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• JSR 275 - Units, Percent per second

  - by I82Much

  Hi all, I need to represent the unit of Percent per second using the JScience.org's JSR 275 units and measures implementation. I am trying to do to the following: Unit<Dimensionless> PERCENT_PER_SECOND = NonSI.PERCENT.divide(Si.SECOND).asType(Dimensionless.class) but I am getting a ClassCastException when I try to do that. The following works, but I'm not sure if there's a better way: public interface PercentOverTime extends Quantity {} public static Unit<PercentOverTime> PERCENT_PER_SECOND = new BaseUnit<PercentOverTime>("%/s"); Any thoughts? The closest I could find to this is the question on Cooking Measurements (which is how I saw how to define your own units).

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• How to maintain a pool of names ?

  - by Jacques René Mesrine

  I need to maintain a list of userids (proxy accounts) which will be dished out to multithreaded clients. Basically the clients will use the userids to perform actions; but for this question, it is not important what these actions are. When a client gets hold of a userid, it is not available to other clients until the action is completed. I'm trying to think of a concurrent data structure to maintain this pool of userids. Any ideas ? Would a ConcurrentQueue do the job ? Clients will dequeue a userid, and add back the userid when they are finished with it.

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• Custom annotations to configure tests

  - by ace

  First of al let me start off by saying I think custom annotations can be used for this but i'm not totally sure. I would like to have a set of annotations that I can decorate some test classes with. The annotations would allow me to configure the test for different environments. Example: public class Atest extends BaseTest{ private String env; @Login(environment=env) public void testLogin(){ //do something } @SignUp(environment=env) public void testSignUp(){ //do something } } The idea here would be that the login annotation would then be used to lookup the username and password to be used in the testLogin method for testing a login process for a particular environment. So my question(s) is this possible to do with annotations? If so I have not been able to find a decent howto online to do something like this. Everything out there seems to be your basic here's how to do your custom annotations and a basic processor but I haven't found anything for a situation like this. Ideas?

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• HQL multiple updates. Is there a better way?

  - by folone

  I have a Map, that I want to persist. The domain object is something like this: public class Settings { private String key; private String value; public String getKey() { ... } public String getValue() { ... } public void setKey() { ... } public void setValue() { ... } } The standard approach is to generate a Setting for each pair, and saveOrUpdate() it. But it generates way too much queries, because I need to save lots of settings at a time, and it really affects perfomance. Is there a way to do this using one update query?

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• Meaning of the "Unloading class" messages

  - by elec

  Anyone can explain why the lines below appear in the output console at runtime ? (one possible answer would be full permGen, but this can be ruled out since the program only uses 24MB out of the max100MB available in PermGen) [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor28] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor14] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor4] [Unloading class sun.reflect.GeneratedMethodAccessor5] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor38] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor36] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor22] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor8] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor39] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor16] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor2] [Unloading class sun.reflect.GeneratedConstructorAccessor1] The program runs with the following params: -Xmx160M -XX:MaxPermSize=96M -XX:PermSize=96M -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCTaskTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -verbose:gc -Xloggc:/logs/gc.log There's plenty of space in the heap and in permGen.

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• How to sanitize log messages in Log4j to save them in database

  - by Rafael

  Hello, I'm trying to save log messages to a central database. In order to do this, I configured the following Appender in log4j's xml configuration: <appender name="DB" class="org.apache.log4j.jdbc.JDBCAppender"> <param name="URL" value="jdbc:postgresql://localhost/logging_test" /> <param name="user" value="test_user" /> <param name="password" value="test_password" /> <param name="sql" value="INSERT INTO log_messages ( log_level, message, log_date ) VALUES ( '%p', '%m', '%d{yyyy-MM-dd HH:mm:ss}' )" /> </appender> This works fine, except some of the messages contain ', and then the appender fails. Is there an easy way to do this?

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• JBoss envers and huge audit tables

  - by LeChe

  All, I am auditing my JEE application with JBoss Evers and the nature of my application causes the audit table to grow very fast. The historic data is queried infrequently and access time is not really an issue, apart from the data from the last week. This data IS queried frequently and access needs to be fast. Ideally, I would split the data and distribute it over two tables, with the older data in compressed format. Unfortunately, Envers does not allow spreading data over multiple tables as far as I can tell from the docs. Does somebody have any idea what would be the best way to achieve this (if possible while still using Envers)? Cheers, LeChe

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• How to reference an embedded JCA resource adapater

  - by cg

  For our current J2EE project based on JBoss, we need to interface with a remote system using message driven beans and a JCA resource adapter provided as a RAR file by a third party. I would like to package and deploy the entire project as an EAR file to our JBoss server. Most notably, the RAR file should be embedded within the EAR file and not be deployed globally. All of this is working fine so far, but I'm not particularly happy with the way the RAR file is referenced. The jboss.xml packaged with the MDB for example, currently looks like this: <jboss> <enterprise-beans> <message-driven> <ejb-name>testBean1</ejb-name> <resource-adapter-name>test1.ear#thirdparty-1.0.rar</resource-adapter-name> </message-driven> </enterprise-beans> </jboss> While this is generally working fine, it will break when the EAR file is renamed to "test2.ear". Is there a way to reference the embedded RAR file without hard-coding the containing archive's name?

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• Is it bad to explicitly compare against boolean constants?

  - by polygenelubricants

  Is it bad to write: if (b == false) //... while (b != true) //... Is it always better to instead write if (!b) //... while (!b) //... Presumably there is no difference in performance (or is there?), but how do you weigh the explicitness, the conciseness, the clarity, the readability, etc between the two?

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• to get columns from Excel files using Apache POI??

  - by posdef

  Hi, In order to do some statistical analysis I need to extract values in a column of an Excel sheet. I have been using the Apache POI package to read from Excel files, and it works fine when one needs to iterate over rows. However I couldn't find anything about getting columns neither in the API (link text) nor through google searching. As I need to get max and min values of different columns and generate random numbers using these values, so without picking up individual columns, the only other option is to iterate over rows and columns to get the values and compare one by one, which doesn't sound all that time-efficient. Any ideas on how to tackle this problem? Thanks,

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• Where to handle fatal exceptions

  - by Stephen Swensen

  I am considering a design where all fatal exceptions will be handled using a custom UncaughtExceptionHandler in a Swing application. This will include unanticipated RuntimeExceptions but also custom exceptions which are thrown when critical resources are unavailable or otherwise fail (e.g. a settings file not found, or a server communication error). The UncaughtExceptionHandler will do different things depending on the specific custom exception (and one thing for all the unanticipated), but in all cases the application will show the user an error message and exit. The alternative would be to keep the UncaughtExceptionHandler for all unanticipated exceptions, but handle all other fatal scenarios close to their origin. Is the design I'm considering sound, or should I use the alternative?

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• What is an "import" called?

  - by Oscar Reyes

  It is not a statement nor an expression. What is that called then? A directive?

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• Use PermGen space or roll-my-own intern method?

  - by Adamski

  I am writing a Codec to process messages sent over TCP using a bespoke wire protocol. During the decode process I create a number of Strings, BigDecimals and dates. The client-server access patterns mean that it is common for the client to issue a request and then decode thousands of response messages, which results in a large number of duplicate Strings, BigDecimals, etc. Therefore I have created an InternPool<T> class allowing me to intern each class of object. Internally, the pool uses a WeakHashMap<T, WeakReferemce<T>>. For example: InternPool<BigDecimal> pool = new InternPool<BigDecimal>(); ... // Read BigDecimal from in buffer and then intern. BigDecimal quantity = pool.intern(readBigDecimal(in)); My question: I am using InternPool for BigDecimal but should I consider also using it for String instead of String's intern() method, which I believe uses PermGen space? What is the advantage of using PermGen space?

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• Recovery time of a date

  - by Mercer

  Hello, i want recovery time of a date Date date = new Date(); SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss"); ..

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• Public static variables and Android activity life cycle management

  - by jsstp24n5

  According to the documentation the Android OS can kill the activity at the rear of the backstack. So, say for example I have an app and open the Main Activity (let's call it Activity A). In this public activity class I declare and initialize a public static variable (let's call it "foo"). In Activity A's onCreate() method I then change the value of "foo." From Activity A the user starts another activity within my app called Activity B. Variable "foo" is used in Activity B. Activity B is then paused after the user navigates to some other activities in other apps. Eventually, after a memory shortage occurs, Activity A then Activity B can be killed. After the user navigates back to my app it restarts (actually "recreates") activity B. What happens: 1) Will variable "foo" at this point have the value that was set to it when Activity A's onCreate() method ran? 2) Variable "foo" does not exist? 3) Variable "foo" exists and but is now the initialized value and not the value set in Activity A's onCreate() method?

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• Jakarta Regexp 1.5 Backreferences?

  - by Matt Smith

  Why does this match: String str = "099.9 102.2" + (char) 0x0D; RE re = new RE("^([0-9]{3}.[0-9]) ([0-9]{3}.[0-9])\r$"); System.out.println(re.match(str)); But this does not: String str = "099.9 102.2" + (char) 0x0D; RE re = new RE("^([0-9]{3}.[0-9]) \1\r$"); System.out.println(re.match(str)); The back references don't seem to be working... What am I missing?

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• Add a listener inside or outside get method

  - by James P.

  I'm learning Swing and have composed an interface using a series of get methods to add components. Is it a good practise to add a Listener inside a get method as follows? I'd like to make things as decoupled as possible. private JButton getConnectButton() { if (connectButton == null) { connectButton = new JButton(); connectButton.setText("Connect"); connectButton.setSize(new Dimension(81, 16)); connectButton.setLocation(new Point(410, 5)); connectButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // actionPerformed code goes here } }); } return connectButton; }

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• hibernate versioning parent entity

  - by Priit

  Consider two entities Parent and Child. Child is part of Parent's transient collection Child has a ManyToOne mapping to parent with FetchType.LAZY Both are displayed on the same form to a user. When user saves the data we first update Parent instance and then Child collection (both using merge). Now comes the tricky part. When user modifies only Child property on the form then hibernate dirty checking does not update Parent instance and thus does not increase optimistic locking version number for that entity. I would like to see situation where only Parent is versioned and every time I call merge for Parent then version is always updated even if actual update is not executed in db.

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• Message Sent time incorrect using javax mail

  - by sword101

  greetings all i have a problem that when sending an email from the server to the client using javax mail and set the sentDate to message.setSentDate(new Date()); the email is sent in the server time and the client receive the email immediately with time 5 hours ago ???? how to fix this to send and receive in correct timing ?

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• Can you return an array from a JAX-WS @WebMethod?

  - by LES2

  I'm pretty sure you can, but in addition to answering the question in the title, could you also explain the pros, cons, caveats, if any, to doing so? I know that you can't return a List, Set, Collection, Map, or any interface, from a WebMethod (which is stupid, IMO, but I don't know what the design reasons were should I should probably withhold judgment). Thanks for any advice. -- LES

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• Pythagoras triangle

  - by Gogolo

  I would like to ask you about this programing part, is it everything ok? the task was: Write the pseudocode or flow diagram and code for the theorem of Pythagoras - for right-angle triangle with three ribs (a, b, and c) of type integer int KendiA = 0; int KendiB = 0; int H = 0; string Trekendeshi = null; int gjetja = 0; for (KendiA = 1; KendiA <= 15; KendiA++) { for (KendiB = 1; KendiB <= 15; KendiB++) { for (H = 1; H <= 30; H++) { if ((Math.Pow(KendiA, 2) + Math.Pow(KendiB, 2) == Math.Pow(H, 2))) { gjetja = gjetja + 1; Trekendeshi = gjetja + "\t" + KendiA + "\t" + KendiB + "\t" + H; Console.WriteLine(Trekendeshi); } } } }

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• Rounding up milliseconds when printing with Joda Time

  - by RoToRa

  I'm implementing a count-down using Joda Time. I only need a display accuracy of seconds. However when printing the time, the seconds are displayed as full seconds, so when the count down reaches, for example, 900ms, then "0" seconds is printed, but as a count-down it would make more sense to display "1" second, until the time actually reaches 0ms. Example: void printDuration(Duration d) { System.out.println( d.toPeriod(PeriodType.time()).toString( new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter() ) ); } printDuration(new Duration(5000)); // Prints "5" => OK printDuration(new Duration(4900)); // Prints "4" => need "5" printDuration(new Duration(1000)); // Prints "1" => OK printDuration(new Duration(900)); // Prints "0" => need "1" printDuration(new Duration(0)); // Prints "0" => OK Basically I need to the seconds to be display rounded up from milliseconds and not rounded down. Is there a way to achieve this with Joda without needing to write my own formatter?

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• Problem with 2 levels of inheritance in hibernate mapping

  - by Seth

  Here's my class structure: class A class B extends A class C extends A class D extends C class E extends C And here are my mappings (class bodies omitted for brevity): Class A: @Entity @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @MappedSuperclass @DiscriminatorColumn( name="className", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class A Class B: @Entity @DiscriminatorValue("B") public class B extends A Class C: @Entity @DiscriminatorValue("C") @MappedSuperclass @DiscriminatorColumn( name="cType", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class C extends A Class D: @Entity @DiscriminatorValue("D") public class D extends C Class E: @Entity @DiscriminatorValue("E") public class E extends C I've got a class F that contains a set of A: @Entity public class F { ... @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL) @JoinTable( name="F_A", joinColumns = @JoinColumn(name="A_ID"), inverseJoinColumns = @JoinColumn(name="F_ID") ) private Set<A> aSet = new HashSet<A>(); ... The problem is that whenever I add a new E instance to aSet and then call session.saveOrUpdate(fInstance), hibernate saves with "A" as the discrimiator string. When I try to access the aSet in the F instance, I get the following exception (full stacktrace ommitted for brevity): org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: path.to.class.A Am I mapping the classes incorrectly? How am I supposed to map multiple levels of inheritance? Thanks for the help!

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• How to export data which are mapped to enumerations

  - by Joshua

  I have a set of data which needs to be imported from a excel sheet, lets take the simplest example. Note: the data might eventually support uploading any locale. e.g. assuming one of the fields denoting a user is gender mapped to an enumeration and stored in the database as 0 for male and 1 for female. 0 and 1 being short values. If I have to import the values I cannot expect the user to punch in numbers (since they are not intuitive and is cumbersome when the enumerations are bigger), what would be the correct way to map to enumerations. Should we ask them to provide a string value in these cases (e.g. male or female) and provide the transformation to a enum in our code by wring a method public static Gender Gender.fromString(String value)

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• Ready to use TSP library

  - by Max

  Hi, I'm currently doing a project that requires some fast TSP solving (about 50-100 nodes in 2 seconds). There are a lots of approximation algorithms out there, but I don't have time nor will to analyze them and code them myself. Are there any free libraries that can solve TSP problem (approximation will do too)? Something like sortedNodes = solveTspPrettyPlease(nodes, 2sec) would be just great. Thanks in advance.

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