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  • Minimize useless tweaking of a numeric app

    - by Potatoswatter
    I'm developing a numeric application (nonlinear optimizer), with a zillion knobs to tweak and rising. It's not my first foray into this domain, but this time there are even more variables in the code and I'm on a tight schedule. Don't want to waste time fiddling. Days or even months can potentially be wasted adjusting variables, recompiling, and reprocessing benchmark datasets. The resulting data is viewed and trouble spots are checked. The overall quality of the solution is reported by the program but the meaning of the report could change over time. (Numeric units for the report are one thing I'm trying to nail down.) One main problem is organizing result files to identify each with specific code changes. Note taking can be a pain, is there software to help with this? Are there agreed best practices to making this kind of development cycle reliably move forward? The solver package converges to its optimal solution with mechanical determination, but I'm all too familiar with the way an excess of design decisions can mire development.

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  • What web technology could I use which would support a decision tree?

    - by Rami Alhamad
    I am a big game development fan but I haven't done any commercial work in the past. I have been asked by a non-profit to look at developing a game similar to the award-winning www.playspent.org They want the following features: support 5 scenarios mobile isn't important but compatibility with older browsers would be a big bonus they want it to be visual and audible bonus is to have it easily modifiable support 4 languages I don't have much knowledge of Flash and would rather avoid using it as a solution. I started breaking down the problem into segments that I will need to examine, they are as follows: ability to read the game flow from a file that they can produce (xml, etc.) db design to store decision tree language challenge browser compatibility I am leaning towards an Google app engine/GWT solution but I am not sure what technology is best for this. I am really hoping to get your opinion/recommendation on my approach and on what technology is best. A special thanks (and beer if you live in Toronto) will be awarded to anyone who can help give me a ballpark estimate on how much such a game should go for. I know it's tough to estimate but any rough figure will help (how much would you charge for building something like playspent.org?) Thanks in advance

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  • Prioritize compiler functionality/tasks, when designing a new language

    - by Mahdi
    Well, the question should be so hard to ask and I expect couple of down votes, however, I'm really interested to have your ideas and recommendations. :) I've already made a very simple compiler, with a few and limited functionality. Now I'm getting more on it to make it more like a real-world compiler. I definitely need to start over 'cause I've much more experience and ideas in this area rather a few years ago. So, I want to know, right now, from the very first step again, which tasks/features for the new compiler should implement first and which tasks has lower priority rather than others? For example, I'd say, first I'd go to decide about the object-oriented structure for the new language, but you might say, hey, just go for a compiler that could define a variable, when you finished that, then start thinking about OOP designs ... I prefer to hear the pros and cons for your suggestions also. Actually I like to start from Bottom to Top, where I could add simplest tasks first, and later adding more complex ones, but I'm totally open for any new ideas, and really appreciate that. Also please consider that I'm thinking about the design concepts. Actually I expect answers like: Priority from Highest to Lowest: variables, because .... functions, because .... loops, because .... ... Not: define a syntax for your new language, and start parsing your source code ...

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  • Novice prototyping a massive multiplayer webpage based gaming system

    - by Sean Hendlin
    I'm trying to build a website based game in which various pages of the site act as different areas of the game. I am wondering what you would recommended as a design structure. Which languages would be best if building what will hopefully becomes a massive system able to scale to massive amounts of users. I am wondering if and how various elements from differing languages could be meshed to interact with each other. For example could I use html5, javascript, and PHP? What about asp.net how might that factor in? I'm a newbie programmer but I've been working on this idea for years and I want to build it to reality. Your comments and suggestions are appreciated. P.S.: The game is not all graphics and animation (though flash like appearance and some animation would be nice). What I am thinking of is essentially a heavily gamified system of forms. And LOTS of data in many different categories cross referencing each-other. I'm not sure how to go about structuring the collection of data. Also while I know javascript can be used to process some functions, I'm wondering what sort of base system I would need to handle the server side processing of what I am expecting to be some pretty significant algorithm processing. That is to say I expect to have many many many functions and I'm not sure how to mange this using javascript. I feel like they would be forgotten, mixed up, disorganizes as they essentially only exist where they are coded. I guess I need to learn something of libraries? OK, Thank you! Is enough from me for now.

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  • Error Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException [migrated]

    - by user134212
    I'm new here. I'm learning how to program on java and I have a problem with my code. I really have no clue why my code is not working. I think my mistake may be here, but I'm not quite sure. m3 = new Matriz(ren2,col2); btSumar.addActionListener(new ActionListener() { Matriz m3;//(ren2,col2); public void actionPerformed(ActionEvent e) { m3 = new Matriz(ren2,col2); if(ventanaAbierta==true) { try { crearMat.SUMA(m1,m2); } catch(Exception nul) { System.out.println(nul); } } else { JOptionPane.showMessageDialog(null,"Ya se realizo la suma"); } } }); My Complete code import java.awt.*; import javax.swing.*; import javax.swing.BorderFactory; import javax.swing.border.Border; import java.awt.event.*; import java.awt.*; import java.io.*; import java.util.*; public class Practica2 { private int opcion,ren2,col2; private JFrame ventana,ventanaPrintMatriz; private JPanel panel,panel2; private Border borderRed2,borderBlue2,borderGreen2,borderGreen4; private Color red,green,blue,white,black; private Font Verdana14,ArialBlack18; private JLabel labelTitulo; public JButton btSalir,btSumar,btRestar,btMultiplica,btTranspuesta,btCrear; private ImageIcon suma,resta,multi,crear,salir,trans; private boolean ventanaAbierta = false; private static ValidacionesMatrices valida; private static Operaciones operacion; private static Matriz m1,m2,m3; private static ImprimirMatriz printMat; public Practica2() { panel = new JPanel(); panel.setLayout(null); ventana = new JFrame("Operaciones con Matrices"); ventana.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); ventana.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { //Sale del programa System.exit(0); } }); ventana.setContentPane(panel); ventana.setVisible(true); ventana.setResizable(false); ventana.setBounds(150,150,300,380); //ventana.setBounds(0,0,650,650); } public void inicializarComponentes() { panel2 = new JPanel(); panel2.setLayout(null); labelTitulo = new JLabel("Practica #2"); suma = new ImageIcon("suma1.png"); resta = new ImageIcon("resta1.png"); multi = new ImageIcon("multi1.png"); trans = new ImageIcon("trans2.png"); crear = new ImageIcon("crear1.png"); salir = new ImageIcon("salir1.png"); btTranspuesta = new JButton("Transpuesta",trans); btMultiplica = new JButton("Multiplica",multi); btRestar = new JButton("Restar",resta); btSumar = new JButton("Sumar",suma); btCrear = new JButton("Crear",crear); btSalir = new JButton("Salir",salir); //Tipo de letra ArialBlack18 = new Font("Arial Black",Font.BOLD,18); //Color green = new Color(0,255,0); //Formato labelTitulo labelTitulo.setBounds(80,-60,200,150); labelTitulo.setFont(ArialBlack18); labelTitulo.setForeground(blue); labelTitulo.setVisible(true); //Formato de CrearMatriz btCrear.setBounds(80,50,130,30); btCrear.setToolTipText("Crea una matriz"); //Formato de Muliplica btMultiplica.setBounds(80,100,130,30); btMultiplica.setToolTipText("Mat[A] * Mat[B]"); //Formato de botonRestar btRestar.setBounds(80,150,130,30); btRestar.setToolTipText("Mat[A] - Mat[B]"); //Formato del botonSumar btSumar.setBounds(80,200,130,30); btSumar.setToolTipText("Mat[A] + Mat[B]"); //Formato de Transpuesta btTranspuesta.setBounds(80,250,130,30); btTranspuesta.setToolTipText("Mat[A]^-1"); //Formato del botonSalir btSalir.setBounds(80,300,130,30); //Agregando componentes al panel1 panel2.add(labelTitulo); panel2.add(btMultiplica); panel2.add(btCrear); panel2.add(btRestar); panel2.add(btSumar); panel2.add(btSalir); panel2.add(btTranspuesta); //Formato panel2 panel2.setBackground(green); panel2.setVisible(true); panel2.setBounds(0,0,300,380); //Argregamos componentes al panelPrincipal= panel.add(panel2); //BotonCrear btCrear.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) //throws IOException { if(ventanaAbierta==false) { ventanaAbierta=true; new CrearMatriz(); } else { JOptionPane.showMessageDialog(null,"Ya se crearon las Matrices"); } } }); m3 = new Matriz(ren2,col2); btSumar.addActionListener(new ActionListener() { Matriz m3;//(ren2,col2); public void actionPerformed(ActionEvent e) { m3 = new Matriz(ren2,col2); if(ventanaAbierta==true) { try { crearMat.SUMA(m1,m2); } catch(Exception nul) { System.out.println(nul); } } else { JOptionPane.showMessageDialog(null,"Ya se realizo la suma"); } } }); //BotonSalir btSalir.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } }); panel.setVisible(true); panel.setBounds(0,0,350,380); } class VentanaMatriz { private JFrame ventana; private JPanel panel; private JTextArea textArea1,textArea2; private JLabel mat1,mat2; private JTextField textField1; public VentanaMatriz() { panel = new JPanel(); panel.setLayout(null); ventana = new JFrame("Creacion de Matrices"); ventana.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { ventana.dispose(); } }); ventana.setContentPane(panel); ventana.setVisible(true); ventana.setResizable(false); ventana.setBounds(200,100,850,420); } public void inicializarComponentes() { //Colores black = new Color(0,0,0); white = new Color(255,255,255); blue = new Color(0,0,255); green = new Color(0,255,0); red = new Color(255,0,0); //Tipo de letra Verdana14 = new Font("Verdana",Font.BOLD,14); //Tipos de borde borderRed2 = BorderFactory.createLineBorder(red,2); borderBlue2 = BorderFactory.createLineBorder(blue,2); borderGreen2 = BorderFactory.createLineBorder(green,2); borderGreen4 = BorderFactory.createLineBorder(green,4); //Agregando componentes al panel1 panel.add(mat1); panel.add(textArea1); panel.add(mat2); panel.add(textArea2); //Formato panel2 panel.setBackground(blue); panel.setVisible(true); panel.setBounds(0,0,850,420); } } class CrearMatriz { public int col1,re1,ren2,col2; public Matriz m1,m2,m3; public CrearMatriz() { int col1,ren1,ren2,col2; ren2 = Integer.parseInt(JOptionPane.showInputDialog("Numero de Renglones Matriz A: ")); col2 = Integer.parseInt(JOptionPane.showInputDialog("Numero de Columnas Matriz A: ")); final Matriz m1= new Matriz(ren2,col2); ren2 = Integer.parseInt(JOptionPane.showInputDialog("Numero de Renglones Matriz B: ")); col2 = Integer.parseInt(JOptionPane.showInputDialog("Numero de Columnas Matriz B: ")); final Matriz m2= new Matriz(ren2,col2); m3 = new Matriz(ren2,col2); m1.llenarMatriz(); m2.llenarMatriz(); m1.printMat(); m2.printMat(); } public void SUMA(Matriz m1,Matriz m2) { Matriz m3; if(ventanaAbierta==false) { m3 = new Matriz(ren2,col2); if(valida.validaSumayResta(m1,m2)) { m3 = operacion.sumaMat(m1,m2); JOptionPane.showMessageDialog(null,"La suma es = "); m3.imprimeMatriz(); } else { JOptionPane.showMessageDialog(null,"No es posible hacer la suma"); } } } public void RESTA() { } //btSumar = new JButton("Sumar",suma); //BotonSumar //Mostrar matriz 1 y 2 // System.out.println("\n\n\nMatriz 1="); // m1.imprimeMatriz(); // System.out.println("\nMatriz 2="); //Poner en botones /* if(valida.validaSumayResta(m1,m2)) { m3 = operacion.sumaMat(m1,m2); JOptionPane.showMessageDialog(null,"La suma es = "); m3.imprimeMatriz(); } else { JOptionPane.showMessageDialog(null,"No es posible hacer la suma"); } if(valida.validaSumayResta(m1,m2)) { m3=operacion.restaMat(m1,m2); JOptionPane.showMessageDialog(null,"La resta es = "); m3.imprimeMatriz(); } else { JOptionPane.showMessageDialog(null,"No es posible hacer la resta"); } if(valida.validaMultiplicacion(m1,m2)){ m3=operacion.multiplicaMat(m1,m2); JOptionPane.showMessageDialog(null,"La multiplicacion es = "); m3.imprimeMatriz(); } else { JOptionPane.showMessageDialog(null,"No es posible hacer la multiplicacion"); } JOptionPane.showMessageDialog(null,"La multiplicacion es = "); m1=operacion.transpuesta(m1); m2=operacion.transpuesta(m2); */ } class Matriz { public JTextField matriz; //public JTextArea texto; private JFrame ventanaPrintMatriz; private JPanel panel2; int ren; int col; int pos[][]; public Matriz(int ren1, int col1) { ren = ren1; col = col1; pos = new int [ren][col];/*una matriz de enteros de renglon por columan*/ } public void llenarMatriz() { for(int i=0;i<ren;i++) for(int j=0;j<col;j++) pos[i][j]=(int) (Math.random()*10);/*la posicion i y j crea un entero random*/ } /*vuelve a recorrer los espacio de i y j*/ } //Esta clase era un metodo de CrearMatriz class ImprimirMatriz { public void ImprimirMatriz() { panel2 = new JPanel(); panel2.setLayout(null); ventanaPrintMatriz = new JFrame("Matriz"); ventana.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { //Practica2.ventanaAbierta=false; ventana.dispose(); } }); int i,j; int x=0,y=0; borderRed2 = BorderFactory.createLineBorder(red,2); white = new Color(255,255,255); red = new Color(255,0,0); black = new Color(0,0,0); blue = new Color(0,0,255); for(i=0;i<ren;i++) { for(j=0;j<col;j++) { matriz = new JTextField(" "+pos[i][j]); matriz.setBorder(borderRed2); matriz.setForeground(white); matriz.setBounds(x+25,y+25,25,25); matriz.setBackground(black); matriz.setEditable(false); matriz.setVisible(true); //Se incrementa la coordenada en X //para el siguiente Textfield no se encime x=x+35; //Agregamos el textField al panel panel2.add(matriz); } //Regreso las cordenadas de X a 0 para que el //siguiente renglon empieze en donde mismo x=0; //Incremento las coordenada Y para que se brinque //de linea y=y+35; } //Formato panel2 panel2.setBounds(150,150,350,380); panel2.setBackground(blue); //panel2.setEditable(false); panel2.setVisible(true); //Formato de Ventana ventanaPrintMatriz.setContentPane(panel2); ventanaPrintMatriz.setBounds(150,150,350,380); ventanaPrintMatriz.setResizable(false); ventanaPrintMatriz.setVisible(true); } } class Operaciones { public Matriz sumaMat(Matriz m1, Matriz m2) { Matriz m3; m3 = new Matriz(m1.ren, m1.col); for(int i=0;i<m1.col;i++) for(int j=0;j<m1.ren;j++) m3.pos[i][j]=m1.pos[i][j]+m2.pos[i][j]; return m3; } public Matriz restaMat(Matriz m1, Matriz m2) { Matriz m3; m3 = new Matriz(m1.ren, m1.col); for(int i=0;i<m1.col;i++) for(int j=0;j<m1.ren;j++) m3.pos[i][j]=m1.pos[i][j]-m2.pos[i][j]; return m3; } public Matriz multiplicaMat(Matriz m1, Matriz m2) { Matriz m3; m3 = new Matriz(m1.ren, m2.col); for(int i=0;i<m1.ren;i++) for(int j=0;j<m2.col;j++) { m3.pos[i][j]=0; for(int k=0;k<m1.col;k++) m3.pos[i][j]+=(m1.pos[i][k]*m2.pos[k][j]); } return m3; } public Matriz transpuesta(Matriz m1) { Matriz m3=new Matriz(m1.col,m1.ren); for(int i=0;i<m1.col;i++) for(int j=0;j<m1.ren;j++) m3.pos[i][j]=m1.pos[j][i]; return m3; } } class ValidacionesMatrices { public boolean validaSumayResta(Matriz m1, Matriz m2) { if((m1.ren==m2.ren) && (m1.col==m2.col)) return true; else return false; } public boolean validaMultiplicacion(Matriz m1, Matriz m2) { if(((m1.ren==m2.ren) && (m1.col==m2.col)) || (m1.col==m2.ren)) return true; else return false; } } public static void main(String[] args) { Practica2 practica2 = new Practica2(); practica2.inicializarComponentes(); } } Exc

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  • DB Object passing between classes singleton, static or other?

    - by Stephen
    So I'm designing a reporting system at work it's my first project written OOP and I'm stuck on the design choice for the DB class. Obviously I only want to create one instance of the DB class per-session/user and then pass it to each of the classes that need it. What I don't know it what's best practice for implementing this. Currently I have code like the following:- class db { private $user = 'USER'; private $pass = 'PASS'; private $tables = array( 'user','report', 'etc...'); function __construct(){ //SET UP CONNECTION AND TABLES } }; class report{ function __construct ($params = array(), $db, $user) { //Error checking/handling trimed //$db is the database object we created $this->db = $db; //$this->user is the user object for the logged in user $this->user = $user; $this->reportCreate(); } public function setPermission($permissionId = 1) { //Note the $this->db is this the best practise solution? $this->db->permission->find($permissionId) //Note the $this->user is this the best practise solution? $this->user->checkPermission(1) $data=array(); $this->db->reportpermission->insert($data) } };//end report I've been reading about using static classes and have just come across Singletons (though these appear to be passé already?) so what's current best practice for doing this?

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  • How should I implement Transaction database EJB 3.0

    - by JamesBoyZ
    In the CustomerTransactions entity, I have the following field to record what the customer bought: @ManyToMany private List<Item> listOfItemsBought; When I think more about this field, there's a chance it may not work because merchants are allowed to change item's information (e.g. price, discount, etc...). Hence, this field will not be able to record what the customer actually bought when the transaction occurred. At the moment, I can only think of 2 ways to make it work. I will record the transaction details into a String field. I feel that this way would be messy if I need to extract some information about the transaction later on. Whenever the merchant changes an item's information, I will not update directly to that item's fields. Instead, I will create another new item with all the new information and keep the old item untouched. I feel that this way is better because I can easily extract information about the transaction later on. However, the bad side is that my Item table may contain a lot of rows. I'd be very grateful if someone could give me an advice on how I should tackle this problem. UPDATE: I'd like to add more information about the current design. public class Customer implements Serializable { @OneToMany private List<CustomerTransactions> listOfTransactions; } public class CustomerTransactions implements Serializable { @ManyToMany private List<Item> listOfItemsBought; } public class Merchant implements Serializable { @OneToMany private List<Item> listOfSellingItems; }

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  • How to solve this error when using kXML for Midlet (java)

    - by hsmit
    I downloaded kXML and included this in my Build Path (Eclipse). Now I'm running a simple Midlet and I get an error: java.lang.NoClassDefFoundError: org/kxml2/io/KXmlParser at clientlibrary.googlecalendar.TestParser.startApp(+8) at javax.microedition.midlet.MIDletProxy.startApp(+7) at com.sun.midp.midlet.Scheduler.schedule(+270) at com.sun.midp.main.Main.runLocalClass(+28) at com.sun.midp.main.Main.main(+80) What did I do wrong? Is there something wrong with the most recent kXML Jar? Does anyone have experience with using kXML? What did you do to get this to work?

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  • Generic collection as a Java method argument

    - by Guido
    Is there any way to make this work in Java? public static void change(List<? extends Object> list, int position1, int position2) { Object obj = list.get(position1); list.set(position1, list.get(position2)); list.set(position2, obj); } The only way I've successfully avoided warnings and errors is this: public static <T> T change(List<T> list, int position1, int position2) { T obj = list.get(position1); list.set(position1, list.get(position2)); list.set(position2, obj); return obj; } but I don't like to be forced to return a value.

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  • Java Applet in JAR File

    - by Jared Revik
    I have created a java applet (.class file) and made a .jar with it and digitally signed the .jar file. Now I need to run the .jar as an applet in firefox. What do I put in the html code to run the .jar file as an applet? I tried and it doesn't work, it tries to get a .class file, how do I load and run my applet as a .jar file using the applet tag in Internet Explorer and Firefox? I searched on the internet and could not find an answer.

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  • Java Google App Engine inconsistent data lose after restarting dev server

    - by user259349
    Hello everyone, I am using Java GAE. So far, i'm just scafolding my data objects and i'm seeing an interesting issue. The records that i am playing around with are getting updated properly as long as my dev server is running up. The second that the my dev server gets restarted, i lose all of my changes. That would be not alarming if i lost all of my records, but, there was a point of time where my data persisted through the server restart. I'm worried that i would lose production data if i launched without fixing this potential bugs? ANy idea on wher ei should look?

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  • download zip file using java?

    - by Mohamed
    I am downloading zip file from web server using Java but somehow I am loosing about 2kb in each file. I don't know why since same code works fine with other formats, e.g, text, mp3 and extra. any help is appreciated? here is my code. public void download_zip_file(String save_to) { try { URLConnection conn = this.url.openConnection(); conn.setDoOutput(true); conn.setDoInput(true); conn.setRequestProperty("content-type", "binary/data"); InputStream in = conn.getInputStream(); FileOutputStream out = new FileOutputStream(save_to + "tmp.zip"); byte[] b = new byte[1024]; int count; while ((count = in.read(b)) > 0) { out.write(b, 0, count); } out.close(); in.close(); } catch (IOException e) { e.printStackTrace(); } }

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  • Extending Throwable in Java

    - by polygenelubricants
    Java lets you create an entirely new subtype of Throwable, e.g: public class FlyingPig extends Throwable { ... } Now, very rarely, I may do something like this: throw new FlyingPig("Oink!"); and of course elsewhere: try { ... } catch (FlyingPig porky) { ... } My questions are: Is this a bad idea? And if so, why? What could've been done to prevent this subtyping if it is a bad idea? Since it's not preventable (as far as I know), what catastrophies could result? If this isn't such a bad idea, why not? How can you make something useful out of the fact that you can extends Throwable?

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  • Create Personalized Controls For Java ME

    - by Nathan Campos
    I'm starting to develop a eBook reader for mobile using Java ME, but for the control were the book will be shown I need a personalized control. For this I need to first know how to do one, to workaround with my needs. Then I need to know how can I do a personalized control as we do with Visual Basic. PS: I want to do a personalized TextBox, that in some parts can be in bold, italic, sublined, that supports topics(as the Edit, the MS-DOS Text Editor) and many other things that make a eBook better viewed than a simple plain text

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  • Java 2D clip area to shape

    - by user2923880
    I'm quite new to graphics in java and I'm trying to create a shape that clips to the bottom of another shape. Here is an example of what I'm trying to achieve: Where the white line at the base of the shape is the sort of clipped within the round edges. The current way I am doing this is like so: g2.setColor(gray); Shape shape = getShape(); //round rectangle g2.fill(shape); Rectangle rect = new Rectangle(shape.getBounds().x, shape.getBounds().y, width, height - 3); Area area = new Area(shape); area.subtract(new Area(rect)); g2.setColor(white); g2.fill(area); I'm still experimenting with the clip methods but I can't seem to get it right. Is this current method ok (performance wise, since the component repaints quite often) or is there a more efficient way? Thanks in advance.

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  • Inheritance in XML Schema definition (XSD) for Java objects

    - by bguiz
    Hi, I need to create an XML schema definition (XSD) that describes Java objects. I was wondering how to do this when the objects in question inherit from a common base class with a type parameter. public abstract class Rule<T> { ... } public abstract class TimeRule extends Rule<XTime> { ... } public abstract class LocationRule extends Rule<Location> { ... } public abstract class IntRule extends Rule<Integer> { ... } .... (where XTime and Location are custom classes define elsewhere) How would I go about constructing an XSD that such that I can have XML nodes that represent each of the subclasses of Rule<T> - without the XSD for each of them repeating their common contents? Thank you!

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  • Using a JSON web service from a Java client application

    - by user383341
    I am developing a client-side Java application that has a bit of functionality that requires getting data from some web services that transmit in JSON (some RESTful, some not). No JavaScript, no web browser, just a plain JAR file that will run locally with Swing for the GUI. This is not a new or unique problem; surely there must be some open source libraries out there that will handle the JSON data transmission over HTTP. I've already found some that will parse JSON, but I'm having trouble finding any that will handle the HTTP communication to consume the JSON web service. So far I've found Apache Axis2 apparently which might have at least part of the solution, but I don't see enough documentation for it to know if it will do what I need, or how to use it. Maybe part of the problem is that I don't have experience with web services so I'm not able to know a solution when I see it. I hope some of you can point me in the right direction. Examples would be helpful.

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  • Retrieving Large Lists of Objects Using Java EE

    - by hallidave
    Is there a generally-accepted way to return a large list of objects using Java EE? For example, if you had a database ResultSet that had millions of objects how would you return those objects to a (remote) client application? Another example -- that is closer to what I'm actually doing -- would be to aggregate data from hundreds of sources, normalize it, and incrementally transfer it to a client system as a single "list". Since all the data cannot fit in memory, I was thinking that a combination of a stateful SessionBean and some sort of custom Iterator that called back to the server would do the trick. How have you successfully solved this problem in the past?

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  • Database migration pattern for Java?

    - by Eno
    Im working on some database migration code in Java. Im also using a factory pattern so I can use different kinds of databases. And each kind of database im using implements a common interface. What I would like to do is have a migration check that is internal to the class and runs some database schema update code automatically. The actual update is pretty straight forward (I check schema version in a table and compare against a constant in my app to decide whether to migrate or not and between which versions of schema). To make this automatic I was thinking the test should live inside (or be called from) the constructor. OK, fair enough, that's simple enough. My problem is that I dont want the test to run every single time I instantiate a database object (it runs a query so having it run on every construction is not efficient). So maybe this should be a class static method? I guess my question is, what is a good design pattern for this type of problem? There ought to be a clean way to ensure the migration test runs only once OR is super-efficient.

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  • Java Hibernate/C3P0 error: "Could not obtain connection metadata. An attempt by a client to checkout

    - by Allan
    I'm trying to get some code I was passed up and running. It appears to use the Hibernate framework. I've gotten past most of the errors tweaking the configuration, but this one has me dead stumped. It's trying to connect to two databases: gameapp and gamelog. Both exist. It seems to have issues connecting to gamelog, but none connecting to gameapp (later in the init, it connects to and loads other DBs just fine). Below, I've pasted the error and exception stack dump. I imaging there's something else in the configs, so I've also included the configuration file for that db. I know this is very vague, but I'm hoping some pro can see the stupid mistake I'm missing. <?xml version="1.0" encoding="GBK"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://127.0.0.1:3306/gamelog</property> <property name="connection.username">root</property> <property name="connection.password"></property> <property name="connection.useUnicode">true</property> <property name="connection.characterEncoding">UTF-8</property> <property name="hibernate.jdbc.batch_size">100</property> <property name="jdbc.fetch_size">1</property> <property name="hbm2ddl.auto">none</property><!-- update --> <property name="connection.useUnicode">true</property> <property name="show_sql">true</property> <!-- c3p0-configuration --> <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.min_size">5</property> <property name="hibernate.c3p0.max_size">10</property> <property name="hibernate.c3p0.timeout">30</property> <property name="hibernate.c3p0.idle_test_period">30</property> <property name="hibernate.c3p0.max_statements">0</property> <property name="hibernate.c3p0.acquire_increment">5</property> </session-factory> </hibernate-configuration> Exception and stack trace: 2010-04-30 17:50:00,411 WARN [org.hibernate.cfg.SettingsFactory] - Could not obtain connection metadata java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106) at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527) at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128) at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:76) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1933) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1216) at com.database.hibernate.util.HibernateFactory.<init>(Unknown Source) at com.database.hibernate.util.HibernateUtil.<clinit>(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.initBreedGoods(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.access$000(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl$1.run(Unknown Source) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351) at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@ca470 -- timeout at awaitAvailable() at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317) at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557) at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525) ... 18 more

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  • Handling file upload in a non-blocking manner

    - by Kaliyug Antagonist
    The background thread is here Just to make objective clear - the user will upload a large file and must be redirected immediately to another page for proceeding different operations. But the file being large, will take time to be read from the controller's InputStream. So I unwillingly decided to fork a new Thread to handle this I/O. The code is as follows : The controller servlet /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub System.out.println("In Controller.doPost(...)"); TempModel tempModel = new TempModel(); tempModel.uploadSegYFile(request, response); System.out.println("Forwarding to Accepted.jsp"); /*try { Thread.sleep(1000 * 60); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }*/ request.getRequestDispatcher("/jsp/Accepted.jsp").forward(request, response); } The model class package com.model; import java.io.IOException; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.utils.ProcessUtils; public class TempModel { public void uploadSegYFile(HttpServletRequest request, HttpServletResponse response) { // TODO Auto-generated method stub System.out.println("In TempModel.uploadSegYFile(...)"); /* * Trigger the upload/processing code in a thread, return immediately * and notify when the thread completes */ try { FileUploaderRunnable fileUploadRunnable = new FileUploaderRunnable( request.getInputStream()); /* * Future<FileUploaderRunnable> future = ProcessUtils.submitTask( * fileUploadRunnable, fileUploadRunnable); * * FileUploaderRunnable processed = future.get(); * * System.out.println("Is file uploaded : " + * processed.isFileUploaded()); */ Thread uploadThread = new Thread(fileUploadRunnable); uploadThread.start(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } /* * catch (InterruptedException e) { // TODO Auto-generated catch block * e.printStackTrace(); } catch (ExecutionException e) { // TODO * Auto-generated catch block e.printStackTrace(); } */ System.out.println("Returning from TempModel.uploadSegYFile(...)"); } } The Runnable package com.model; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; public class FileUploaderRunnable implements Runnable { private boolean isFileUploaded = false; private InputStream inputStream = null; public FileUploaderRunnable(InputStream inputStream) { // TODO Auto-generated constructor stub this.inputStream = inputStream; } public void run() { // TODO Auto-generated method stub /* Read from InputStream. If success, set isFileUploaded = true */ System.out.println("Starting upload in a thread"); File outputFile = new File("D:/06c01_output.seg");/* * This will be changed * later */ FileOutputStream fos; ReadableByteChannel readable = Channels.newChannel(inputStream); ByteBuffer buffer = ByteBuffer.allocate(1000000); try { fos = new FileOutputStream(outputFile); while (readable.read(buffer) != -1) { fos.write(buffer.array()); buffer.clear(); } fos.flush(); fos.close(); readable.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("File upload thread completed"); } public boolean isFileUploaded() { return isFileUploaded; } } My queries/doubts : Spawning threads manually from the Servlet makes sense to me logically but scares me coding wise - the container isn't aware of these threads after all(I think so!) The current code is giving an Exception which is quite obvious - the stream is inaccessible as the doPost(...) method returns before the run() method completes : In Controller.doPost(...) In TempModel.uploadSegYFile(...) Returning from TempModel.uploadSegYFile(...) Forwarding to Accepted.jsp Starting upload in a thread Exception in thread "Thread-4" java.lang.NullPointerException at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:512) at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:497) at org.apache.coyote.http11.InternalInputBuffer$InputStreamInputBuffer.doRead(InternalInputBuffer.java:559) at org.apache.coyote.http11.AbstractInputBuffer.doRead(AbstractInputBuffer.java:324) at org.apache.coyote.Request.doRead(Request.java:422) at org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:287) at org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:407) at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:310) at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:202) at java.nio.channels.Channels$ReadableByteChannelImpl.read(Unknown Source) at com.model.FileUploaderRunnable.run(FileUploaderRunnable.java:39) at java.lang.Thread.run(Unknown Source) Keeping in mind the point 1., does the use of Executor framework help me in anyway ? package com.utils; import java.util.concurrent.Future; import java.util.concurrent.ScheduledThreadPoolExecutor; public final class ProcessUtils { /* Ensure that no more than 2 uploads,processing req. are allowed */ private static final ScheduledThreadPoolExecutor threadPoolExec = new ScheduledThreadPoolExecutor( 2); public static <T> Future<T> submitTask(Runnable task, T result) { return threadPoolExec.submit(task, result); } } So how should I ensure that the user doesn't block and the stream remains accessible so that the (uploaded)file can be read from it?

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  • Physics in my game confused after restructuring the Game loop

    - by Julian Assange
    Hello! I'm on my way with making a game in Java. Now I have some trouble with an interpolation based game loop in my calculations. Before I used that system the calculation of a falling object was like this: Delta based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(float timeDeltaSeconds, Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity * timeDeltaSeconds); parentObject.yVelocity -= SPEED_OF_GRAVITY * timeDeltaSeconds; ...... What you see here is that I used that delta value from previous frame to the current frame to calculate the physics. Now I switched and implement a interpolation based system and I actually left the current system where I used delta to calculate my physics. However, with the interpolation system the delta time is removed - but now are my calculations screwed up and I've tried the whole day to solve this: Interpolation based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity); parentObject.yVelocity -= SPEED_OF_GRAVITY; ...... I'm totally clueless - how should this be solved? The rendering part is solved with a simple prediction method. With the delta system I could see my object be smoothly rendered to the screen, but with this interpolation/prediction method the object just appear sticky for one second and then it's gone. The core of this game loop is actually from here deWiTTERS Game Loop, where I trying to implement the last solution he describes. Shortly - my physics are in a mess and this need to be solved. Any ideas? Thanks in advance!

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  • Simple Java networking game engine [on hold]

    - by Florian Peschka
    I want to create a simple java networking game and search a networking engine that eases use of sockets etc. I have already read some questions on here and the internet about java networking for games, but many of them were over 10 years old or not really answered. I have no idea whatsoever about what exactly I need to send in terms of messages, but I figured simple strings or integers will be enough for my purposes. It's basically a peer to peer game, so I don't need a centralized server structure. Messaging doesn't have to have an extremely low ping, yet of course all players need to have a synchronized view. What are the possibilities I have here?

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  • BPM Business Value Patterns

    - by JuergenKress
    Together with Matthias Ziegler from Accenture we presented the BPM Business Value Patterns at the SOA & BPM Integration Days in Germany in October: BPM Business Value Patterns View more presentations by Jürgen Kress Please visit the website http://soa-bpm-days.de/  for the next SOA & BPM Integration Days III February 29th & March 1st in Munich If you'd like to learn more please feel free to contact us any time: Matthias Ziegler Jürgen Kress For regular information on Oracle SOA Suite become a member of the SOA Partner Community. To register please visit  www.oracle.com/goto/emea/soa (OPN account required) Blog Twitter LinkedIn Mix Forum Technorati Tags: Matthias Ziegler,Jürgen Kress,SOA & BPM Integration Days,BPM,BPM Value Patterns,BPM ROI,Oracle,OPN,Accenture

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  • Patterns for implementing field change tracking.

    - by David
    Hi all For one of my recent projects, I had to implement field change tracking. So anytime the user changed a value of a field, the change was recorded in order to allow full auditing of changes. In the database, I implemented this as a single table 'FieldChanges' with the following fields: TableName, FieldName, RecordId, DateOfChange, ChangedBy, IntValue, TextValue, DateTimeValue, BoolValue. The sproc saving changes to an object determines for each field whether it has been changed and inserts a record into FieldChanges if it has: if the type of the changed field is int, it records it in the IntValue field in the FieldChanges table, etc. This means that for any field in any table with any id value, I can query the FieldChanges table to get a list of changes. This works quite well but is a bit clumsy. Can anyone else who has implemented similar functionality suggest a better approach, and why they think it's better? I'd be really interested - thanks. David

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