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  Build Hadoop environment in Linux

Hadoop standalone installation: 1. Install JDK Install JDK with below command: sudo apt-get install sun-java6-jdk Configure Java environment, open /etc/profile, add below contents: export JAVA_HOME = （Java installation directory） export CLASSPATH =".:$JAVA_HOME/lib:$CLASSPATH" export PATH = "$JAVA_HOME/:PATH" Verify installation of Java Type java --version, if it outputs Java version information, then Java is successfully installed. 2. Install SSH Install SSH with below command: sudo ...

   Hadoop.Linux,Configuration     2013-07-31 23:22:27

  JavaScript efficiency catch up

JavaScript is a very flexible language, we can write JavaScript code freely with various styles, different kinds of codes will have different execution efficiency. Here we summarize some tips we get from our development. Efficiency of JavaScript itself JavaScript has execution context chain, closures, prototype inheritance, eval etc. It brings us some magic features, but it also introduces the performance issue, if we don't use them properly, it will affect the codes execution efficiency. 1. Glo...

   JavaScript,efficiency,event delegation,eval     2013-04-02 04:08:46

  Migrate from MySQL to MariaDB in Ubuntu

The biggest movement of escaping from MySQL in this century starts, openSUSE,Fedora and Arch have started to use MariaDB instead of MySQL as their default database. Many people also dislike the attitude of Oracle on MySQL, so it's reasonable to migrate from MySQL to MariaDB. The whole process is not complicated. Here we share the steps to migrate from MySQL to MariaDB in Ubuntu. Installation procedure: sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0xcbcb082a1bb943db Modify /etc/a...

   MySQL,MariaDB,Ubuntu     2013-08-13 11:14:51

  You can get properties of pseudo-element using JavaScript now

The pseudo-element6 in CSS is extremely useful, you can use it to create CSS triangles and lots of other elements without overuse many HTML elements. In the past, you cannot get the property value of pseudo-element in CSS using JavaScript. Now you can call a new method in JavaScript to get them easily. Assume you have below CSS codes: .element:before { content: 'NEW'; color: rgb(255, 0, 0); } To get the properties in .element:before, you can use below JavaScript method: var color = window.getC...

   pseudo-element,property,JavaScript     2014-04-05 20:58:25

  Convert number to string in C++

Prior to C++11, there is no built-in function in C++ standard library which can be used to convert numbers such as interger and double number to string.  There are many ways which can convert number to string. Since C++ is C compatible, we can use itoa() function to convert an integer to C style string. But this one can only convert integer to string, not double. For different types of numbers, we need to use different functions. string s = string(itoa(a)); Actually, we can also use strings...

   C++,conversion,number,string     2012-08-14 15:52:48

  Write HTML easily with Emmet and Haml

Writing HTML codes is very boring and tedious as it has many tags and it's static. One solution is to use template, filling content based on other's skeleton. One another solution is high speed writing. We can write HTML codes with Emmet and Haml. These two ways have similar functions but with different characteristics. Haml is based on Ruby, so when working on Ruby/Rails projects, we recommend to use Haml, otherwise we recommend to use Emmet. 1. Emmet Emmet is a editor plugin, the official webs...

   HTML,Emmet,Haml     2013-06-11 19:46:02

  Run MySQL on Command Line in Windows

Sometimes if we want to run MySQL but we don't have phpMyAdmin installed. What should we do?On Windows we can run MySQL in following steps:Open Console Window->Type "mysqld -u root". This means we start the mysql server with username root. This program will handle all the communications between our console window and the actual data;After starting the server, we need to use a client to connect to the server and communicate with it. the mysql program is right for this. Next in the command cons...

   mysql,console,command line,windows,defau     2011-08-21 04:14:58

  Performance comparison of string concatenation in Go language

In Go language, string concatenation is an inevitable operation during development, and efficient string concatenation is crucial for improving application performance. This article will delve into several common ways of string concatenation, provide performance comparisons, and offer optimization suggestions aimed at helping developers write more efficient code. Common ways of string concatenation In Go language, common ways of string concatenation include the following: Using the + operator fo...

   COMPARISON,PERFORMANCE,STRING CONCATENATION     2024-05-13 00:33:20

  Binary tree iterator algorithm

Binary tree pre-order,in-order and post-order traversal are basics in algorithm and data structure.And the recursive binary tree traversal is a classical application of recursion. We define a binary tree node as : // C++ struct Node { int value; Node *left; Node *right; } In order binary tree traversal can be: // C++ void inorder_traverse(Node *node) { if (NULL != node->left) { inorder_traverse(node->left); } do_something(node); if (NULL != node->righ...

   Binary tree,Iterator,Traversal     2013-07-14 21:51:09

  Sort an array with only one local variable

Array sorting algorithm question is frequently asked during technical interviews. There are lots of sort algorithms including bubble sort, selection sort, insertion sort, quick sort, merge sort etc. Usually interviewees will be asked to implement sort algorithms. But have you ever been asked to sort an array which you are allowed to define ONLY ONE local variable in your algorithm?  Bubble sort can be used to do this actually. Normally a bubble sort algorithm may need three local ...

   JAVASCRIPT,ALGORITHM,SORTING,BUBBLE SORT     2016-10-07 09:46:49

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