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  • Java - short and casting

    - by chr1s
    Hi all, I have the following code snippet. public static void main(String[] args) { short a = 4; short b = 5; short c = 5 + 4; short d = a; short e = a + b; // does not compile (expression treated as int) short z = 32767; short z_ = 32768; // does not compile (out of range) test(a); test(7); // does not compile (not applicable for arg int) } public static void test(short x) { } Is the following summary correct (with regard to only the example above using short)? direct initializations without casting is only possible using literals or single variables (as long as the value is in the range of the declared type) if the rhs of an assignment deals with expressions using variables, casting is necessary But why exactly do I need to cast the argument of the second method call taking into account the previous summary?

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  • Encrypted AES key too large to Decrypt with RSA (Java)

    - by Petey B
    Hello, I am trying to make a program that Encrypts data using AES, then encrypts the AES key with RSA, and then decrypt. However, once i encrypt the AES key it comes out to 128 bytes. RSA will only allow me to decrypt 117 bytes or less, so when i go to decrypt the AES key it throws an error. Relavent code: KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); kpg.initialize(1024); KeyPair kpa = kpg.genKeyPair(); pubKey = kpa.getPublic(); privKey = kpa.getPrivate(); updateText("Private Key: " +privKey +"\n\nPublic Key: " +pubKey); updateText("Encrypting " +infile); //Genereate aes key KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192/256 SecretKey aeskey = kgen.generateKey(); byte[] raw = aeskey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); updateText("Encrypting data with AES"); //encrypt data with AES key Cipher aesCipher = Cipher.getInstance("AES"); aesCipher.init(Cipher.ENCRYPT_MODE, skeySpec); SealedObject aesEncryptedData = new SealedObject(infile, aesCipher); updateText("Encrypting AES key with RSA"); //encrypt AES key with RSA Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] encryptedAesKey = cipher.doFinal(raw); updateText("Decrypting AES key with RSA. Encrypted AES key length: " +encryptedAesKey.length); //decrypt AES key with RSA Cipher decipher = Cipher.getInstance("RSA"); decipher.init(Cipher.DECRYPT_MODE, privKey); byte[] decryptedRaw = cipher.doFinal(encryptedAesKey); //error thrown here because encryptedAesKey is 128 bytes SecretKeySpec decryptedSecKey = new SecretKeySpec(decryptedRaw, "AES"); updateText("Decrypting data with AES"); //decrypt data with AES key Cipher decipherAES = Cipher.getInstance("AES"); decipherAES.init(Cipher.DECRYPT_MODE, decryptedSecKey); String decryptedText = (String) aesEncryptedData.getObject(decipherAES); updateText("Decrypted Text: " +decryptedText); Any idea on how to get around this?

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  • Java Audit table logging, MySQL equivalent of CONTEXT_INFO.

    - by Julia
    Hi, I am looking for the MySQL equivalent of CONTEXT_INFO that is present in SQL Server. Or any other session variable like thing using which I can pass the username to the trigger. I am currently working on logging table data for audit. I need to pass the username of the logged in user to the delete trigger. Any ideas? We are deleting the rows from the table in a few cases and marking them as deleted in others. Any alternate solutions are welcome. I thought of using AOP but it could prove problematic when deleting a cascade. I want to look into Hibernate Interceptors, not sure at this point if that works. If I can find the MySQL equivalent of CONTEXT_INFO, my job is done and elegant as well. Thanks, Julia.

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  • java Regular expression matching html

    - by user121196
    I want to match and capture the enclosing content of the <pre></pre> tag tried the following, not working, what's wrong? String p="<pre>.*</pre>"; Matcher m=Pattern.compile(p,Pattern.MULTILINE|Pattern.CASE_INSENSITIVE).matcher(input); if(m.find()){ String g=m.group(0); System.out.println("g is "+g); }

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  • java.lang.NoSuchMethodError: main when starting HelloWorld with Eclipse Scala plugin

    - by Matt Sheppard
    I've just been playing with Scala, and installed the Eclipse plugin as described at http://www.scala-lang.org/node/94, but after entering the "Hello World" test example and setting up the run configuration as described, I get the following error Exception in thread "main" java.lang.NoSuchMethodError: main For reference the code is package hello object HelloWorld extends Application { println("Hello World!") } I've tinkered a bit with the obvious solutions (adding a main method, adding a singleton object with a main method) but I'm clearly doing something wrong. Can anyone get their test example to work, or point out what I am doing wrong?

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  • making a java panel fullscreen

    - by clamp
    hello, how would you make a JComponent (panel, frame, window, etc.) fullscreen so that it also overlaps everything on the screen including the windows startbar? i dont want to change the resolution or anything with the graphics device like bitdepth etc, i just want to overlap everything else. thanks!

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  • Java JGraph subgraph

    - by Jeff Storey
    Is there a way to create a subgraph from a full graph in JGraph? When I update the subgraph, I want changes to propagate to the main graph. Does JGraph provide a relatively easy way for doing that out of the box (I couldn't seem to find one...)? thanks, Jeff

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  • Java complex validation in Dropwizard?

    - by miku
    I'd like to accept JSON on an REST endpoint and convert it to the correct type for immediate validation. The endpoint looks like this: @POST public Response createCar(@Valid Car car) { // persist to DB // ... } But there are many subclasses of Car, e.g. Van, SelfDrivingCar, RaceCar, etc. How could I accept the different JSON representations on the endpoint, while keeping the validation code in the Resource as concise as something like @Valid Car car? Again: I send in JSON like (here, it's the representation of a subclass of Car, namely SelfDrivingCar): { "id" : "t1", // every Car has an Id "kind" : "selfdriving", // every Car has a type-hint "max_speed" : "200 mph", // some attribute "ai_provider" : "fastcarsai ltd." // this is SelfDrivingCar-specific } and I'd like the validation machinery look into the kind attribute, create an instance of the appropriate subclass, here e.g. SelfDrivingCar and perform validation. I know I could create different endpoints for all kind of cars, but thats does not seem DRY. And I know that I could use a real Validator instead of the annotation and do it by hand, so I'm just asking if there's some elegant shortcut for this problem.

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  • cryptic error message: Length of Bind host variable exceeds MaxLength

    - by janetsmith
    Hi, I've encountered a cryptic error message thrown by Sybase IQ server. com.sybase.jdbc2.jdbc.SybSQLException: ASA Error -1001019: Function not supported on varchars longer than 255 Length of Bind host variable exceeds MaxLength , -- (df_Heap.cxx 2145) at com.sybase.jdbc2.tds.Tds.processEed(Tds.java:2636) at com.sybase.jdbc2.tds.Tds.nextResult(Tds.java:1996) at com.sybase.jdbc2.jdbc.ResultGetter.nextResult(ResultGetter.java:69) at com.sybase.jdbc2.jdbc.SybStatement.nextResult(SybStatement.java:204) at com.sybase.jdbc2.jdbc.SybStatement.nextResult(SybStatement.java:187) at com.sybase.jdbc2.jdbc.SybStatement.updateLoop(SybStatement.java:1642) at com.sybase.jdbc2.jdbc.SybStatement.executeUpdate(SybStatement.java:1625) at com.sybase.jdbc2.jdbc.SybPreparedStatement.executeUpdate(SybPreparedStatement.java:91) at ibs.dao.CM3RM1DAO.updateToTable(CM3RM1DAO.java:197) at ibs.dao.CM3RM1DAO.isXMLProcessed(CM3RM1DAO.java:88) at ibs.xml.parser.XMLParser.parsingXMLIntoBO(XMLParser.java:2125) at ibs.common.util.MainClass.main(MainClass.java:74) We have several columns (DESCRIPTION etc.) which are of type varchar(4000). However I can update them directly without having any error. And, I don't see any code specifying any bind variables, so I have no idea where the message comes from. This is the code (I've modified it a bit): String sql = "UPDATE TABLEX SET " + "COMPANY = ?, CUSTOMER_REFERENCE= ?, " + "STATUS = ?, CONTACT_FIRST_NAME = ?, CONTACT_LAST_NAME = ?, " + "SEVERITY = ?, PRIORITY_CODE = ?, REQUESTEDDATE = ?, " + "CLOSE_TIME = ?, LEAD_TIME = ?, CHANGE_REASON = ?, MODTIME = ? WHERE NUMBER = ?"; stmt = conn.prepareStatement(sql); for loop here { stmt.setString(...); . . stmt.executeUpdate(); } Any help is appreciated

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  • Java - When to use Iterators?

    - by Walter White
    Hi all, I am trying to better understand when I should and should not use Iterators. To me, whenever I have a potentially large amount of data to iterate through, I write an Iterator for it. If it also lends itself to the Iterator interface, then it seems like a win. I was reading a little bit that there is a lot of overhead with using an Iterator. A good example of where I used an Iterator was to iterate through a bunch of SQL scripts to execute one query at a time, reading it in, then executing it. Is there another performance trade off I should be aware of? Before I used iterators, I would read the entire String of SQL commands to execute into an ArrayList, and the iterate through that. If the import is rather large (like for geolocation data, then the server tends to get bogged down). Walter

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  • Bitwise AND, Bitwise Inclusive OR question, in Java

    - by Dave
    I've a few lines of code within a project, that I can't see the value of... buffer[i] = (currentByte & 0x7F) | (currentByte & 0x80); It reads the filebuffer from a file, stored as bytes, and then transfers then to buffer[i] as shown, but I can't understand what the overall purpose is, any ideas? Thanks

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  • Java (Tomcat): how to configure a cookieless subdomain to serve static content

    - by Webinator
    One of the tip given by both Google and Yahoo! to speed up webpages loading is to configure a cookieless subdomain to server static content. How do you configure a "cookieless subdomain" using Tomcat in standalone mode (this question is not about how to use Apache to serve static content in a cookieless-way, but about how to do it in Tomcat-standalone mode)? Note that I don't care about filters supporting If-Modified-Since nor care about filters supporting gzipping: the static content I'm serving is forever cacheable (or its name will change) and it is already compressed data (so gzip would only slow down the transfer). Do I need two different Tomcat webapps? (one "cookiefull" and one "cookieless") Do I need two different servlets? (as of now I've got only one dispatcher/controller servlet). Why would a "regular" link to, say, a static image be called in a cookiefull way when it would be on the same domain as the main webapp and then be called in a "cookie-less" way when it is on a subdomain? I don't understand exactly what is going on: is it the browser that decides to append or not cookies to the query? If so, why would it not append the cookies to a static query on a "cookieless" subdomain. Any example as to what is going on behind the scene is most welcome :)

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  • Text extraction with java html parsers

    - by zenmonkey
    I want to use an html parser that does the following in a nice, elegant way Extract text (this is most important) Extract links, meta keywords Reconstruct original doc (optional but nice feature to have) From my investigation so far jericho seems to fit. Any other open source libraries you guys would recommend?

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  • Java servlet and UTF-8 problem

    - by Gabriele
    I have some problem with UTF-8. My client (realized in GWT) make a request to my servlet, with some parametres in the URL, as follow: http://localhost:8080/servlet?param=value When in the servlet I retrieve the URL, I have some problem with UTF-8 characters. I use this code: protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); String reqUrl = request.getRequestURL().toString(); String queryString = request.getQueryString(); System.out.println("Request: "+reqUrl + "?" + queryString); ... So, if I call this url: http://localhost:8080/servlet?param=così the result is like this: Request: http://localhost:8080/servlet?param=cos%C3%AC What can I do to set up properly the character encoding?

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  • Java Generics Type Safety warning with recursive Hashmap

    - by GC
    Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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  • Getting Active Session counts with JMX (Java Management Extensions) API

    - by bLee
    I'm trying to use JMX API to get active session counts for a web application. Is it possible to use JMX API to get this kind of information? If yes, how reliable would it be? Any example code on how to get this done? I've been reading JMX tutorial and documentation, but they are giving me the overview of what the technology is. I just can't pinpoint to what I need, yet.

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  • What are some Java memory management best practices?

    - by Ascalonian
    I am taking over some applications from a previous developer. When I run the applications through Eclipse, I see the memory usage and the heap size increase a lot. Upon further investigation, I see that they were creating an object over-and-over in a loop as well as other things. I started to go through and do some clean up. But the more I went through, the more questions I had like "will this actually do anything?" For example, instead of declaring a variable outside the loop mentioned above and just setting its value in the loop... they created the object in the loop. What I mean is: for(int i=0; i < arrayOfStuff.size(); i++) { String something = (String) arrayOfStuff.get(i); ... } versus String something = null; for(int i=0; i < arrayOfStuff.size(); i++) { something = (String) arrayOfStuff.get(i); } Am I incorrect to say that the bottom loop is better? Perhaps I am wrong. Also, what about after the second loop above, I set "something" back to null? Would that clear out some memory? In either case, what are some good memory management best practices I could follow that will help keep my memory usage low in my applications? Update: I appreciate everyones feedback so far. However, I was not really asking about the above loops (although by your advice I did go back to the first loop). I am trying to get some best practices that I can keep an eye out for. Something on the lines of "when you are done using a Collection, clear it out". I just really need to make sure not as much memory is being taken up by these applications.

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  • Java SQL database independence.

    - by Paul
    Hello, I have been looking for an alternative to Hibernate for various reasons. I came across Liquibase and i like the idea so i am willing to try it. Liquibase will cater for database creation/modification in a SQL independent fashion. My main question is how does my code in my application execute SQL statements without being database dependent? Is there some other project that acts like Hibernates Dialect classes? Thanks, Paul

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  • Recursive String Function (Java)

    - by Jake Brooks
    Hi, I am trying to design a function that essentially does as follows: String s = "BLAH"; store the following to an array: blah lah bah blh bla bl ba bh ah al So basically what I did there was subtract each letter from it one at a time. Then subtract a combination of two letters at a time, until there's 2 characters remaining. Store each of these generations in an array. Hopefully this makes sense, Jake

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