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• Computing, storing, and retrieving values to and from an N-Dimensional matrix

  - by Adam S

  This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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• best web database solution for scala for a high traffic site?

  - by egervari

  I am in charge of a rebuilding a website that gets about 250,000 visitors a day. We'd like to use Scala, but it does not work very well with Spring (in some minor cases) and Hibernate (there is a major and very annoying mismatch here if you want to use scala collections, which we do). The application itself is going to have about 40-50 tables. Other than Hibernate, is there an ORM that works awesome with Scala and is as performant and reliable as Hibernate? Does it also have the same capabilities, or are we going to run into leaky-abstractions if we don't use Hibernate? It would be a big risk for us to go with a framework that is newer and doesn't seem to have a lot of industry backing... and at the same time, Hibernate is a real pain to program against when using Scala. 1) The Java Collection <- Scala Collection is absolutely painful. There is a lot more boilerplate and crap to write. 2) The IDE doesn't import JavaConversions and java interfaces automatically... so we this needs to be done manually. Optimizing Imports in IDEA is going to destroy all the manual work. 3) There is also a performance cost to converting back and forth all the time in your domain objects and your dao classes. 4) Not to mention there needs to be a lot of casting, which produces code ugly as sin. I actually would love to write my own orm that is 100% tailored to scala, but obviously this is really outside of the scope of our project for now. So what is the best approach?

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• can I put my sqlite connection and cursor in a function?

  - by steini

  I was thinking I'd try to make my sqlite db connection a function instead of copy/pasting the ~6 lines needed to connect and execute a query all over the place. I'd like to make it versatile so I can use the same function for create/select/insert/etc... Below is what I have tried. The 'INSERT' and 'CREATE TABLE' queries are working, but if I do a 'SELECT' query, how can I work with the values it fetches outside of the function? Usually I'd like to print the values it fetches and also do other things with them. When I do it like below I get an error Traceback (most recent call last): File "C:\Users\steini\Desktop\py\database\test3.py", line 15, in <module> for row in connection('testdb45.db', "select * from users"): ProgrammingError: Cannot operate on a closed database. So I guess the connection needs to be open so I can get the values from the cursor, but I need to close it so the file isn't always locked. Here's my testing code: import sqlite3 def connection (db, arg): conn = sqlite3.connect(db) conn.execute('pragma foreign_keys = on') cur = conn.cursor() cur.execute(arg) conn.commit() conn.close() return cur connection('testdb.db', "create table users ('user', 'email')") connection('testdb.db', "insert into users ('user', 'email') values ('joey', 'foo@bar')") for row in connection('testdb45.db', "select * from users"): print row How can I make this work?

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• Capturing wildcards in java generics

  - by Rollerball

  From this orcale java tutorial: The WildcardError example produces a capture error when compiled: import java.util.List; public class WildcardError { void foo(List<?> i) { i.set(0, i.get(0)); } } After this error demonstration, they fix the problem by using a helper method: public class WildcardFixed { void foo(List<?> i) { fooHelper(i); } // Helper method created so that the wildcard can be captured // through type inference. private <T> void fooHelper(List<T> l) { l.set(0, l.get(0)); } } First, they say that the list input parameter (i) is seen as an Object: In this example, the compiler processes the i input parameter as being of type Object. Why then i.get(0) does not return an Object? if it was already passed in as such? Furthermore what is the point of using a <?> when then you have to use an helper method using <T>. Would not be better using directly which can be inferred?

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• loop is cut one element of the array

  - by Walaa

  The problem is : Write a program that reads a number n and then declares an array of n elements. The program then fills the array with the first n numbers, where each number is two to the power of the previous. Finally, display array’s contents. My code : import java.util.*; public class Q1 { static Scanner scan = new Scanner (System.in); public static void main(String args [] ) { int num; int i = 0; System.out.println("Enter a number :"); num = scan.nextInt(); double [] a=new double[num]; a[0]= num ; for ( ;i<=a.length-1 ; i++) { a[i+1] = Math.pow(2,a[i]); System.out.println((int)(a[i]) ); } } } The error is : ----jGRASP exec: java Q1 Enter a number : 4 4 16 65536 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 at Q1.main(Q1.java:16) ----jGRASP wedge2: exit code for process is 1. why it says that? And the number by user printed twice!

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• Flex Tree Properties, Null Reference?

  - by mvrak

  I am pulling down a large XML file and I have no control over it's structure. I used a custom function to use the tag name to view the tree structure as a flex tree, but then it breaks. I am guessing it has something to do with my other function, one that calls attribute values from the selected node. See code. <mx:Tree x="254" y="21" width="498" height="579" id="xmllisttree" labelFunction="namer" dataProvider="{treeData}" showRoot="false" change="treeChanged(event)" /> //and the Cdata import mx.rpc.events.ResultEvent; [Bindable] private var fullXML:XMLList; private function contentHandler(evt:ResultEvent):void{ fullXML = evt.result.page; } [Bindable] public var selectedNode:Object; public function treeChanged(event:Event):void { selectedNode=Tree(event.target).selectedItem; } public function namer(item:Object):String { var node:XML = XML(item); var nodeName:QName = node.name(); var stringtest:String ="bunny"; return nodeName.localName; } The error is TypeError: Error #1009: Cannot access a property or method of a null object reference. Where is the null reference?

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• Stop writing blank line at the end of CSV file (using MATLAB)

  - by Grant M.

  Hello all ... I'm using MATLAB to open a batch of CSV files containing column headers and data (using the 'importdata' function), then I manipulate the data a bit and write the headers and data to new CSV files using the 'dlmwrite' function. I'm using the '-append' and 'newline' attributes of 'dlmwrite' to add each line of text/data on a new line. Each of my new CSV files has a blank line at the end, whereas this blank line was not there before when I read in the data ... and I'm not using 'newline' on my final call of 'dlmwrite'. Does anyone know how I can keep from writing this blank line to the end of my CSV files? Thanks for your help, Grant EDITED 5/18/10 1:35PM CST - Added information about code and text file per request ... you'll notice after performing the procedure below that there appears to be a carriage return at the end of the last line in the new text file. Consider a text file named 'textfile.txt' that looks like this: Column1, Column2, Column3, Column4, Column 5 1, 2, 3, 4, 5 1, 2, 3, 4, 5 1, 2, 3, 4, 5 1, 2, 3, 4, 5 1, 2, 3, 4, 5 Here's a sample of the code I am using: % import data importedData = importdata('textfile.txt'); % manipulate data importedData.data(:,1) = 100; % store column headers into single comma-delimited % character array (for easy writing later) columnHeaders = importedData.textdata{1}; for counter = 2:size(importedData.textdata,2) columnHeaders = horzcat(columnHeaders,',',importedData.textdata{counter}); end % write column headers to new file dlmwrite('textfile_updated.txt',columnHeaders,'Delimiter','','newline','pc') % append all but last line of data to new file for dataCounter = 1:(size(importedData.data,2)-1) dlmwrite('textfile_updated.txt',importedData.data(dataCounter,:),'Delimiter',',','newline','pc','-append') end % append last line of data to new file, not % creating new line at end dlmwrite('textfile_updated.txt',importedData.data(end,:),'Delimiter',',','-append')

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• How do I differentiate between different descendents with the same name?

  - by zotty

  I've got some XML I'm trying to import with c#, which looks something like this: <run> <name = "bob"/> <date = "1958"/> </run> <run> <name = "alice"/> <date = "1969"/> </run> I load my xml using XElement xDoc=XElement.Load(filename); What I want to do is have a class for "run", under which I can store names and dates: public class RunDetails { public RunDetails(XElement xDoc, XNamespace xmlns) { var query = from c in xDoc.Descendants(xmlns + "run").Descendants(xmlns + "name") select c; int i=0; foreach (XElement a in query) { this.name= new NameStr(a, xmlns); // a class for names Name.Add(this.name); //Name is a List<NameStr> i++; } // Here, i=2, but what I want is a new instance of the RunDetails class for each <run> } } How can I set up my code to create a new instance of the RunDetails class for every < run, and to only select the < name and < date inside a given < run?

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• Elegant and 'correct' multiton implementation in Objective C?

  - by submachine

  Would you call this implementation of a multiton in objective-c 'elegant'? I have programmatically 'disallowed' use of alloc and allocWithZone: because the decision to allocate or not allocate memory needs to be done based on a key. I know for sure that I need to work with only two instances, so I'm using 'switch-case' instead of a map. #import "Multiton.h" static Multiton *firstInstance = nil; static Multiton *secondInstance = nil; @implementation Multiton + (Multiton *) sharedInstanceForDirection:(char)direction { return [[self allocWithKey:direction] init]; } + (id) allocWithKey:(char)key { return [self allocWithZone:nil andKey:key]; } + (id)allocWithZone:(NSZone *)zone andKey:(char)key { Multiton **sharedInstance; @synchronized(self) { switch (key) { case KEY_1: sharedInstance = &firstInstance; break; case KEY_2: sharedInstance = &secondInstance; break; default: [NSException raise:NSInvalidArgumentException format:@"Invalid key"]; break; } if (*sharedInstance == nil) *sharedInstance = [super allocWithZone:zone]; } return *sharedInstance; } + (id) allocWithZone:(NSZone *)zone { //Do not allow use of alloc and allocWithZone [NSException raise:NSObjectInaccessibleException format:@"Use allocWithZone:andKey: or allocWithKey:"]; return nil; } - (id) copyWithZone:(NSZone *)zone { return self; } - (id) retain { return self; } - (unsigned) retainCount { return NSUIntegerMax; } - (void) release { return; } - (id) autorelease { return self; } - (id) init { [super init]; return self; } PS: I've not tried out if this works as yet, but its compiling cleanly :)

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• Solr - DeltaImport doenst run the parentDeltaQuery

  - by rails

  I have 1:n relation between my main entity(PackageVersion) and its tag in my DB. I add a new tag with this date to the db at the timestamp and I run delta import command. the select retrieves the line but i dont see any other sql. Here are my data-config.xml configurations: <entity name="PackageVersion" pk="PackageVersionId" query= "select ... from [dbo].[Package] Package inner join [dbo].[PackageVersion] PackageVersion on Package.Id = PackageVersion.PackageId" deltaQuery = "select PackageVersion.Id PackageVersionId from [dbo].[Package] Package inner join [dbo].[PackageVersion] PackageVersion on Package.Id = PackageVersion.PackageId where Package.LastModificationTime > '${dataimporter.last_index_time}' OR PackageVersion.Timestamp > '${dataimporter.last_index_time}'" deltaImportQuery="select ... from [dbo].[Package] Package inner join [dbo].[PackageVersion] PackageVersion on Package.Id = PackageVersion.PackageId Where PackageVersionId=='${dih.delta.id}'" > <entity name="PackageTag" pk="ResourceId" processor="CachedSqlEntityProcessor" cacheKey="ResourceId" cacheLookup="PackageVersion.PackageId" query= "SELECT ResourceId,[Text] PackageTag from [dbo].[Tag] Tag" deltaQuery="SELECT ResourceId,[Text] PackageTag from [dbo].[Tag] Tag Where Tag.TimeStamp > '${dataimporter.last_index_time}'" parentDeltaQuery="select PackageVersion.PackageVersionId from [dbo].[Package] where Package.Id=${PackageTag.ResourceId}"> </entity> </entity>

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• How to setup and teardown temporary django db for unit testing?

  - by blokeley

  I would like to have a python module containing some unit tests that I can pass to hg bisect --command. The unit tests are testing some functionality of a django app, but I don't think I can use hg bisect --command manage.py test mytestapp because mytestapp would have to be enabled in settings.py, and the edits to settings.py would be clobbered when hg bisect updates the working directory. Therefore, I would like to know if something like the following is the best way to go: import functools, os, sys, unittest sys.path.append(path_to_myproject) os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings' def with_test_db(func): """Decorator to setup and teardown test db.""" @functools.wraps def wrapper(*args, **kwargs): try: # Set up temporary django db func(*args, **kwargs) finally: # Tear down temporary django db class TestCase(unittest.TestCase): @with_test_db def test(self): # Do some tests using the temporary django db self.fail('Mark this revision as bad.') if '__main__' == __name__: unittest.main() I should be most grateful if you could advise either: If there is a simpler way, perhaps subclassing django.test.TestCase but not editing settings.py or, if not; What the lines above that say "Set up temporary django db" and "Tear down temporary django db" should be?

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• What is the correct approach to using GWT with persistent objects?

  - by dankilman

  Hi, I am currently working on a simple web application through Google App engine using GWT. It should be noted that this is my first attempt at such a task. I have run into to following problem/dilema: I have a simple Class (getters/setters and nothing more. For the sake of clarity I will refer to this Class as DataHolder) and I want to make it persistent. To do so I have used JDO which required me to add some annotations and more specifically add a Key field to be used as the primary key. The problem is that using the Key class requires me to import com.google.appengine.api.datastore.Key which is ok on the server side, but then I can't use DataHolder on the client side, because GWT doesn't allow it (as far as I know). So I have created a sister Class ClientDataHolder which is almost identical, though it doesn't have all the JDO annotations nor the Key field. Now this actually works but It feels like I'm doing something wrong. Using this approach would require maintaining to separate classes for each entity I wish to have. So my question is: Is there a better way of doing this? Thank you.

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• In Excel 2010, how can I show a count of occurrences on a specific date within multiple time ranges?

  - by Justin

  Here's what I'm trying to do. I have three columns of data. ID, Date(MM/DD/YY), Time(00:00). I need to create a chart or table that shows the number of occurrences on, say, 12/10/2010 between 00:00 and 00:59, 1:00 and 1:59, etc, for each hour of the day. I can do countif and get results for the date, but I cannot figure out how to show a summary of the count of occurrences per hour for the 24 hour period. I have months of data and many times each day. Example of data set is below. Any help is greatly ID Date Time 221 12/10/2010 00:01 223 12/10/2010 00:45 227 12/10/2010 01:13 334 12/11/2010 14:45 I would like the results to read: Date Time Count 12/10/2010 00:00AM - 00:59AM 2 12/10/2010 01:00AM - 01:59AM 1 12/10/2010 02:00AM - 02:59AM 0 ......(continues for every hour of the day) 12/11/2010 00:00AM - 00:59AM 0 ......... 12/11/2010 14:00PM - 14:59PM 1 And so on. Sorry for the length but I wanted to be clear. EDIT Here is a sample spreadsheet. Very little data, but I couldn't figure out a better way without having a huge file. Tested in notepad for formatting and worked ok on import as csv. PID,Date,Time 2888759,12/10/2010,0:10 2888760,12/10/2010,0:10 2888761,12/10/2010,0:10 2888762,12/10/2010,0:11 2889078,12/10/2010,15:45 2889079,12/10/2010,15:57 2889080,12/10/2010,15:57 2889081,12/10/2010,15:58 2889082,12/10/2010,16:10 2889083,12/10/2010,16:11 2889084,12/10/2010,16:11 2889085,12/10/2010,16:12 2889086,12/10/2010,16:12 2889087,12/10/2010,16:12 2889088,12/10/2010,16:13 2891529,12/14/2010,16:21

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• Django: Create custom template tag -> ImportError

  - by Alexander Scholz

  I'm sorry to ask this again, but I tried several solutions from stack overflow and some tutorials and I couldn't create a custom template tag yet. All I get is ImportError: No module named test_tag when I try to start the server via python manage.py runserver. I created a very basic template tag (found here: django templatetag?) like so: My folder structure: demo manage.py test __init__.py settings.py urls.py ... templatetags __init__.py test_tag.py test_tag.py: from django import template register = template.Library() @register.simple_tag def test_tag(input): if "foo" == input: return "foo" if "bar" == input: return "bar" if "baz" == input: return "baz" return "" index.html: {% load test_tag %} <html> <head> ... </head> <body> {% cms_toolbar %} {% foobarbaz "bar" %} {% foobarbaz "elephant" %} {% foobarbaz "foo" %} </body> </html> and my settings.py: INSTALLED_APPS = ( ... 'test_tag', ... ) Please let me know if you need further information from my settings.py and what I did wrong so I can't even start my server. (If I delete 'test_tag' from installed apps I can start the server but I get the error that test_tag is not known, of course). Thanks

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• Problem in calling a function from different class using protocols-iphone

  - by Muniraj

  I use cocos2d for my game. In which I play a movie and have a separate overlay view for controls.The touches are detected in the overlay view. Now when the touches are detected the function in the game code has to be invoked. But the function is not detected and there is no error. I dont know what has gone wrong. Someone please help me. The code are as follows The protocol part is @protocol Protocol @required -(void) transition1:(id) sender; @end The function which is to be invoked in the game code is (void) transition1:(id) sender { [[Director sharedDirector] replaceScene: [ [Scene node] addChild: [Layer4 node] z:0] ]; } The code in the overlay view in MovieOverlayViewController.h import "Protocol.h" @interface MovieOverlayViewController : UIViewController { UIImageView *overlay; NSObject <Protocol> *transfer; } @end The code in the overlay view in MovieOverlayViewController.m @implementation MovieOverlayViewController (id)init { if ((self = [super init])) self.view = [[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]] autorelease]; return self; } -(void) viewWillAppear:(BOOL)animated { overlay = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"overlay.png"]] autorelease]; [self.view addSubview:overlay]; } (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint point = [touch locationInView:self.view]; NSLog(@"pointx: %f pointy:%f", point.x, point.y); if (CGRectContainsPoint(CGRectMake(1, 440, 106, 40), point)) { // the function is called here [transfer transition1: nil]; } else if (CGRectContainsPoint(CGRectMake(107, 440, 106, 40), point)) NSLog(@"tab 2 touched"); } (void)dealloc { [overlay release]; [super dealloc]; } @end

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• Porting Python algorithm to C++ - different solution

  - by cb0

  Hello, I have written a little brute string generation script in python to generate all possible combinations of an alphabet within a given length. It works quite nice, but for the reason I wan't it to be faster I try to port it to C++. The problem is that my C++ Code is creating far too much combination for one word. Heres my example in python: ./test.py gives me aaa aab aac aad aa aba .... while ./test (the c++ programm gives me) aaa aaa aaa aaa aa Here I also get all possible combinations, but I get them twice ore more often. Here is the Code for both programms: #!/usr/bin/env python import sys #Brute String Generator #Start it with ./brutestringer.py 4 6 "abcdefghijklmnopqrstuvwxyz1234567890" "" #will produce all strings with length 4 to 6 and chars from a to z and numbers 0 to 9 def rec(w, p, baseString): for c in "abcd": if (p<w - 1): rec(w, p + 1, baseString + "%c" % c) print baseString for b in range(3,4): rec(b, 0, "") And here the C++ Code #include <iostream> using namespace std; string chars="abcd"; void rec(int w,int b,string p){ unsigned int i; for(i=0;i<chars.size();i++){ if(b < (w-1)){ rec(w, (b+1), p+chars[i]); } cout << p << "\n"; } } int main () { int a=3, b=0; rec (a+1,b, ""); return 0; } Does anybody see my fault ? I don't have much experience with C++. Thanks indeed

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• Python lists/arrays: disable negative indexing wrap-around

  - by wim

  While I find the negative number wraparound (i.e. A[-2] indexing the second-to-last element) extremely useful in many cases, there are often use cases I come across where it is more of an annoyance than helpful, and I find myself wishing for an alternate syntax to use when I would rather disable that particular behaviour. Here is a canned 2D example below, but I have had the same peeve a few times with other data structures and in other numbers of dimensions. import numpy as np A = np.random.randint(0, 2, (5, 10)) def foo(i, j, r=2): '''sum of neighbours within r steps of A[i,j]''' return A[i-r:i+r+1, j-r:j+r+1].sum() In the slice above I would rather that any negative number to the slice would be treated the same as None is, rather than wrapping to the other end of the array. Because of the wrapping, the otherwise nice implementation above gives incorrect results at boundary conditions and requires some sort of patch like: def ugly_foo(i, j, r=2): def thing(n): return None if n < 0 else n return A[thing(i-r):i+r+1, thing(j-r):j+r+1].sum() I have also tried zero-padding the array or list, but it is still inelegant (requires adjusting the lookup locations indices accordingly) and inefficient (requires copying the array). Am I missing some standard trick or elegant solution for slicing like this? I noticed that python and numpy already handle the case where you specify too large a number nicely - that is, if the index is greater than the shape of the array it behaves the same as if it were None.

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• Google Maps Controls panel size is displayed wrong

  - by Andrea Giachetto

  I have a weird problem with Google Maps Control. I've tested in a blank page my custom maps with custom markers and everything seems to be ok, also with the control panel. When I tried to import all my code in the page I'm working with ( I use a full screen fluid grid system ) the control panel is displayed with strange size. I tried everything for disable/enable the ui of the Google Maps but the problem remain. The code of my maps are exactly the same, both in my blank page and in my site, but in the site the ui control panel is displayed very strange. Here's the code: <div id="map_canvas2" style="height: 580px; width: 100%;"></div> <script> var image = 'path/to/your/image.png'; var mapOptions = { zoom: 17, center: new google.maps.LatLng(45.499290, 12.621510), mapTypeId: google.maps.MapTypeId.ROADMAP, scrollwheel: false } var map = new google.maps.Map(document.getElementById('map_canvas2'), mapOptions); var myPos = new google.maps.LatLng(45.499290,12.621510); var myMarker = new google.maps.Marker({position: myPos, map: map, icon: 'http://www.factory42.it/jtaca/wordpress/wp-content/uploads/2014/06/pin-map.png' }); </script> </div> Here's an img: http://www.factory42.it/jtaca/wordpress/wp-content/uploads/2014/06/img-maps.png

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• Exceptions over remote methods

  - by Andrei Vajna II

  What are the best practices for exceptions over remote methods? I'm sure that you need to handle all exceptions at the level of a remote method implementation, because you need to log it on the server side. But what should you do afterwards? Should you wrap the exception in a RemoteException (java) and throw it to the client? This would mean that the client would have to import all exceptions that could be thrown. Would it be better to throw a new custom exception with fewer details? Because the client won't need to know all the details of what went wrong. What should you log on the client? I've even heard of using return codes(for efficiency maybe?) to tell the caller about what happened. The important thing to keep in mind, is that the client must be informed of what went wrong. A generic answer of "Something failed" or no notification at all is unacceptable. And what about runtime (unchecked) exceptions?

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• Can I share code & resources between Android projects without using a library?

  - by Tom

  The standard advice for sharing code & resources between Android projects is to use a library. Personally I find this works poorly if (a) the shared code changes a lot, or (b) your computer isn't fast enough. I also don't want to get into deploying multiple APK's, which seems to be necessary when I use dependent projects (i.e. Java Build Path, Projects Tab). On the other hand, sharing a folder of source code by using the Eclipse linked source feature works great (Java Build Path, Source tab, Link Source button), but for these two issues: 1) I can't use the same technique to share resources. I can create the link to the resources parent folder but then things get wonky and the shared resources don't get compiled (I'm using ADT 21). 2) So then I settle for copying the shared resources into each project, but this doesn't work because either. The shared code can't import the copy of its resources because it doesn't know the package name of the project that uses it. The solution I've been using is to access the resources dynamically, but that has become cumbersome as the number of resources grows. So, I need a solution to either (1) or (2), or I'll have to go back to a library project. (Or maybe there is another option I haven't thought of?)

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• Java constructor using generic types

  - by user37903

  I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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• Can I control object creation using MEF?

  - by Akash

  I need to add some extension points to our existing code, and I've been looking at MEF as a possible solution. We have an IRandomNumberGenerator interface, with a default implementation (ConcreteRNG) that we would like to be swappable. This sounds like an ideal scenario for MEF, but I've been having problems with the way we instantiate the random number generators. Our current code looks like: public class Consumer { private List<IRandomNumberGenerator> generators; private List<double> seeds; public Consumer() { generators = new List<IRandomNumberGenerator>(); seeds = new List<double>(new[] {1.0, 2.0, 3.0}); foreach(var seed in seeds) { generators.Add(new ConcreteRNG(seed); } } } In other words, the consumer is responsible for instantiating the RNGs it needs, including providing the seed that each instance requires. What I'd like to do is to have the concrete RNG implementation discovered and instantiated by MEF (using the DirectoryCatalog). I'm not sure how to achieve this. I could expose a Generators property and mark it as an [Import], but how do I provide the required seeds? Is there some other approach I am missing?

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• If statement String trouble

  - by Jeremy Stone

  I'm trying to create a program which takes user input of two words and determines whether or not these words are the same. import java.util.Scanner; public class L7E3 { public static void main(String[] args) { Scanner keyboard = new Scanner(System. in ); String word1, word2; System.out.println("Please enter a word: "); word1 = keyboard.nextLine(); System.out.println("Please enter a word: "); word2 = keyboard.nextLine(); if (word1 == word2) { System.out.println("The words are " + word1 + " and " + word2 + ". These words are the same."); } else { System.out.println("The words are " + word1 + " and " + word2 + ". These words are not the same."); } } } I figured that word1==word2 would have worked to determine whether the two strings were equal, I'm using JGrasp and it goes directly to my else option regardless of input. Am I doing something wrong with strings?

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• Cannot disable index during PL/SQL procedure

  - by nw

  I've written a PL/SQL procedure that would benefit if indexes were first disabled, then rebuilt upon completion. An existing thread suggests this approach: alter session set skip_unusable_indexes = true; alter index your_index unusable; [do import] alter index your_index rebuild; However, I get the following error on the first alter index statement: SQL Error: ORA-14048: a partition maintenance operation may not be combined with other operations ORA-06512: [...] 14048. 00000 - "a partition maintenance operation may not be combined with other operations" *Cause: ALTER TABLE or ALTER INDEX statement attempted to combine a partition maintenance operation (e.g. MOVE PARTITION) with some other operation (e.g. ADD PARTITION or PCTFREE which is illegal *Action: Ensure that a partition maintenance operation is the sole operation specified in ALTER TABLE or ALTER INDEX statement; operations other than those dealing with partitions, default attributes of partitioned tables/indices or specifying that a table be renamed (ALTER TABLE RENAME) may be combined at will The problem index is defined so: CREATE INDEX A11_IX1 ON STREETS ("SHAPE") INDEXTYPE IS "SDE"."ST_SPATIAL_INDEX" PARAMETERS ('ST_GRIDS=890,8010,72090 ST_SRID=2'); This is a custom index type from a 3rd-party vendor, and it causes chronic performance degradation during high-volume update/insert/delete operations. Any suggestions on how to work around this error? By the way, this error only occurs within a PL/SQL block.

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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