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  • Which is the 'correct' way to do this (if statement)

    - by frinkz
    I've got plenty of these lying around, and I'm wondering if I'm going to face any trouble - or performance problems. I have method A: MyClass monkey; ... if(monkey != null) { ... } Or method B: boolean hasMonkey; //This is set to TRUE when monkey is not null MyClass monkey; ... if(hasMonkey) { ... } On a functional level, they both do the same thing. Right now, I'm using method A. Is that a bad way of doing things? Which is going to perform better?

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  • JPA 2.0 Provider Hibernate Spring MVC 3.0

    - by user558019
    Dear All i have very strange problem we are using jpa 2.0 with hibernate and spring 3.0 mvc annotations based Database generated through JPA DDL is true and MySQL as Database; i will provide some refference classes and then my porblem. public abstract class Common implements serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; @ManyToOne @JoinColumn private Address address; //with all getter and setters //as well equal and hashCode } public class Parent extends Common{ private String name; @OneToMany(cascade = {CascadeType.MERGE,CascadeType.PERSIST}, mappedBy = "parent") private List<Child> child; //setters and rest of class } public class child extends Common{ //some properties with getter/setters } public class Address implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id", updatable = false) private Long id; private String street; //rest of class with get/setter } as in code you can see that parents and child classes extends Common class so both have address property and id , the problem occurs when change the address refference in parent class it reflect same change in all child objects in list and if change address refference in child class then on merge it will change address refference of parent as well i am not able to figure out is it is problem of jpa or hibernate or spring thanks in advance

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  • I asked a question about arrays before, but this one won't compile

    - by unit
    I asked about this array a little while ago, and I can't see what the problem is. Too tired. What have I done wrong? Basically, I am taking a string array and trying to check to see if it contains numbers or an x (ISBN number validation). I want to take the number from a given input (bookNum), check the input, and feed any valid input into a new array (book). At the line 'bookNum.charAt[j]==book[i]' I get the 'not a statement error'. What gives? String[] book = new String [ISBN_NUM]; bookNum.replaceAll("-",""); if (bookNum.length()!=ISBN_NUM) throw new ISBNException ("ISBN "+ bookNum + " must be 10 characters"); for (int i=0;i<bookNum.length();i++) { if (Character.isDigit(bookNum.charAt(i))) bookNum.CharAt[j]==book[i]; j++; if (book[9].isNotDigit()|| book[9]!="x" || book[9]!="X") throw new ISBNException ("ISBN " + bookNum + " must contain all digits" + "or 'X' in the last position");

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  • Controlling race condition at startup.

    - by Will Hartung
    I have some code that I want to have some one time initialisation performed. But this code doesn't have a definite lifecycle, so my logic can be potentially invoked by multiple threads before my initialisation is done. So, I want to basically ensure that my logic code "waits" until initialisation is done. This is my first cut. public class MyClass { private static final AtomicBoolean initialised = new AtomicBoolean(false); public void initialise() { synchronized(initialised) { initStuff(); initialised.getAndSet(true); initialised.notifyAll(); } } public void doStuff() { synchronized(initialised) { if (!initialised.get()) { try { initialised.wait(); } catch (InterruptedException ex) { throw new RuntimeException("Uh oh!", ex); } } } doOtherStuff(); } } I basically want to make sure this is going to do what I think it's going to do -- block doStuff until the initialised is true, and that I'm not missing a race condition where doStuff might get stuck on a Object.wait() that will never arrive. Edit: I have no control over the threads. And I want to be able to control when all of the initialisation is done, which is why doStuff() can't call initialise(). I used an AtomicBoolean as it was a combination of a value holder, and an object I could synchronize. I could have also simply had a "public static final Object lock = new Object();" and a simple boolean flag. AtomicBoolean conveniently gave me both. A Boolean can not be modified. The CountDownLatch is exactly what I was looking for. I also considered using a Sempahore with 0 permits. But the CountDownLatch is perfect for just this task.

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  • value from resource bundle as pattern in formatDate

    - by binary_runner
    I want to read pattern for JST formatDate also from resource bundle but this naive approach does not working, what I'm doing wrong ? in com/company/MyPortlet.properties is this key: company.date.format = yyyy-MM-dd HH:mm:ss In page I have: <fmt:setBundle basename="com.company.MyPortlet"/> <fmt:formatDate value="${date}" pattern="${company.date.format}" />

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  • Different lib directories of JBpss

    - by Serafeim
    There is a number of different lib directories JBoss (5.1.0) uses: I can find jboss/lib, jboss/lib/endorsed, jboss/common/lib, jboss/server/default/lib and of course the jboss/server/default/deploy/myapp/WEB-INF/lib (am I missing something ?). From the above, I know that I need to use the last one (WEB-INF/lib) to put any jars my app needs. What about all the others ? What is their use and what should I put there ? Why put it there and not in the WEB-INF/lib ? Thanks !

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  • Should i use lock.lock(): in this method?

    - by user962800
    I wrote this method whose purpose is to give notice of the fact that a thread is leaving a specific block of code A thread stands for a car which is leaving a bridge so other cars can traverse it . The bridge is accessible to a given number of cars (limited capacity) and it's one way only. public void getout(int diection){ // release the lock semaphore.release(); try{ lock.lock(); //access to shared data if(direction == Car.NORTH) nNordTraversing--; //decreasing traversing threads else nSudTraversing--; bridgeCond.signal(); }finally{ lock.unlock(); } } My question is: should I use lock.lock(); or it's just nonsense? thanks in advance

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  • How can you remove a Criterion from a criteria?

    - by ChuckM
    Hello, For instance if I do something like: Criteria c = session.createCriteria(Book.class) .add(Expression.ge("release",reDate); .add(Expression.ge("price",price); .addOrder( Order.asc("date") ) .setFirstResult(0) .setMaxResults(10); c.list(); How can I use the same criteria instance, but remove (for example) the second criterion? I'm trying to build a dynamic query in which I'd like to let the user remove a filter, without the backend having to reconstruct the criteria from scratch. Thank you

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  • What is the event dispatching thread?

    - by Roman
    I know what "thread" means and if I understand the event dispatching thread (EDT) as "just a thread", it explains a lot but, apparently, it does not explain everything. I do not understand what is special about this thread. For example I do not understand why we should start a GUI in a the EDT? Why the "main" thread is bed for GUI? Well, if we just do not want to occupy the main thread why we cannot start GUI just in "another thread" why it should be some "special" thread called EDT? Then I do not understand why we cannot start the EDT like any other thread? Why we should use some special tool (called invokeLater). And why GUI, unlike any other thread, does not start immediately. We should wait until it is ready to accept our job. Is it because EDT can, potentially execute several task simultaneously? If you decide to answer this question, could you pleas use a really simple terminology because otherwise, I am afraid, I will not be able to understand the answer.

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  • AJAX Problem - No response text in FireFox, but ok in IE

    - by Taiba
    Hi, I am making a simple AJAX call to an external site. It works ok in IE, but in Firefox, not response text is returned. I think it might have something to do with the response being "chunked", but I'm not sure. Any ideas? Thanks. function loadXMLDoc() { var xmlhttp; var urlString = "http://drc.edeliver.com.au/ratecalc.asp?Pickup_Postcode=6025&Destination_Postcode=6055&Country=AU&Weight=100&Service_Type=STANDARD&Length=100&Width=100&Height=100&Quantity=2"; if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4) { window.alert(xmlhttp.responseText); } } xmlhttp.open("GET", urlString, true); xmlhttp.send(); }

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  • Should filters write to the response during or after filtering?

    - by Mark
    I have a filter which processes generated HTML and rewrites certain elements. For example, it adds class attributes to some anchors. Finally, it writes the processed HTML to the response (a subclass of HttpServletResponseWrapper). Naturally, this means that the processed HTML is a different length after it has passed through the filter. I can see two ways of approaching this. One is to iterate over the HTML, using a StringBuilder to build up the processed HTML, and write the processed HTML to the response once all filtering is complete. The other is to iterate over the HTML but to write it to the response as soon as each element has been processed. Which is the better way for this operation, or is there another option which would be preferable? I am looking to minimise temporary memory usage primarily.

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  • Image not getting displayed on a JPanel.

    - by Myth17
    class Deal implements ActionListener { public void actionPerformed(ActionEvent e) { dl.setDeck(); dl.shuffle(); dl.firstDraw(pl); for(Card c:pl.showHand()) panelplay.add(new JLabel(c.getImageIcon())); panelplay.validate(); } } This is an event handler for a Jbutton. The method pl.showHand() returns a ArrayList of a user defined class 'Card'. Inserting a println() inside the loop shows the print, so the code is being executed but the Panel panelplay isnt showing card Images.

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  • Determining an object's variable name dynamically?

    - by ZenBlender
    Let's say I have some objects: ArrayList<SomeObject> list = new ArrayList<SomeObject>(); SomeObject A = new SomeObject(); SomeObject B = new SomeObject(); SomeObject C = new SomeObject(); SomeObject D = new SomeObject(); These constructors automatically add each object to the ArrayList so I can iterate over them but still maintain the variable names for direct access: public SomeObject(){ // init stuff here list.add(this); } But then, let's say I want to output some debug info, and iterate through list and print out the NAME of each object? How can I do that? Essentially, when "SomeObject A = new SomeObject();" is executed, I want to use reflection (if possible) to determine that this variable's name is "A" (a String) and either store that in the object when the constructor executes, or determine it dynamically through reflection when referencing this object with the variable named "A". Does that make sense? How can I do this? Thanks!

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  • Do null SQLite Data fields take up extra memory?

    - by CSharperWithJava
    I'm using the built in sqlite library on the Android platform. I'm considering adding several general purpose fields that users will be able to use for their own custom applications, but these fields will be blank most of the time. My question is, how much overhead will these blank fields add to my database? Do null fields even take up per record memory in sqlite? If so, how much? I don't quite understand the inner workings of a sqlite database.

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  • DocumentBuilder.parse() / Parsing Entities

    - by stormin986
    I'm new to parsing XML and am having an issue with entities. (Am doing this on Android, if it makes a difference). Is there a way to have it turn an entity into the character it represents? I have this in the child of an element: "isn&#39;t" (minus quotes). I would prefer it parse it and the end result be a single text node. However, right now this is turned in to TEXT, ENTITY, TEXT. Is there a way to automatically have it parse the entity into text, or a manual way to do it?

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  • Please explain how Trial Division works for Primality Test

    - by mister_dani
    I came across this algorithm for testing primality through trial division I fully understand this algorithm static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i <= Math.sqrt(N); i++) if (N % i == 0) return false; return true; } It works just fine. But then I came across this other one which works just as good but I do not fully understand the logic behind it. static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i * i<N; i++) if (N % i == 0) return false; return true; } It seems like i *i < N behaves like i <= Math.sqrt(N). If so, why?

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  • j2me: How to use setCommandListener on a TextField?

    - by SmRndGuy
    I wanted to make it so that when I select a specific TextField in a Form, I get a specific list of Commands, for example TextField: OK, CancelTextField2: OK, Back, Help And I succeeded by using addCommand() on each of TextFields but I can't tell it what to happen when when I activate one of these commands since there is no setCommandListener method for them. It throws a NullPointerException when I click it.I also tried to get the commands from their Form but it is receiving only the commands that it contains, not the commands that TextFields have Any help how to get arround this? Thanks in advance

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  • Adding a MouseOverHandler to an Element?

    - by JP
    I would like to listen for the mouse over event in GWT 1.6. Since GWT 1.6 has introduced handlers and deprecated listeners I'm unsure as to how I can accomplish this with what little information exists. Note: I have an Element object. That's what I need to add the mouse handler to. I apologize for my lack of clarity. Thanks!

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