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  Singleton Design Pattern in Java

Singleton is frequently used in applications where resource may be expensive to create and no instance specific state needs to be maintained. For example, when creating database connection, a singleton may be needed. Today we will share the famous Singleton design pattern in Java. 1. Definition Singleton design pattern is a design pattern that restricts the instantiation of a class to one object. It is one of the most well-known design patterns. 2. Application Singleton ...

   DESIGN PATTERN,SINGLETON,MULTITHREAD,JAVA     2020-04-11 02:16:28

  Update parent window after closing the window opened by window.open()

Imagine we have a webpage which has a text field to let user enter a date. Usually, we may create a calendar window to ask the user to pick one date from the calendar window, when the date is picked, the calendar window will close and the date picked will be put into the text field. This way involves the window.open() method in JavaScript, and we may think how the opened window knows its parent window and then updates the parent window. I give a simple demo on this.We have two pages, on is the p...

   window.open, JavaScript,update, return value     2012-06-23 01:36:32

  Turn on SecurityManager in Java

SecurityManager in Java is to check whether the application codes can access some restricted resource such as file, socket etc. This can be used in applications which have high security requirements. With this feature turned on, our system resources can be secured with only permitted operations. When JVM starts, it will first check whether the SecurityManager is on by checking the system property java.security.manager, if it's on, then an instance of SecurityManager will be created and it can be...

   SecurityManager,enable,program     2013-12-16 05:03:53

  Arrays.equals() vs MessageDigest.isEqual()

Both Arrays.equals() and MessageDigest.isEqual() are used to compare the equality of two arrays. They can be interchangeably in many cases. However, they do have some differences which lead to different use cases in real applications. One difference is that the arrays passed to MessageDigest.isEqual() cannot be null while it's ok for Arrays.equals(). The one major difference between these two methods is that Arrays.equals() is not time-constant while MessageDigest.isEqual() is time-constant. Thi...

   Arrays.equal(),MessageDigest.isEqual(),Java,Security     2015-05-14 22:03:29

  Why using + to concatenate string in Java loop is not a good option

String concatenation is a common operation in Java programming. It is to concatenate multiple strings into a single string. Java provides a String class which is an immutable class which means the object cannot be mutated once instantiated. Once a String object is instantiated, its properties cannot be changed anymore, so when concatenating strings, it's actually create a new String instance to store the concatenated string values. For example, below is a simple string concatenation example. Str...

   JAVA,STRING,JAVA 8     2019-01-18 22:07:12

  How to be jQuery-free?

jQuery is now the most famous JavaScript library. There are around 57.3% websites in the world using jQuery, i.e, 6 out of 10 websites are using jQuery. If we only consider those websites which use libraries, then the percentage is even higher which is 91.7%. Although jQuery is very popular, its size is still a headache to many websites maintainers. The uncompressed jQuery 2.0 has a size of 235KB, the size is 81KB after optimization.The jQuery 1.8.3 which supports IE 6/7/8 has a uncompressed si...

   jQuery,JavaScript,ECMAScript,CSS3     2013-05-13 11:53:20

  JavaScript-style object literals in PHP

The object literal notation in JavaScript looks like: var fido = {name: "Fido", barks: true}; or var fido = {}; fido.name = "Fido"; fido.barks = true; From assoc arrays to objects In PHP you would call that an associative array. $fido = array( 'name' => "Fido", 'barks' => true ); And you can easily make it an object too: $fido = (object)$fido; echo gettype($fido); // "object" Or if you want to start with a blank object and add stuff to it: $fido = (object)array(); or $fido...

   PHP,JavaScript,Object,Function call,Self vs this     2011-11-30 11:11:45

  Tips to improve JavaScript efficiency

Writing JavaScript code is tedious and error prone. You not only need to implement the necessary functions, but also need to ensure cross browser compatibility. This often causes the low efficiency of JavaScript developers. Here we recommend 12 tips you can benefit from. 1. Remove array element by index If we want to remove one element in an array, we can use splice. function removeByIndex(arr, index) { arr.splice(index, 1); } test = new Array(); test[0] = ’Apple’; test[1] = &rsq...

   JavaScript,Tips,Array     2013-07-27 20:50:40

  Stream API in Java 8

Overview In this lesson on Stream API in Java, we will study how we can put Streams to use to write efficient and much more maintainable code. We will also write code with and without Streams so that we are able to compare the two versions. Before doing all this, we must know how to create a Stream and process it and that is what we will get started with. Introduction to Streams We will be starting with creating Streams. Let us get started with the Stream<T> API which enables us to play w...

   STREAM API,JAVA 8,DEVELOPMENT,TEAM     2018-01-30 00:14:46

  git reset vs git revert

When maintaining code using version control systems such as git, it is unavoidable that we need to rollback some wrong commits either due to bugs or temp code revert. In this case, rookie developers would be very nervous because they may get lost on what they should do to rollback their changes without affecting others, but to veteran developers, this is their routine work and they can show you different ways of doing that. In this post, we will introduce two major ones used frequently by develo...

   GIT,GIT RESET,GIT REVERT     2019-02-02 08:26:39

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