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  • Why am I getting a Java NoSuchPortException when the port exists?

    - by user258526
    Got the following production code below, I'm using it for a new driver. portName is COM4 and this port exists on the PC (and I can connect to it with hyperterminal), so why does Javacomm throw a NoSuchPortException? COM4 shows up fine in device mgr. too final String portName = getSerialPort(); try { final CommPortIdentifier id = CommPortIdentifier.getPortIdentifier(portName); port = (SerialPort) id.open(getName(), 1000); } catch (NoSuchPortException nspe) { report(SeverityCode.LEVEL2, getName(), "PIN Pad is not connected to " + portName + " port, or the port does not exist."); return; } catch (PortInUseException piue) { report(SeverityCode.LEVEL2, getName(), portName + " port is already in-use by some other device. Reason: " + piue.getMessage()); return; }

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  • How to encrypt a RSAKey using another RSAKey?

    - by Tom Brito
    I know its not the usual thing to do. But the specification I'm implementing is discribed this way, and I cannot run out. I was trying to encrypt the modulus and exponent of the private key, but the following test code raises an exception because the byte array is 1 byte larger then the maximum allowed by RSA block: import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import javax.crypto.Cipher; import org.apache.commons.lang.ArrayUtils; public class TEST { public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, NoSuchProviderException { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(1024); return keyPairGenerator.generateKeyPair(); } public static void main(String[] args) throws Exception { KeyPair keyPair = generateKeyPair(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); System.out.println("Priv modulus len = " + privateKey.getModulus().bitLength()); System.out.println("Priv exponent len = " + privateKey.getPrivateExponent().bitLength()); System.out.println("Priv modulus toByteArray len = " + privateKey.getModulus().toByteArray().length); byte[] byteArray = privateKey.getModulus().toByteArray(); // the byte at index 0 have no value (in every generation it is always zero) byteArray = ArrayUtils.subarray(byteArray, 1, byteArray.length); System.out.println("byteArray size: " + byteArray.length); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); Cipher cipher = Cipher.getInstance("RSA", "BC"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); byte[] encryptedBytes = cipher.doFinal(byteArray); System.out.println("Success!"); } } (obs. its just a test, i would never encrypt the private key with its pair public key) The byte array is 128 bytes, the exactly maximum allowed by a RSA block, so why the exception? And how to fix it?

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  • Is this use of PreparedStatements in a Thread in JAVA correct?

    - by Gormcito
    I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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  • How to access a subset of XML data in Java when the XML data is too large to fit in memory?

    - by Michael Jones
    What I would really like is a streaming API that works sort of like StAX, and sort of like DOM/JDom. It would be streaming in the sense that it would be very lazy and not read things in until needed. It would also be streaming in the sense that it would read everything forwards (but not backwards). Here's what code that used such an API would look like. URL url = ... XMLStream xml = XXXFactory(url.inputStream()) ; // process each <book> element in this document. // the <book> element may have subnodes. // You get a DOM/JDOM like tree rooted at the next <book>. while (xml.hasContent()) { XMLElement book = xml.getNextElement("book"); processBook(book); } Does anything like this exist?

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  • Is it possible to get Java fmt messages bundle from database ?

    - by newbie
    I nedd to localize application and now files are loaded from text files. Is it possible to change source to database? This is how localized messages are now loaded: <!-- Application Message Bundle --> <bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource"> <property name="basename" value="/WEB-INF/messages/messages" /> <property name="cacheSeconds" value="0" /> </bean>

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  • How to check if String value is Boolean type in Java?

    - by Ragnar
    I did a little search on this but couldn't find anything useful. The point being that if String value is either "true" or "false" the return value should be true. In every other value it should be false. I tried these: String value = "false"; System.out.println("test1: " + Boolean.parseBoolean(value)); System.out.println("test2: " + Boolean.valueOf(value)); System.out.println("test3: " + Boolean.getBoolean(value)); All functions returned false :(

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  • How to implement event listener in background of the main program in java?

    - by Johny
    Hi im a beginner so sorry for my question if it sounds naive. I want to implement a thread that runs in the background and listens all the time. By listening i mean, say it keeps check on a value returned from main thread and if the vaue exceeds certain figure, it executes some method, or say exits the program. If you could give me some idea or at least refer me to something useful, that'll be great.

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  • Convert bit vector (array of booleans) to an integer, and integer to bit vector, in Java.

    - by dreeves
    What's the best way to unstub the following functions? // Convert a bit-vector to an integer. int bitvec2int(boolean[] b) { [CODE HERE] } // Convert an integer x to an n-element bit-vector. boolean[] int2bitvec(int x, int n) { [CODE HERE] } Or is there a better way to do that sort of thing than passing boolean arrays around? This comes up in an Android app where we need an array of 20 booleans to persist and the easiest way to do that is to write an integer or string to the key-value store. I'll post the way we (Bee and I) wrote the above as an answer. Thanks!

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  • How to ensure consistency of enums in Java serialization?

    - by Uri
    When I serialize an object, I can use the serialVersionUID mechanism at the class level to ensure the compatibility of the two types. However, what happens when I serialize fields of enum values? Is there a way to ensure that the enum type has not been manipulated between serialization and deserialization? Suppose that I have an enum like OperationResult {SUCCESS, FAIL}, and a field called "result" in an object that is being serialized. How do I ensure, when the object is deserialized, that result is still correct even if someone maliciously reversed the two? (Suppose the enum is declared elsewhere as a static enum) I am wondering out of curiosity - I use jar-level authentication to prevent manipulation.

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  • Is it compulsory to learn about Data Structures if you want to be a Java/C++ programmer ?

    - by happysoul
    So do I like really need to learn about them ? Isn't there an interesting way to learn about stacks, linked lists, heaps ,etc ? I found it a boring subject. **While posting this question it showed some warning.Am I not allowed to post such a question ? Admins please clarify and I will delete it :/ Warning :: The question you're asking appears subjective and is likely to be closed.

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  • Java: most efficient way to defensively copy an int[]?

    - by Jason S
    I have an interface DataSeries with a method int[] getRawData(); For various reasons (primarily because I'm using this with MATLAB, and MATLAB handles int[] well) I need to return an array rather than a List. I don't want my implementing classes to return the int[] array because it is mutable. What is the most efficient way to copy an int[] array (sizes in the 1000-1000000 length range) ? Is it clone()?

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  • Is it guaranteed that new Integer(i) == i in Java?

    - by polygenelubricants
    Consider the following snippet: int i = 99999999; byte b = 99; short s = 9999; Integer ii = Integer.valueOf(9); // should be within cache System.out.println(new Integer(i) == i); // "true" System.out.println(new Integer(b) == b); // "true" System.out.println(new Integer(s) == s); // "true" System.out.println(new Integer(ii) == ii); // "false" It's obvious why the last line will ALWAYS prints "false": we're using == reference identity comparison, and a new object will NEVER be == to an already existing object. The question is about the first 3 lines: are those comparisons guaranteed to be on the primitive int, with the Integer auto-unboxed? Are there cases where the primitive would be auto-boxed instead, and reference identity comparisons are performed? (which would all then be false!)

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  • In Java, can a final field be initialized from a constructor helper?

    - by csj
    I have a final non-static member: private final HashMap<String,String> myMap; I would like to initialize it using a method called by the constructor. Since myMap is final, my "helper" method is unable to initialize it directly. Of course I have options: I could implement the myMap initialization code directly in the constructor. MyConstructor (String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... // other initialization stuff unrelated to myMap } I could have my helper method build the HashMap, return it to the constructor, and have the constructor then assign the object to myMap. MyConstructor (String someThingNecessary) { myMap = InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } private HashMap<String,String> InitializeMyMap(String someThingNecessary) { HashMap<String,String> initializedMap = new HashMap<String,String>(); initializedMap.put("blah","blahblah"); // etc... return initializedMap; } Method #2 is fine, however, I'm wondering if there's some way I could allow the helper method to directly manipulate myMap. Perhaps a modifier that indicates it can only be called by the constructor? MyConstructor (String someThingNecessary) { InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } // helper doesn't work since it can't modify a final member private void InitializeMyMap(String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... }

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  • JAVA : How to get the positions of all matches in a String?

    - by user692704
    I have a text document and a query (the query could be more than one word). I want to find the position of all occurrences of the query in the document. I thought of the documentText.indexOf(query) and using regular expression but I could not make it work. I end up with the following method: First, I have create a dataType called QueryOccurrence public class QueryOccurrence implements Serializable{ public QueryOccurrence(){} private int start; private int end; public QueryOccurrence(int nameStart,int nameEnd,String nameText){ start=nameStart; end=nameEnd; } public int getStart(){ return start; } public int getEnd(){ return end; } public void SetStart(int i){ start=i; } public void SetEnd(int i){ end=i; } } Then, I have used this datatype in the following method: public static List<QueryOccurrence>FindQueryPositions(String documentText, String query){ // Normalize do the following: lower case, trim, and remove punctuation String normalizedQuery = Normalize.Normalize(query); String normalizedDocument = Normalize.Normalize(documentText); String[] documentWords = normalizedDocument.split(" ");; String[] queryArray = normalizedQuery.split(" "); List<QueryOccurrence> foundQueries = new ArrayList(); QueryOccurrence foundQuery = new QueryOccurrence(); int index = 0; for (String word : documentWords) { if (word.equals(queryArray[0])){ foundQuery.SetStart(index); } if (word.equals(queryArray[queryArray.length-1])){ foundQuery.SetEnd(index); if((foundQuery.End()-foundQuery.Start())+1==queryArray.length){ //add the found query to the list foundQueries.add(foundQuery); //flush the foundQuery variable to use it again foundQuery= new QueryOccurrence(); } } index++; } return foundQueries; } This method return a list of all occurrence of the query in the document each one with its position. Could you suggest any easer and faster way to accomplish this task. Thanks

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