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  • How much memory does a hashtable use?

    - by Michael
    Would a hashtable/hashmap use a lot of memory if it only consists of object references and int's? As for a school project we had to map a database to objects (that's what being done by orm/hibernate nowadays) but eager to find a good way not to store id's in objects in order to save them again we thought of putting all objects we created in a hashmap/hashtable, so we could easily retrieve it's ID. My question is if it would cost me performance using this, in my opinion more elegant way to solve this problem.

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  • problem in jdbc preparestatement

    - by akshay
    i am geting error when i try to use following,why is it so? ResultSet findByUsername(String tablename,String field,String value) { pStmt = cn.prepareStatement("SELECT * FROM" + tablename +" WHERE ? = ? "); pStmt.setString(1, tablename); pStmt.setString(2,field); pStmt.setString(3,value); return(pStmt.executeQuery()); } also i tried following , but its not working too ResultSet findByUsername(String tablename,String field,String value) { String sqlQueryString = " SELECT * FROM " + tablename +" WHERE " + filed + "= ? ") cn.prepareStatement(sqlQuery); pStmt.setString(1, value); return(pStmt.executeQuery()); }

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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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  • Android Convert Central Time to Local Time

    - by chedstone
    I have a MySql database that stores a timestamp for each record I insert. I pull that timestamp into my Android application as a string. My database is located on a server that has a TimeZone of CST. I want to convert that CST timestamp to the Android device's local time. Can someone help with this?

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  • How do I write a Guice Provider that doesn't explicitly create objects?

    - by ripper234
    Say I have a ClassWithManyDependencies. I want to write a Guice Provider for this class, in order to create a fresh instance of the class several times in my program (another class will depend on this Provider and use it at several points to create new instances). One way to achieve this is by having the Provider depend on all the dependencies of ClassWithManyDependencies. This is quite ugly. Is there a better way to achieve this? Note - I certainly don't want the Provider to depend on the injector. Another option I considered is having ClassWithManyDependencies and ClassWithManyDependenciesProvider extend the same base class, but it's butt ugly.

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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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  • How do I iterate over an Array field reflectively?

    - by kunjaan
    I have Class<? extends Object> class1 = obj.getClass(); Field[] fields = class1.getDeclaredFields(); for (Field aField : fields) { aField.setAccessible(true); if (!Modifier.isStatic(aField.getModifiers()) && Modifier.isPublic((aField.getModifiers()))) { if (aField.getType().isArray()) { for (?? vals : aField) { System.out.println(vals); } } } }

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  • How can I implement log4j logging to an existing J2EE Struts web application?

    - by Ruepen
    I have recently inherited a J2EE Struts web app that was written back in 2002. There is no logging in the application other than the odd System.out.println(). I have added log4j logging so that I can write out some info to the console, but I'm concerned on how best to approach this. Any suggestions, tips, best practices would be welcome as I don't want to spend too much time adding logging to every method or class (or trying to find what places where logging would be best - ie. bad code blocks/defects). My current approach is to just add some logging to the few classes that I have been looking at to understand the code, but are there a few key places where I can add logging to maximize my use of adding log4j?

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  • Google App Engine + AWS S3 file protection!

    - by grep
    Hi all, I have an application running on GAE/J that streams video from AWS S3. I need a solution for protecting the video from being stolen and I found that pre-signed URLs might be it (??). How can I create pre-signed URLs from GAE/J or there's a better solution to secure the videos? thanks

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  • Indexing through Android string resources

    - by gssi
    OK, I've got the code to allow me to index through the string resources. Now, how do I get the value of a specific resource item without knowing its name? Here's the index loop: Field[] fLst = R.string.class.getFields(); for(Field f : fLst){ Log.i(dbgTag, "Field Entry: R.string." + f.getName()); } Thanks for your efforts ...

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  • Hibernate OneToMany and ManyToOne confusion! Null List!

    - by squizz
    I have two tables... For example - Company and Employee (let's keep this real simple) Company( id, name ); Employee( id, company_id ); Employee.company_id is a foreign key. My entity model looks like this... Employee @ManyToOne(cascade = CascadeType.PERSIST) @JoinColumn(name = "company_id") Company company; Company @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name = "company_id") List<Employee> employeeList = new ArrayList<Employee>(); So, yeah I want a list of employees for a company. When I do the following... Employee e = new Employee(); e.setCompany(c); //c is an Company that is already in the database. DAO.insertEmployee(e); //this works fine! If I then get my Company object it's list is empty! Ive tried endless different ways from the Hibernate documentation! Obviously not tried the correct one yet! I just want the list to be populated for me or find out a sensible alternative. Help would be greatly appreciated, thanks!

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  • BlackBerry - Handle and translate messages (sms/email/pim/pin)?

    - by humble coffee
    Does the native Blackberry API allow for the modification of any messaging interface? For example, I'd like to be able to build an app that added a button at the bottom of a received message which says 'translate this'. I've heard that this kind of thing is possible using J2ME plus the native BlackBerry API. Can this be done for all kinds of messages, eg SMS, email and BB messaging? The translation aspect is not relevant, it just provides the context for the kind of feature I'm after.

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  • Lucene case sensitive & insensitive search

    - by zvikico
    I have a Lucene index which is currently case sensitive. I want to add the option of having a case insensitive search as a fall-back. This means that results that match the case will get more weight and will appear first. For example, if the number of results is limited to 10, and there are 10 matches which match my case, this is enough. If I only found 7 results, I can add 3 more results from the case-insensitive search. My case is actually more complex, since I have items with different weights. Ideally, having a match with "wrong" case will add some weight. Needless to say, I do not want duplicate results. One possible approach is to have 2 indexes. One with case and one without and search both. Naturally, there's some redundancy here, since I need to index twice. Is there a better solution? Ideas?

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  • Service Discovery in J2ME

    - by thiagolee
    Hello, I have an application to run on a cell phone equipped with Wi-Fi and an application on a desktop which I want to communicate with. The problem is that I want to find in a Local Area Network the IP and port of the machine who has my service running. I can guarantee that there will be at maximum only one machine running it. I searched a lot for a way to do this but I ended up with nothing. I read something about WebServices, but it didn't seen to be what I wanted, what I want is really simple. I actually found a solution for it, but it can't be ported to J2ME. Anyone can help? Thanks.

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  • Group Objects by Common Key

    - by Marshmellow1328
    I have a list of Customers. Each customer has an address and some customers may actually have the same address. My ultimate goal is to group customers based on their address. I figure I could either put the customers in some sort of list-based structure and sort on the addresses, or I could drop the objects into some sort of map that allows multiple values per key. I will now make a pretty picture: List: A1 - C1, A1 - C2, A2 - C3, A3 - C4, A3 - C5 Map: A1 A2 A3 C1 C3 C4 C2 C5 Which option (or any others) do you see as the best solution? Are there any existing classes that will make development easier?

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  • division problems

    - by David
    This line of code: System.out.println ("aray[j], "+aray[j]+", divided by sum, "+sum+", equals: aray[j]/sum: "+ aray[j]/sum) ; is yeilding this line of text: aray[j], 21, divided by sum, 100, equals: aray[j]/sum: 0 why is it doing this? (everything is right eccept that the answer should be .21)

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  • Explicit constructor still has default values even though a default constructor is not invoked.

    - by Phoenix
    According to my understanding a default constructor initializes the state of the object to default values, so if i provide an explicit no-arg public constructor like this then how are the values of d and e still getting initialized to zero because in this case the default constructor is not invoked. public class B extends A{ private int d; private int e; public B() { System.out.println(d); System.out.println(e); } } EDIT:: The only thing default constructor does is call to super() then how come if i have a explicitly mentioned a constructor here and A has a protected variable say c which is initialized to 17 in its constructor. Should I not be explicitly calling super() to be able to see that change since I'm using my own constructor ? Why is B still getting the value of 17 through inheritance ?

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