.setEnabled(false); } return false; } } else if (name.equals("LnTF")) { String text = ((JTextField) input).getText(); if (text.matches(".*\\d.*") || text.length() == 0) { //disable dependent components for (JComponent r : component) { r.setEnabled(false); } return false; } } //enable dependent components for (JComponent r : component) { r.setEnabled(true); } fNamePicLbl.setVisible(true); lNamePicLbl.setVisible(true); return true; } } } }

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  • Implementing clone on a LinkedList

    - by devoured elysium
    I am trying to implement a clone() method on a DoubleLinkedList. Now, the problem is that implementing it by "the convention" is a lot more troublesome than just creating a new DoubleLinkedList and filling it with all the elements of my current DoubleLinkedList. Is there any inconvenient I am not seeing when doing that? Here is my current approach: @Override public DoubleLinkedList<T> clone() { DoubleLinkedList<T> dll = new DoubleLinkedList<T>(); for (T element : dll) { dll.add(element); } return dll; } Here is what it would be by the convention: @Override public DoubleLinkedList<T> clone() { try { DoubleLinkedList<T> dll = (DoubleLinkedList<T>)super.clone(); //kinda complex code to copy elements return dll; } catch (CloneNotSupportedException e) { throw new InternalError(e.toString()); } }

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  • Is this a correct iText design?

    - by Lucas
    I´m making some pdf reports to be used on a web app. I wonder if the way I´m taking to make the designs is appropriated. This would be a screenshot of the way I´m doing the things. As you can see, I´m using tables to position everything in the document. I think this is a pretty much similar design to HTML. But I want to know is there is a better way to get the same result I got. This is the document without cell borders: I could post the code if necessary. By the way, why should I spend long hours programming these kind of stuff with iText tool when I could do things faster and maybe better looking with iReport? I like iText, it´s just a question. Sorry for my english and thanks!

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  • Having 'mvn deploy' in Hudson's build goals and the standard approach of releasing

    - by user68759
    I set up Hudson for my project with the build goals mvn clean deploy site:site, run a build every midnight and whenever there are new changes. One thing I have been wondering is whether I should include deploy in the build goals because it could happen that if I had just released version 1.0.0 of my project (I've changed the pom to be version 1.0.0 and committed it) but not yet increased the version number to 1.0.1-SNAPSHOT for several days, I could end up with multiple different 1.0.0 builds being deployed at different times. But I've seen people are using deploy in their Hudson's build goals - I wonder how they deal with this issue. What's the correct way of doing a release with Maven actually? Thanks for any pointers!

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  • Page Refresh problem

    - by Abhi
    I have a jsp in which there are certain buttons when i am clicking on one of those, the page is refreshing but the problem is that I want to show that section of jsp where the button is on which the user has done the on click event...but the section which is coming is the top of the page but I don't want that. Please provide me with a solution to rectify the situation.

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  • How to use @BeforeClass and @AfterClass in JunitPerf?

    - by allenzzzxd
    Hi, I want to do some actions before the whole test suite (also after the suite). So I wrote like: public class PerformanceTest extends TestCase { @BeforeClass public static void suiteSetup() throws Exception { //do something } @AfterClass public static void suiteSetup() throws Exception { //do something } @Before public void setUp() throws Exception { //do something } @After public void tearDown() throws Exception { //do something } public PerformanceTest(String testName){ super(testName); } public static Test suite() { TestSuite suite = new TestSuite(); Test testcase1 = new PerformanceTest("DoTest1"); Test loadTest1 = new LoadTest(testcase1, n); Test testcase2 = new PerformanceTest("DoTest2"); Test loadTest2 = new LoadTest(testcase2, n); } public void DoTest1 throws Throwable{ //do something } public void DoTest2 throws Throwable{ //do something } } But I found that it never reach the code in @BeforeClass and @AfterClass. So how could I do to solve this problem? Or is there other way to realize this? Thank you for your help.

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