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  • Why doesn't java.lang.Number implement Comparable?

    - by Julien Chastang
    Does anyone know why java.lang.Number does not implement Comparable? This means that you cannot sort Numbers with Collections.sort which seems to me a little strange. Post discussion update: Thanks for all the helpful responses. I ended up doing some more research about this topic. The simplest explanation for why java.lang.Number does not implement Comparable is rooted in mutability concerns. For a bit of review, java.lang.Number is the abstract super-type of AtomicInteger, AtomicLong, BigDecimal, BigInteger, Byte, Double, Float, Integer, Long and Short. On that list, AtomicInteger and AtomicLong to do not implement Comparable. Digging around, I discovered that it is not a good practice to implement Comparable on mutable types because the objects can change during or after comparison rendering the result of the comparison useless. Both AtomicLong and AtomicInteger are mutable. The API designers had the forethought to not have Number implement Comparable because it would have constrained implementation of future subtypes. Indeed, AtomicLong and AtomicInteger were added in Java 1.5 long after java.lang.Number was initially implemented. Apart from mutability, there are probably other considerations here too. A compareTo implementation in Number would have to promote all numeric values to BigDecimal because it is capable of accommodating all the Number sub-types. The implication of that promotion in terms of mathematics and performance is a bit unclear to me, but my intuition finds that solution kludgy.

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  • Link error for user defined class type template parameter

    - by isurulucky
    Hi, I implemented a Simple STL map in C++. Factored out the comparison as a type as I was instructed to, then implemented the comparison as shown below: template <typename T> int KeyCompare<T>::operator () (T tKey1, T tKey2) { if(tKey1 < tKey2) return -1; else if(tKey1 > tKey2) return 1; else return 0; } here, tKey1 and tKet2 are the two keys I'm comparing. This worked well for all the basic data types and string. I added a template specialization to compare keys of a user defined type named Test and added a specialization as follows: int KeyCompare<Test>::operator () (Test tKey1, Test tKey2) { if(tKey1.a < tKey2.a) return -1; else if(tKey1.a > tKey2.a) return 1; else return 0; } when I run this, I get a linking error saying SimpleMap.obj : error LNK2005: "public: int __thiscall KeyCompare::operator()(class Test,class Test)" (??R?$KeyCompare@VTest@@@@QAEHVTest@@0@Z) already defined in MapTest.obj SimpleMap.obj : error LNK2005: "public: __thiscall KeyCompare::~KeyCompare(void)" (??1?$KeyCompare@VTest@@@@QAE@XZ) already defined in MapTest.obj SimpleMap.obj : error LNK2005: "public: __thiscall KeyCompare::KeyCompare(void)" (??0?$KeyCompare@VTester@@@@QAE@XZ) already defined in MapTest.obj MapTest.cpp is the test harness class in which I wrote the test case. I have used include guards as well, to stop multiple inclusions. Any idea what the matter is?? Thank you very much!!

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  • Sync version of the project with Java

    - by Alexadar
    I have a problem, I need to sync version of the project. Changes are performed on main project that resides on central Coldfusion server. There are about 30 remote Coldfusion servers, that has to sync with latest version on central server. New synch application will to be done in Java! I have a direct link to each remote location. Mostly Windows OS and Windows tools are used. My idea: The synchronization is performed at the level of synchronization of folders. I would like to avoid the use of SVN and similar tools. My idea is to carry out comparison of folders on the local server (comparison is performed between the old and new versions),with NO communication with remote servers, make the difference between the versions and the same is sent to the remote machines. We will install Tomcat on every remote server. "Sync application" deployed on Tomcat will take care about differences. Remote server will return me an answer, about the success of the sync. Any kind of suggestion or completely new approach on this topic is more than welcome. Thanks Best regards

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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • AWK: compare apache dates without using regular expression

    - by smallmeans
    I'm writing a loganalysis application and wanted to grab apache log records between two certain dates. Assume that a date is formated as such: 22/Dec/2009:00:19 (day/month/year:hour:minute) Currently, I'm using a regular expression to replace the month name with its numeric value, remove the separators, so the above date is converted to: 221220090019 making a date comparison trivial.. but.. Running a regex on each record for large files, say, one containing a quarter million records, is extremely costly.. is there any other method not involving regex substitution? Thanks in advance Edit: here's the function doing the convertion/comparison function dateInRange(t, from, to) { sub(/[[]/, "", t); split(t, a, "[/:]"); match("JanFebMarAprMayJunJulAugSepOctNovDec", a[2]); a[2] = sprintf("%02d", (RSTART + 2) / 3); s = a[3] a[2] a[1] a[4] a[5]; return s >= from && s <= to; } "from" and "to" are the intervals in the aforementioned format, and "t" is the raw apache log date/time field (e.g [22/Dec/2009:00:19:36)

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  • Finding missing files by checksum

    - by grw
    Hi there, I'm doing a large data migration between two file systems (let's call them F1 and F2) on a Linux system which will necessarily involve copying the data verbatim into a differently-structured hierarchy on F2 and changing the file names. I'd like to write a script to generate a list of files which are in F1 but not in F2, i.e. the ones which weren't copied by the migration script into the new hierarchy, so that I can go back and migrate them manually. Unfortunately for reasons not worth going into, the migration script can't be modified to list files that it doesn't migrate. My question differs from this previously answered one because of the fact that I cannot rely on filenames as a comparison. I know the basic outline of the process would be: Generate a list of checksums for all files, recursing through F1 Do the same for F2 Compare the lists and generate a negative intersection of the checksums, ignoring the file names, to find files which are in F1 but not in F2. I'm kind of stuck getting past that stage, so I'd appreciate any pointers on which tools to use. I think I need to use the 'comm' command to compare the list of file checksums, but since md5sum, sha512sum and the like put the file name next to the checksum, I can't see a way to get it to bring me a useful comparison. Maybe awk is the way to go? I'm using Red Hat Enterprise Linux 5.x. Thanks.

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  • Objective-c: Comparing two strings not working correctly.

    - by Mr. McPepperNuts
    - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section { id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section]; if(tempArray != nil){ for (int i = 0; i < [tempArray count]; i++) { if([[sectionInfo indexTitle] isEqualToString:[tempArray objectAtIndex:i]]) // if([sectionInfo indexTitle] == [tempArray objectAtIndex:i]) { NSLog(@"found"); break; } else { NSLog(@"Not found %@", [sectionInfo indexTitle]); [tempArray addObject:[sectionInfo indexTitle]]; NSLog(@"array %@", tempArray); return [tempArray objectAtIndex:i]; } } } } The comparison of the strings in the if statement never resolves to true. The sample data has two instances of duplicates for testing purposes. The commented line is an alternate, although I believe incorrect, attempt to compare the section with the string in the tempArray. What am I doing incorrectly? Also, all data is in capital letters, so the comparison is not a matter of lower to upper case.

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  • What is the n in O(n) when comparing sorting algorithms?

    - by Mumfi
    The question is rather simple, but I just can't find a good enough answer. I've taken a look at the most upvoted question regarding the Big-Oh notation, namely this: Plain English explanation of Big O It says there that: For example, sorting algorithms are typically compared based on comparison operations (comparing two nodes to determine their relative ordering). Now let's consider the simple bubble sort algorithm: for (int i = arr.length - 1; i > 0 ; i--) { for (int j = 0; j<i; j++) { if (arr[j] > arr[j+1]) { switchPlaces(...) } } } I know that worst case is O(n^2) and best case is O(n), but what is n exactly? If we attempt to sort an already sorted algorithm (best case), we would end up doing nothing, so why is it still O(n)? We are looping through 2 for-loops still, so if anything it should be O(n^2). n can't be the number of comparison operations, because we still compare all the elements, right? This confuses me, and I appreciate if someone could help me.

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  • c# logic to get the first non-repeating(distinct) character from the string

    - by NoviceToDotNet
    In c# i want to create logic that if i a string like abcabda is passed to a method then it should return first non repeative character from string like in above it should return c. i am unable to convert a string to array of character then how to make comparison of each array character to the string and return the first non repeative character. CanI make it like this? class A { static void main() { A a=new A(); char ch=a.m1(abcabd); } } class B { char m1(string s) { string s1=s; char[] ch1=new char[s.length]; for(int x=0; x<s.length;x++) { ch1[x]=s[x]; } for(int x=0; x<s.length; x++) { for(int y=0; y<s.lenth; y++) { if(s[x]=ch1[y]) { /// here i am confused how to create logic for comparison please let me know // and how to return the character } } } } }

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  • SQL Server 2008 - "Enhanced read-ahead and scan"?

    - by Chris J
    Hi all, Can anyone point me to, or does anyone know what this "feature" of SQL Server is? Googling for it (also for "Super scan" which seems to be a synonym for the feature) reveals no information other than all the edition comparison pages that exist out there for SQL Server. I'm also not sure whether this is a stackoverflow or a serverfault question. I'll try here on serverfault first, but if folk think stackoverflow may be a better forum, drop me a comment to that effect - ta :-)

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  • How can i recover a zip password using CUDA (GPU) ?

    - by marc
    How can i recover a zip password on linux using CUDA (GPU). For the past two days i tried using "fcrackzip" but it's too slow Few months back i saw some application that can use GPU / CUDA and get large performance boost in comparison to CPU. If brute-force using cuda is not possible, please tell me what's the best application for performing a dictionary attack, and where can i find best (largest) dictionary. Regards

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  • List full timestamps of files in a tarball

    - by Mechanical snail
    I have a large tar archive and want to see the exact (nanosecond) timestamps that are stored for each file in the archive. In case it's relevant, the tarball is in POSIX-2001 format (tar --format=posix). tar --list --verbose displays the timestamps rounded off to the minute. For comparison, ls --full-time does what I want, but I'd rather not have to extract everything first because it's huge. For my purposes, command-line and GUI tools are both fine.

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  • Mobile CPU vs. Ultra-low CPU: performance

    - by Mike
    I'm choosing a new laptop and one of the questions is a type of CPU — mobile or ultra-low voltage. If to be more precise, I'm torn between two models of Intel Core i5 — i5-2410M and i5-3317U. Here is a comparison table. According to official specs the first-one has 2.3 GHz clock speed, while the second-one has only 1.7 GHz, that's about 25% difference. Is it really important parameter and which CPU is more preferable for a laptop for development, media and internet purposes?

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  • JBOSS App Server vs. Glassfish

    - by codingbear
    I'm quite newbie on Glassfish. What are some differences between JBoss and Glassfish? Why would you chooose one over the other. I'm trying to read up on Glassfish, but it is really hard to pinpoint things that I may need before I start installing and trying to deploy some applications on it. UPDATE It would be good if any additional information on JBoss and Glassfish comparison is provided (e.g. technologies they support, performance, etc.)

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  • multiple VM vs multiple named instance

    - by thushya
    Hi , I am looking for some comparison or data for sql 2008 deployment , what are the advantages and disadvantages installing multiple VM vs multiple named instance ? How can i save license cost using VMs vs physical server for sql 2008 ? is there a way to find out what is maximum number of connections to database at any time or in the past - need to calculate needed CAL license ? Thanks.

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  • Few questions on dvd ram/rom

    - by Nrew
    Why other dvd rom/ram can read data from scratched disk and others cannot. For me its a comparison between LG and Lite On. Lite on, gets errors while reading disk with scratches. LG can read disk with scratches with no problems. Why is that? Is it possible to modify the software or the driver of the dvd rom so that it won't get errors when copying data from disk with scratches?

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  • Terminal server for Linux

    - by Hubert Kario
    What are the features of graphical terminal servers and technologies available for Linux? is it open source/free how well does it scale management (?) what's the network usage, susceptibility to latency support for session pause/resume what client platforms does it support support for sound (playback and record) directory/local disk sharing local printing other cons/pros This question is supposed to be a community wiki for comparison between the different technologies, but it looks like I don't have enough points to make questions into wikis(?)

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  • Internet Speed for Webserver

    - by René
    That should be kind of dumb question in comparison to all other questions here. What minimum upload and download is required for a small home webserver with one webpage? Or is there a schema that shows me the required upload and download speed for a number of visitors? We talk about a Windows Server, but not really sure this is relevant. That's just for a practice project.

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  • VLC or ffserver for http streaming

    - by Maciek Sawicki
    Hi, I don't like asking "OR" questions, but I can't find any comparison on the Internet. I need live http streaming using h264 in flv container. I managed to achieve this with VLC, but with big latency. I have some problems with ffmpeg and I can not make it to work, but I wonder if would it works better then VLC?

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  • Varnish + Tomcat vs Apache + mod_jk + Tomcat

    - by Adrian Ber
    Does anyone have some comparison data in terms of performance for using in front of Tomcat either Varnish or Apache with mod_jk. I know that AJP connector suppose to be faster than HTTP, but I was thinking that in combination Varnish which is lighter and highly optimized could perform better. There is also the discussion between static resources (which I think will perform faster with Varnish than Apache, even with mod_cache) and dynamic pages.

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