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  Permutation implementation in Java

Permutation is a very basic and important mathematic concept we learned in school. It has very practical applications in real world. For example, in football. In simple, permutation describes all possible ways of doing something. For example, there are six permutations of the set {1,2,3}, namely: (1,2,3), (1,3,2), (2,1,3), (2,3,1), (3,1,2), and (3,2,1). In general, for n items, there are n! number of permutations to arrange these items. How can we implement this algorithm in programming programm...

   Permutation,Implementation,Java,Sample     2015-03-26 02:18:14

  Becoming a Better Developer, Part 1: Making Fans

If you're trying to grow your startup you've come to the right place. Get my 170-page ebook on how to grow a startup and join thousands of self-funded entrepreneurs by subscribing to my newsletter at right. This is the first of what I hope to become an ongoing series about non-technical ways to improve yourself as a developer. Becoming a better developer involves more than learning new technical skills; learning about your company and co-workers will dramatically improve the software y...

   Developer,Tips     2011-06-29 08:38:26

  Output a file with HTTP range header in PHP

When downloading a large file, we may encounter some network issues which causes download termination and only part of the file is downloaded. When the network connection resumes next time, we may need to redownload the file again from the beginning. In order to save bandwidth, http provides a Range parameter in its header which can control the file transfer flow. With the range parameter in the header, we can resume the download from where we stop. Here is a piece of PHP code snippet which uses...

   PHP, range,http, file transfer     2013-01-09 05:55:05

  ConcurrentHashMap vs Collections.synchronizedMap()

ConcurrentHashMap and Collections.synchronizedMap() both provide thread-safe operations of collections of data. They are used in multithreaded programs to provide both thread safety and performance improvements. In many cases, we can use either of them. But the realization of thread safety is different for these two implementations. ConcurrentHashMap will create an HashEntry[] array internally to store the elements passed in from a Map, while Collections.synchronizedMap() will return a Synchroni...

   ConcurrentHashMap,Collections.synchronizedMap     2014-09-18 05:04:59

  How to find which process a file is being written by in Linux?

Some people ask a file is being written by one process and they want to check this process, but they cannot find the process even with sof. This question is very common and there are many solutions, here we introduce a straightforward method. In Linux, each file will be stored on one device and of course there will be a relative inode, then we can use vfs.write to know who is writing the inode on one specified device continuously. Luckily there is inodewatch.stp in the installation package of s...

   Linux,process,file write     2013-03-16 21:44:35

  My love… for Expressive Programming Languages

I started out my journey with programming as a teenager learning GW-BASIC. Soon I learnt C language followed by C++.  I was impressed with the OO syntactic constructs C++ had on offer but I felt a little uneasy with a few constructs such as the scope resolution. I started studying Java. It immediately caught my attention with the syntactic improvements and simplifications it brought over C++. I was still in academics, so learning(precisely trying) programming languages on su...

   descriptive,programming,language,prefere     2011-08-17 07:31:09

  Oracle database to execute multiple statements at command line

Oracle database is now a mature and popular RDBMS which is used by lots of enterprises. With its evolution, many utilities and applications are developed around it as well. Now Oracle database also provides cloud support. As a DBA, managing Oracle database is daily routine work and some tools may be used frequently. One of them is sqlplus, the command line tool for executing SQL command. sqlplus is installed while the Oracle database is installed. To start sqlplus, one just needs to open a termi...

   ORACLE,ORACLE DATABASE,SQLPLUS     2016-12-09 20:11:28

  Why cannot compare double values directly for equality?

A question in PHP: Get some value from the database and use floatval() to convert it to floatint point value, then compare it with another value which is also converted to floating point value with floatval(). These two values are the same when using var_dump() to output, the two outputs are float(8.87), they are the same. But when comparing them for equality, the result is weird., they are not equal. Why?To analyze this question, we need to start with PHP data types. PHP uses weak types. In PHP...

   PHP,floating, precision,compare,equality     2012-06-27 09:01:36

  Forgotten TODOs: ideas for contributing to open-source projects

I often talk to students that want to contribute to open-source projects, but just don't have an idea what to work on. Here's a tip if you're in a similar situation (e.g. you want to apply for GSOC) : 1 git clone repository_url_of_some_open_source_project target_directory 2 grep -RIn TODO target_directory/* So, find the URL of the repository project you want to contribute to, checkout the repository using git/mercurial/svn and then find all the TODOs in the source code using grep. The -RI...

   Open source,constribution,TODO,participation     2012-03-03 22:30:28

  File upload once again

File upload is one of the oldest operation of web design. After 20 years, it's still has no big change, difficult to handle, lack of interaction and poor user experience. Web developers have thought many methods to improve the experience of uploading file in web apps, they developed various plugins based on different JavaScript libraries. However, because of the difference among different web browsers, there is no common interface which makes these plugins work properly or easily on all web brow...

   Web design, File upload, Asynchronous,HTML5     2012-09-02 11:52:21

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