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  • Nesting arbitrary objects in Java

    - by user1502381
    I am having trouble solving a particular problem in Java (which I did not find by search). I do not know how to create a nested lists of objects - with a different type of object/primitive type at the end. For example: *Note: only an example. I am actually doing this below with something other than Employee, but it serves as simple example. I have an array of an object Employee. It contains information on the Employee. public class Employee { int age int salary int yearsWorking public Employee () { // constructor... } // Accessors } What I need to do is organize the Employees by quantiles/percentiles. I have done so by the following: import org.apache.commons.math.stat.descriptive.rank.Percentile; public class EmployeeSort { public void main(String args[]) { Percentile p = new Percentile(); Employee[] employeeArray = new Employee(100); // filled employeeArray double[] ageArray new double[100]; // filled ageArray with ages from employeeArray int q = 25; // Percentile cutoff for (int i = 1; i*q < 100; i++) { // assign percentile cutoff to some array to contain the values } } } Now, the problem I have is that I need to organize the Employees first by the percentiles of age, then percentiles of yearsWorking, and finally by percentiles of salary. My Java knowledge is inadequate right now to solve this problem, but the project I was handed was in Java. I am primarily a python guy, so this problem would have been a lot easier in that language. No such luck.

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  • Callers block until getFoo() has a value ready?

    - by Sean Owen
    I have a Java Thread which exposes a property which other threads want to access: class MyThread extends Thread { private Foo foo; ... Foo getFoo() { return foo; } ... public void run() { ... foo = makeTheFoo(); ... } } The problem is that it takes some short time from the time this runs until foo is available. Callers may call getFoo() before this and get a null. I'd rather they simply block, wait, and get the value once initialization has occurred. (foo is never changed afterwards.) It will be a matter of milliseconds until it's ready, so I'm comfortable with this approach. Now, I can make this happen with wait() and notifyAll() and there's a 95% chance I'll do it right. But I'm wondering how you all would do it; is there a primitive in java.util.concurrent that would do this, that I've missed? Or, how would you structure it? Yes, make foo volatile. Yes, synchronize on an internal lock Object and put the check in a while loop until it's not null. Am I missing anything?

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  • Is there a better way to declare an empty, typed matrix in MATLAB?

    - by Arthur Ward
    Is there a way to "declare" a variable with a particular user-defined type in MATLAB? zeros() only works for built-in numeric types. The only solution I've come up with involves using repmat() to duplicate a dummy object zero times: arr = repmat(myClass(), [1 0]) Without declaring variables this way, any code which does "arr(end+1) = myClass()" has to include a special case for the default empty matrix which is of type double. Have I missed something a little more sensible?

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  • [C++] Multiple inheritance from template class

    - by Tom P.
    Hello, I'm having issues with multiple inheritance from different instantiations of the same template class. Specifically, I'm trying to do this: template <class T> class Base { public: Base() : obj(NULL) { } virtual ~Base() { if( obj != NULL ) delete obj; } template <class T> T* createBase() { obj = new T(); return obj; } protected: T* obj; }; class Something { // ... }; class SomethingElse { // ... }; class Derived : public Base<Something>, public Base<SomethingElse> { }; int main() { Derived* d = new Derived(); Something* smth1 = d->createBase<Something>(); SomethingElse* smth2 = d->createBase<SomethingElse>(); delete d; return 0; } When I try to compile the above code, I get the following errors: 1>[...](41) : error C2440: '=' : cannot convert from 'SomethingElse *' to 'Something *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1> [...](71) : see reference to function template instantiation 'T *Base<Something>::createBase<SomethingElse>(void)' being compiled 1> with 1> [ 1> T=SomethingElse 1> ] 1>[...](43) : error C2440: 'return' : cannot convert from 'Something *' to 'SomethingElse *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast The issue seems to be ambiguity due to member obj being inherited from both Base< Something and Base< SomethingElse , and I can work around it by disambiguating my calls to createBase: Something* smth1 = d->Base<Something>::createBase<Something>(); SomethingElse* smth2 = d->Base<SomethingElse>::createBase<SomethingElse>(); However, this solution is dreadfully impractical, syntactically speaking, and I'd prefer something more elegant. Moreover, I'm puzzled by the first error message. It seems to imply that there is an instantiation createBase< SomethingElse in Base< Something , but how is that even possible? Any information or advice regarding this issue would be much appreciated.

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  • How to declare ASP classic constants to a data type?

    - by Guy
    In asp classic and vbscript, you can declare a Const with a hexidecial value, and a date type value: Const C_LIGHTCYAN = &hCCFFEE Const C_STARTDATE = #1 JAN 2000# But how can I declare currency, single or doubles data types? Const C_LONG = 1024 '# I want this to be a LONG, not an INT! I'm sure I've seen something like Const C_LNG = L12345 or some other prefix/suffix combination for longs or doubles but can't find the source now

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  • Using static variables for Strings

    - by Vivart
    below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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  • Generate .sql files using rake task

    - by Prasanna
    Hi, I have a table called 'choices' in this table i am storing static data for my site like Blood Groups , qualification, job types etc., I have to create rake tasks one is for to create backup choices.sql file from choices table data, second one is dump the data from .sql file to choice table. How can I create the rake tasks. Any other best way to take backup data from a table and load data into the table Thanks

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  • When is it okay to reference WindowsBase.dll?

    - by Tyler
    I've heard/read about people not wanting to reference the assembly because of the Windows component (e.g. "I don't want to reference Windows for my Web App). I'd like to hear what a large community feels about this. For which project types (business, data access, etc.) is it considered acceptable to reference WindowsBase.dll.

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  • Best database (mysql) structure for this case:

    - by robert
    we have three types of data (tables): Book (id,name,author...) ( about 3 million of rows) Category (id,name) ( about 2000 rows) Location (id,name) ( about 10000 rows) A Book must have at least 1 type of Category (up to 3) AND a Book must have only one Location. I need to correlate this data to get this query faster: Select Books where Category = 'cat_id' AND Location = 'loc_id' Select Books where match(name) against ('name of book') AND Location = 'loc_id' Please I need some help. Thanks

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  • (database design):Which tables should be created for all kindes files (images, attached email files,

    - by meyosef
    Hi, I new in database design: I have question with my own few solution,what do you thinks?: Which tables should be created for all kinds files (images, attached email files,text files for store email body, etc..) that stored in my online store? *option 1:use seperate table for files types * files{ id files_types_id FK file_path file_extension } files_types{ id type_name (unique) } *option 2: use bool field for each file type * files{ id file_path file_extension is_image_main is_image_icon is_image_logo is_pdf_file is_text_file } **option 3: use 1 enum field 'file_type' for each file type ** files{ id file_path file_extension file_type (image_main,image_icon,image_logo,image_main,pdf,text) **enum** } Thanks you, Yosef

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  • Idiomatic scheme and generic programming, why only on numbers ?

    - by Skeptic
    Hi, In Scheme, procedures like +, -, *, / works on different types of numbers, but we don't much see any other generic procedures. For example, length works only on list so that vector-length and string-length are needed. I guess it comes from the fact that the language doesn't really offer any mechanism for defining generic procedure (except cond of course) like "type classes" in Haskell or a standardized object system. Is there an idiomatic scheme way to handle generic procedures that I'm not aware of ?

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  • recognizing a link in an email

    - by Rob Bonner
    Is there a mechanism where I can identify a string in an email, say a order number, and have it route to my iPhone application? I know that base types do this, but not sure if I can create a new type for my app. Thanks!

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  • SQL, Auxiliary table of numbers

    - by vzczc
    For certain types of sql queries, an auxiliary table of numbers can be very useful. It may be created as a table with as many rows as you need for a particular task or as a user defined function that returns the number of rows required in each query. What is the optimal way to create such a function?

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  • Additional concerns when compiling for x64

    - by dotnetdev
    I know that the additional consideratiosn when compiling for x64 is that some data types, like ints, can hold larger values. Are there any concerns? VS2010, released a few days ago, can support compiling for x64 and x32, just like VS2008. The app is x32/86 only. I keep thinking that the app needs to be 64 bit however. What am I missing? Obviously this is not the case. Thanks

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  • how to do new lines? [ textarea -> jquery -> p tag ]

    - by Haroldo
    I'm doing something very similar to the stackoverflow question preview only much more basic. user types in text area - keyup shows what they've typed in preview new lines aren't working $('input, textarea').keyup(function(){ var value = $this.attr('value').replace('\n', '<br />').replace('\r', '<br />'); $('p.preview').html(value); })

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  • Generics and anonymous type

    - by nettguy
    I understood,normally generics is for compile time safe and allow us to keep strongly typed collection.Then how do generic allow us to store anonymous types like List<object> TestList = new List<object>(); TestList.Add(new { id = 7, Name = "JonSkeet" }); TestList.Add(new { id = 11, Name = "Marc Gravell" }); TestList.Add(new { id = 31, Name = "Jason" });

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  • Keep data with specific value on top when sorting a gridview

    - by aspNetAficionado
    Hi i have a gridview with information about documents: name, document type (policy, guidelines, forms, etc), category, etc. I want to sort the gridview alphabetically (name) and by document type, but always having the 'policy' above the other document types when document name is the same. How do I do that? eg If I do sort by DocumentName, DocumentType ('policy' maybe not be the first one in the list) but if I do sort by DocumentType , DocumentName (I would get for example all guidelines first in alphabetical order, then procedures, then policies, etc)

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  • can I have an abstract base class with the key attribute being generic

    - by Greg
    Hi, I want to create a re-usable library. I was going to use extension methods however I run into some issues in some cases for the client to have to specify in the calling method the types. QUESTION - If I use an abstract base class as the basis, can I specify an attribute/property in the class to be generic (e.g. the key property might be an 'int' in one case, or a 'string' in another)?

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  • Java - Regex problem

    - by Yatendra Goel
    I have list of urls of types: http://www.abc.com/pk/etc http://www.abc.com/pk/etc/ http://www.abc.com/pk/etc/etc where etc can be anything. So I want to search only those urls that contains www.abc.com/pk/etc or www.abc.com/pk/etc/

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