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• dao as a member of a servlet - normal?

  - by EugeneP

  I guess, DAO is thread safe, does not use any class members. So can it be used without any problem as a private field of a Servlet ? We need only one copy, and multiple threads can access it simultaneously, so why bother creating a local variable, right?

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• Where can I find "reference barcodes" to verify barcode library output?

  - by mjustin

  This question is not about 'best' barcode library recommendation, we use various products on different platforms, and need a simple way to verify if a given barcode is correct (according to its specification). There are some free online bar code generators in the Internet, and I found many differences between their output and our library output regarding graphics and text field below the code. Now I am not sure which one is wrong, and before filing bug report I want to make sure how the correct barcode should look like. We mainly need Code128 and UCC/EAN-128 with A/B/C subcodes. Which resource would you suggest?

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• How to draw 'biohazard' with swing

  - by mike_hornbeck

  I'm practicing my swing abilities for the upcoming test, and fried gave me idea to draw biohazard sign like this : I could draw the circles with Elipse2D, but then I somehow need to cut those 3 triangles. Any ideas how I can do that ?

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• What happens if an exception is thrown in finalize()

  - by Psykocyber

  What would happen if an exception is thrown during the execution of finalize()? Is the stack unwind like normally? Does it continue finalize() and ignore the exception? Does it stop finalize() and continue GC the object? Or something else? I'm not looking for guidelines of using finalize() there are plently of pages explaining that.

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• How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

  - by Blankman

  I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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• Set reference = null in finally block?

  - by deamon

  A colleague of mine sets reference to null in finally blocks. I think this is nonsense. public Something getSomething() { JDBCConnection jdbc=null; try { jdbc=JDBCManager.getConnection(JDBCTypes.MYSQL); } finally { JDBCManager.free(jdbc); jdbc=null; // <-- Useful or not? } } What do you think of it?

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• Error when running a basic Hadoop code

  - by Abhishek Shivkumar

  I am running a hadoop code that has a partitioner class inside the job. But, when I run the command hadoop jar Sort.jar SecondarySort inputdir outputdir I am getting a runtime error that says class KeyPartitioner not org.apache.hadoop.mapred.Partitioner. I have ensured that the KeyPartitioner class has extended the Partitioner class, but why am I getting this error? Here is the driver code: JobConf conf = new JobConf(getConf(), SecondarySort.class); conf.setJobName(SecondarySort.class.getName()); conf.setJarByClass(SecondarySort.class); conf.setInputFormat(TextInputFormat.class); conf.setOutputFormat(TextOutputFormat.class); conf.setMapOutputKeyClass(StockKey.class); conf.setMapOutputValueClass(Text.class); conf.setPartitionerClass((Class<? extends Partitioner<StockKey, DoubleWritable>>) KeyPartitioner.class); conf.setMapperClass((Class<? extends Mapper<LongWritable, Text, StockKey, DoubleWritable>>) StockMapper.class); conf.setReducerClass((Class<? extends Reducer<StockKey, DoubleWritable, Text, Text>>) StockReducer.class); and here is the code of the partitioner class: public class KeyPartitioner extends Partitioner<StockKey, Text> { @Override public int getPartition(StockKey arg0, Text arg1, int arg2) { int partition = arg0.name.hashCode() % arg2; return partition; } }

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• Text to speech(TTS)-Android

  - by bharathi

  Hi, I am new to this android platform.now I am Working on TTS(Text to Speech).what I am trying to do is that when i enter the text in the Text area it has to be converted to speech,when i click the speak button.can anyone help me out.Thanks in Advance.

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• Free JVM profilers for websites

  - by 2Real

  I'm looking for a JVM profiler (preferably open source) so I can look at the heap and cpu usage of my personal website. I've used Lambda Probe, and I like it because it provides a web interface for my remote Unix computer that has no display. I was wondering what else is available Thanks,

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• Table per subclass inheritance relationship: How to query against the Parent class without loading a

  - by Arthur Ronald F D Garcia

  Suppose a Table per subclass inheritance relationship which can be described bellow (From wikibooks.org - see here) Notice Parent class is not abstract @Entity @Inheritance(strategy=InheritanceType.JOINED) public class Project { @Id private long id; // Other properties } @Entity @Table(name="LARGEPROJECT") public class LargeProject extends Project { private BigDecimal budget; } @Entity @Table(name="SMALLPROJECT") public class SmallProject extends Project { } I have a scenario where i just need to retrieve the Parent class. Because of performance issues, What should i do to run a HQL query in order to retrieve the Parent class and just the Parent class without loading any subclass ???

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• Get first character of each word and its position in a sentence/paragraph

  - by Radhika

  I am trying to create a map by taking the first character of each word and it's position in a sentence/paragraph. I am using regex pattern to achieve this. Regex is a costly operation. Are there are any ways to achieve this? Regex way: public static void getFirstChar(String paragraph) { Pattern pattern = Pattern.compile("(?<=\\b)[a-zA-Z]"); Map newMap = new HashMap(); Matcher fit = pattern.matcher(paragraph); while (fit.find()) { newMap.put((fit.group().toString().charAt(0)), fit.start()); } }

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• Mutable objects and hashCode

  - by robert

  Have the following class: public class Member { private int x; private long y; private double d; public Member(int x, long y, double d) { this.x = x; this.y = y; this.d = d; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + x; result = (int) (prime * result + y); result = (int) (prime * result + Double.doubleToLongBits(d)); return result; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof Member) { Member other = (Member) obj; return other.x == x && other.y == y && Double.compare(d, other.d) == 0; } return false; } public static void main(String[] args) { Set<Member> test = new HashSet<Member>(); Member b = new Member(1, 2, 3); test.add(b); System.out.println(b.hashCode()); b.x = 0; System.out.println(b.hashCode()); Member first = test.iterator().next(); System.out.println(test.contains(first)); System.out.println(b.equals(first)); System.out.println(test.add(first)); } } It produces the following results: 30814 29853 false true true Because the hashCode depends of the state of the object it can no longer by retrieved properly, so the check for containment fails. The HashSet in no longer working properly. A solution would be to make Member immutable, but is that the only solution? Should all classes added to HashSets be immutable? Is there any other way to handle the situation? Regards.

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• Does importing of packages change visibility of classes?

  - by Roman

  I jsut learned that A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package. This is a clear statement. But this information interfere with my understanding of importing of packages (which easily can be wrong). I thought that importing a package I make classes from the imported package visible to the importing class. So, how does it work? Are public classes visible to all classes everywhere under condition that the package containing the public class is imported? Or there is not such a condition? What about the package-private classes? They are invisible no mater if the containing package was imported or not? ADDED: It seems to me that I got 2 answers which are marked as good (up-voted) and which contradict eachother.

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• select multiple double side

  - by Mercer

  hello, i want to do a select multiple double side like this : http://www.senamion.com/blog/jmultiselect2side.html (Demo2) but i don't know how i can retrieve my data when i click submit button..?

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• query on display tag

  - by sarah

  Hi, I have the following code to display <display:table name="sessionScope.userList" id="userList" export="false" pagesize="1"> <display:column title="Select" style="width: 90px;"> <input type="checkbox" name="optionSelected" value=""/> </display:column> <display:column property="userName" sortable="false" title="UserName" paramId="userName" style="width: 150px; text-align:center" href="#"/> </display:table> On click of the checkbox i need to get the corresponding row value that is the username how would i get that?

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• Why does /**[newline] not always insert the Javadoc template including @param and @return in Eclipse

  - by Bas van den Broek

  I'm documenting code in Eclipse and have been using the /** followed by Enter alot to insert the Javadoc template. However this does not always work for some reason, it will create the template for writing comments but it won't automatically insert the @param and @return text. If I copy the exact same method to another class it will insert the full template. It would be a big help if anyone could tell me why it won't do this in some situations.

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• Can twitter do callbacks?

  - by RenegadeAndy

  Hi! I am wondering if the twitter API supports the following: Whenever I make a post to my twitter account - it also calls a specific URL which I define so I can do something else? Thanks very much, Andy

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• Junit 4 test suite and individual test classes

  - by Hypnus

  I have a JUnit 4 test suite with BeforeClass and AfterClass methods that make a setup/teardown for the following test classes. What I need is to run the test classes also by them selves, but for that I need a setup/teardown scenario (BeforeClass and AfterClass or something like that) for each test class. The thing is that when I run the suite I do not want to execute the setup/teardown before and after each test class, I only want to execute the setup/teardown from the test suite (once). Is it possible ? Thanks in advance.

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• What are good Opensource Billing Solution with Customer Portal?

  - by krunaloverflow

  I'm looking for an Online Billing Solution along with a Customer Portal in open source space so that I can customize it the way as required in future. My requires are: Flat & Subscription(Periodical) based Billing (orders/invoices) Able to set products/services, its prices add customers or customers can register themselves from client end (a web page) and mange their profile themselves from customer portal, pay online, order products, check invoices, cancel order / subscription, etc. An interface (web service or API) that would provide a mechanism to check when customer recieves service, his current status and then allow them access to the services (similar to subscription membership website ) Please provide me with the options I should consider.

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• How do I create different Objects using Google Guice?

  - by kunjaan

  I have a Module which binds an Interface to a particular implementation. I use that module to create an object. How do I create a different kind of object with the the interface bound to a different implementation? Do I need to create a new module with the Interface bound to a different implementation?

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• OnClickListener onClick=true and selector

  - by azerto00

  I have not found any answer for my problem, so I need your help ... I have an LinearLayout which I want to be clickable in order to lunch another activity. So I implement an onClickListener to it. I created an selector for this LinearLayout in order that what someone click on it, the background change. I just don't understand that : If my LinearLayout doesn't have android:clickable="true" in the xml, I'm able to click on it and get what I want but the selector doesn't work. If I remove this line, it is the opposite .. the selector work but not the onClick event. So, can anyone can explain me why ? Just in case, here is my the content of my selector file : <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@drawable/btn_restaurants_background_state_pressed" android:state_pressed="true"></item> <item android:drawable="@drawable/btn_restaurants_background_state_pressed" android:state_focused="true"></item> <item android:drawable="@drawable/btn_restaurants_background_state_pressed" android:state_selected="true"></item> <item android:drawable="@drawable/btn_restaurants_background_state_normal"></item> </selector> Thanks you in advance

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• What is the effect of final variable declaration in methods?

  - by Finbarr

  Classic example of a simple server: class ThreadPerTaskSocketServer { public static void main(String[] args) throws IOException { ServerSocket socket = new ServerSocket(80); while (true) { final Socket connection = socket.accept(); Runnable task = new Runnable() { public void run() { handleRequest(connection); } }; new Thread(task).start(); } } } Why should the Socket be declared as final? Is it because the new Thread that handles the request could refer back to the socket variable in the method and cause some sort of ConcurrentModificationException?

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• LinkedList.contains execution speed

  - by Le_Coeur

  Why Methode LinkedList.contains() runs quickly than such implementation: for (String s : list) if (s.equals(element)) return true; return false; I don't see great difference between this to implementations(i consider that search objects aren't nulls), same iterator and equals operation

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• How to get deployed jars in Jboss

  - by Filip

  How can I get the list of jars deployed in JBoss? I want to compile some classes at runtime in EJB, but they may use some of the deployed jars, so I need to specify classpath during compilation.

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• How to debug JBoss out of memory problem?

  - by user561733

  Hello, I am trying to debug a JBoss out of memory problem. When JBoss starts up and runs for a while, it seems to use memory as intended by the startup configuration. However, it seems that when some unknown user action is taken (or the log file grows to a certain size) using the sole web application JBoss is serving up, memory increases dramatically and JBoss freezes. When JBoss freezes, it is difficult to kill the process or do anything because of low memory. When the process is finally killed via a -9 argument and the server is restarted, the log file is very small and only contains outputs from the startup of the newly started process and not any information on why the memory increased so much. This is why it is so hard to debug: server.log does not have information from the killed process. The log is set to grow to 2 GB and the log file for the new process is only about 300 Kb though it grows properly during normal memory circumstances. This is information on the JBoss configuration: JBoss (MX MicroKernel) 4.0.3 JDK 1.6.0 update 22 PermSize=512m MaxPermSize=512m Xms=1024m Xmx=6144m This is basic info on the system: Operating system: CentOS Linux 5.5 Kernel and CPU: Linux 2.6.18-194.26.1.el5 on x86_64 Processor information: Intel(R) Xeon(R) CPU E5420 @ 2.50GHz, 8 cores This is good example information on the system during normal pre-freeze conditions a few minutes after the jboss service startup: Running processes: 183 CPU load averages: 0.16 (1 min) 0.06 (5 mins) 0.09 (15 mins) CPU usage: 0% user, 0% kernel, 1% IO, 99% idle Real memory: 17.38 GB total, 2.46 GB used Virtual memory: 19.59 GB total, 0 bytes used Local disk space: 113.37 GB total, 11.89 GB used When JBoss freezes, system information looks like this: Running processes: 225 CPU load averages: 4.66 (1 min) 1.84 (5 mins) 0.93 (15 mins) CPU usage: 0% user, 12% kernel, 73% IO, 15% idle Real memory: 17.38 GB total, 17.18 GB used Virtual memory: 19.59 GB total, 706.29 MB used Local disk space: 113.37 GB total, 11.89 GB used

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