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  • Must JDBC Resultsets and Statements be closed separately although the Connection is closed afterwards?

    - by Mulmoth
    It is said to be a good habit to close all JDBC resources after usage. But if I have the following code, is it necessary to close the Resultset and the Statement? Connection conn = null; PreparedStatement stmt = null; ResultSet rs = null; try { conn = // Retrieve connection stmt = conn.prepareStatement(// Some SQL); rs = stmt.executeQuery(); } catch { // Error Handling } finally { try { if (rs != null) rs.close(); } catch (Exception e) {}; try { if (stmt != null) stmt.close(); } catch (Exception e) {}; try { if (conn != null) conn.close(); } catch (Exception e) {}; } The question is if the closing of the connection does the job or if it leaves some resources in use.

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  • Data persistance with BufferedReader and PrintWriter?

    - by Nazgulled
    I have this simple application with a couple of classes which are all related. There's one, the main one, for which there is only one instance of. I need to save save and load that using a text stream. My instructor requirement is BufferedReader to load the stream and PrintWriter to save it. But is this even possible? To persist a data object/class with a text stream? I know how to do it with and object, using serialization. But I don't see how am I supposed to do it using text streams. Suggestions?

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  • Creating objects makes the VM faster?

    - by Sudhir Jonathan
    Look at this piece of code: MessageParser parser = new MessageParser(); for (int i = 0; i < 10000; i++) { parser.parse(plainMessage, user); } For some reason, it runs SLOWER (by about 100ms) than for (int i = 0; i < 10000; i++) { MessageParser parser = new MessageParser(); parser.parse(plainMessage, user); } Any ideas why? The tests were repeated a lot of times, so it wasn't just random. How could creating an object 10000 times be faster than creating it once?

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  • ImageIcon loads no image

    - by neville
    I'm trying to get image built from tiled set of images So to JPanel I'm adding JButtons with ImageIcons. All images are in folder with my classes (NetBeans), and they're named u1, u2, ..., u16. But on button there is no image shown. What am I doing wrong ? JPanel panel = new JPanel(new GridLayout(4, 4, 3, 3)); for (int i = 1; i < 17; i++) { JLabel l = new JLabel(new ImageIcon("u"+i+".jpg"), JLabel.CENTER); l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED)); panel.add(l); }

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  • When accessing ResultSets in JDBC, is there an elegant way to distinguish between nulls and actual z

    - by Uri
    When using JDBC and accessing primitive types via a result set, is there a more elegant way to deal with the null/0 than the following: int myInt = rs.getInt(columnNumber) if(rs.wasNull())? { // Treat as null } else { // Treat as 0 } I personally cringe whenever I see this sort of code. I fail to see why ResultSet was not defined to return the boxed integer types (except, perhaps, performance) or at least provide both. Bonus points if anyone can convince me that the current API design is great :) My solution was to write a wrapper that returns an Integer (I care more about elegance of client code than performance), but I'm wondering if I'm missing a better way to do this.

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  • adding elements in to the doubly linked list

    - by user329820
    Hi this is my code for main class and doubly linked class and node class but when I run the program ,in the concole will show this"datastructureproject.DoublyLinkedList@19ee1ac" instead of the random numbers .please help me thanks! main class: public class Main { public static int getRandomNumber(double min, double max) { Random random = new Random(); return (int) (random.nextDouble() * (max - min) + min); } public static void main(String[] args) { int j; int i = 0; i = getRandomNumber(10, 10000); DoublyLinkedList listOne = new DoublyLinkedList(); for (j = 0; j <= i / 2; j++) { listOne.add(getRandomNumber(10, 10000)); } System.out.println(listOne); } } doubly linked list class: public class DoublyLinkedList { private Node head ; private Node tail; private long size = 0; public DoublyLinkedList() { head= new Node(0, null, null); tail = new Node(0, head, null); } public void add(int i){ head.setValue(i); Node newNode = new Node(); head.setNext(newNode); newNode.setPrev(head); newNode = head; } } and the node class is like the class that you have seen before (Node prev,Node next,int value)

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  • KXML library Problem

    - by Hesham
    i'm working j2me with netbeans platform and i had a problem while i was trying to read a XML file and i added the library kxml.zip to my project's libraries and i used some of it's functions, there r no errors or red lines in the code, but the problem is that i cant run the project cos it come up with errors while compiling and all these errors are on the kxml functions, so any on can help me through this cos i really dont know what to do to make it run properly

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  • Hibernate Annotation for Entity existing in more than 1 catalog

    - by user286395
    I have a Person entity mapped by Hibernate to a database table in a database catalog "Active". After a period of time, records in this database table in the "Active" catalog are archived/moved to an exact copy of the table in a database Catalog "History". I have the need to retrieve from both the Active and History Catalogs. Is there a better way to model this with Hibernate annotations than making an abstract class that 2 classes extend from. This is what I have now. @MappedSuperclass public abstract class Person { @Id private Integer id; private String name; } @Entity @Table(name="Person", catalog="Active") public class PersonActive extends Person { } @Entity @Table(name="Person", catalog="History") public class PersonHistory extends Person { }

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  • Eclipse with JSR 250 (annotation) yields "Access Restriction" errors.

    - by edstafford
    Hi, Hopefully someone has come across this before. I'm running Spring STS 2.3.0 and when attempting to use the @Resource annotation from javax.annotations.Resource I get "Access restriction: The type Resource is not accessible due to restriction on required library". I'm using the JDK 6u18. I've tried changing the JDK Compliance to 1.5 and 1.6 and both yield the same error. Cheers, -Ed

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  • how to implement a callback in runnable to update other swing class

    - by wizztjh
    I have a thread like this public class SMS { class Read implements Runnable { Read(){ Thread th = new Thread(this); th.start(); } @Override public void run() { // TODO Auto-generated method stub while (true){ Variant SMSAPIReturnValue = SMSAPIJava.invoke("ReadSMS"); if (SMSAPIReturnValue.getBoolean()){ String InNumber = SMSAPIJava.getPropertyAsString("MN"); String InMessage = SMSAPIJava.getPropertyAsString("MSG"); } } } } } How do I update the message to another GUI class in the same package(I understand how to put nested class to another package ....). Should I implement a callback function in SMS class? But how? Or should I pass in the Jlabel into the class?

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  • Is there programming language with better approach for switch's break statements ?

    - by Vitaly Polonetsky
    It's the same syntax in a way too many languages: switch (someValue) { case OPTION_ONE: case OPTION_LIKE_ONE: case OPTION_ONE_SIMILAR: doSomeStuff1(); break; // EXIT the switch case OPTION_TWO_WITH_PRE_ACTION: doPreActionStuff2(); // the default is to CONTINUE to next case case OPTION_TWO: doSomeStuff2(); break; // EXIT the switch case OPTION_THREE: doSomeStuff3(); break; // EXIT the switch } Now all you know that break statements are required, because the switch will continue to the next case when break statement is missing. We have an example of that with OPTION_LIKE_ONE, OPTION_ONE_SIMILAR and OPTION_TWO_WITH_PRE_ACTION. The problem is that we only need this "skip to next case" very very very rarely. And very often we put break at the end of case. It very easy for a beginner to forget about it. And one of my C teachers even explained it to us as if it was a bug in C language (don't want to talk about it :) I would like to ask if there are any other languages that I don't know of (or forgot about) that handle switch/case like this: switch (someValue) { case OPTION_ONE: continue; // CONTINUE to next case case OPTION_LIKE_ONE: continue; // CONTINUE to next case case OPTION_ONE_SIMILAR: doSomeStuff1(); // the default is to EXIT the switch case OPTION_TWO_WITH_PRE_ACTION: doPreActionStuff2(); continue; // CONTINUE to next case case OPTION_TWO: doSomeStuff2(); // the default is to EXIT the switch case OPTION_THREE: doSomeStuff3(); // the default is to EXIT the switch } The second question: is there any historical meaning to why it is like this in C? May be continue to next case was used far more often than we use it these days ?

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  • jsf and eclipse setup. Lib in Explorer is different than lib in tomcat. How come?

    - by user384706
    Hi, I am starter in JSF2.0, and I have a question related to Eclipse (I am using Helios). 1)I create a Dynamic Project 2)I add JSF project facet. 3)I choose JSF user library (I have created it using MyFaces) All ok so far. I notice though that in the Project Explorer in WebContent/WEB-INF/lib the lib directory is empty instead of having MyFaces jars. The application works fine though. I looked into this and the jars are actually being placed in the corresponding lib directory of the app deployed under wtpwebapps of the Tomcat instance of eclipse in the .pluggins directory. Ok, it works but IMHO it is incorrect to have the Project Explorer inconsistent with the directories actually deployed. I.e. lib is shown empty in Project Explorer but with jars under wtpwebapps. Am I wrong to dislike this inconsistency? Is this how it should work or am I doing something wrong in the way I am setting my project? Thanks!

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  • jtable update data not visible

    - by Thomas n
    I am running into a problem similar to what I have read here about inserted data and added data not showing up on jtable. I have tried repaint() and revalidate(), but to no avail. Basically, I have two classes say A and B. A calls a function in class B to add a row of data to the table. Here is the code.(By the way I am using Netbeans 7.1.2 to add a table and then add some code to handle the update.) public void callUpdateTable(){ DefaultTableModel myModel = (DefaultTableModel)jTable1.getModel(); DateFormat dateFormate = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss"); Object[] str = new Object[3]; Date date = new Date(); str[0] = dateFormate.format(date); str[1] = "Robot"; str[2] = "hello"; // myModel.addRow(str); myModel.insertRow(1, str); myModel.setValueAt("Hello", 1, 2); System.out.println("count = " + myModel.getValueAt(1, 2)); jTable1.repaint(); } The funny thing is on system print it prints out the value at the cell(1,2) I set the value, but doesn't show up on the table. Thank you for your help.

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  • What are the interets of synthetic methods?

    - by romaintaz
    Problem One friend suggested an interesting problem. Given the following code: public class OuterClass { private String message = "Hello World"; private class InnerClass { private String getMessage() { return message; } } } From an external class, how may I print the message variable content? Of course, changing the accessibility of methods or fields is not allowed. (the source here, but it is a french blog) Solution The code to solve this problem is the following: try { Method m = OuterClass.class.getDeclaredMethod("access$000", OuterClass.class); OuterClass outerClass = new OuterClass(); System.out.println(m.invoke(outerClass, outerClass)); } catch (Exception e) { e.printStackTrace(); } Note that the access$000 method name is not really standard (even if this format is the one that is strongly recommanded), and some JVM will name this method access$0. Thus, a better solution is to check for synthetic methods: Method method = null; int i = 0; while ((method == null) && (i < OuterClass.class.getDeclaredMethods().length)) { if (OuterClass.class.getDeclaredMethods()[i].isSynthetic()) { method = OuterClass.class.getDeclaredMethods()[i]; } i++; } if (method != null) { try { System.out.println(method.invoke(null, new OuterClass())); } catch (Exception e) { e.printStackTrace(); } } So the interesting point in this problem is to highlight the use of synthetic methods. With these methods, I can access a private field as it was done in the solution. Of course, I need to use reflection, and I think that the use of this kind of thing can be quite dangerous... Question What is the interest - for me, as a developer - of a synthetic method? What can be a good situation where using the synthetic can be useful?

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  • Eclipselink and update trigger on multiple access to the database

    - by Raven
    Hi, in my project I have a database which many clients connect to. Concurrent access and writing works well. The problem now is not to reload the data every second from the database to always have the current status of the data. Does Eclipselink provide a trigger mechanism on (automatically?) reload the data if the database is changed? How would one use this trigger? Thanks!

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  • How can I force the text go to the button of the panel?

    - by Roman
    At the moment I have the following code which works fine. label = new JLabel(panelLabel,SwingConstants.CENTER); outputPanel.add(label,BorderLayout.CENTER); I get the text in the center of the panel (in terms of the left-right position as well as in terms of the top-bottom). Now I want to set the position to the bottom (and center in terms of "left-right"). I tried to use SOUTH instead of the CENTER in the first line. Compiler does not complains but during the execution i get IllegalArgumentException: HorizontalAlignment. What is that?

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  • How does Object Oriented Programming work?

    - by venom
    Hello, I am not sure about some things in OOP. If I have Class1, which has some private field, for example private Field field1, and make getField1 () { return field1; } then I have some class with constructor public Class2 (Field field) { someMethod(field); } And then I call constructor of Class2 in Class3 like: Class2 cl = new Class2(instanceOfClass1.getField1()); And now the question: Am I working with field1 of instanceOfClass1 in someMethod(field)?

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  • Hibernate mapping to manage bidirectional relationship using intermediate table

    - by shikarishambu
    I have an object hierarchy that is as follows. Party inherited by Organization and Person Organization inherited by Customer, Vendor Person inherited by Contact In the database I have the following tables Party, Customer, Vendor, Contact. All of them have a corresponding row in Party table. Contact belongs to either Vendor or Customer. I have a field on the Contact table for org_party_id. However, since the organization can be either a Customer or Vendor I need to be able to look at different tables. Is there a way to map this in hibernate? Or, a better way to manage it in DB/ hibernate?

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  • Trying to write junit test missing some basisc

    - by Gandalf StormCrow
    When I try to use assertNotLesser or assertNotGreater I get compile error .. and eclipse suggest me to create a new method called like this .. http://junit-addons.sourceforge.net/junitx/framework/ComparableAssert.html I found it here I never used these options before but I need to write this test, I can do it jmock as well but I don't know how .. I need to compare my expected results let say 0, if the real result is greater that the test should fail.

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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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  • I have a feeling that adding fields marked with @Transient annotation to entity is very bug-prone. A

    - by Roman
    I have some philosophical feeling that adding to an entity fields which doesn't mapped to the DB is a wrong way of solving problems. But are there any concrete situations where using @Transient fields leads to implicit and hard fixing problems? For example, is it possible that adding/removing 2nd level cache will break our app when there are @Transient fields in our entities?

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  • Spring MVC: easiest way to see incoming requests

    - by flybywire
    I am debugging a Spring MVC (3.0) app, deployed on tomcat. I want to see in my console or log files all the incoming requests. Including 404s, both generated by my app or by spring because it didn't find an appropriate controller. I'd like to see something like this: GET /index.html GET /img/logo.png GET /js/a.js GET /style/b.css POST /ajax/dothis?blah=yes POST /ajax/dothat?foo=np GET /nextpage.html ... What is the easiest way to see that.

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