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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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  • servlet ArrayList and HashMap problem witch result

    - by nonameplum
    Hi, I have that code List<Map<String, Object>> data = new ArrayList<Map<String, Object>>(); Map<String, Object> item = new HashMap<String, Object>(); data.clear(); item.clear(); int i = 0; while (i < 5){    item.put("id", i);    i++;    out.println("id: " + item.get("id"));    out.println("--------------------------");    data.add(item); } for(i=0 ; i<5 ; i++){    out.println("print data[" + i + "]" + data.get(i)); } Result of that is: id: 0 -------------------------- id: 1 -------------------------- id: 2 -------------------------- id: 3 -------------------------- id: 4 -------------------------- print data[0]{id=4} print data[1]{id=4} print data[2]{id=4} print data[3]{id=4} print data[4]{id=4} Why only last element is stored?

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  • Android: Referring to a string resource when defining a log name

    - by spookypeanut
    In my Android app, I want to use a single variable for the log name in multiple files. At the moment, I'm specifying it separately in each file, e.g. public final String LOG_NAME = "LogName"; Log.d(LOG_NAME, "Logged output); I've tried this: public final String LOG_NAME = (String) getText(R.string.app_name_nospaces); And while this works in generally most of my files, Eclipse complains about one of them: The method getText(int) is undefined for the type DatabaseManager I've made sure I'm definitely importing android.content.Context in that file. If I tell it exactly where to find getText: Multiple markers at this line - Cannot make a static reference to the non-static method getText(int) from the type Context - The method getText(int) is undefined for the type DatabaseManager I'm sure I've committed a glaringly obvious n00b error, but I just can't see it! Thanks for all help: if any other code snippets would help, let me know.

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  • @ExceptionHandler doesn't handle the thrown exceptions

    - by Javi
    Hello, I have a method in my controller which will handle the exceptions thrown by the application. So I have a method like this one. @Controller public class ExceptionController { @RequestMapping(value="/error") @ExceptionHandler(value={Exception.class, NullPointerException.class}) public String showError(Exception e, Model model){ return "tiles:error"; } } And to try I if it works I throw a NullPointerException in another method in other method controller: boolean a = true; if(a){ throw new NullPointerException(); } After the exception is thrown it is printed in the JSP, but it doesn't go throw my showError() method (I've set a breakpoint there and it never enters). showError() method will catch the exception and will show different error pages depending on the exception type (though now it always shows the same error page). If I go to the url /error it shows the error page so the showError() method is OK. I'm using Spring 3. What can be the problem? Thanks.

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  • red5: how can i extend ISharedObject ?

    - by ufk
    Hiya. Red5 uses ISharedObject interface to create shared objects and to operate them. because ISharedObject is an interface I'm having issues extending it. I would like to extend the getAttribute, setAttribute, get{Int/String/Map}Attribute so the values will be checked before entered or pulled out. how is it possible to do so ? thanks

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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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  • Exception handling pattern

    - by treefrog
    It is a common pattern I see where the error codes associated with an exception are stored as Static final ints. when the exception is created to be thrown, it is constructed with one of these codes along with an error message. This results in the method that is going to catch it having to look at the code and then decide on a course of action. The alternative seems to be- declare a class for EVERY exception error case Is there a middle ground ? what is the recommended method ?

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  • i have a arraylist where i am verifying particular object is existing or not but even it exists it always returns false

    - by Raghavender Reddy
    hi i have class called userdata which returns the Userarraylist which is of type User. when ever i try to use contains method to check particular property is existing or not it always returns false why? Actually i want the array list to be generic which should return the objects that are set in array list. String className = data.getUserData().get(0).getClass().getSimpleName(); if(className.equalsIgnoreCase("User")) { ArrayList<User> userdata=new ArrayList(); userdata = data.getUserData(); System.out.println(data.getUserData().contains(u.getUserId())); if(userdata.contains(u.getUserName())) { System.out.println(userdata.get(0).getEmailId()); } }

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  • Spring OpenSessionInViewFilter with @Transactional annotation

    - by Gautam
    This is regarding Spring OpenSessionInViewFilter using with @Transactional annotation at service layer. i went through so many stack overflow post on this but still confused about whether i should use OpenSessionInViewFilter or not to avoid LazyInitializationException It would be great help if somebody help me find out answer to below queries. Is it bad practice to use OpenSessionInViewFilter in application having complex schema. using this filter can cause N+1 problem if we are using OpenSessionInViewFilter does it mean @Transactional not required? Below is my Spring config file <context:component-scan base-package="com.test"/> <context:annotation-config/> <bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource"> <property name="basename" value="resources/messages" /> <property name="defaultEncoding" value="UTF-8" /> </bean> <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" p:location="/WEB-INF/jdbc.properties" /> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" p:driverClassName="${jdbc.driverClassName}" p:url="${jdbc.databaseurl}" p:username="${jdbc.username}" p:password="${jdbc.password}" /> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="configLocation"> <value>classpath:hibernate.cfg.xml</value> </property> <property name="configurationClass"> <value>org.hibernate.cfg.AnnotationConfiguration</value> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">${jdbc.dialect}</prop> <prop key="hibernate.show_sql">true</prop> <!-- <prop key="hibernate.hbm2ddl.auto">create</prop> --> </props> </property> </bean> <tx:annotation-driven /> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="sessionFactory" /> </bean>

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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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  • 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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  • 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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  • 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 to remove strings of certain lengths

    - by Macosx Iam
    So I have this array, and I want to delete strings that are 2 or 4 characters in length (strings that contain 2 or 4 characters). I am doing this method, and it doesn't work, even though logically, it SHOULD work. public static void main(String[] args) { ArrayList<String> list = new ArrayList<String>(); list.add("This"); list.add("is"); list.add("a"); list.add("test"); for (int i=0; i<list.size(); i++) { if(list.get(i).length()==2 || list.get(i).length()==4) { list.remove(i); } } } I'd like to stick to this method of doing it. Can you please give me some suggestions as to how to correct this code? The output of this code when I run it is: [is, a] Even though I want the output to be [a] because "is" is 2 characters long.

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  • What Happens if i create a byte array continuously in a while loop with different size and add read an stream into it?

    - by SajidKhan
    I want to read an audio file into multiple byte arrays , with different size . And then add into a shared memory. What will happen if use below code. Does the byte array gets over written. I understand it will creat multiple byte array , how do i erase those byte arrays after my code does what it needs to do. int TotalBuffer = 10; while (TotalBuffer !=0){ bufferData = new byte[AClipTextFileHandler.BufferSize.get(j)]; input.read(bufferData); Sharedbuffer.put(bufferData); i++; j++; TotalBuffer--; }

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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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  • 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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  • Recurssion Question : Revision

    - by stan
    My slides say that A recurssive call should always be on a smaller data structure than the current one There must be a non recurssive option if the data structure is too small You need a wrapper method to make the recurssive method accessible Just reading this from the slides makes no sence, especially seeing as it was a topic from before christmas! Could anyone try and clear up what it means please? Thank you

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  • Uploading Files to AWS S3 from an Android App

    - by Abhishek Kaushik
    Edited 7th June,14 My Android app needs to have a feature where clients can upload their files. I want AWS S3 as my storage. Moreover i dont want to use SECRET_KEY and ACCESS_KEY_ID on client side. What is the the best way to do this. Can someone provide the working code too ? I read that i can request to AWS for a signed URL and then make client directly upload to that URL. How to achieve this ?

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