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  Top 10 essential Java classes

When we write Java programs, we will frequently use some classes such as java.lang.String. There are some essential Java classes which we may use frequently, there is no strict rules for the selection of essential Java classes, in fact there are no rules followed. It depends on what projects you are doing or what you have done,, so every one may have his own choices about the top essential Java classes in his mind. Here we list the top 10 essential Java classes you may agree with.1. java.lang.St...

   Java,class,essential class,top 10     2012-06-04 09:44:19

  Convert HTML to DOM elements using JavaScript

In some cases, one would want to convert a HTML string to the DOM elements so that JavaScript can handle them easily. This is frequently used when one get some data from third party APIs where the data is in HTML format. In JavaScript, there are a couple of ways one can use to convert HTML to DOM elements. DOMParser document.createElement DOMParser DOMParser can parse XML or HTML source stored in a string into a DOM Document. After the conversion, the normal JavaScript call of h...

   JAVASCRIPT,DOMPARSER,DOCUMENT.CREATEELEMENT,HTML,DOM     2017-08-18 22:51:46

  Reflection in Java

What is Reflection? Reflection is a feature in Java that allows a program to obtain information about itself at runtime and dynamically manipulate the properties, methods, and constructors of classes or objects. With reflection, we can instantiate objects, call methods, and set properties without knowing the exact class name beforehand. The core of the reflection mechanism is the Class object, which represents a class. The Java Virtual Machine (JVM) automatically creates this Class object when i...

   JAVA REFLECTION,TUTORIAL,FIELD,METHOD     2024-06-27 07:52:12

  Output control functions in PHP

The Output Control functions in PHP allow you to control when output is sent from the script. This can be useful in several different situations, especially if you need to send headers to the browser after your script has began outputting data. The Output Control functions do not affect headers sent using header() or setcookie(), only functions such as echo and data between blocks of PHP code. These output control functions include ob_start(0, ob_clean(),ob_get_contents(), etc. To be honest, I a...

   PHP,output buffer,relationship,ob     2012-06-15 10:11:58

  The Strange Behavior of the void Type in TypeScript

Preface In TypeScript (TS), there is a type called void. It represents "nothing" but it's important to note that it's not the same as "nothing" in JavaScript(JS). Typically, void is used to declare the return type of functions. Although you can declare a variable as void, we generally don't do this because it serves no meaningful purpose. Let's explore why in the examples below. The void Type Declaring a Variable as void let name: void; // Declare a variable `name` with type `void`. name = 'nan...

   TYPESCRIPT,JAVASCRIPT,VOID,TYPE     2024-09-13 23:44:26

  Why exception would be thrown when deleting element while looping through HashMap in Java

HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List. Below is a sample code snippet demonstrating the exception thrown. Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1"); map.put("ke...

   JAVA,HASHMAP,CONCURRENTMODIFICATIONEXCEPTION     2018-06-30 12:49:09

  Convert time to Unix time

Unix time is defined as the number of seconds that have elapsed since midnight Coordinated Universal Time (UTC), 1 January 1970,not counting leap seconds. It is used widely in Unix-like and many other operating systems and file formats. It is neither a linear representation of time nor a true representation of UTC. Unix time may be checked on some Unix systems by typing date +%s on the command line. Sometimes it's a bit difficult to compare times stored in different applications or systems with ...

   UNIX time, Oracle DATE, conversion, timestamp     2013-01-19 09:04:17

  Fastjson just fixed a bug which might cause out of memory issue

Fastjson just fixed a bug which might cause service down a few days ago. This bug is caused by some mishandling of special character \x which is an escaped character to indicate hexdecimal number. The impact of this bug would be big if the attacker constructs a malicious data which would cause the service down.  The code which causes the issue is in com.alibaba.fastjson.parser.JSONLexerBase#scanString, when a JSON string is passed in, fastjson would parse the string character by c...

   FASTJSON,ALIBABA,BUG,NEWS     2019-09-07 06:03:49

  How regular expression works

Rob Pike wrote 30 lines of codes to realize a simple regular expression matcher in his book The practice of Programming. This piece of code is really cool. Let's take a look at the code.Meaning of different characters.Character Meaning c General character . Match any single character ^ Match start of a string $ Match end of a string * Match zero or many occurrences of a character /*match ：Test the regexp in text*/int match(char* regexp,char* text){    if(regexp[0] == '^')&n...

   Regular expression,Implementation,Rob Pike,C     2012-06-25 05:23:41

  Java AbstractMethodError explained and demonstrated

According to Oracle Java API documentation, AbstractMethodError is a kind of runtime error where the application is having some incompatible changes which leads to a missing implementation of an abstract method. Below is the official description. Thrown when an application tries to call an abstract method. Normally, this error is caught by the compiler; this error can only occur at run time if the definition of some class has incompatibly changed since the currently executing method was last co...

   JAVA,ABSTRACTMETHODERROR     2016-07-22 22:03:20

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