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  Set file permission in Java

Prior to Java 6,  there is no good solution at the Java level to provide file permission management. You need to implement your own native methods or call the Runtime.exec() to invoke the system routine such as chmod in LInux. Since Java 6, Java introduces a set of methods which can be used to set the file permission at Java level. These methods include: File.setReadable(boolean); File.setWritable(boolean); FIle.setExecutable(boolean); File.setReadable(boolean, boolean); File.setWritable(bo...

   JAVA, FILE PERMISSION, POSIX,learnjava     2015-08-29 03:37:37

  How Kafka achieves high throughput low latency

Kafka is a message streaming system with high throughput and low latency. It is widely adopted in lots of big companies. A well configured Kafka cluster can achieve super high throughput with millions of concurrent writes. How Kafka can achieve this? This post will try to explain some technologies used by Kafka. Page cache + Disk sequential write Every time when Kafka receives a record, it will write it to disk file eventually. But if it writes to disk every time it receives a record, it would ...

   BIG DATA,KAFKA     2019-03-08 09:42:57

  A boolean value interview question

Someone asked a question on StackOverflow, he was asked an interview question. The question is : Given 3 boolean variables a, b, c, return true if at least 2 out of the 3 are true. He gave the solution as follows :boolean atLeastTwo(boolean a, boolean b, boolean c) {    if ((a && b) || (b && c) || (a && c)) {        return true;    } else {        ret...

   bool,return,expression,conditional     2012-04-30 08:49:32

  Why 0.1+0.2 != 0.3

In programming languages such as JavaScript, c/c++, Java and Matlab, you will find that you will get unexpected result when doing float point calculation. For example, when calculating 0.1 + 0.1, you will not get 0.3: > 0.1 + 0.2 == 0.3 false > 0.1 + 0.2 0.30000000000000004 Don't be surprised of this result, this is the end result of IEEE 754 standard, float point number cannot be accurately represented according to IEEE 754 because: No enough memory is allocated for representing the num...

   float point,comparison,JavaScript     2014-11-19 05:32:46

  Web design trends for 2014

Now, it's age of web, many resource and manpower have been invested in web to extend and enhance the capability of web. Every year there are new web designs and technologies emerging. In recent years, with the popularity of handhold devices such as smart phones and smart devices like iPads,Surface, responsive design is becoming a requirement, also we can find flat design in many places. The web design trend is changing dramatically. Many people may wonder what's the web design trend in 2014? Jow...

   web design,trend,2014     2014-06-01 08:27:35

  Add ContextMenu to a customized View in Android

In Android, we may sometimes need to add ContextMenu to a View, it's not so easy to add ContextMenu to a customized View. Here we explain how to add ContextMenu to a customized View. First, we may need to create View.OnCreateContextMenuListener so that the customized view can register for it. Here is the class definition: public class GraphView extends View {     private View.OnCreateContextMenuListener vC = new View.OnCreateContextMenuListener() {       &...

   Android, ContextMenu,Customized view     2012-11-04 07:10:40

  JavaScript to open link in new window without being popup blocked

To ensure security and reduce spamming, modern browsers have implemented very strict rules on when a new window can be opened in a web page. Currently browsers restrict that any new web page to be opened in a new window must be initiated with an user action. The action is usually an user click event. Otherwise, a popup blocker would show on the browser address bar which indicates that something is blocked. To workaround this issue, normally you should implement the window open logic in a click e...

   JAVASCRIPT,IFRAME,NEW WINDOW,OPEN LINK     2018-09-22 04:29:30

  Using JSON in PHP

Currently JSON has become one of the most popular data exchange formats. Many website APIs support it. Since PHP 5.2, PHP provides json_encode() and json_decode() method to handle JSON encoding and decoding.1. json_encode()This function is used to transform array and objects to JSON format. First let's look one array example.        $arr = array ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5); 　　echo json_encode($arr);the result is{"a":1,"b"...

   JSON,PHP,json_decode(0,json_encode()     2012-05-06 06:04:42

  Cleansing data with Pig and storing JSON format to HBase with Pig UDF

Introduction This post will explain you the way to clean data and store JSON format to HBase. Hadoop architect experts also explain Apache Pig and its advantages in Hadoop in this post. Read more and find out how they do it. This post contains steps to do some basic clean the duplication data and convert the data to JSON format to store to HBase. Actually, we have some built-in lib to parse JSON in Pig but it is important to manipulate the JSON data in Java code before store to HBase. Apache Pig...

   JSON,HADOOP ARCHITECT,APACHE HBASE,PIG UDF     2016-06-10 01:13:41

  Do NOT use boolean variable as function parameters

We follow lots of coding styles and coding standards when we do programming, but we may frequently forget one. The forgotten one is that do not use boolean parameter as the function parameters. The reason is it would greatly reduce the readability of the code. Don't believe it? When you read the following code, what does this code mean? widget->repaint(false); Do not repaint? Or what does this mean? After looking at the document, we know that this parameter is whether ...

   CODING STYLE,BOOLEAN,FUNCTION PARAMETER,CODING STANDARD,METHOD PARAMETER     2012-04-22 02:38:45

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