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  • Issue reading in a cell from Excel with Apache POI

    - by Nick
    I am trying to use Apache POI to read in old (pre-2007 and XLS) Excel files. My program goes to the end of the rows and iterates back up until it finds something that's not either null or empty. Then it iterates back up a few times and grabs those cells. This program works just fine reading in XLSX and XLS files made in Office 2010. I get the following error message: Exception in thread "main" java.lang.NumberFormatException: empty String at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) at java.lang.Double.parseDouble(Unknown Source) at the line: num = Double.parseDouble(str); from the code: str = cell.toString(); if (str != "" || str != null) { System.out.println("Cell is a string"); num = Double.parseDouble(str); } else { System.out.println("Cell is numeric."); num = cell.getNumericCellValue(); } where the cell is the last cell in the document that's not empty or null. When I try to print the first cell that's not empty or null, it prints nothing, so I think I'm not accessing it correctly.

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  • GlassFish 3: how do you change the (default) logging format?

    - by Kawu
    The question originated from here: http://www.java.net/forum/topic/glassfish/glassfish/configuring-glassfish-logging-format - without an answer. The default GlassFish 3 logging format of is very annoying, much too long. [#|2012-03-02T09:22:03.165+0100|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=113;_ThreadName=AWT-EventQueue-0;| MESSAGE... ] This is just a horrible default IMO. The docs just explain all the fields, but not how to change the format: http://docs.oracle.com/cd/E18930_01/html/821-2416/abluk.html Note, that I deploy SLF4J along with my webapp which should pick up the format as well. How do you change the logging format? FYI: The links here are outdated: Install log formater in glassfish... The question here hasn't been answered: How to configure GlassFish logging to show milliseconds in timestamps?... The posting here resulted in nothing: http://www.java.net/forum/topic/glassfish/glassfish/cant-seem-configure-... It looks like GlassFish logging configuration is an issue of its own. Can anybody help?

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  • Understanding Hibernate saveOrUpdate and the Persistence Life Cycle

    - by Stephano
    The books that I've read regarding hibernate are, at best, reference tomes. They very seldom have good code examples, so I tend to use online resources for those needs. However, I've always had a problem understanding the basic idea of hibernate persistence. I've read the books and understand the concepts, but in practice, I often see results that I don't understand. Perhaps you all can help, as you have in the past. Let's look at a simple example of a dog and a cat that are friends. This isn't a rare occurrence. It also has the benefit of being much more interesting than my business case. We want a function called "saveFriends" that takes a dog name and a cat name. We'll save the Dog and then the Cat. For this example to work, the cat is going to have a reference back to the dog. I understand this isn't an ideal example, but it's cute and works for our purposes. FriendService.java public int saveFriends(String dogName, String catName) { Dog fido = new Dog(); Cat felix = new Cat(); fido.name = dogName; fido = animalDao.saveDog(fido); felix.name = catName; [ex.A]felix.friend = fido; [ex.B]felix.friend = animalDao.getDogByName(dogName); animalDao.saveCat(felix); } AnimalDao.java (extends HibernateDaoSupport) public Dog saveDog(Dog dog) { getHibernateTemplate().saveOrUpdate(dog); return dog } public Cat saveCat(Cat cat) { getHibernateTemplate().saveOrUpdate(cat); return cat; } public Dog getDogByName(String name) { return (Dog) getHibernateTemplate().find("from Dog where name=?", name).get(0); } Now, assume for a minute that I would like to use either example A or example B to save my friend. Is one better than the other to use? I'll understand if neither of those examples work, but please explain why.

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  • Can you return an array from a JAX-WS @WebMethod?

    - by LES2
    I'm pretty sure you can, but in addition to answering the question in the title, could you also explain the pros, cons, caveats, if any, to doing so? I know that you can't return a List, Set, Collection, Map, or any interface, from a WebMethod (which is stupid, IMO, but I don't know what the design reasons were should I should probably withhold judgment). Thanks for any advice. -- LES

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  • Limit TCP requests per IP

    - by asmo
    Hello! I'm wondering how to limit the TCP requests per client (per specific IP) in Java. For example, I would like to allow a maximum of X requests per Y seconds for each client IP. I thought of using static Timer/TimerTask in combination with a HashSet of temporary restricted IPs. private static final Set<InetAddress> restrictedIPs = Collections.synchronizedSet(new HashSet<InetAddress>()); private static final Timer restrictTimer = new Timer(); So when a user connects to the server, I add his IP to the restricted list, and start a task to unrestrict him in X seconds. restrictedIPs.add(socket.getInetAddress()); restrictTimer.schedule(new TimerTask() { public void run() { restrictedIPs.remove(socket.getInetAddress()); } }, MIN_REQUEST_INTERVAL); My problem is that at the time the task will run, the socket object may be closed, and the remote IP address won't be accessible anymore... Any ideas welcomed! Also, if someone knows a Java-framework-built-in way to achieve this, I'd really like to hear it.

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  • Problem painting JLabel class to another JPanel class

    - by jjpotter
    I have created a class that extends JLabel to use as my object moving around a JPanel for a game. import javax.swing.*; public class Head extends JLabel { int xpos; int ypos; int xvel; int yvel; ImageIcon chickie = new ImageIcon("C:\\Users\\jjpotter.MSDOM1\\Pictures\\clavalle.jpg"); JLabel myLabel = new JLabel(chickie); public Head(int xpos, int ypos, int xvel, int yvel){ this.xpos = xpos; this.ypos = ypos; this.xvel = xvel; this.yvel = yvel; } public void draw(){ myLabel.setLocation(xpos, ypos); } public double getXpos() { return xpos; } public double getYpos() { return ypos; } public int getXvel() { return xvel; } public int getYvel() { return yvel; } public void setPos(int x, int y){ xpos = x; ypos = y; } } I am then trying to add it onto my JPanel. From here I will randomly have it increment its x and y coordinates to float it around the screen. I can not get it to paint itself onto the JPanel. I know there is a key concept I am missing here that involves painting components on different panels. Here is what I have in my GamePanel class import java.awt.Dimension; import java.util.Random; import javax.swing.*; public class GamePanel extends JPanel { Random myRand = new Random(); Head head = new Head(20,20,0,0); public GamePanel(){ this.setSize(new Dimension(640, 480)); this.add(head); } } Any suggestions on how to get this to add to the JPanel? Also, is this a good way to go about having the picture float around the screen randomly for a game?

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  • Is this the intention behavior in JComboBox? How I can avoid this behavior?

    - by Yan Cheng CHEOK
    I realize that if you are having a same selection in JComboBox, using up/down arrow key, will not help you to navigate the selection around. How I can avoid this behavior? See the below screen shoot /* * To change this template, choose Tools | Templates * and open the template in the editor. */ /* * NewJFrame.java * * Created on May 8, 2010, 7:46:28 PM */ package javaapplication26; /** * * @author yccheok */ public class NewJFrame extends javax.swing.JFrame { /** Creates new form NewJFrame */ public NewJFrame() { initComponents(); /* If you are having 3 same strings here. Using, up/down arrow key, * will not move the selection around. */ this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ @SuppressWarnings("unchecked") // <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() { jComboBox1 = new javax.swing.JComboBox(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); jComboBox1.setEditable(true); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(105, 105, 105) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 158, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(137, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(63, 63, 63) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(217, Short.MAX_VALUE)) ); pack(); }// </editor-fold> /** * @param args the command line arguments */ public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new NewJFrame().setVisible(true); } }); } // Variables declaration - do not modify private javax.swing.JComboBox jComboBox1; // End of variables declaration }

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  • Google AppEngine + Local JUnit Tests + Jersey framework + Embedded Jetty

    - by xamde
    I use Google Appengine for Java (GAE/J). On top, I use the Jersey REST-framework. Now i want to run local JUnit tests. The test sets up the local GAE development environment ( http://code.google.com/appengine/docs/java/tools/localunittesting.html ), launches an embedded Jetty server, and then fires requests to the server via HTTP and checks responses. Unfortunately, the Jersey/Jetty combo spawns new threads. GAE expects only one thread to run. In the end, I end up having either no datstore inside the Jersey-resources or multiple, having different datastore. As a workaround I initialise the GAE local env only once, put it in a static variable and inside the GAE resource I add many checks (This threads has no dev env? Re-use the static one). And these checks should of course only run inside JUnit tests.. (which I asked before: "How can I find out if code is running inside a JUnit test or not?" - I'm not allowed to post the link directly here :-|)

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  • How to get the compression ratio for a GZipped file ?

    - by Enigma
    Here is how I compressed the data: <%@ page import="javax.servlet.jsp.*,java.io.*,java.util.zip.*" %> <% String encodings = request.getHeader("Accept-Encoding"); PrintWriter outWriter = null; if ((encodings != null) && (encodings.indexOf("gzip") != -1)) { OutputStream outA = response.getOutputStream(); outWriter = new PrintWriter(new GZIPOutputStream(outA), false); response.setHeader("Content-Encoding", "gzip"); int a = response.getBufferSize(); System.out.println("ZIPPED VERSION BF:"+a); } else { System.out.println("UN-ZIPPED VERSION"); outWriter = new PrintWriter(response.getOutputStream(), false); } outWriter.println("<HTML><BODY>"); for(int i=0; i<1000; i++) { outWriter.println(" blah blah blah<br>"); } outWriter.println("</BODY></HTML>"); outWriter.close(); %>

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  • How to link different Servlet together?

    - by Harry Pham
    First of all, I did not use Spring MVC. :) :) Just want to get it out first. Now what I have is different JSP pages that making calls to different Servlets. All the pieces work great individually but I kind of need to link them together. If all of jsp pages make GET request then it would be easy, since I would just pass a type via the web address, and on my servlet side, I would just enumerated through all the parameter, determine which type is it, and delegate to the right servlet. But not all jsp pages make GET request, some make POST request via form. Let see example A.jsp $.getJSON('GenericServlet?type=A', ... GenericServlet.java String type = request.getParameter("type"); if(type.equals("A")){ //Somehow delegate to Servlet A (Not sure how to do that yet :)) } but in B.jsp I would have something like this B.jsp <form action="GenericServlet" method="post"> <table border=0 cellspacing=10 cellpadding=0> <tr> <td>User Name:</td> <td><input type="text" name="username" size=22/></td> </tr> <tr> <td>Password:</td> <td><input type="password" name="password" size=22/></td> </tr> </table> <input type="submit" value="Create User" /> </form> It kind of hard for me to determine in GenericServlet.java that this need to go to servletB

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  • Wrapper class that creates objects at runtime and stores data in an array.

    - by scriptingalias
    I tried making a wrapper class that encapsulates an object, a string (for naming and differentiating the object instance), and an array to store data. The problem I'm having now is accessing this class using methods that determine the "name" of the object and also reading the array containing some random variables. import java.util.Arrays; import java.util.Random; public class WrapperClass { String varName; Object varData; int[] array = new int[10]; public WrapperClass(String name, Object data, int[] ARRAY) { varName = name; varData = data; array = ARRAY; } public static void getvalues() { } public static void main(String[] args) { int[] array = new int[10]; Random random = new Random(3134234); for(int i = 0; i < 10; i++) { for (int c = 0; c < 10; c++) { array[c] = random.nextInt();//randomly creates data } WrapperClass w = new WrapperClass("c" + i, new Object(),array); } } }

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  • how to display values of an arraylist defined in servlet using ajax call

    - by veena123
    can anyone please help me with below code servlet: below servlet is for statically defining an array. import java.io.; import javax.servlet.; import javax.servlet.http.; import java.util.; public class SampleAjax extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException,IOException { response.setContentType("text/html"); string plociyno = "abd1234"; PrintWriter pw = response.getWriter(); if (policyno.equals("abc1234")) { List dataList= new ArrayList(); dataList.add("automated refund possible"); request.setAttribute("data",dataList); RequestDispatcher dispatcher = request.getRequestDispatcher("refund.jsp"); if (dispatcher != null){ dispatcher.forward(request, response); } } } and my jsp: jsp for displayng the values of the arraylist in a table.... i want to do the same thing but using ajax.... please help <html <body><table id= "table" border="0" width="303"> <tr> <td width="250"><b>Your Policy Refund Details is:</b></td> </tr> <%Iterator itr; %> <% ArrayList refund= (ArrayList)request.getAttribute("data"); if(refund != null){ for(itr=refund.iterator(); itr.hasNext();){ %> <tr> <td><%=itr.next()%></td> </tr> <%}}%> </table> </body> </html> how can i display this arraylist values using ajax??? please help

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  • Dice Emulation - ImageView

    - by Michelle Harris
    I am trying to emulate dice using ImageView. When I click the button, nothing seems to happen. I have hard coded this example to replace the image with imageView4 for debugging purposes (I was making sure the random wasn't fail). Can anyone point out what I am doing wrong? I am new to Java, Eclipse and Android so I'm sure I've probably made more than one mistake. Java: import java.util.Random; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.ArrayAdapter; import android.widget.ImageView; import android.widget.Spinner; import android.widget.Toast; public class Yahtzee4Activity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Spinner s = (Spinner) findViewById(R.id.spinner); ArrayAdapter adapter = ArrayAdapter.createFromResource( this, R.array.score_types, android.R.layout.simple_spinner_dropdown_item); adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); s.setAdapter(adapter); } public void onMyButtonClick(View view) { ImageView imageView1 = new ImageView(this); Random rand = new Random(); int rndInt = 4; //rand.nextInt(6) + 1; // n = the number of images, that start at index 1 String imgName = "die" + rndInt; int id = getResources().getIdentifier(imgName, "drawable", getPackageName()); imageView1.setImageResource(id); } } XML for the button: <Button android:id="@+id/button_roll" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/roll" android:onClick="onMyButtonClick" />

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  • StoreFilterField input doesn't react

    - by user1289877
    I'm trying to build grid with build in column filtering (using sencha gxt), here is my code: public Grid<Stock> createGrid() { // Columns definition ColumnConfig<Stock, String> nameCol = new ColumnConfig<Stock, String>(props.name(), 100, "Company"); // Column model definition and creation List<ColumnConfig<Stock, ?>> cl = new ArrayList<ColumnConfig<Stock, ?>>(); cl.add(nameCol); ColumnModel<Stock> cm = new ColumnModel<Stock>(cl); // Data populating ListStore<Stock> store = new ListStore<Stock>(props.key()); store.addAll(TestData.getStocks()); // Grid creation with data final Grid<Stock> grid = new Grid<Stock>(store, cm); grid.getView().setAutoExpandColumn(nameCol); grid.setBorders(false); grid.getView().setStripeRows(true); grid.getView().setColumnLines(true); // Filters definition StoreFilterField<Stock> filter = new StoreFilterField<Stock>() { @Override protected boolean doSelect(Store<Stock> store, Stock parent, Stock item, String filter) { // Window.alert(String.valueOf("a")); String name = item.getName(); name = name.toLowerCase(); if (name.startsWith(filter.toLowerCase())) { return true; } return false; } }; filter.bind(store); cm.addHeaderGroup(0, 0, new HeaderGroupConfig(filter, 1, 1)); filter.focus(); return grid; } My problem is: after I run this code, I cannot write anything to filter input, I'm using test data and classes (Stock.java and StockProperties.java) from this example: http://sencha.com/examples-dev/#ExamplePlace:filtergrid I try to put allert in doSelect method to check if this function was called, but it wasn't. Any idea will be welcome. Thanks.

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  • How can I create global context variables in JBOSS?

    - by NobodyMan
    This is a follow-up to a question I posted a while back: "Can I use a single WAR in multiple environments?". I was able to create a single-war solution in Tomcat, but now we are migrating our app to JBoss 4.2 and I can't figure out how to set up global environment variables. In Tomcat 6 this was pretty straightforward: I simply put the following snippet in tomcat/conf/Catalina/myappname.xml: <Context ...> <Environment name="TARGET_ENV" value="DEV" type="java.lang.String" override="false"/> </Context> Then in my app I was able to resolve the environment name with the following: Context context = (Context) InitialContext().lookup("java:comp/env"); String targetEnvironment = (String) context.lookup("TARGET_ENV"); The problem is that I can't find out where/how to place global variables in JBoss. I've tried putting the <Environment> tag in the following files to no avail: server/all/deploy/jboss-web.deployer/context.xml server/default/deploy/jboss-web.deployer/context.xml I know that I can put environment variables in my app's web.xml but that defeats the purpose of having a unified war - I'd still need custom .war's for dev, qa and prod. I'm a JBoss newbie so if there's any additional information that would help just let me know and I'll append to this question. Many thanks! --N

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  • JAXB code generation: how to remove a zero occurrence field?

    - by reef
    Hi all, I use JAXB 2.1 to generate Java classes from several XSD files, and I have a problem related to complex type restriction. On of the restrictions modifies the occurence configuration from minOccurs="0" maxOccurs="unbounded" to minOccurs="0" maxOccurs="0". Thus this field is not needed anymore in the restricted type. But actually JAXB generates the restricted class with a [0..1] cardinality instead of 0. By the way the generation is tuned with <xjc:treatRestrictionLikeNewType / so that a XSD restriction is not mapped to a Java class inheritance. Here is an example: Here is the way a field is defined in a complex type A: <element name="qualifier" type="CR" maxOccurs="unbounded" minOccurs="0"/ Here is the way the same field is restricted in another complex type B that restricts A: <element name="qualifier" type="CR" minOccurs="0" maxOccurs="0"/ In the A generated class I have: @XmlElement(name = "qualifier") protected List<CR qualifiers; And in the B generated class I have: protected CR qualifiers; With my poor understanding of JAXB the absence of the XmlElement annotation tells JAXB not to marshall/unmarshall this field. Am I wrong? If I am right is there a way to tell JAXB not to generate the qualifiers field at all? This would be in my opinion a much better generation as it respects the constraints. Any idea, thougths on the topic? Thanks!!

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  • J-Monkey subclass

    - by user2971104
    I'm new in java and J-monkey and I'm trying to make a java game so for the Menu I have made a enum so I can Switch between any of my State but I want to keep the main file shorter so it can be easily to read so I'm making subclass the problem is that when run the game it give me an error that say "Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main] NullPointerException" I think this problem has to be something whit the pipeline Here is the code of my main file: package mygame; import com.jme3.app.SimpleApplication; import com.jme3.font.BitmapText; import com.jme3.material.Material; import com.jme3.math.ColorRGBA; import com.jme3.math.Vector3f; import com.jme3.renderer.RenderManager; import com.jme3.scene.Spatial; import com.jme3.scene.Geometry; import com.jme3.input.*; import com.jme3.input.controls.*; public class Main extends SimpleApplication { //GameStates enum GameState{Logo, Menu, Playing, Option}; GameState gameState = GameState.Logo; //Class Variables Logo logo; public Main() { logo = new Logo(); } public static void main(String[] args) { Main app = new Main(); app.start(); } public static void logo(String[] args) { Logo app = new Logo(); app.start(); } @Override public void simpleInitApp() { //Load flyCam.setMoveSpeed(20); if(gameState == GameState.Logo){ logo.simpleInitApp(); } } @Override public void simpleUpdate(float tpf) { } @Override public void simpleRender(RenderManager rm) { //TODO: add render code //Load if(gameState == GameState.Logo) { } } } And here is my Logo subclass: package mygame; import com.jme3.app.SimpleApplication; import com.jme3.renderer.RenderManager; import com.jme3.scene.Spatial; public class Logo extends SimpleApplication { @Override public void simpleInitApp() { Spatial Logo_Model = assetManager.loadModel("Models/Teapot/Logo.obj"); rootNode.attachChild(Logo_Model); } public void simpleRender(RenderManager rm) { //Load } }

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  • Wicket application + Apache + mod_jk - AJP queues are filling up!

    - by nojyarg
    Dear community, We are having a Wicket-based Java application deployed in a production server cluster using Apache (2.2.3) with mod_jk (1.2.30) as load balancing component w/ sticky session and Jboss 5 as application container for the Java application. We are inconsistently seeing an issue in our production environment where our AJP queues between Apache and Jboss as shown in the JMX console fill up with requests to the point where the application server is no longer taking on any new requests. When looking at all involved system components (overall traffic, load db, process list db, load of all clustered application server nodes) nothing points towards a capacity issue which would explain why the calls are being stalled in the AJP queue. Instead all systems appear sufficiently idle. So far, our only remedy to this issue is to restart the appservers and the load balancer which only occasionally clears the AJP queues. We are trying to figure out why the queues are filling up to the point that no calls get returned to the end user although the system is not under a high load. Has anyone else experienced similar problems? Are there any other system metrics we should monitor that could explain the queuing behavior? Is this potentially a mod_jk issue? If so, is it advisable to swap mod_jk with mod_cluster to resolve the issue? Any advice is highly appreciated. If I can provide additional information for the sake of troubleshooting I would be more than willing to do so. /Ben

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  • Google App Engine datastore encoding?

    - by sernaferna
    I'm using the GAE datastore for a Java application, and storing some text that will be in numerous languages. In my servlet, I'm first checking to see if there's any data in the data store, and, if not, I'm creating some, similar to the following: ArrayList<Lang> list = new ArrayList<Lang>(); list.add(new Lang("EN", "English", 1)); list.add(new Lang("ES", "Español", 0)); //more languages here... PersistenceManager pm = PMF.get().getPersistenceManager(); for(Lang l : list) { pm.makePersistent(l); } Since this is using JDO, I guess I should include the relevent parts of the Lang class too: @PersistenceCapable public class Lang { @PrimaryKey private String code; @Persistent private String name; @Persistent private int popularity; // getters & setters & constructors... } However, the non-ASCII characters are giving me grief. I've set my Eclipse project to use the UTF-8 encoding instead of the default Cp1252, so I think I'm okay from that perspective, but when I use the App Engine Data Viewer to look at my data, that Español entry becomes Español, and when I click on it to view it, I get a 500 Server Error. (There are some other entries with right-to-left text that don't even show up in the Data Viewer at all, but one problem at a time...) Is there anything special I can do in my code to set the character encoding, or specify to GAE that the data I'm storing is UTF-8? Or is the problem on the Eclipse side, and is there something I should be doing with my Java code?

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  • What i am doing wrong with Class Overview?

    - by RFM software
    This code not work. Anyone can helpme? .java package rfmsoftware.util.test1; import android.app.Activity; import android.os.Bundle; public class test1 extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button button = (Button)findViewById(R.id.Button01); <---- Error at this line !? } } .xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <EditText android:id="@+id/EditText01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="10"></EditText> <Button android:id="@+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/Scan"></Button> <View android:id="@+id/View01" android:layout_width="wrap_content" android:layout_height="wrap_content"></View> </LinearLayout> .error Button cannot be resolved to a type (type Java problem) ???

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  • Weird compile-time behavior when trying to use primitive type in generics

    - by polygenelubricants
    import java.lang.reflect.Array; public class PrimitiveArrayGeneric { static <T> T[] genericArrayNewInstance(Class<T> componentType) { return (T[]) Array.newInstance(componentType, 0); } public static void main(String args[]) { int[] intArray; Integer[] integerArray; intArray = (int[]) Array.newInstance(int.class, 0); // Okay! integerArray = genericArrayNewInstance(Integer.class); // Okay! intArray = genericArrayNewInstance(int.class); // Compile time error: // cannot convert from Integer[] to int[] integerArray = genericArrayNewInstance(int.class); // Run time error: // ClassCastException: [I cannot be cast to [Ljava.lang.Object; } } I'm trying to fully understand how generics works in Java. Things get a bit weird for me in the 3rd assignment in the above snippet: the compiler is complaining that Integer[] cannot be converted to int[]. The statement is 100% true, of course, but I'm wondering WHY the compiler is making this complaint. If you comment that line, and follow the compiler's "suggestion" as in the 4th assignment, the compiler is actually satisfied!!! NOW the code compiles just fine! Which is crazy, of course, since like the run time behavior suggests, int[] cannot be converted to Object[] (which is what T[] is type-erased into at run time). So my question is: why is the compiler "suggesting" that I assign to Integer[] instead for the 3rd assignment? How does the compiler reason to arrive to that (erroneous!) conclusion?

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  • Why am I getting a ClassCastException here?

    - by Holly
    I'm creating an android application and i'm trying to use a PreferenceActivity. I'm getting the java.lang.ClassCastException: java.lang.String error when it gets to this line return PreferenceManager.getDefaultSharedPreferences(context).getInt(USER_TERM, USER_TERM_DEF); I thought it might be because I'm not converting it properly from it's string value in the EditText box to the int I need but I can't figure out how to fix this, or is that even the cause? I'm flummoxed. Here's my preference activity class: public class UserPrefs extends PreferenceActivity { //option names and default vals private static final String USER_TERM = "term_length"; private static final String USER_YEAR = "year_length"; private static final int USER_TERM_DEF = 12; private static final int USER_YEAR_DEF = 34; @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); addPreferencesFromResource(R.xml.preferences); } public static int getTermLength(Context context){ try{ return PreferenceManager.getDefaultSharedPreferences(context).getInt(USER_TERM, USER_TERM_DEF); }catch (ClassCastException e){Log.v("getTermLength", "error::: " + e); } //return 1;//temporary, needed to catch the error and couldn't without adding a return outside the block.// } public static int getYearLength(Context context){ return PreferenceManager.getDefaultSharedPreferences(context).getInt(USER_YEAR, USER_YEAR_DEF); } And here's the bit of code where I'm trying to use the the preferences inside another class: public float alterForFrequency(Context keypadContext, float enteredAmount, String spinnerPosition){ int termLength = UserPrefs.getTermLength(keypadContext); int yearLength = UserPrefs.getYearLength(keypadContext); } The complete android logcat, i've uploaded here: http://freetexthost.com/v3t4ta3wbi

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