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  Difference between ConcurrentHashMap and Hashtable

Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them. ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHa...

   ConcurrentHashMap,Hashtable     2013-11-18 08:06:54

  Undefined property or variable in JavaScript

JavaScript is a weak type language, and also you can use a variable or property where it's undefined. If we don't have correct ways to check whether a property or variable is defined, we may get unexpected results when we try to access the,. How can we check whether a property or variable is undefined? This is actually a somewhat tricky question. Let's start off with some facts about undefined and then see what kind of function is consistent with the ones we care about. JavaScript attaches type...

   Property,Undefined,Array,JavaScript     2014-07-24 06:56:07

  What does super.clone() do?

Object class has a protected clone() method declared to make it possible for all classes make a clone of itself when needed. The clone() is often used when a new instance of the class is needed while at the same time to maintain the same state as the original object. Any class which wants to have clone enabled has to implement the marker interface Cloneable. If a class which implements Cloneable doesn't override the Object.clone() method, the Object.clone() method will be called to just make a b...

   Cloneable,super.clone(),clone,Java     2015-01-07 05:25:52

  Amazon is a good company but doesn't have the best business model

Public opinion about a company is usually based on its performance. If it performs well, people will praise it, otherwise people will blame it. In 1999, Apple was still a broken apple(Steve Jobs's talent and effort was paid off yet). Public opinion about Apple was the closed model caused Apple's failure. They built hardware themselves, developed software themselves and delivered service themselves, this is certainly not sustainable. But Steve Jobs let everyone see this new model. In order to con...

   Business model,Amazon,Apple, Microsoft     2013-07-02 11:34:45

  Use Java ThreadLocal with caution

According to Oracle documentation, ThreadLocal is a class provides thread-local variables. These variables differ from their normal counterparts in that each thread that accesses one (via its get or set method) has its own, independently initialized copy of the variable. ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread. In short, ThreadLocal variables are variables belong to a thread, not a class or an instance of a class. One common...

   JAVA,MEMORY LEAK, THREADLOCAL     2015-11-03 07:31:57

  A trap in PDOStatement::bindParam

First, let's check out below codes: <?php $dbh = new PDO('mysql:host=localhost;dbname=test', "test"); $query = <<prepare($query); $bind_params = array(':username' => "laruence", ':password' => "weibo"); foreach( $bind_params as $key => $value ){ $statement->bindParam($key, $value); } $statement->execute(); What is the SQL executed finally? Is there any problem with above codes? Many people may think the query executed is : INSERT INTO `user` (`username`, `password...

   PHP,Trap,bindParam     2013-08-29 10:48:55

  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

  3 meanings of Stack

We may frequently see stack when we read programming books. But many times we may be confused about the different meanings of it. This term actually has three common meanings. Here we explain the three different meanings of Stack in programming. 1. Data structure The first meaning of Stack defines a method for storing data. Its feature is LIFO9Last In First Out). In this data structure, data are accumulated level by level. The data last put in is added at the top of the stack. When using the dat...

   Stack,Memory,Data structure     2014-02-24 04:56:46

  How Java Application Developers Can Build Secure Internet Based Apps?

There are few compiled solution tested by experts to guide Java application development and maintenance team how they can start safe journey on Internet. Strong encryption, wise passwords, secure hardware are few of the tech tools that should be used by Java app development team to secure their Internet based apps.   The Internet is most amazing yet most risky platform where nobody knows either they are doing safe transaction on Internet or there is some dog watching out for data packets t...

   JAVA APPLICATION MAINTENANCE,JAVA APPLICATION DEVELOPMENT     2015-09-16 02:13:17

  Android socket programming example

Socket is a kind of interface for different sides t communicate, it usually identified by an IP and a port. There are many server side software on a server and they would provide different service. Each server many create some sockets and bind them to some ports so that clients can listen to. Software on the Internet will exchange data though a bidirectional connection established. Each end of the connection has a socket created. In Java, Socket and ServerSocket are in java.net package, ServerSo...

   Android,Socket,Java     2013-05-11 22:17:16

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