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  • null pointer exception on list.add

    - by Eric
    I've been working on this one error for a few hours so I thought I'd pick the brains of some pros. I am getting a null pointer exception at the modelData.add(i, es) method. I know from debugging that es isn't null. I'm really confused, thanks. public class EventTableModel extends AbstractTableModel { //private int rowCount = 0; protected List<EventSeat> modelData; private static final int COLUMN_COUNT = 3; private Event e; Event j = GUIpos.m; int i = 1; public EventTableModel(Event e) { this.e = e; try { System.out.println(modelData); for (EventSeat es : e.getEventSeats()) { modelData.add(i, es); i++; } } catch (DataException ex) { Logger.getLogger(EventTableModel.class.getName()).log(Level.SEVERE, null, ex); } }

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  • Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

    - by Ricket
    Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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  • A hard Question ?

    - by the-ifl
    Hi Guys , I try To find a solution to a question .... we have a number , example : 20 ... and we have 6 number :{ a ,b , c , d , e , f} < 20 , t try to find all values of these numbers , but only if we can combinate (whit + or -) whit 2 of this numbers and getting all the value below to 20 : for example we choose 31 : a = 22 b = 21 c = 14 d = 11 e = 9 f = 5 we have : 22 - 21 = 1 ; 11 - 9 = 2 ; 14 - 11 = 3 ; 9 - 5 = 4 ; f = 5 ; 11 - 5 = 6 ; 21 - 14 = 7 ; .... .... .... .... .... 21 + 9 = 30 ; 9 + 22 = 31 ;

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  • How do I limit JPQ output?

    - by den-javamaniac
    I need to limit number of entities returned by a query to some certain value inside a JPA query (through JPQL). Particularly: select m from Manual m //constraint e.g. in sql (mysql syntax) I would do it like: select * from Manual limit 1 The only solution that comes up is simply to get all entities and then choose first one, which is out of the issue. Any ideas?

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  • Please help with my twodimensional array source code

    - by Baiba
    Here is what i have done but i have some questions: class masivins { public static void main (String args[]) { int mas[][] = {{0, 2, 7, 0, 8, 5, 3}, {0, 4, 0, 6, 0, 0, 0}, {0, 0, 0, 0, 3, 0, 0}, {7, 0, 0, 9, 1, 0, 7}, {5, 0, 4, 0, 0, 2, 0}}; int nulmas[] = new int [7]; int nul=0; for(int j=0; j<7; j++) { nul=0; for(int i=0; i<5; i++) { if(mas[i][j]==0) { nul++; } } nulmas[j]=nul; } for(int i=0; i<5; i++) { for(int j=0; j<7; j++) { System.out.println(mas[i][j]); } System.out.println(); } System.out.println(); for(int i=0; i<5; i++) { System.out.println("Zeros in each array column: " + nulmas[i]); } System.out.println(); } } so my questions are: 1) why after running project there are only 5 "Zeros in each array column....." shown? 2) what and where i need to change in this code to get out the number of column in which zeros are least?

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  • I'm confused about Polymorphism

    - by Vtanathip
    I'm know polymorphism rule that we can send it via parameter like this code interface Animal { void whoAmI(); } class A implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("A"); } } class B implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("B"); } } class RuntimePolymorphismDemo { public void WhoRU(List t){ System.out.println(t.getClass()); } public static void main(String[] args) { A a = new A(); B b = new B(); RuntimePolymorphismDemo rp = new RuntimePolymorphismDemo(); rp.WhoRU(a); rp.WhoRU(b); } } but List<Example> examples = new ArrayList<Example>(); This code,I'm don't understand why we must use List. why we can't use like this? ArrayList<Example> examples = new ArrayList<Example>(); Because when we use List we can't use method that only have in ArrayList class like trimToSize() and How I know when to use or not use?

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  • Passing bundle to activity set as singletask

    - by Falmarri
    So I have a MapActivity that runs an asynchtask that occasionally updates what exactly it's displaying on the map (via a string). I originally pass this string in from the intent when the activity is first created. And then if you click on one of the drawables on the map, it opens a new activity, which can then create a new mapview (same class) with a different string setting. The problem I have is that I only want one instance of the mapview to be running at once. Thus I set android:launchmode="singletask" in the manifest. This works in that it brings the mapactivity to the front, but is there any way to send it a new intent bundle to get a new setting for the string it needs? I tried regetting the extras from the bundle, but it seems to retain the old bundle, not the new intent that was passed to it. I'm not sure I want to do startActivityForResult because the 2nd activity may or may not want to update the original activity. I hope that made sense. I can post code if necessary, but I think that should explain my situation.

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  • Using low level api for datastore in google app engine ? is it bad ?

    - by Chez
    There is little documentation on how to use the low level api for datastore and quite a lot on JPA and JDO and how it translates to it. My question is: is there any advantage in coding against the JPA or JDO specs instead of accessing directly the low level api for datastore ? From an initial look, it seems simple and straight forward but I am not sure if there are good reasons why not to do it. Thanks Cx

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  • Why is J2EE scalable?

    - by py213py
    I heard from various sources that J2EE is highly scalable, but to me it seems that you could never scale a J2EE application to the level of the google search engine or any other large website. I would like to hear the technical reasons why it is so scalable.

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  • Using Maven with Sourceforge.net

    - by mjn
    For a new project which uses Maven I would like to add distributionManagement configuration in the pom.xml which will connect the project with the Sourceforge.net file upload system. I have found this information (of 2007), is it still valid or do you know updated resources? http://docs.codehaus.org/display/MAVENUSER/MavenAndSourceforge Related question: How can I deploy artifacts from a Maven build to the SourceForge File Release System?

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  • How to make a swing app aware of screen size change?

    - by Marton Sigmond
    Hi, while my swing app is running I change the size of the screen (e.g. from 1024x768 to 800x600). Is there any event I can listen to to be notified about this? Alternatively I could check the screen size in every couple of second, but the Toolkit.getScreenSize() keeps telling me the old value. How could I get the real screen size after the change? Environment: Linux (tested on SuSE ES 11 and Ubuntu 9.04) I appreciate your help. Marton

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  • Tomcat memory issue

    - by user305210
    Hello, I have noticed that my application that is running on Tomcat 5 starts with 1gig of memory and as soon as it starts receiving requests from client, the memory starts dropping until it is down to 100MBs and troubles start from there. I am looking at /manager/status page of tomcat under JVM section where "Free Memory", "Total Memory", "Max Memory" is listed. Is this an indicator of memory leak? Memory does not seem to be freed-up automatically even if there are no requests coming from client machines.

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  • Is it possible to tie nested generics?

    - by Michael Deardeuff
    Is it possible to tie nested generics/captures together? I often have the problem of having a Map lookup of class to genericized item of said class. In concrete terms I want something like this (no, T is not declared anywhere). private Map<Class<T>, ServiceLoader<T>> loaders = Maps.newHashMap(); In short, I want loaders.put/get to have semantics something like these: <T> ServiceLoader<T> get(Class<T> klass) {...} <T> void put(Class<T> klass, ServiceLoader<T> loader) {...} Is the following the best I can do? Do I have to live with the inevitable @SuppressWarnings("unchecked") somewhere down the line? private Map<Class<?>, ServiceLoader<?>> loaders = Maps.newHashMap();

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  • Not able to get the data from the JSON in OpenSocial App!

    - by Abhishek
    I have follwing JSON: {"mykey":[{name:"Jak",interests:"movies"}]} and following opensocial app code: <script type="text/os-template" require="mykey"> <ul> <li repeat="${mykey}"> <span>Offer id: ${Cur.name}</span> <span>Offer: ${Cur.interests}</span> </li> </ul> </script> but the App is not able to get the data from the JSON? Not able to find out the issue!

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  • How to trigger an application in mobile automatically

    - by san6086
    My idea is to make an application start automatically when a message from a specific user reaches the inbox of the mobile . For example if my friend sends some numbers to my mobile, the sms has to be read and validated first and then calculator ( inbuilt mobile application) has to be triggered and process the numbers from the message. Please help me with the above query.

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  • Hibernate Queries

    - by Schildmeijer
    Using Named Queries (located in your hibernate mapping xml file) is a nice way to separate your queries from your buisness logic. But what are the alternatives if your are using Hibernate Annotations for mapping?

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  • About NullPointer Exception in Arraylist

    - by user2234456
    List<PrcSubList> listSl = new ArrayList<PrcSubList>(); if (listSl == null || listSl.size() == 0) { PrcSubList subListAdd=coreService.addSubListByAddAlert(childSub); System.out.println("sublist after insert db :" + subListAdd.getName()); listSl.add(subListAdd); System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); } Ouput with first System.out.println("sublist after insert db :" + subListAdd.getName()); sublist after insert db :SYSTEM_ALERT_12312313 Problem But i have NullPointerException with 2nd System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); Can you help me!

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  • multiple search fields

    - by user234194
    What will be the best approach if I have search fields for 20 or more and any combination should be valid. Is there any special way to do it in openJPA or native SQL is better. Any idea would be helpful.Thanks.

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  • multiple search fields

    - by user234194
    What will be the best approach if I have search fields for 20 or more and any combination should be valid. Is there any special way to do it in openJPA or native SQL is better. Any idea would be helpful.Thanks.

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  • Integrate with Google calendar ?

    - by Karthick
    Hi all.I am using the following code to integrate with google calendar. CalendarService myService = new CalendarService("CalService"); myService.setUserCredentials("[email protected]", "xxxxxxx"); URL feedUrl = new URL("https://www.google.com/calendar/feeds/default/private/"); CalendarFeed resultFeed = myService.getFeed(feedUrl, CalendarFeed.class); System.out.println("Your calendars:"); for (int i = 0; i < resultFeed.getEntries().size(); i++) { CalendarEntry entry = resultFeed.getEntries().get(i); System.out.println("\t" + entry.getTitle().getPlainText()); } But it gives the Exception: Invalid credentials ERROR: JDWP Unable to get JNI 1.2 environment, jvm->GetEnv() return code = -2 JDWP exit error AGENT_ERROR_NO_JNI_ENV(183): [../../../src/share/back/util.c:820] Help me to solve this. Can anyone please list the needed jar files to adding calendar events to Google calendar

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