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• Laying out JPanels to make a simple GUI

  - by Elvis

  Hello, first of all, this is more or less my first GUI and ive learned Java for not more then a week, so it might contain some serious programming errors. What i have right now is: Buttons and labels are part of OptionPanel and are on the left, DrawingPanel is about 5x5 px in size and is on the right. What I am trying to do is a simple test, to get me more familiar with the GUI. The rectangle should be movable and re-sizeable by the user when clicking the respective buttons: http://www.upload.ee/image/612005/JFrame2.jpg Right now i have: JFrame MainFrame - Makes JFrame (Not using the setSize function. using .pack() instead. not sure about it) JPanel MergedPanel - FlowLayout - Adds JPanel OptionsPanel and JPanel DrawingPanel together and gets injected to JFrame MainFrame JPanel DrawPanel - This JPanel is responsible of drawing the rectangle. JPanel OptionPanel - FlowLayout - This JPanel is responsible of the buttons. Help please.

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• simple modification results in error

  - by lgwest

  When I tried to do a simple modification of the "hello android" program that eclipse adt plugin generates I get error and can't get the program to run again even if I restore the file to its original contents. The modification was that I changed a string in strings.xml. the line was: <string name="app_name">Todo List</string> and the app was runnable, then I changed it to <string name="app_name">Todo List1</string> and it was an error: [2010-04-21 23:18:03 - Todo_list] Error in an XML file: aborting build. And a new empty file also showed up called: strings.out.xml And then I can't get the prrogram back into runnable state even if I delete the empyt file and restore the original line, I'm a confused beginner of java, android and eclipse.

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• What's the purpuse behind wildcards and how are they different from generics?

  - by Nazgulled

  Hi, I never heard about wildcars until a few days ago and after reading my teacher's Java book, I'm still not sure about what's it for and wwhy would I need to use it. Let's say I have a super class Animal and few sub classes like Dog, Cat, Parrot, etc... Now I need to have a list of animals, my first thought would be something like: List<Animal> listAnimals Instead, my colleagues are recommending something like: List<? extends Animal> listAnimals Why should I use wildcards instead of simple generics? Let's say I need to have a get/set method, should I use the former or the later? How are they so different?

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• how to represent negative number to array of integers ?

  - by stdnoit

  I must convert string of 1324312321 to array of integers in java this is fine. I could use integer parseint and string substring method but how do I repesent -12312312 to my original array of integer.. the fact that - is a char / string and convert to array of integer would alter the value ( even though I convert - to integer-equivalent , it would change the rest of 12312312) it must be an array of integers and how should I convert negative numbers and still keeep the same value somehow reminding me of two complements trick but i dont think i need to go down to binary level in my program.. any other trick for doing this? thanks!

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• Concatinate integer arrays iteratively

  - by Ojtwist

  I have a methode in2.getImagesOneDim() which gives me an array of integers, to be more precise the pixel values of an image. Now i want to create one big array with all the pixel values of all the images. Therefore I have to call this method several times. Now I would like to concatenate the previous output to the current output until all images are read. In some kind of pseudo code, where the + is a concatination ... : for (int i = 1; i < 25; i++) { ConArray = ConArray + in2.getImagesOneDim("../images/"+i); } How would I do this in java ?

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• Jump-To-Code-Line Eclipse Shortcuts

  - by scrr

  Hello, is it possible, in Eclipse, to mark certain lines with Shortcuts and be able to quickly jump to those lines? Example: Let's say I have maintenanceHeavyMethod() at line 120 in my class, gameLoop() at line 800 and some listener at line 1460. I'd like to f.ex. press CTRL-SHIFT-1, 2, 3 etc. to mark those positions, and then use f.ex. CTRL-1, 2, 3 to immediately jump to them. I don't like split-screens etc, but I need to jump around when writing. Is there such a feature? I'm using latest Eclipse to write Java-programs.

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• How to convert string to integer?

  - by user1260584

  So I'm having a hard time with my situation and need some advice. I'm trying to convert my two Strings that I have into integers, so that I can use them in math equations. Here is what I tried, however it brings me an error in the app. ' equals.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // TODO Auto-generated method stub num1 = edit.getText().toString(); num2 = edit.getText().toString(); int first = Integer.parseInt(num1); int second = Integer.parseInt(num2); edit.setText(first + second); } }); Is there something that I am doing wrong? Thank you for any help. EDIT: Yes this is Java. num1 and num2 are strings that I have previously named. What do you mean by trim?

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• How to test if an array contains a pair of numbers whose product is odd?

  - by John

  How can I write a function that takes an array of integers and returns true if their exists a pair of numbers whose product is odd? What are the properties of odd integers? And of course, how do you write this function in Java? Also, maybe a short explanation of how you went about formulating an algorithm for the actual implementation. Yes, this is a function out of a textbook. No, this is not homework—I'm just trying to learn, so please no "do your own homework comments."

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• Search in big text log files

  - by 0xFF

  Hi, let's say you have an game server which creating text log files of gamers actions, and from time to time you need to lookup something in those logs files (like investigating an scam or loosing an item). Just for example you have 100 files and each file have size between 20MB and 50MB - How you would search them quickly? What I have already tried to do is create several threads and each invidual thread will map his own file to memory (let say memory should not be problem if it not exceed 500MB of ram) perform search here, result was something around 1 second per file : File:a26.log - read in: 0.891, lines: 625282, matches: 78848 Is there better way how to do that ? - because it seems to me kinda slow. thanks. (java was used for this case)

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• Converting audio files(.3gp) to video with Album cover and uploading to YouTube

  - by Samuh

  I have an audio file in .3gp format on my Android device which I wish to upload to YouTube. I know that YouTube is a video upload site and that I need to convert this sound file to video. I just want an image to display all the time the audio is playing. Google tells me there are number of tools that can help me. But I want to do this via java code from my Android device. Please help. Thanks.

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• how to find number of weekdays in array

  - by Chamal

  i hav a array of date. In this array, i want to find how many weekdays in that array. So how can i do that using java.. *here i read lines from csv file & put those into values. *values[2] contain the dates of that csv file. *So now i want to find number of weekdays in values[2]. FileInputStream fis=new FileInputStream("c:/sample.csv"); InputStreamReader isr=new InputStreamReader(fis); BufferedReader bf = new BufferedReader(isr); while (bf.ready()) { String line = bf.readLine(); String[] values=line.split(","); String date=values[2]; }

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• ask. help me to compare two array of integers and the order does not matter.

  - by stdnoit

  [Example] <1 2 3 4 = <3 1 2 4 <1 2 3 4 != <3 4 1 1 and ummm it is in java. cant use hashmap table or anything just pure without library. I know there are two ways. 1. sort them and compare the array index by index 2. use two for loops and compare the outer index with the inner index. ( i have been trying with this but still not working) for(int i = 0; i < n; i++) { for(int j = 0; j < n; j++) { if(a[i] != a[j] && j == n) return false; } } return true; anything wrong with the code ? thanks

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• What the best way to convert from String to HashMap?

  - by eugenn

  I would like to serialize a Java HashMap to string representation. The HashMap will contains only primitive values like string and integer. After that this string will be stored to db. How to restore back the HashMap? Is it make sense to use BeanUtils and interface Converter or use JSON? For example: List list = new ArrayList(); list.add(new Long(1)); list.add(new Long(2)); list.add(new Long(4)); Map map = new HashMap(); map.put("cityId", new Integer(1)); map.put("name", "test"); map.put("float", new Float(-3.2)); map.put("ids", list); map.toString() -> {float=-3.2,ids=[1, 2, 4],name=test,cityId=1} map.toJSON -> {"float":-3.2,"ids":[1,2,4],"name":"test","cityId":1}

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• Override the methods of classes from a .war file.

  - by Sweety

  I have a base application war file say homeApp.war. This contains default operations which user can carry out on the web browser. Now I need to extend the operations available on the same application using that .war file. Like I need to add the extra menus, some shortcuts like icon for log out etc. Please let me know how can I use this .war file to extend the operations and also fix the already existing issues on the application. This web application uses java server faces.

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• What is the absolute fastest way to implement a concurrent queue with ONLY one consumer and one producer?

  - by JohnPristine

  java.util.concurrent.ConcurrentLinkedQueue comes to mind, but is it really optimum for this two-thread scenario? I am looking for the minimum latency possible on both sides (producer and consumer). If the queue is empty you can immediately return null AND if the queue is full you can immediately discard the entry you are offering. Does ConcurrentLinkedQueue use super fast and light locks (AtomicBoolean) ? Has anyone benchmarked ConcurrentLinkedQueue or knows about the ultimate fastest way of doing that? Additional Details: I imagine the queue should be a fair one, meaning the consumer should not make the consumer wait any longer than it needs (by front-running it) and vice-versa.

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• How to export javascript generated report to pdf?

  - by Parhs

  Hello... I made a reporting engine with javascript for my project... The problem is with printing.. Although with page-break and css i can produce a good looking report, i want to export that report to a pdf in order to be printed better without ,the url,page title and other stuff that browsers add. Note in Chrome there isnt page setup!!! I am using java for server side. i think sending via ajax the Html of the report somehow and return a url for the pdf report maybe... i am looking for a good tool for this thank you

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• How do I ensure data consistency in this concurrent situation?

  - by MalcomTucker

  The problem is this: I have multiple competing threads (100+) that need to access one database table Each thread will pass a String name - where that name exists in the table, the database should return the id for the row, where the name doesn't already exist, the name should be inserted and the id returned. There can only ever be one instance of name in the database - ie. name must be unique How do I ensure that thread one doesn't insert name1 at the same time as thread two also tries to insert name1? In other words, how do I guarantee the uniqueness of name in a concurrent environment? This also needs to be as efficient as possible - this has the potential to be a serious bottleneck. I am using MySQL and Java. Thanks

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• How to update mutual entries in DB?

  - by Sthita

  I am not able to perform mutual update to my Database. My Requirement is like this : Insert IDS UPDate DB Entries ID ConnectedTo ID connectedTo connectedVia 2 1 --- No Entry ----- 2 3 -- No Entry ----- When ID 1 Comes in to picture (Enties happened to Table) 1 4 1 3 2 1 5 2 4 1 1 2 2 5 1 When ID 3 Comes into picture (Enties happened to Table) 3 4 3 5 1 3 1 ---- 3 2 ---- Similarly when ID 4 Comes in to picture 4 9 4 2 3 4 10 4 5 1 4 3 4 2 1 4 1 1 9 4 1 10 4 Its basically Updating the mutual connections.No Duplicate entries should happen. Like for example 2 3 and 3 2 are mutually connected and 1 is associated with them so there is no need to insert (3 2 via 1). I think this is my requirement. Anything possible combinations i have missed please let me know. i will Update. Please help me writing the logic or any example using jdbc and java.

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• How can I make a recursive version of my iterative method?

  - by user247679

  Greetings. I am trying to write a recursive function in Java that prints the numbers one through n. (n being the parameter that you send the function.) An iterative solution is pretty straightforward: public static void printNumbers(int n){ for(int i = 1; i <= n; i++){ System.out.println(i); i++; } As a novice programmer, I'm having troubles figuring out how a recursive version of this method would work. Any bright ideas? Thanks for reading my problem!

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• is there some lightweight tecnique for adding type safety to identifier properties?

  - by shoren

  After using C++ I got used to the concept of Identifier which can be used with a class for the type, provides type safety and has no runtime overhead (the actual size is the size of the primitive). I want to do something like that, so I will not make mistakes like: personDao.find(book.getId());//I want compilation to fail personDao.find(book.getOwnerId());//I want compilation to succeed Possible solutuions that I don't like: For every entity have an entity id class wrapping the id primitive. I don't like the code bloat. Create a generic Identifier class. Code like this will not compile: void foo(Identifier book); void foo(Identifier person); Does anyone know of a better way? Is there a library with a utility such as this? Is implementing this an overkill? And the best of all, can this be done in Java without the object overhead like in C++?

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• Adding behaviour to a set of classes

  - by devoured elysium

  I have defined an Event class: Event and all the following classes inherit from Event: SportEventType1 SportEventType2 SportEventType3 SportEventType4 Right now I will only have SportEvents but I don't know if in the future I'll want some other kind of events that doesn't even have anything to do with Sports. Later, I will want to draw some graphics with info taken from Events, and the drawing logic can be a bit complex. But, for the moment, I think I shouldn't think of how the drawing will be done and I believe that maybe it'd be better if that drawing part was not put as an integral part of the Event/SportEventX class chain. I am looking for solutions for this problem. I know I could just make Event have an instance variable(attribute, for the java crowds) pointing to something as an IDrawInterface, but that would make the Event class "assume" it will be later used for drawing. I would like to make the Event class oblivious to this if possible. Thanks!

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• Eclipse buildpath automatically taking all JARs of a internal directory

  - by Niko

  How do I configure my project buildpath to have a set of .jar files located in the same directory automatically included in the buildpath ? Meaning that adding a new .jar file to this directory (and refreshing the project) updates the buildpath ? Rem : I am not working in a Webapp but in a standalone Java app. I know that it is possible in a Dynamic Web Project to have all the .jars located in WEB-INF/lib to be included in the build path. Is it possible to do kind of the same include but in standalone app ? I am using Eclipse 3.4

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• Architect desperately wants to use SOAP over JMS

  - by Aerosteak

  Hello, I have used JMS in the past to build application and it works great. Now I work with Architects that would love to use the Spec : SOAP over Java Message Service 1.0. This spec seams overly complicated. I do not see many implementation (Beside the vendors pushing for the spec). Does anyone here is using this specification in a production environment? What is your main benefit of using this spec? Link: http://www.w3.org/TR/2009/CR-soapjms-20090604/

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• Using JLists and ListModels

  - by devoured elysium

  I have defined a DirectoryListModel class that extends the AbstractListModel class from the Java Api. Internally, I have a list of File objects. I have defined the getElementAt(int index) method as: @Override public Object getElementAt(int index) { return directoryElements.get(index) } The problem is that when I try to run my JList with my DirectoryListModel, it is going to show up the full paths of files instead of just the filenames. I could change this code to: @Override public Object getElementAt(int index) { return directoryElements.get(index).getName(); } and it'd work wonders, but the problem is that in the onclick event I'll want to have the File objects so I can do some checking with them (check if they're directories, etc). If I make getElementAt() return a String, I'm losing that possibility, thus I'd like to konw if there is a way I can format my File objects before the JList shows them in my window. Thanks

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• JNAerator Unnamed Union Missing in Structure

  - by Nick

  I'm trying to get JNAerator to generate some JNA backed Java code from a C shared library and everything is fine except that it failed to generate an unnamed union nested inside a structure. Example: typedef struct MY_STRUCTURE { union { My_Type1 var1; My_Type2 var2; }; }MY_STRUCTURE; If I change the header to make the union have a name it will work. But for obvious reasons I can't just change the header without breaking the shared library I'm trying to use. Any solutions other than changing the header file and shared library to named union?

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