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• Guide for http://www.ch-werner.de/javasqlite java wrapper library for SQlite?

  - by Tom Nielsen

  I'm working on a large computer science school project using java and SQlite. After finding out that the zentus.org wrapper errors on databases with ON DELETE and ON UPDATE clauses set, I have changed to the other wrapper found at http://www.ch-werner.de/javasqlite. However, I find the documentation lacking somewhat when trying to get an overview on how it works and how to use it, and the function descriptions are very very short, and you have to scan through every function and somewhat guess how they work and what they do. I wasn't able to find any guides on google on how to use it. My question: Does anyone know a link for a guide or tutorial for the ch-werner.de/javasqlite wrapper, or else can give me a basic code example, or give a quick overview of querying the database and the most used functions, and how to use them?

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• Java swing examples - Ants running around a world getting food from piles?

  - by Charlie

  I haven't done any swing programming in a while, so I'm looking for some GUI examples that are at least close to what I'm trying to do. The gui that I'll need to be representing is small nodes (let's say ants) travelling around collecting food from food piles (which just means small nodes travelling to bigger nodes). Once the node (ant) takes a piece of food, the pile shrinks a bit and the ant takes it back home (to ANOTHER circle). This SOUNDS pretty trivial, but all of the boilerplate involved in setting up a java GUI just makes little logical sense to me, and the GUI is such a small piece of my project. Any examples that would be great for this style of project would be greatly appreciated. Thanks!

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• Java: confirm method Binary division and find remainder is correct?

  - by cadwag

  I am parsing binary files and have to implement a CRC algorithm to ensure the file is not corrupted. Problem is that I can't seem to get the binary math working when using larger numbers. The example I'm trying to get working: BigInteger G = new BigInteger("11001", 2); BigInteger M = new BigInteger("1110010000", 2); BigInteger R = M.remainder(G); I am expecting: R = "0101" But I am getting: R = "1100" I am assuming the remainder of 0101 is correct since it is given to me in this book I am using as a reference for the CRC algorithm (it's not based in Java), but I can't seem to get it working. I can get small binary calculations to work that I have solved by hand, but not the larger ones. I'll admit that I haven't worked the larger ones by hand yet, that is my next step, but I wanted to see if someone could point out a glaring flaw I have in my code. Can anyone confirm or deny that my methodology is correct? Thanks

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• JAVA: How to use paint() method to update the previously drawn object?

  - by GamDroid

  How to use paint() such that when repaint() is called the previously drawn object should not get deleted when drawing the new object. That is the drawing area must get UPDATED only and not REDRAWN. In my code when one of many button is clicked, some aplhabet get displayed. I want to have functionality such that when other buttons are clicked the previously drawn alhabets must be present.Take is as if a string of alphabets getting created as the buttons are clicked. Im using Java Swing for coding. Some piece of my code: if(source == btnAlpha[i] ) bollyDraw.repaint(); //bollydraw is an object of a JPanel extended class having implemented the paintComponent(Graphics g) method In the paint() method: if (word[i] == key) { g.drawChars(word, i, 1, x, y); }

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• All possible values of int from the smallest to the largest, using Java.

  - by Totophil

  Write a program to print out all possible values of int data type from the smallest to the largest, using Java. Some notable solutions as of 8th of May 2009, 10:44 GMT: 1) Daniel Lew was the first to post correctly working code. 2) Kris has provided the simplest solution for the given problem. 3) Tom Hawtin - tackline, came up arguably with the most elegant solution. 4) mmyers pointed out that printing is likely to become a bottleneck and can be improved through buffering. 5) Jay's brute force approach is notable since, besides defying the core point of programming, the resulting source code takes about 128 GB and will blow compiler limits. As a side note I believe that the answers do demonstrate that it could be a good interview question, as long as the emphasis is not on the ability to remember trivia about the data type overflow and its implications (that can be easily spotted during unit testing), or the way of obtaining MAX and MIN limits (can easily be looked up in the documentation) but rather on the analysis of various ways of dealing with the problem.

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• How can I add methods from a Java class as global functions in Javascript using Rhino?

  - by gooli

  I have a simple Java class that has some methods: public class Utils { public void deal(String price, int amount) { // .... } public void bid(String price, int amount) { // .... } public void offer(String price, int amount) { // .... } } I would like to create an instance of this class and allow the Javascript code to call the methods directly, like so: deal("1.3736", 100000); bid("1.3735", 500000); The only way I could figure out for now was to use ScriptEngine engine = new ScriptEngineManager().getEngineByName("js"); engine.put("utils", new Utils()); and then use utils.deal(...) in the Javascript code. I can also write wrapper functions in Javascript for each method, but there should be a simpler way to do this automatically for all the public methods of a class.

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• Setting up java configurations in eclipse. multiple .param files

  - by Charlie

  I'm going to be using ECJ for doing genetic programming and I haven't touched java in years. I'm working on setting up the eclipse environment and I'm catching a few snags. The ECJ source has several packages, and several sample programs come along with it. I ran one sample program (called tutorial1) by going to the run configurations and adding -file pathToParamsFile to the program arguments. This made it point to the params file of that tutorial and run that sample. In a new example I am testing (from the package gui) there are TWO params files. I tried pointing to just one param file and a program ran in the console, but there was supposed to be a GUI which did not load. I'm not sure what I'm doing wrong. Any help would be greaaatly appreciated.

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• how can I develop Apple Java Extensions on Windows?

  - by carneades

  When I do multi-platform testing on Windows it gets annoying that Eclipse shows errors in the project because of the com.apple.eawt code that I have in a special Mac customization task. Worse yet, if I export a runnable jar on Windows, it won't run on mac because of the unresolved compilation problems. What's the best way to let Windows Java and com.apple.eawt live in peace? I can't see how I would be able to spin off the code to a jar, since it requires access to lots of the program's state. Thanks for your help! UPDATE: I've posted a jar to Sourceforge that solves this problem: http://sourceforge.net/projects/javaextensions/

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• Java generics: What is the compiler's issue here? ("no unique maximal instance")

  - by Epaga

  I have the following methods: public <T> T fromJson( Reader jsonData, Class<T> clazz ) { return fromJson( jsonData, (Type)clazz ); } public <T> T fromJson( Reader jsonData, Type clazz ) { ... } The compiler is saying about the first method: type parameters of <T>T cannot be determined; no unique maximal instance exists for type variable T with upper bounds T,java.lang.Object return fromJson( jsonData, (Type)clazz ); ^ What is the problem?

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• Why does Java's TreeSet not specify that its type parameter must extend Comparable?

  - by Tarski

  e.g. The code below throws a ClassCastException when the second Object is added to the TreeSet. Couldn't TreeSet have been written so that the type parameter can only be a Comparable type? i.e. TreeSet would not compile because Object is not Comparable. That way generics actually do their job - of being typesafe. import java.util.TreeSet; public class TreeSetTest { public static void main(String [] args) { TreeSet<Object> t = new TreeSet<Object>(); t.add(new Object()); t.add(new Object()); } }

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• How do I make a specific word (variable) in a message box bold in Java?

  - by typoknig

  Hi all, I'm trying to make one word (variable) of a message box bold in my Java program. Here is my code: int n = messageBox.showConfirmDialog(frame, "The File "+ file +" already exists." + "\n" + "Do you want to replace it?", "File Already Exists!", messageBox.YES_NO_OPTION); I want to make the variable "file" appear in bold text in my message box. So far I have only been able to get the entire message box to appear in bold, or none of it at all. How do I do this?

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• [Java/Android] Multidimensional array to ListView.. how?

  - by Yverman

  I have a query result set which I like to edit first and then put it to my ListView. Without editing my data first, I could use SimpleCursorAdapter like that: ListAdapter adapter = new SimpleCursorAdapter( this, R.layout.list_item, mCursor, new String[] { "address", "city" }, new int[] { R.id.address, R.id.zip_city }); this.setListAdapter(adapter); But now, I put everything in a multidimensional array like that: if(mCursor.isFirst()) { //create a new array String[][] listData = new String[mCursor.getCount()][3]; int i = 0; do { listData[i] = new String[] { mCursor.getString(mCursor.getColumnIndex("address")), mCursor.getString(mCursor.getColumnIndex("zip")) + " " + mCursor.getString(mCursor.getColumnIndex("city")), calculateDistance(Double.parseDouble(mCursor.getString(mCursor.getColumnIndex("diff")))) }; i++; } while(mCursor.moveToNext()); } So my problem is now, I have no idea how to put this to my ListView. Could someone help me here? Sorry for my bad english and Java knowledge. :)

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• How to change line thickness in iText? (iText is Java pdf framework)

  - by drasto

  I'm drawing images to pdf using Java framework iText. I need to draw lines of specified width. There is a method setLineWidth(float width) in class PdfContentByte that should change it. However no matter what value I pass as its parameter the lines drawn are always extra thin. There is following line in javadoc of setLineWidth: The line width specifies the thickness of the line used to stroke a path and is measured in user space units. I don't know what is "space unit". Everything else in iText seems to be measured in point(around 1/72 inch). I cant find any reference to what are those "space units" and how to change them. code: to.setLineWidth(thickness); to.moveTo(x, y); to.lineTo(x + 100, y + 100);

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• Make a connection to a HTTPS server from Java and ignore the validity of the security certificate

  - by justinhj

  I've been testing some that works with a bunch of https servers with different keys, some of which are invalid and all of them are not in the local key store for my JVM. I am really only testing things out, so I don't care about the security at this stage. Is there a good way to make POST calls to the server and tell Java not to worry about the security certificates? My google searches for this have brought up some code examples that make a class to do the validation, that always works, but I cannot get it to connect to any of the servers.

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• Any simple Java way to pass parts of a hashmap to another hashmap?

  - by Arvanem

  Hi folks, For my trading program, a Merchant object has a qualities HashMap of enumerated Qualities with Boolean values. public class Merchants { private Map<Qualities, Boolean> qualities = new HashMap<Qualities, Boolean>(); I would like to give each Merchant object a further ratedQualities HashMap of True Qualities with Byte or Integer values representing the Rating of those Qualities. For example, a given Merchant could have a "1" Rating associated with their True Stockbroking Quality. The problem is Java does not let me do this easily. The following code demonstrates my intentions but doesn't compile: private Map<qualities-TRUE, Byte> ratedQualities = new HashMap<qualities-TRUE, Byte>(); According to this link text one solution is to create a Wrapper for the qualities HashMap. Is this the only solution or is there a better way? Thanks in advance for your help.

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• Which containers / graphics components to use in a simple Java Swing game?

  - by rize

  I'm creating a simple labyrinth game with Java + Swing. The game draws a randomized labyrinth on the screen, places a figure in the middle, and the player is then supposed to find the way out by moving the figure with arrow-keys. As for now, I'm using a plain background and drawing the walls of the labyrinth with Graphics.drawLine(). I have a custom picture of the figure in a .gif file, which I load as a BufferedImage object. However, I want the player to see only part of the labyrinth at a time, and the screen should follow the figure in the game, as the player moves around. I'm planning to do this by creating an Image object of the whole labyrinth when it is created, and then "cutting" a square around the current position of the figure and displaying this with Graphics.drawImage(). I'm new with Swing though, and I can't figure out how to draw the figure at different positions "above" the labyrinth without redrawing the whole thing. Which container/component should I use for the labyrinth and then for the figure to achieve this?

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• How to efficiently manage files on a filesystem in Java?

  - by Tuukka Mustonen

  I am creating a few JAX-WS endpoints, for which I want to save the received and sent messages for later inspection. To do this, I am planning to save the messages (XML files) into filesystem, in some sensible hierarchy. There will be hundreds, even thousands of files per day. I also need to store metadata for each file. I am considering to put the metadata (just a couple of fields) into database table, but the XML file content itself into files in a filesystem in order not to bloat the database with content data (that is seldomly read). Is there some simple library that helps me in saving, loading, deleting etc. the files? It's not that tricky to implement it myself, but I wonder if there are existing solutions? Just a simple library that already provides easy access to filesystem (preferrably over different operating systems). Or do I even need that, should I just go with raw/custom Java?

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• URL valid characters. java to validate.

  - by Chez

  a string like: 'www.test.com' is good. a string like: 'www.888.com' is good. a string like: 'stackoverflow.com' is good. a string like: 'GOoGle.Com' is good. why ? because those are valid urls. it does not necessarely matter if they have been registered or not. now bad strings are: 'goog*d\x' 'manydots...com' why because you can't register those urls. if I have a string in java which is supposed to be a good url what's the best way to validate it ? thanks a lot

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• Why does A* path finding sometimes go in straight lines and sometimes diagonals? (Java)

  - by Relequestual

  I'm in the process of developing a simple 2d grid based sim game, and have fully functional path finding. I used the answer found in my previous question as my basis for implementing A* path finding. (http://stackoverflow.com/questions/735523/pathfinding-2d-java-game). To show you really what I'm asking, I need to show you this video screen capture that I made. I was just testing to see how the person would move to a location and back again, and this was the result... http://www.screenjelly.com/watch/Bd7d7pObyFo Different choice of path depending on the direction, an unexpected result. Any ideas?

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• How to send a Timestamp field to Oracle stored proc. from Java despite the DB config?

  - by Alfabravo

  I'm making a request from a java webapp to an Oracle' stored procedure which happens to have a Timestamp IN parameter. In the testing environment, it works sending: SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yyyy hh:mm:ss a"); input.setTimestampField(dateFormat.format(new Date())); But in the production environment, it raises an exception ORA-01830: date format picture ends before converting entire input string. I know the testing environment should be a replica of the production site, but it is not in my hands to set them properly. And I need to send the Timestamp field despite the way they setup the database. Any ideas? Thanks in advance.

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• Why does Java Logging API create so many files?

  - by rgksugan

  I am using java logging api to log errors in my exception. I am writing these errors to a log file. When i run my program i find a lot of files created.There are around 50 files created. Is there any mistake in my code or is it normal? Here goes the code try { logger = Logger.getLogger(Reciever.class.getName()); fileHandler = new FileHandler("Applicationlog.log", true); logger.addHandler(fileHandler); logger.setLevel(Level.ALL); SimpleFormatter formatter = new SimpleFormatter(); fileHandler.setFormatter(formatter); } catch (IOException ex) { logger.log(Level.SEVERE, null, ex); } catch (SecurityException ex) { logger.log(Level.SEVERE, null, ex); }

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• How to deal with databases for websites written in Java, more specifically Wicket?

  - by John

  Hi there. I'm new to website development using Java but I've got started with Wicket and make a little website. I'd like to expand on what I've already made (a website with a form, labels and links) and implement database connectivity. I've looked at a couple of examples, in example Mystic Paste, and I see that they're using Hibernate and Spring. I've never touched Hibernate or Spring before and to be honest the heavy use of annotations scare me a little bit as I haven't really made use of them before, with the exception of supressing warnings and overriding. At this point I have one Connection object which I set up in the WebApplication class upon initialization. I then retrieve this connection object whenever I need to perform queries. I don't know if this is a bad approach or not for a production web application. All help is greatly appreciated.

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• Code understanding, reverse engineering, best concepts and tools. Java.

  - by core07

  One of most demanding tasks for any programmer, architect is understanding other's code. E.g. I am contractor, hired to rescue some project very quickly. Fix bugs, plan global refactoring and therefore I need most efficient way to understand the code. What is the list of concepts, their priority and best tools for this? Of what I know: reverse code engineering to create object models (creating of diagram per package is not so convenient), create sequence diagrams (the tool connects in debug mode to the system and generates diagrams from runtime). Some visualizing techniques, using some tools to work not just with .java but also with e.g. JPA implementors like Hibernate. Generate diagram for not all the codebase, but add some class and then classes used by it. Is Sparx Enterprise Architect state of the art in reverse engineering or far from that. Any other better tools? Ideally would be that tool makes me understand the code as if I wrote it myself :)

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• Which SOA architecture is most appropriate for a Java application?

  - by Robert Greiner

  I am currently working on a pretty large Java 6 application where we are looking to split some of our functionality out into a service oriented architecture. It seems that the primary SOA framework for the application space is OSGi and I have been looking into Felix and Knopplerfish but I wanted to make sure that this isn't my only option. Does it make sense to use an actual web service protocol for our application like SOAP, even though we are not building a web app? Is this even acceptable? Have any of you used an implementation of OSGi (Felix, etc.) with your desktop application? if so, how did it go? Do you know of anything better? We're all pretty new to SOA here so any help would be greatly appreciated.

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• Java Annotations - Is there any helper library to read/process annotations?

  - by mjlee

  I start to use Java annotations heavily. One example is taking method with annotations and converting them into 'telnet'-based command-line command. I do this by parsing annotations and hook into jopt option parser. However, I do a lot of these manually. For example, Method parameter annotation processing.. Method method = ... //; Class[] parameters = method.getParamterTypes(); Annotation[][] annotations = method.getparamterAnnotations(); for( int i = 0; i < parameters.length; i++ ) { // iterate through the annotation , see if each param has specific annotation ,etc. } It is very redundant and tedious. Is there any opensource project that help processing Annotations?

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