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  • Standard Place for an Empty String Array in the JDK

    - by Simon B
    Hi is there a standard place for accessing empty array constants in the JDK 1.5. When I want to do a conversion from a String Collection (e.g. ArrayList)to a String Array I find myself using my own which is defined in my own Constants class: public static final String[] EMPTY_STRING_ARRAY = new String[0]; And then in my client code something like: String[] retVal = myStringList.toArray(Constants.EMPTY_STRING_ARRAY); return retVal; I was wondering if this is the "idiomatic" of doing it or if I'm missing something I get the impression from the brief search I did that this kind of thing is prevalent in many people's code. Any ideas, answers, comment (aside from that I shouldn't really use String Arrays) greatly appreciated, Cheers Simon

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  • how can I convert String to SecretKey

    - by Alaa
    I want to convert String to secretKey public void generateCode(String keyStr){ KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192 and 256 bits may not be available // Generate the secret key specs. secretKey skey=keyStr; //How can I make the casting here //SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); } I try to use BASE64Decoder instead of secretKey, but I face a porblem which is I cannot specify key length. EDIT: I want to call this function from another place static public String encrypt(String message , String key , int keyLength) throws Exception { // Get the KeyGenerator KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(keyLength); // 192 and 256 bits may not be available // Generate the secret key specs. //decode the BASE64 coded message SecretKey skey = key; //here is the error raw = skey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); // Instantiate the cipher Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); System.out.println("msg is" + message + "\n raw is" + raw); byte[] encrypted = cipher.doFinal(message.getBytes()); String cryptedValue = new String(encrypted); System.out.println("encrypted string: " + cryptedValue); return cryptedValue; } Any one can help, i'll be very thankful.

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  • Eclipse RCP: Actions VS Commands

    - by Dot
    Hi, What are differences between Actions and Commands in the context of Eclipse RCP? I know that they both contribute to the menu entries, but which one is better? And why? Of all the online resources I read, I could not get a firm understanding of the differences between both. I have not actually tried to use them, but just wanted to understand them to start with from higher level point of view. Thanks

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  • Restlet/Jackson works differently when object implements Serializable

    - by ravyoli
    I am sending an object with some primitive fields using Restlet with Jackson converter. Up until now it worked great. But then I needed my object to implement Serializable, because I need to store it in memcache of GAE. For some reason - when the class implements Serializable, things stop working. Restlet sends a different string representation from before, and I can't even print that string in the server. I tried printing its byte value, char-by-char and the first numbers are: 0xfffd 0xfffd 0x0000 0x0005 0x0073 0x0072 Thanks a lot!

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  • Counter that will remember it's value

    - by owca
    I have a task to operate on complex number. Each number consists of double r = real part, double i = imaginary part and String name. Name must be set within constructor, so I've created int counter, then I'm sending it's value to setNextName function and get name letter back. Unfortunately incrementing this 'counter' value works only within costructor and then it is once again set to 0. How to deal with that?Some constant value? And second problem is that I also need to provide setNextNames(char c) function that will change the counter current value. The code : public class Imaginary { private double re; private double im; private String real; private String imaginary; private String name; private int counter=0; public Imaginary(double r, double u){ re = r; im = u; name = this.setNextName(counter); counter++; } public static String setNextName(int c){ String nameTab[] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N", "O","P","Q","R","S","T","U","W","V","X","Y","Z"}; String setName = nameTab[c]; System.out.println("c: "+c); return setName; } public static String setNextName(char c){ // //don't know how to deal with this part // }

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  • How to avoid serializing zero values with Simple Xml

    - by Bram Vandenbussche
    I'm trying to serialise an object using simple xml (http://simple.sourceforge.net/). The object setup is pretty simple: @Root(name = "order_history") public class OrderHistory { @Element(name = "id", required = false) public int ID; @Element(name = "id_order_state") public int StateID; @Element(name = "id_order") public int OrderID; } The problem is when I create a new instance of this class without an ID: OrderHistory newhistory = new OrderHistory(); newhistory.OrderID = _orderid; newhistory.StateID = _stateid; and I serialize it via simple xml: StringWriter xml = new StringWriter(); Serializer serializer = new Persister(); serializer.write(newhistory, xml); it still reads 0 in the resulting xml: <?xml version='1.0' encoding='UTF-8'?> <order_history> <id>0</id> <id_order>2</id_order> <id_order_state>8</id_order_state> </order_history> I'm guessing the reason for this is that the ID property is not null, since integers can't be null. But I really need to get rid of this node, and I'd rather not remove it manually. Any clues anyone?

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  • Computing unique index for every poker starting hand

    - by Aly
    As there are 52 cards in a deck we know there are 52 choose 2 = 1326 distinct matchups, however in preflop poker this can be bucketed into 169 different hands such as AK offsuit and AK suited as whether it is A hearts K hearts or A spade K spades it makes no difference preflop. My question is, is there a nice mathematical property in which I can uniquely index each of these 169 hands (from 0 to 168 preferably). I am trying to create a look up table as a double[][] = new double [169][169] but have no way of changing a hand representation such as AKs (an Ace and a King of the same suit) to a unique index in this array.

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  • Python code translation to JVM

    - by jldupont
    Is there such a thing as a "translator" (for lack of a better word in my mind now) that translates Python code directly to JVM / Dalvik bytecode? Would be great for writing Android applications in Python! NOTE: I know about the scripting capabilities of the Android platform but I am looking for something that would generate a '.apk' without having to install the 'scripting' package... annoying for end-users.

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  • JavaFX: Update of ListView if an element of ObservableList changes

    - by user1828169
    I would like to display a list of persons (coded in POJOS, and containing a name and surname property) using a JavaFX ListView control. I created the ListView and added the list of persons as an ObservableList. Everything works fine if I delete or add a new person to the ObservableList, but changes in the POJO do not trigger an update of the ListView. I have to remove and add the modified POJO from the ObservableList to trigger the update of the ListView. Is there any possibility to display changes in POJOS without the workaround described above?

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  • Is an "infinite" iterator bad design?

    - by Adamski
    Is it generally considered bad practice to provide Iterator implementations that are "infinite"; i.e. where calls to hasNext() always(*) return true? Typically I'd say "yes" because the calling code could behave erratically, but in the below implementation hasNext() will return true unless the caller removes all elements from the List that the iterator was initialised with; i.e. there is a termination condition. Do you think this is a legitimate use of Iterator? It doesn't seem to violate the contract although I suppose one could argue it's unintuitive. public class CyclicIterator<T> implements Iterator<T> { private final List<T> l; private Iterator it; public CyclicIterator<T>(List<T> l) { this.l = l; this.it = l.iterator(); } public boolean hasNext() { return !l.isEmpty(); } public T next() { T ret; if (!hasNext()) { throw new NoSuchElementException(); } else if (it.hasNext()) { ret = it.next(); } else { it = l.iterator(); ret = it.next(); } return ret; } public void remove() { it.remove(); } }

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  • getting JSlider bar to move on mouse click event

    - by Aly
    Hi, I have a JSlider which shows bet sizes (for a poker game) I am trying to achieve the effect that when a mouse click occurs the slider jumps forward by a bet amount (i.e. a big blind amount) rather than just incrementing by one. If the mouse click happens to the left of the bar i want it to decrement by a fixed amount else increment. I looked into attaching a mouse listener, but do not know how I can use the event to find out on what side of the bar the mouse was clicked. Any ideas?

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  • Mismatched coordinate systems in LWJGL with Mouse and Textures

    - by Braains
    I'm not really sure how to expand on this other than to say that it appears that my LWJGL seems to have different coordinate systems for the Mouse and for painting Textures. It seems that Textures have the usual Java2D way of putting (0, 0) in the upper-left corner, while the Mouse goes by the more sensible way of having the origin in the lower-left corner. I've checked my code a bunch but I don't see anything modifying the values between where I read them and where I use them. It's thrown me for a loop and I can't quite figure it out. I'll post all the code that involves the Mouse input and Texture painting for you guys to look at. private static void pollHelpers() { while(Mouse.next()) { InputHelper.acceptMouseInput(Mouse.getEventButton(), Mouse.getEventX(), Mouse.getEventY()); } while (Keyboard.next()) { if (Keyboard.getEventKeyState()) { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), true); } else { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), false); } } } public static void acceptMouseInput(int mouseButton, int x, int y) { for(InputHelper ie: InputHelper.instances) { if(ie.checkRectangle(x, y)) { ie.sendMouseInputToParent(mouseButton); } } } private void sendMouseInputToParent(int mouseButton) { parent.onClick(mouseButton); } public boolean checkRectangle(int x, int y) { //y = InputManager.HEIGHT - y; See below for explanation return x > parent.getX() && x < parent.getX() + parent.getWidth() && y > parent.getY() && y < parent.getY() + parent.getHeight(); } I put this line of code in because it temporarily fixed the coordinate system problem. However, I want to have my code to be as independent as possible so I want to remove as much reliance on other classes as possible. These are the only methods that touch the Mouse input, and as far as I can tell none of them change anything so all is good here. Now for the Texture methods: public void draw() { if(!clicked || deactivatedImage == null) { activatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(activatedImage, x, y, width, height); } glEnd(); } else { deactivatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(deactivatedImage, x, y, width, height); } glEnd(); } } public static void drawGLQuad(Texture texture, float x, float y, float width, float height) { glTexCoord2f(x, y); glVertex2f(x, y); glTexCoord2f(x, y + texture.getHeight()); glVertex2f(x, y + height); glTexCoord2f(x + texture.getWidth(), y + texture.getHeight()); glVertex2f(x + width, y +height); glTexCoord2f(x + texture.getWidth(), y); glVertex2f(x + width, y); } I'll be honest, I do not have the faintest clue as to what is really happening in this method but I was able to put it together on my own and get it to work. my guess is that this is where the problem is. Thanks for any help!

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  • JPA - Performance with using multiple entity manager

    - by Nguyen Tuan Linh
    My situation is: The code is not mine I have two kinds of database: one is Dad, one is Son. In Dad, I have a table to store JNDI name. I will look up Dad using JNDI, create entity manager, and retrieve this table. From these retrieved JNDI names, I will create multiple entity managers using multiple Son databases. The problem is: Son have thousands of entities. It takes each Son database around 10 minutes to load all entities. If there is 4 Son databases, it will be 40 minutes. My question: Is there any way to load all entities and use them for all entity manager? Please look at the code below For each Son JNDI: Map<String, String> puSonProperties = new HashMap<String, String>(); puSonProperties.put("javax.persistence.jtaDataSource", sonJndi); EntityManagerFactory emf = Persistence.createEntityManagerFactory("PUSon", puSonProperties); PUSon - All of them use the same persistence unit log.info("Verify entity manager for son: {0} - {1}", sonCode, emSon.find(Son_configuration.class, 0) != null ? "ok" : "failed!"); This is the actual code where the loading of all entities begins. 10 mins.

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  • Highlight field in source code pane of Findbugs UI

    - by Ryan Fernandes
    I'm using a class that extends BytecodeScanningDetector to check for some problematic fields in a class. After detecting whether the field is problematic, I add it to the bug report like below: Once I run findbugs, it identifies the bug, lists it in the left pane, but does not highlight the corresponding source line. Any hints/help on this will be very appreciated. public void visit(Field f) { if (isProblematic(getXField())) { bugReporter.reportBug(new BugInstance(this, tBugType, HIGH_PRIORITY) .addClass(currentClass) //from visit(JavaClass) .addField(this)); } } public void visit(JavaClass someObj) { currentClass = someObj.getClassName(); } P.S. I tried posting this on the findbugs list but... no joy.

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  • How mature is apache sshd (MINA)?

    - by Yaneeve
    Has anyone ever used apache sshd (based on Apache MINA)? I would like to get some user input. Is it mature? Does it have (annoying) bugs? How is the API? Can useful documentation/tutorials be found? etc. Thanks all for your feedback.

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  • Why do transfer objects need to implement Serializable?

    - by smaye81
    I realized today that I have blindly just followed this requirement for years without ever really asking why. Today, I ran across a NotSerializableException with a model object I created from scratch and I realized enough is enough. I was told this was because of session replication between load-balanced servers, but I know I've seen other objects at session scope that do not implement Serializable. Is this the real reason?

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  • What's in an Eclipse .classpath/.project file?

    - by totalEclipse
    We recently had an issue with an Eclipse project for one of our team members. Tomcat was not deploying JARs of the application. We eventually noticed the .classpath Eclipse file was not the same as for the team members where the project was OK. We replaced the .classpath file with one from a project that was OK and the Tomcat deploy was complete. Just out of curiosity and to know at what to look in the future if something is wrong, what is inside the .classpath and .project files. What can I add in there, what does it all mean?

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  • How to enable logs for sitemesh

    - by atomsfat
    Is ther any form to enable logs for sitemesh ? I already put this in the log4j configuration but it doesn't work <!-- Appenders --> <appender name="console" class="org.apache.log4j.ConsoleAppender"> <param name="Target" value="System.out" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%-5p: %c - %m%n" /> </layout> </appender> <logger name="com.opensymphony"> <level value="debug"/> </logger> <logger name="org.springframework.beans"> <level value="warn" /> </logger> <logger name="org.springframework.binding"> <level value="debug" /> </logger> <logger name="org.springframework.jdbc"> <level value="warn" /> </logger> <logger name="org.springframework.transaction"> <level value="warn" /> </logger> <logger name="org.springframework.orm"> <level value="warn" /> </logger> <logger name="org.springframework.web"> <level value="debug" /> </logger> <logger name="org.springframework.webflow"> <level value="debug" /> </logger> <!-- Root Logger --> <root> <priority value="warn" /> <appender-ref ref="console" /> </root>

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  • With the introduction of the HTML5 <canvas> element, could Swing be implemented in GWT?

    - by knorv
    With the introduction of the HTML5 <canvas> element, could Swing theoretically be implemented in Google Web Toolkit (GWT) by using the <canvas> tag for drawing? I'm aware of efforts to port source code from using Swing calls to GWT calls, but what I'm after is a pure behind the scenes port where a Swing application would compile under GWT without any source code modifications. Is that theoretically possible? Why? Why not?

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