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  • How to prompt a streamed file for downloading in Java / Tomcat

    - by Clem
    Hello, I'm creating a java web application runing on a Tomcat server. One of the functions fill in a StringBuffer variable with data. At the end, I would like to propose the user to download the generated content packaged in a text file. This without having to store the file on the server. I've been searching for a code snippet but couldn't find anything corresponding ... I hope I've been clear enough on my problem. Thanks in advance,

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  • Why Java interfaces can't have constructors?

    - by AndrejaKo
    This question showed up on my mid-term exams and I've been searching for correct answer for some time. I know that Java interfaces can't be directly instantiated so they don't need constructors and that they can have only public static final attributes so they don't need constructors to set them up but that's not the expected answer.

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  • hardware detail using Java

    - by Anup Prakash
    I want to make a java application software which give the current status/information of the running computer. So, for this, is there any inbuilt/extrnal library present or not? Can anyone give a simple code which will just. "What is the current status of laptop battery?" or "Is AC adapter is pluged in or not?" Please help me.

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  • Java configuration framework

    - by Steen
    I'm in the process of weeding out all hardcoded values in a java library and was wondering what framework would be the best (in terms of zero- or close-to-zero configuration) to handle run-time configuration? I would prefer xml-based config-files, but it's not essential. Please do only reply if you have practical experience with a framework. I'm not looking for examples, but experience... Thanks for taking the time.

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  • Java. Best procedure to de-serialize a Java generic object?

    - by Jake
    What is the best procedure for storing and retrieving, using native Java serialization, generic objects like ArrayList<String>? Edit: To clarify. When I serialize an object of type ArrayList<String> I'd like to de-serialize to the same type of object. However, I know of no way to cast back to this generic object without causing warnings.

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  • Java GUI libraries

    - by Dan
    I have been working with the Swing library for a long time, I'm working on a new project for school and due to the nature of the program it can't look like a generic/boring swing gui. So my question is does anyone know of an interesting java gui library that is not swing or awt?

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  • java array manipulation

    - by sachin
    Hi, I'm a beginner in java. I want the logic of the small program. I have two arrays array = {a1,a2,a3,a4,a5,,,,,,,,,an} and array2 = {b1,b2,b3,b4,,,,,,,,,,,bn} I want string as: a1b1,a2a3b2b3,a4a5a6b4b5b6,..........an Please tell me what will be the logic.

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  • Java FilePath Android

    - by user654460
    I have an android app that I am trying to get a file path for a SAX parser. I have the following structure: assets:(Where my xml file is) src(same level as assets) com msi androidrss(The calling java file is in here) I tried several variations of this: InputSource is = new InputSource("file://../../../../assets/Rss.xml"); But I always get a FNF Exception Any suggestions? Thanks

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  • StringBuffer wont read whole stream into a string (JAVA/Android)

    - by Levara
    Hi all! I'm making an android program that retrieves content of a webpage using HttpURLConnection. I'm new to both Java and Android. Problem is: Reader reads whole page source, but in the last while iteration it doesn't append to stringBuffer that last part. Using debbuger I have determined that, in the last loop iteration, string buff is created, but stringBuffer just doesnt append it. I need to parse retrieved content. Is there any better way to handle the content for parsing than using strings. I've read on numerous other sites that string size in Java is limited only by available heap size. I've tried with StringBuilder too. Anyone know what could be the problem. Btw feel free to suggest any improvements to the code. Thanks! URL u; try { u = new URL("http://feeds.timesonline.co.uk/c/32313/f/440134/index.rss"); HttpURLConnection c = (HttpURLConnection) u.openConnection(); c.setRequestProperty("User-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; InfoPath.1; .NET CLR 2.0.50727)"); c.setRequestMethod("GET"); c.setDoOutput(true); c.setReadTimeout(3000); c.connect(); StringBuffer stringBuffer = new StringBuffer(""); InputStream in = c.getInputStream(); InputStreamReader inp = new InputStreamReader(in); BufferedReader reader = new BufferedReader(inp); char[] buffer = new char[3072]; int len1 = 0; while ( (len1 = reader.read(buffer)) != -1 ) { String buff = new String(buffer,0,len1); stringBuffer.append(buff); } String stranica = new String(stringBuffer); c.disconnect(); reader.close(); inp.close(); in.close();

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  • MVC design in Cocoa - are all 3 always necessary? Also: naming conventions, where to put Controller

    - by Nektarios
    I'm new to MVC although I've read a lot of papers and information on the web. I know it's somewhat ambiguous and there are many different interpretations of MVC patterns.. but the differences seem somewhat minimal My main question is - are M, V, and C always going to be necessary to be doing this right? I haven't seen anyone address this in anything I've read. Examples (I'm working in Cocoa/Obj-c although that shouldn't much matter).. 1) If I have a simple image on my GUI, or a text entry field that is just for a user's convenience and isn't saved or modified, these both would be V (view) but there's no M (no data and no domain processing going on), and no C to bridge them. So I just have some aspects that are "V" - seems fine 2) I have 2 different and visible windows that each have a button on them labeled as "ACTIVATE FOO" - when a user clicks the button on either, both buttons press in and change to say "DEACTIVATE FOO" and a third window appears with label "FOO". Clicking the button again will change the button on both windows to "ACTIVATE FOO" and will remove the third "FOO" window. In this case, my V consists of the buttons on both windows, and I guess also the third window (maybe all 3 windows). I definitely have a C, my Controller object will know about these buttons and windows and will get their clicks and hold generic states regarding windows and buttons. However, whether I have 1 button or 10 button, my window is called "FOO" or my window is called "BAR", this doesn't matter. There's no domain knowledge or data here - just control of views. So in this example, I really have "V" and "C" but no "M" - is that ok? 3) Final example, which I am running in to the most. I have a text entry field as my View. When I enter text in this, say a number representing gravity, I keep it in a Model that may do things like compute physics of a ball while taking in to account my gravity parameter. Here I have a V and an M, but I don't understand why I would need to add a C - a controller would just accept the signals from the View and pass it along to the Model, and vice versa. Being as the C is just a pure passthrough, it's really "junk" code and isn't making things any more reusable in my opinion. In most situations, when something changes I will need to change the C and M both in nearly identical ways. I realize it's probably an MVC beginner's mistake to think most situations call for only V and M.. leads me in to next subject 4) In Cocoa / Xcode / IB, I guess my Controllers should always be an instantiated object in IB? That is, I lay all of my "V" components in IB, and for each collection of View objects (things that are related) I should have an instantiated Controller? And then perhaps my Models should NOT be found in IB, and instead only found as classes in Xcode that tie in with Controller code found there. Is this accurate? This could explain why you'd have a Controller that is not really adding value - because you are keeping consistent.. 5) What about naming these things - for my above example about FOO / BAR maybe something that ends in Controller would be the C, like FancyWindowOpeningController, etc? And for models - should I suffix them with like GravityBallPhysicsModel etc, or should I just name those whatever I like? I haven't seen enough code to know what's out there in the wild and I want to get on the right track early on Thank you in advance for setting me straight or letting me know I'm on the right track. I feel like I'm starting to get it and most of what I say here makes sense, but validation of my guessing would help me feel confident..

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  • Simple RSA encryption (Java)

    - by jake blue
    This is simply for fun. This will not be used for any actual encryption. I'm only first year comp sci student and love cryptography. This took a long time to get working. At approximately N = 18, it begins breaking down. It won't encrypt messages properly after that point. I'm not sure why. Any insights? I'd also appreciate any links you could provide me to tutorials or interesting reading about Cryptography. import java.math.BigInteger; import java.security.SecureRandom; /** * Cryptography. * * Generates public and private keys used in encryption and * decryption * */ public class RSA { private final static BigInteger one = new BigInteger("1"); private final static SecureRandom random = new SecureRandom(); // prime numbers private BigInteger p; private BigInteger q; // modulus private BigInteger n; // totient private BigInteger t; // public key private BigInteger e; // private key private BigInteger d; private String cipherText; /** * Constructor for objects of class RSA */ public RSA(int N) { p = BigInteger.probablePrime(N/2, random); q = BigInteger.probablePrime(N/2, random); // initialising modulus n = p.multiply(q); // initialising t by euclid's totient function (p-1)(q-1) t = (p.subtract(one)).multiply(q.subtract(one)); // initialising public key ~ 65537 is common public key e = new BigInteger("65537"); } public int generatePrivateKey() { d = e.modInverse(t); return d.intValue(); } public String encrypt(String plainText) { String encrypted = ""; int j = 0; for(int i = 0; i < plainText.length(); i++){ char m = plainText.charAt(i); BigInteger bi1 = BigInteger.valueOf(m); BigInteger bi2 = bi1.modPow(e, n); j = bi2.intValue(); m = (char) j; encrypted += m; } cipherText = encrypted; return encrypted; } public String decrypt() { String decrypted = ""; int j = 0; for(int i = 0; i < cipherText.length(); i++){ char c = cipherText.charAt(i); BigInteger bi1 = BigInteger.valueOf(c); BigInteger bi2 = bi1.modPow(d, n); j = bi2.intValue(); c = (char) j; decrypted += c; } return decrypted; } }

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  • How to import your own non-packaged Java classes in Jython

    - by thepandaatemyface
    I know in Jython you can do import java.util.Random as Random Random().nextInt() But if I have a class I wrote myself, how can I import it into Jython without putting the class itself in a package? If I have a testclass Test: public class Test { public void foo() { System.out.println("bar"); } } that's not inside a package. Can I even import that into jython by using something along the lines offrom Test import Test?

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  • Get query from java.sql.PreparedStatement

    - by llm
    In my code I am using java.sql.PreparedStatement. I then execute the setString() method to populate the wildcards of the prepared statement. Is there a way for me to retrieve (and print out) the final query before the executeQuery() method is called and the query is executed? I Just want this for debugging purposes. Thanks.

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  • Java for a C programmer?

    - by Brian
    Hi, I have a lot of experience in C and Python, but I'd like to pick up some Java. I was curious if there was a "quick and dirty" guide tailored for people with previous CS background. I'd prefer free online resources but appreciate any suggestion. Thanks, Brian

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  • add more than 30 days with Calendar's add() method in Java

    - by Haes
    Hi, I'm not quite sure what field to use when adding more than 30 days to a Java Calendar object. Is there any difference in between Calendar.DAY_OF_MONTH and Calendar.DAY_OF_YEAR? Example: GregorianCalendar d = new GregorianCalendar(); d.add(Calendar.DAY_OF_YEAR, 90); vs GregorianCalendar d = new GregorianCalendar(); d.add(Calendar.DAY_OF_MONTH, 90); Thanks.

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  • DB2 AS400 Java function always returns same value

    - by Nimrod Shory
    Hello, I am writing a user defined function to DB2 on AS/400 in Java and the strangest thing happen.. I am always getting the same result from the function even when i am changing it, even if i am dropping it and create it again and even when i specify NOT DETERMINISTIC.. Does any one have ever encountered a behavior like that?

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