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  • How to use JNI, but only when available for current platform?

    - by Mecki
    What is the common way (or best practice) to optionally use JNI? E.g. I have a Java class and this class is 100% pure Java, so it can run on all platforms. However, on some platforms I'd like to speed up some heavy calculations using JNI - which works fine. Unfortunately I cannot support any existing Java platform in the world. So I guess it is fine to initially only support the big three: Linux, Windows, Mac OS X. So what I'd like to do is to use JNI on those three platforms and use the 100% pure Java version on all other platforms. Now I can think of various ways how to do that (loading class dynamically for example and either loading the JNI class or the pure Java one), but thinking that this is a common issue that thousands of projects had to solve in the past for sure, I'm really surprised to not find any documentation or references to the question how to solve this most elegantly or effectively.

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  • Using an empty column as a divider in a JTable.

    - by Catalina Island
    I'm trying to use an empty column as a divider between pairs of columns in a JTable. Here's a picture and code for what I have so far. I know I can change the look using a custom TableCellRenderer. Before I go down that road, is there a better way to do this? Any ideas appreciated. import javax.swing.*; import javax.swing.table.*; public class TablePanel extends JPanel { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame f = new JFrame("TablePanel"); f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); f.add(new TablePanel()); f.pack(); f.setVisible(true); } }); } public TablePanel() { TableModel dataModel = new MyModel(); JTable table = new JTable(dataModel); table.getColumnModel().getColumn(MyModel.DIVIDER).setMaxWidth(0); JScrollPane jsp = new JScrollPane(table); jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); this.add(jsp); } private static class MyModel extends AbstractTableModel { private static final int DIVIDER = 2; private final String[] names = { "A1", "A2", "", "B1", "B2" }; @Override public int getRowCount() { return 32; } @Override public int getColumnCount() { return names.length; } @Override public String getColumnName(int col) { if (col == DIVIDER) return ""; return names[col]; } @Override public Object getValueAt(int row, int col) { if (col == DIVIDER) return ""; return (row + 1) / 10.0; } @Override public Class<?> getColumnClass(int col) { if (col == DIVIDER) return String.class; return Number.class; } } }

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  • Directly Jump to another C++ function

    - by maligree
    I'm porting a small academic OS from TriCore to ARM Cortex (Thumb-2 instruction set). For the scheduler to work, I sometimes need to JUMP directly to another function without modifying the stack nor the link register. On TriCore (or, rather, on tricore-g++), this wrapper template (for any three-argument-function) works: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { typedef void (* __attribute__((interrupt_handler)) Jump3)( A1, A2, A3); ( (Jump3)func )( a1, a2, a3 ); } //example for using the template: JUMP3( superDispatch, this, me, next ); This would generate the assembler instruction J (a.k.a. JUMP) instead of CALL, leaving the stack and CSAs unchanged when jumping to the (otherwise normal) C++ function superDispatch(SchedulerImplementation* obj, Task::Id from, Task::Id to). Now I need an equivalent behaviour on ARM Cortex (or, rather, for arm-none-linux-gnueabi-g++), i.e. generate a B (a.k.a. BRANCH) instruction instead of BLX (a.k.a. BRANCH with link and exchange). But there is no interrupt_handler attribute for arm-g++ and I could not find any equivalent attribute. So I tried to resort to asm volatile and writing the asm code directly: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { asm volatile ( "mov.w r0, %1;" "mov.w r1, %2;" "mov.w r2, %3;" "b %0;" : : "r"(func), "r"(a1), "r"(a2), "r"(a3) : "r0", "r1", "r2" ); } So far, so good, in my theory, at least. Thumb-2 requires function arguments to be passed in the registers, i.e. r0..r2 in this case, so it should work. But then the linker dies with undefined reference to `r6' on the closing bracket of the asm statement ... and I don't know what to make of it. OK, I'm not the expert in C++, and the asm syntax is not very straightforward... so has anybody got a hint for me? A hint to the correct __attribute__ for arm-g++ would be one way, a hint to fix the asm code would be another. Another way maybe would be to tell the compiler that a1..a3 should already be in the registers r0..r2 when the asm statement is entered (I looked into that a bit, but did not find any hint).

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  • PHP5: restrict access to function to certain classes

    - by Tim
    Is there a way in PHP5 to only allow a certain class or set of classes to call a particular function? For example, let's say I have three classes ("Foo", "Bar", and "Baz"), all with similarly-named methods, and I want Bar to be able to call Foo::foo() but deny Baz the ability to make that call: class Foo { static function foo() { print "foo"; } } class Bar { static function bar() { Foo::foo(); print "bar"; } // Should work } class Baz { static function baz() { Foo::foo; print "baz"; } // Should fail } Foo::foo(); // Should also fail There's not necessarily inheritance between Foo, Bar, and Baz, so the use of protected or similar modifiers won't help; however, the methods aren't necessarily static (I made them so here for the simplicity of the example).

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  • java reflection

    - by user622222
    Hi all, System.out.println("Class name : "); BufferedReader reader= new BufferedReader(new InputStreamReader(System.in)); String line = reader.readLine(); Class<?> writeoutClass = Class.forName(line); Method Writeout = null; for (Method mth : writeoutClass.getDeclaredMethods()) { if (mth.getName().startsWith("Writeout")) { Writeout = mth; break; } It's giving error like that; java.lang.ClassNotFoundException: a How can i generate that class?

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  • Who needs singletons?

    - by sexyprout
    Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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  • why my customized marker not showing up in openstreet maps

    - by troy
    I have following java script used for showing the customized marker. But for some reasons its showing up the default marker.. function init() { map = new OpenLayers.Map("basicMap"); var mapnik = new OpenLayers.Layer.OSM(); var fromProjection = new OpenLayers.Projection("EPSG:4326"); var toProjection = new OpenLayers.Projection("EPSG:900913"); var position = new OpenLayers.LonLat(-6.242981,53.331201).transform( fromProjection, toProjection); var zoom = 12; map.addLayer(mapnik); var markers = new OpenLayers.Layer.Markers( "Markers" ); map.addLayer(markers); var size = new OpenLayers.Size(16,28); var offset = new OpenLayers.Pixel(-(size.w*0), -(size.h*1)); var icon = new OpenLayers.Icon('http://m.osmtools.de/images/pin_red.png',size,offset); markers.addMarker(new OpenLayers.Marker(position),icon); map.setCenter(position, zoom ); } And here is my html: <body onload="init();"> <div id="basicMap"></div> </body> I dont understand what wrong with my code .... Please help me.. THank You

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  • JDOQL Any way to avoid multiple .contains() calls in the query when searching for the presence of on

    - by Finbarr
    The question pretty much says it all. If I have a class Class A public class A { ... private List<String> keys; ... } And I want to select all A instances from the DataStore that have atleast one of a List of keys, is there a better way of doing it than this: query = pm.newQuery(A.class); query.setFilter("keys.contains(:key1) || keys.contains(:key2) || keys.contains(:key3)"); List<A> results = (List<A>)query.execute(key1, key2, key3); This has not yet been implemented, so I am open to radical suggestions.

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  • Is there an efficient way to write this PHP if / else statement?

    - by nvoyageur
    I've written a simple issue tracker for my web app. I have some comments that I want to keep private (only a role of 'root' can see them). Is there a better way to write the following so I do not need the empty else section? $role will be 'root' or some other values $is_private will be true if the comment is private <?php // Don't show private comments to non-root users if ($is_private && 'root' != $role): // NON Root cannot see private else: ?> <div class="comment <?= $is_private ? 'private' : '' ; ?>"> <div class="comment-meta toolbar"> <?= $is_private ? 'PRIVATE - ': ''; ?> <span class="datestamp"><?= $created_at; ?></span> - <span class="fullname"><?= $fname . ' ' . $lname; ?></span></div> <p class="content"><?= nl2br($body); ?></p> </div> <?php endif; ?>

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  • dynamic inheritance without touching classes

    - by Jasper
    I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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  • Zend Framework Handle One to Many

    - by user192344
    I have 2 tables "user", "contact", the relation between two tables is one user has many contact Table member m_id name ------------ Table Contact c_id c_m_id value in zend model class, i do it in this way /* Member.php */ class Default_Model_DbTable_Member extends Zend_Db_Table_Abstract { protected $_name = 'member'; protected $_dependentTables = array('Default_Model_DbTable_Contact'); } /* Contact.php */ class Default_Model_DbTable_Contact extends Zend_Db_Table_Abstract { protected $_name = 'contact'; protected $_referenceMap = array( 'Member' => array( 'columns'=> array('c_id'), 'refTableClass'=> 'Default_Model_DbTable_Member', 'refColumns'=> array('c_m_id') ) ); /* IndexController.php */ class IndexController extends Zend_Controller_Action { public function indexAction() { $m= new Default_Model_DbTable_Member(); $row = $m->find(1); $data = $row->current(); $data = $data->findDependentRowset('Default_Model_DbTable_Contact'); print_r($data->toArray()); } } But i just get Invalid parameter number: no parameters were bound , my goal is to search a member detail record, and it also contains a array which store all contact info (i can use join method to do that, but i just want to try zend feature)

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  • Java: Reflection against casting when you know superclass

    - by Ema
    I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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  • Purpose of singletons in programming

    - by thecoshman
    This is admittedly a rather loose question. My current understanding of singletons is that they are a class that you set up in such a way that only one instance is ever created. This sounds a lot like a static class to me. The main differnce being that with a static class you don't / can't instance it, you just use it such as Math.pi(). With a singletong class, you would still need to do something like singleton mySingleton = new singleton(); mysingleton.set_name("foo"); singleton otherSingleton = new singleton(); // correct me if i am wrong, but mysingleton == othersingleton right now, yes? // this the following should happen? otherSingleston.set_name("bar"); mysingleton.report_name(); // will output "bar" won't it? Please note, I am asking this language independently, more about the concept. So I am not so worried about actually how to coed such a class, but more why you would wan't to and what thing you would need to consider.

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  • Getting list of fields back from 'use fields' pragma?

    - by makenai
    So I'm familiar with the use fields pragma in Perl that can be used to restrict the fields that are stored in a class: package Fruit; use fields qw( color shape taste ); sub new { my ( $class, $params ) = @_; my $self = fields::new( $class ) unless ref $class; foreach my $name ( keys %$params ) { $self->{ $name } = $params->{ $name }; } return $self; } My question is.. once I've declared the fields at the top, how I can get the list back.. say because I want to generate accessors dynamically? Is keys %FIELDS the only way? Secondarily, is there a more efficient way to pre-populate the fields in the constructor than looping through and assigning each parameter as I am above? Thanks!

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  • Fluent NHibernate Mappings ClassMap<Entities>....

    - by Pandiya Chendur
    I was going through fluent hibernate getting started tutorial.... In my asp.net mvc web application i have created Entities and Mapping folder as they stated... I created an entity class and i tried to map it my mapping class using this, using System; using System.Collections.Generic; using System.Linq; using System.Web; using FluentNhibernateMVC.Entities; namespace FluentNhibernateMVC.Mappings { public class ClientMap : ClassMap<Client> { } } I cant able to find a ClassMap keyword in my autosuggest list why? This is my entity class using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace FluentNhibernateMVC.Entities { public class Client { public int ClientId { get; set; } public string ClientName { get; set; } public string ClientMobNo { get; set; } public string ClientAddress { get; set; } public DateTime CreatedDate { get; set; } public byte IsDeleted { get; set; } public int CreatedBy { get; set; } } } I have added all references to my project...Am i missing some thing...

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  • Find the right value in recursive array

    - by fire
    I have an array with multiple sub-arrays like this: Array ( [0] => Array ( [Page_ID] => 1 [Page_Parent_ID] => 0 [Page_Title] => Overview [Page_URL] => overview [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 2 [Page_Parent_ID] => 1 [Page_Title] => Team [Page_URL] => overview/team [Page_Type] => content [Page_Order] => 1 ) ) [2] => Array ( [Page_ID] => 3 [Page_Parent_ID] => 0 [Page_Title] => Funds [Page_URL] => funds [Page_Type] => content [Page_Order] => 2 ) [3] => Array ( [0] => Array ( [Page_ID] => 4 [Page_Parent_ID] => 3 [Page_Title] => Strategy [Page_URL] => funds/strategy [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 7 [Page_Parent_ID] => 4 [Page_Title] => A Class Fund [Page_URL] => funds/strategy/a-class-fund [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [0] => Array ( [Page_ID] => 10 [Page_Parent_ID] => 7 [Page_Title] => Information [Page_URL] => funds/strategy/a-class-fund/information [Page_Type] => content [Page_Order] => 1 ) [1] => Array ( [Page_ID] => 11 [Page_Parent_ID] => 7 [Page_Title] => Fund Data [Page_URL] => funds/strategy/a-class-fund/fund-data [Page_Type] => content [Page_Order] => 2 ) ) [2] => Array ( [Page_ID] => 8 [Page_Parent_ID] => 4 [Page_Title] => B Class Fund [Page_URL] => funds/strategy/b-class-fund [Page_Type] => content [Page_Order] => 2 ) I need a function to find the right Page_URL so if you know the $url is "funds/strategy/a-class-fund" I need to pass that to a function that returns a single array result (which would be the Page_ID = 7 array in this example). Having a bit of a stupid day, any help would be appreciated!

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  • Undefined behaviour with non-virtual destructors - is it a real-world issue?

    - by Roddy
    Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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  • in vb.net an error is coming

    - by user275111
    Compiler Error Message: ASPNET: Make sure that the class defined in this code file matches the 'inherits' attribute, and that it extends the correct base class (e.g. Page or UserControl). in vb code-i used namespace and a class.

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  • how does serializable work in java?

    - by Karl Trumstedt
    If I have an instance of a class that I store in a session I need to make it serializable. This class has a static variable, will this be serialized in every instance stored? The static variable is a reference to a cache containing a lot of data in the background. Will all of this data be serialized? If so, it seems preferable to make this variable transient and re-fetch the cache instance each time the instance is restored. Maybe not store the cache instance at all in the class. Will the constructor execute when a class is restored from a serialized state? if not is there any other method I can use to re-instate a transient variable?

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  • PropertyGrid + interface

    - by nilphilus
    public interface ITest { void Somethink(); } public class Test1 : ITest { public void Somethink() { /* do stuff */ } public int Test1Property { get; set; } } public class Test2 : ITest { public void Somethink() { /* do stuff */ } public float Test2Property { get; set; } } //Main class public class MainClass { [TypeConverter(ExpandableObjectConverter)] public ITest test { get; set; } } Ok, i have sth like this. Instance of MainClass is selected by PropertyGrid. How to make a DropDownList of objects of classes which implement ITest (here Test1 and Test2)

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  • Showing multiple elements onClick

    - by Nimbuz
    HTML: <ul id="mode"> <li><a href="#tab1">tab1</a> <div class="extra">tada</div> </li> <li><a href="#tab2">tab2</a> <div class="extra">tada</div> </li> </ul> <div id="tab1" class="tab-content" style="display: none">content 1</div> <div id="tab2" class="tab-content" style="display: none">content 2</div> ? jQuery: $(function(){ var mode = $('#mode'); var arrow = $('<span/>', {'class': 'arrow'}); $('li a', mode).bind('click.mytabs', function() { $('li', mode).removeClass('active'); $(this).parent().addClass('active').append(arrow); var a = $(this).attr('href'); $('.tab-content').hide(); $(a).show(); return false; }).filter(':first').triggerHandler('click.mytabs'); // eq(0) works as well }); JSFiddle here: http://jsfiddle.net/wwMJL/ I'd like to also show each li's 'extra' div on click and hide when the tab is inactive, what do I need to change in the code? Thanks!

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  • ruby subclass filter

    - by Nik
    Hey! Maybe I am getting the idea of a subclass wrong, but I have a Person model and it has an attrib called "age" so Person.first.age #=> '20' Now I want to have a model that's basically persons 55 or older so I know I can have a class like this: class Senior < Person end But how can I "pre-filter" the Senior class so that every object belonging to that class has age = 55? Senior.first.age #=> 56 Thanks!

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  • Comparing objects and inheritance

    - by ereOn
    Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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  • Using svn remove - preserve file on disk instead of having it deleted?

    - by user246114
    Hi, I am creating an eclipse project, which generates a lot of files I don't want to keep under version control. For example, it creates a project folder like: project/ bin/ horse.class cow.class src/ horse.java cow.java so what I do is add the project folder to svn, like: svn add project this puts everything under control, even the bin and .class files. All of those files will have the little 'a' next to them. How can I simply remove the 'add' status from those files? If I try: svn remove bin/horse.class I have to use the --force option and it deletes the file from disk. Is there a way to simply remove it from source but not delete the file from disk? Thanks

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