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  • Creating ActionEvent object for CustomButton in Java

    - by Crystal
    For a hw assignment, we were supposed to create a custom button to get familiar with swing and responding to events. We were also to make this button an event source which confuses me. I have an ArrayList to keep track of listeners that would register to listen to my CustomButton. What I am getting confused on is how to notify the listeners. My teacher hinted at having a notify and overriding actionPerformed which I tried doing, but then I wasn't sure how to create an ActionEvent object looking at the constructor documentation. The source, id, string all confuses me. Any help would be appreciated. Thanks! code: import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.List; import java.util.ArrayList; public class CustomButton { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { CustomButtonFrame frame = new CustomButtonFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }); } public void addActionListener(ActionListener al) { listenerList.add(al); } public void removeActionListener(ActionListener al) { listenerList.remove(al); } public void actionPerformed(ActionEvent e) { System.out.println("Button Clicked!"); } private void notifyListeners() { ActionEvent event = new ActionEvent(CONFUSED HERE!!!!; for (ActionListener action : listenerList) { action.actionPerfomed(event); } } List<ActionListener> listenerList = new ArrayList<ActionListener>(); } class CustomButtonFrame extends JFrame { // constructor for CustomButtonFrame public CustomButtonFrame() { setTitle("Custom Button"); CustomButtonSetup buttonSetup = new CustomButtonSetup(); this.add(buttonSetup); this.pack(); } } class CustomButtonSetup extends JComponent { public CustomButtonSetup() { ButtonAction buttonClicked = new ButtonAction(); this.addMouseListener(buttonClicked); } // because frame includes borders and insets, use this method public Dimension getPreferredSize() { return new Dimension(200, 200); } public void paintComponent(Graphics g) { Graphics2D g2 = (Graphics2D) g; // first triangle coords int x[] = new int[TRIANGLE_SIDES]; int y[] = new int[TRIANGLE_SIDES]; x[0] = 0; y[0] = 0; x[1] = 200; y[1] = 0; x[2] = 0; y[2] = 200; Polygon firstTriangle = new Polygon(x, y, TRIANGLE_SIDES); // second triangle coords x[0] = 0; y[0] = 200; x[1] = 200; y[1] = 200; x[2] = 200; y[2] = 0; Polygon secondTriangle = new Polygon(x, y, TRIANGLE_SIDES); g2.drawPolygon(firstTriangle); g2.setColor(firstColor); g2.fillPolygon(firstTriangle); g2.drawPolygon(secondTriangle); g2.setColor(secondColor); g2.fillPolygon(secondTriangle); // draw rectangle 10 pixels off border int s1[] = new int[RECT_SIDES]; int s2[] = new int[RECT_SIDES]; s1[0] = 5; s2[0] = 5; s1[1] = 195; s2[1] = 5; s1[2] = 195; s2[2] = 195; s1[3] = 5; s2[3] = 195; Polygon rectangle = new Polygon(s1, s2, RECT_SIDES); g2.drawPolygon(rectangle); g2.setColor(thirdColor); g2.fillPolygon(rectangle); } private class ButtonAction implements MouseListener { public void mousePressed(MouseEvent e) { System.out.println("Click!"); firstColor = Color.GRAY; secondColor = Color.WHITE; repaint(); } public void mouseReleased(MouseEvent e) { System.out.println("Released!"); firstColor = Color.WHITE; secondColor = Color.GRAY; repaint(); } public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mouseClicked(MouseEvent e) {} } public static final int TRIANGLE_SIDES = 3; public static final int RECT_SIDES = 4; private Color firstColor = Color.WHITE; private Color secondColor = Color.DARK_GRAY; private Color thirdColor = Color.LIGHT_GRAY; }

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  • Alternative to latex / a way to typeset good looking documents from Java to PDF

    - by drasto
    I'm working on application in Java that will maintain database of song lyrics in plain text and print out some songbooks/chordbooks(that is create PDF file from selected songs). I was planing that the Java application will generate source code for pdflatex and after compiling this source user will get PDF file. Lately I've run into a lot of problems because of latex limitation: fixed memory size (some pictures will also be drawn to PDF) - error when exceeded, no way to query end of line or and of page dynamically, it's very hard to override latex placement algorithm in a complex way,... see also some my other questions regarding latex. I come to conclusion that latex is not good option for automated PDF generation. So I need replacement. I need to be able to typeset: Chords over lyrics when the lyrics are in variable char width so I need to be able to measure text width Chord diagrams that means I'll have to draw quite complex pictures Each song on separate double page Different fonts etc. Thanks for all answers

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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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  • Best ways to reuse Java methods

    - by carillonator
    I'm learning Java and OOP, and have been doing the problems at Project Euler for practice (awesome site btw). I find myself doing many of the same things over and over, like: checking if an integer is prime/generating primes generating the Fibonacci series checking if a number is a palindrome What is the best way to store and call these methods? Should I write a utility class and then import it? If so, do I import a .class file or the .java source? I'm working from a plain text editor and the Mac terminal. Thanks!

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  • Run java with highest security setting

    - by Ankiov Spetsnaz
    I'm currently writing an in house coding challenge web application and I am wondering if there is any other security precaution I would need to have other than below java option at runtime. java -Djava.security.manager=default Basically, challenges would be more of single threaded math and algorithm focused. So I would need to enable basic data structure objects and disable any file, sockets, threading or any thing that might be not so important. Based on my quick search turning on security manager as above seems to be a solution but since this is a security related I would like to be sure before it goes alive. Is there anything else I could do more?

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  • Error preverifying class java during build (BlackBerry)

    - by Davide Vosti
    I'm trying do build and debug a small project for BlackBerry. During the build I'm getting this error Error preverifying class java ... I read on the net this error could be caused by referencing multiple projects but I tried to move every package in a single project but the error is still there. I tried with multiple JDE version (currently 4.7) and the Java compiler is set to 1.6. Eclipse version is 3.4.1 as recommended by RIM's documentations. Does someone have some clue?

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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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  • how to upload a audio file using REST webservice in Google App Engine for Java

    - by sathya
    Am using google app engine with eclipse IDE and trying to upload a audio file. I used the File Upload in Google App Engine For Java and can able to upload the file successfully. Now am planning to use REST web service for it. I had analyzed in developers.google but i failed. Can anyone suggest me how to implement REST Web services in google app engine using Eclipse. The code google provided is shown below, // file Upload.java public class Upload extends HttpServlet { private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { Map<String, BlobKey> blobs = blobstoreService.getUploadedBlobs(req); BlobKey blobKey = blobs.get("myFile"); if (blobKey == null) { res.sendRedirect("/"); } else { res.sendRedirect("/serve?blob-key=" + blobKey.getKeyString()); }}} // file Serve.java public class Serve extends HttpServlet { private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException { BlobKey blobKey = new BlobKey(req.getParameter("blob-key")); blobstoreService.serve(blobKey, res); }} // file index.jsp <%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %> <%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %> <% BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); %> <form action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data"> <input type="file" name="myFile"> <input type="submit" value="Submit"> </form> // web.xml <servlet> <servlet-name>Upload</servlet-name> <servlet-class>Upload</servlet-class> </servlet> <servlet> <servlet-name>Serve</servlet-name> <servlet-class>Serve</servlet-class> </servlet> <servlet-mapping> <servlet-name>Upload</servlet-name> <url-pattern>/upload</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>Serve</servlet-name> <url-pattern>/serve</url-pattern> </servlet-mapping> Now how to provide a rest web service for the above code. Kindly suggest me an idea.

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  • Serialization java to c#

    - by tom
    Hi, I have manged to serialize an arraylist in java using xstream, send it to my c# application via http and then write that to file (just for now). The serialized data was an arraylist in java. I want to try and re form this arraylist in c# from the xml i have. I have been looking at http://code.google.com/p/xstream-dot-net/ to do this. Does anyone know if that is the right way to go or is there a better way of reforming the serialized data in c#?

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  • Pattern for database-wrapper in java

    - by Space_C0wb0y
    I am currently writing a java-class that wraps an SQLite database. This class has two ways to be instantiated: Open an existing database. Create a new database. This is what I cam up with: public class SQLiteDatabaseWrapper { public static SQLiteDatabaseWrapper openExisting(File PathToDB) { return new SQLiteDatabaseWrapper(PathToDB); } public static SQLiteDatabaseWrapper createNew(File PathToDB) { CreateAndInitializeNewDatabase(PathToDB); return new SQLiteDatabaseWrapper(PathToDB); } private SQLiteDatabaseWrapper(File PathToDB) { // Open connection and setup wrapper } } Is this the way to go in Java, or is there any other best practice for this situation?

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  • Java program runtime error

    - by Sam
    public class BooksTestDrive { public static void main(String[] args) { Books [] myBooks = new Books[3]; int x=0; myBooks[0].title = "The Grapes of Jave"; myBooks[1].title = "The Java Gatsby"; myBooks[2].title = "The Java Cookbook"; myBooks[0].author = "bob"; myBooks[1].author = "sue"; myBooks[2].author = "ian"; while (x < 3) { System.out.print(myBooks[x].title); System.out.print("by"); System.out.println(myBooks[x].author); x = x+1; } } } This code compiles but while runtime, its giving nullpointer exception.

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  • Map generics in Java

    - by Amir Rachum
    Hi all, I seem to have a bit of misunderstanding with Java Generics and I hope you can help me. I tried to create a map like so: Map<Debater, int> (Debater is an Interface I declared) but java complained about the int, so I did: Map<Debater, Integer> I suppose it's because int is not a class while Integer is, is this correct? Also, Now I get a Debater and I need to add 1 to its value in the map. How do I do that?

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  • Java: how to get mercurial current changeset number for use in program

    - by Rabarberski
    I've recently started using mercurial for version control in a Java project. When I run my program, the input parameters it has used to produce certain a output, are written to a specific file. It would be nice if I could add the current mercurial changeset number (indicating the version of my program) to that output file as well. What would be the easiest way to do so on Windows? I could write a simple Java parser to fetch the output of the first line of the hg log -l 1 command, but perhaps there is an easier way (i.e., less code lines)?

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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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  • 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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