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  • Is it a good practice to have trim in setter?

    - by zibi
    I'm doing a code review and I noticed such a code: @Entity @Table(name = "SOME_TABLE") public class SomeReportClass { @Column(name = "REPORT_NUMBER", length = 6, nullable = false) private String reportNumber; ..... public String getReportNumber() { return reportNumber; } public void setReportNumber(String reportNumber) { this.reportNumber = StringUtils.trimToNull(reportNumber); } } Every time I see trimming inside of a setter I feel that its not the clearest solution - what is the general practice with that issue?

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  • Hibernate 1:M relationship ,row order, constant values table and concurrency

    - by EugeneP
    table A and B need to have 1:M relationship a and b are added during application runtime, so A created, then say 4 B's created. Each B instance has to come in order, so that I could later extract them in the same order as I added them. The app will be a web-app running on Tomcat, so 10 instances may work simultaneously. So my question are: 1) How to preserve inserting order, so that I could extract B instances that A references in the same order as I persisted them. That's tricky, because we add to a Collection and then it gets saved (am I right?). So, it depends on how Hibernate saves it, what if it changes the order in what we added instances? I've seen something like LIST instead of SET when describing relationships, is that what I need? 2) How to add a 3-rd column to B so that I could differentiate the instances, something like SEX(M,F,U) in B table. Do I need a special table, or there's and easy way to describe constants in Hibernate. What do you recommend? 3) Talking about concurrency, what methods do you recommend to use? There should be no collisions in the db and as you see, there might easily be some if rows are not inserted (PK added) right where it is invoked without delays ?

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  • When should I define an hash code function for my types?

    - by devoured elysium
    Is there any other reason for implementing an hash code function for my types other than allowing for good use of hash tables? Let's say I am designing some types that I intend to use internally. I know that types are "internal" to the system, and I also know I will never use those types in hash tables. In spite of this, I decide I will have to redefine the equals() method. Theory says I should also redefine the hash code method, but I can't see any reason why, in this case, I should do it. Can anyone point me out any other reason? This question can be rephrased to : in which situations should we implement a hash code method in our types. PS : I am not asking how to implement one. I am asking when.

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  • How can I improve the performance of this algorithm

    - by Justin
    // Checks whether the array contains two elements whose sum is s. // Input: A list of numbers and an integer s // Output: return True if the answer is yes, else return False public static boolean calvalue (int[] numbers, int s){ for (int i=0; i< numbers.length; i++){ for (int j=i+1; j<numbers.length;j++){ if (numbers[i] < s){ if (numbers[i]+numbers[j] == s){ return true; } } } } return false; }

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  • What is the security risk of object reflection?

    - by Legend
    So after a few hours of workaround the limitation of Reflection being currently disabled on the Google App Engine, I was wondering if someone could help me understand why object reflection can be a threat. Is it because I can inspect the private variables of a class or are there any other deeper reasons?

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  • Spring @Transactional - Can I Override rollbackFor

    - by user475039
    Hi all, I am calling a service which has the following annotation: @Transactional(rollbackFor=ExceptionA.class) public void myMethodA(....) throws ExceptionA { . . } I am calling this method from an other method in another Spring Bean. @Transactional(rollbackFor=ExceptionB.class) public void mainEntryPointMethod(....) throws ExceptionB { . try { myMethodA() } catch (ExceptionA exp) { . } . } My problem is that if myMethodA throws an exception, my transaction (which is passed from mainEntryPointMethod - myMethodA by default propagation) will be marked for rollback. Is there a way in which the 'rollbackFor' for the inner method can be overriden? Thanks in advance Chris

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  • Project to learn J2EE technologies.

    - by Chandra
    Attended a 2 week j2EE course and learnt the concepts. Want to try in a simple project and wanted ideas on what that could be? PetStore or Small Business App are so boring... Anything interesting that can be done to learn the breadth but at the same time it not being a full fledged project?

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  • Best practice for an application with GUI

    - by chronosphenomena
    Hi, I'm about to start an application which will have both console and GUI interfaces. What I wan't to achieve is COMPLETE decoupling of application logic from interface. In future, I may also add web interface, and I don't want to change anything in my application. Is there a good example (perhaps some open source project) where I can learn how this should be done properly.... also I'd appreciate advices/guidelines on how to do this. Thanks

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  • servlet authentication and further reference to the credentials

    - by user553592
    What I got so far: It all begins with an HTML form which prompts the user for a username and password. From there it post the acquired user/pass to a servlet, GateKeeper. GateKeeper determines if the user/pass combination match any records in the MySQL database. Here is the sql I use: SELECT id FROM Users WHERE username='?' AND password=MD5('?') where the ? indicate information provided the previous HTML form. What I need now: I need some way to store the username and id of the record in the database. GateKeeper redirects the user to a control panel upon success. Therefore, I need a method to reference the username to display simple greetings, etc and also the id so it eliminates unnecessary calls to the database. The control panel may make AJAX calls to Servlets that preform some sort of task to the MySQL database.

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  • Ordered Data Structure that allows to efficiently remove duplicate items

    - by devoured elysium
    I need a data structure that Must be ordered (adding elements a, b and c to an empty structure, will make them be at positions 0, 1 and 2). Allows to add repeated items. This is, I can have a list with a, b, c, a, b. Allows removing all ocurrences of a given item (if I do something like delete(1), it will delete all ocurrences of 1 in the structure). I can't really pick what the best data structure could be in here. I thought at first about something like a List(the problem is having an O(n) operation when removing items), but maybe I'm missing something? What about trees/heaps? Hashtables/maps? I'll have to assume I'll do as much adding as removing with this data structure. Thanks

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  • What to prefer in the following case?

    - by GK
    say suppose I have class as : public class Age { private int age; public int getAge() { return this.age; } } In my Main class I am calling the getAge() method many times. So I wanted to know is it advisable to call so many times or call once and assign it to some variable and use that variable. Which is best and why?

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  • What's an effective way to reuse ArrayLists in a for loop?

    - by Patrick
    hi, I'm reusing the same ArrayList in a for loop, and I use for loop results = new ArrayList<Integer>(); experts = new ArrayList<Integer>(); output = new ArrayList<String>(); .... to create new ones. I guess this is wrong, because I'm allocating new memory. Is this correct ? If yes, how can I empty them ? Added: another example I'm creating new variables each time I call this method. Is this good practice ? I mean to create new precision, relevantFound.. etc ? Or should I declare them in my class, outside the method to not allocate more and more memory ? public static void computeMAP(ArrayList<Integer> results, ArrayList<Integer> experts) { //compute MAP double precision = 0; int relevantFound = 0; double sumprecision = 0; thanks

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  • Why does the compiler complain "while expected" when I try to add more code?

    - by user1893578
    Write a program with a word containing @ character as an input. If the word doesn't contain @, it should prompt the user for a word with @. Once a word with @ is read, it should output the word then terminate. This is what I have done so far: public class find { public static void main(String[] args) { System.out.println(" Please enter a word with @ "); Scanner scan = new Scanner(System.in); String bad = "@"; String word = scan.next(); do if (!word.contains(bad)) System.out.println(" Please try again "); else System.out.println(" " + word); while (!word.contains(bad)); } } I can get it to terminate after a word containing "@" is given as input, but if I try to add a Scanner to the line after "please try again", it says while expected.

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  • One log4j.xml - many scripts

    - by psed
    One of my utility jar files is used by different nix scripts, located in different categories. Problem: unable to initialize log4j framework (unable to find log4j.xml). Solution, that allows to configure logger correctly while launching jar classes by different scripts - usage of env vars and force configuring using DOMConfigurtor.configure(pathToConfXml) method. is it possible to avoid path hardcoding and configure logger inside of a script? Appreciate all your help. Thanks.

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  • which loop is faster?

    - by Mansuro
    I have this loop for (it= someCollection.iterator; it.hasNext(); ) { //some code here } I changed it to: for (it= someCollection.iterator;; ) { if (!it.hasNext()) break; //some code here } The second code ran a little bit faster in unit tests in junit on eclipse. Is the second loop faster? I'm asking because the times given by Junit are not too exact, but they give an approximate value

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