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  • How to create initializeDB() method for java database

    - by Holly
    I am working on a Java project for class and have not worked much with incorporating databases into Java. I can't find much on the initializeDB() method, but if I could get some help I would really appreciate it. Below is the code being used for the intializeDB() method: private void initializeDB() { try { // Load the JDBC driver System.out.println("Driver loaded"); // Establish a connection System.out.println("Database connected"); // Create a statement // Create a SQL Query string // Execute the query to create a recordset } catch (Exception ex) { ex.printStackTrace(); } }

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  • Scripting language to embed into a Java server application

    - by Alexey Kalmykov
    I want to make a business logic of server side Java application as a set of scripts. So I need from a scripting engine: Maximum Java interoperability (i.e. Spring framework) Script reloading and recompiling Easy DB access from scripting language Clear and simple syntax (some DSL capabilities would be nice to have), easy learning curve for non-hardcore developers Performance and stability I had some experience in the similar project with Rhino and it was pretty good. But I want to see if there is something better. Currently I'm looking into Groovy. JRuby and Jython are a bit more complex than I need for this task. Any other suggestion? What to take into consideration?

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  • Measuring time spent in application / thread

    - by Adamski
    I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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  • 'void' type not allowed here error (java) help?

    - by David
    When i try to compile this: import java.awt.* ; class obj { public static void printPoint (Point p) { System.out.println ("(" + p.x + ", " + p.y + ")"); } public static void main (String[]arg) { Point blank = new Point (3,4) ; System.out.println (printPoint (blank)) ; } } i get this error: obj.java:12: 'void' type not allowed here System.out.println (printPoint (blank)) ; ^ 1 error I don't really know how to start asking about this other than to ask: What went wrong here? What does this error message mean?

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  • drawImage in Java applet flickers in Safari

    - by lcvinny
    I'm having a flicker problem in a Java applet in Safari (Mac). However, it's not the usual double buffering problem. I have isolated it down to one single drawImage call (no redundant repaint, no clear is called), which gives a white flicker before painting the image but not on every repaint. In fact, I measured the duration of the drawImage call, which is normally about 1ms, but up to 30ms about every 5th time paint is called, which is when it flickers. Repaints are triggered when I drag a component or when the window is scrolled. Is this a bug in the java implementation on OSX, and is there a fix for it?

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  • reading html from an inputstream java

    - by randeel wimalagunarathne
    hello everyone, I am reading a html file using an inputstream from a java servlet. But the contents of the original and the read one are in a different format although when displayed in a web browser they are the same. These are the two links for the html files after reading output http://www.fileflyer.com/view/gQREGAe orginal output http://www.fileflyer.com/view/mWXHVAE Is there a way to get the original html when reading? why is this happening? my java code is as follows; InputStreamReader isr = new InputStreamReader(inputStream); BufferedReader br = new BufferedReader(isr); String line = null; while ( (line = br.readLine()) != null) { System.out.println(line); } Any help would be greatly appreciated!! Thank you, rana.

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  • casting a generic array in java

    - by liloboy
    The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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  • Java and Different Types of Stacks

    - by Rarge
    Currently the only stack I know anything about is Vector, I normally use this in place of an array but I understand that there is other types of stacks and they all suit different jobs. The project I am currently working on requires me to be inserting objects in a certain position inside a stack, not always the front of the stack and I am under the impression that a Vector may not be the best class for this job. Could somebody please give me a brief description of the other types of stacks available to me with the Java language and their advantages and disadvantages? Are these names homogeneous? E.g. Are they only used in the Java language or are they used as general terms in Computer Science? Thank you

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  • get entire line with java.util.scanner.hasNext(regex)

    - by Hussain
    I'm doing something in Java that requires input to be matched against the pattern ^[1-5]$. I should have a while loop looping through each line of input, checking it against the pattern, and outputting an error message if it does not. Sudo code: while (regex_match(/^[^1-5]$/,inputLine)) { print ("Please enter a number between 1 and 5! "); getNextInputLine(); } I can use java.util.Scanner.hasMatch("^[^1-5]$"), but that will only match a single token, not the entire line. Any idea on how to make hasMatch match against the entire line? (Setting the delimiter to "\n" or "\0" doesn't work.)

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  • Deploy java (command line) app using Netbeans / ant

    - by Haes
    I've finally managed to create a Netbeans project out of an old standalone (not Web-) Java application which consisted only out of single .java sources. Now I have basically two questions regarding Netbeans Subversion interaction and application deployment: Do you check in all the Netbeans project files into the repository, normally? If I build the project using Netbeans (or ant) I get a .jar file and some additional jar libraries. In order for the app to run properly on the server, some additional config files and directories (log/ for example) are needed. The application itself is a J2SE application (no frameworks) which runs from the command line on a Linux platform. How would you deploy and install such an application? It would also be nice if I could see what version of app is currently installed (maybe by appending the version number to the installed app path). Thanks for any tips.

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  • what the java command's -jar option really does

    - by JBoy
    Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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  • Java/C++ communication via pipe on Windows

    - by Warlax
    Hi, I have two separate programs, one in Java and one in C++, both running on Windows. We need to do bidirectional interprocess communication between the two. Up until now, we were using this awkward solution of writing to text files and reading them on the other side, where the producer would generate a .lock file when it's done writing and the consumer would remove that when it's done reading... like I said, awkward. If we were on *nix, we would use a pipe using popen() on the C++ and RadomAccessFile on the Java side. It seems to work well. What can we do on Windows? Can we use named pipes? Thank you.

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  • The best alternative for String flyweight implementation in Java

    - by Dan
    My application is multithreaded with intensive String processing. We are experiencing excessive memory consumption and profiling has demonstrated that this is due to String data. I think that memory consumption would benefit greatly from using some kind of flyweight pattern implementation or even cache (I know for sure that Strings are often duplicated, although I don't have any hard data in that regard). I have looked at Java Constant Pool and String.intern, but it seems that it can provoke some PermGen problems. What would be the best alternative for implementing application-wide, multithreaded pool of Strings in java?

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  • Java + Eclipse + Pulpcore

    - by cable729
    I've never programmed in java or eclipse before, although I have used c# and visual studio. I'm trying to get started with java development, and develop 2d games, but I can't get the project to run. I've followed the tutorial here: http://cloningtheclassics.com/getting-started-with-pulpcore/ I've retried the tutorial at least 5 times, and I still can't get it to work. The error it displays is: Buildfile: C:\workspace\javapulp\project\build.xml [taskdef] Could not load definitions from resource tasks.properties. It could not be found. [taskdef] Could not load definitions from resource tasks.properties. It could not be found. -init: BUILD FAILED C:\workspace\javapulp\project\build.xml:127: Required file not found: ../../build/pulpcore-applet-debug-0.11.jar Total time: 1 second Thanks in advance!

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  • How does java LoginContext.login() work?

    - by tangens
    I have this code to create a configuration of a java client to connect to a JBoss application server: System.setProperty( "java.security.auth.login.config", "auth.conf" ); LoginContext auth = new LoginContext( "myAuth", new LoginCallbackHandler( username, password ) ); auth.login(); The file auth.conf contains the following lines: myAuth { org.jboss.security.ClientLoginModule required; }; Now, somewhere else in the code (the LoginContext auth isn't known there) I have an EJB that does a initialContext.lookup( jndiName ) and a narrow() to access a Bean on the JBoss application server. This narrow only succeeds if the login information of the first step was correct. Question How does the login information propagate from the LoginContext to the narrow()? I don't see any connection between these two places. And further, how could I do two or more different logins inside of one client?

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  • How to run AWS sample JAVA code on an EC2

    - by SeaPlusPlus
    I just started with Amazon web services, and I have an EC2 instance. I downloaded the JAVA SDK and the Eclipse toolbox. I am able to run a sample program locally on my PC and connect to the Amazon databases, etc. My question is, what do I need to do to get this working on my EC2 instance? This may not even be specific to AWS. On Eclipse, I can just "Run as Application" and run any code. On the server side, what do I need to do? Should I ftp over my .java files? Should I export it to a jar and upload that? Do I need to install anything special to actually run it? I'm just trying to run the basic DynamoDB example that connects to the database and adds a new table and row

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  • how to show image from ms access to jpanel in java netbeans

    - by Shiv
    I have used this code : private void okActionPerformed(java.awt.event.ActionEvent evt) { try { String Update = name.getText(); Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); Connection connection = DriverManager.getConnection("jdbc:odbc:NewPData"); PreparedStatement psmnt = connection.prepareStatement("SELECT Image FROM Table1 where Name='" + Update + "'"); ResultSet rs = psmnt.executeQuery(); Blob blob = rs.getBlob("Image"); int b; InputStream bis = rs.getBinaryStream("Image"); FileOutputStream f = new FileOutputStream("Image.jpg"); while ((b = bis.read()) >= 0) { f.write(b); } f.close(); bis.close(); icon = new ImageIcon(blob.getBytes(1L, (int) blob.length())); lblImage.setIcon(icon); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } Exception it show is java.lang.UnsupportedOperationException i have stored image first in ms access and now i want to show it on a label plz help

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  • A better way to do XML in Java

    - by jboyd
    There are a lot of questions that ask the best XML parser, I am more interested in what is the XML parser that is the most like Groovy for Java? I want: SomeApiDefinedObject o = parseXml( xml ); for( SomeApiDefinedObject it : o.getChildren() ) { System.out.println( it.getAttributes() ); } The most important things are that I don't want to create an object for every type of filed, I'd rather just deal with them all as strings, and that building the XML doesn't require any converters or anything, just a simple object that is already defined If you have used the Groovy XML parser, you will know what I'm talking about Alternatively, would it be better for me to just use Groovy from Java?

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  • Java respawn process

    - by Bart van Heukelom
    I'm making an editor-like program. If the user chooses File-Open in the main window I want to start a new copy of the editor process with the chosen filename as an argument. However, for that I need to know what command was used to start the first process: java -jar myapp.jar blabalsomearguments // --- need this information Open File (fileUrl) exec("java -jar myapp.jar blabalsomearguments fileUrl"); I'm not looking for an in-process solution, I've already implemented that. I'd like to have the benefits that seperate processes bring.

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  • Benchmark of Java Try/Catch Block

    - by hectorg87
    I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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  • Detect file system changes on Samba share with Java on Windows

    - by GHad
    Hi, for a recent project I need to detect file system changes on a mapped Samba share from java on windows: Creates, updates and removes. At the moment I am using a folder poll that maintains a list of files and their modified timestamp to look for events. But my problem is that this folder poll only peeks into the folder at certain times (every 10 seconds for example), so an updated file can be updated twice between two polls without recognizing. Is there any way to get events from windows inside Java whenever a file event occours on that mappep Samba share? Thanks!

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