SEARCH KEYWORD -- Assign default value
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
Why should we keep column as NOT NULL instead of NULL in MySQL?
Keep table column as NOT NULL instead of NULL except in some special cases. This statement is cited by many articles of MySQL optimization, but they don't say why we should do this. Here we discuss about this. First why are there many people using NULL when defining table? The reasons may be: NULL the the default when defining table, the rookies or people who don't want to have much troubles will keep this default setting Many people think NOT NULL will require more space Many people don't want...
Three images to understand immutability of String in Java
String is immutable in Java. This means once a String object is created and instantiated, that object cannot be changed. Any operation on the String object will create a new Object instead of operating on the original content. Below are three images to help you understand String immutability in Java. Declare a String String s = "abcd"; s stores the reference to the string content created in the heap. Assign the String reference to another String variable String s2 = s; s2 stores the same ...
Some tricks and tips for using for range in GoLang
GoLang provides two major ways to loop through elements of array, slice and map. They are for and for range. Many people find that for range is very convenient when don't care about the index of the element. In this post, some tricks and tips would be talked about regarding for range. 1. Loop and get pointer of each element Assume there is a code snippet like below which is to get the pointer of each element in an array and create a new array with the corresponding pointer. arr := [2]int{1, 2} r...
Some short code snippets which use all JavaScript keywords
In JavaScript, keywords are reserved and cannot be used as variable or function names. For example void, function and this are JavaScript keywords, they are keywords which are reserved for special use. Here is list of the keywords in JavaScript. We also show you some short code snippets which use all the keywords in JavaScript.void function() {//abcd do break;while(typeof delete this); for(var a;;) if (true) with(null) try{}catch(a){}finally{} else throw new 1;&nbs...
Code snippet,JavaScript,keyword 2012-07-16 12:12:05
What can select do in GoLang
In Go language, select is a keyword used to listen to and perform IO operations related to channels. With the select statement, we can simultaneously listen to multiple channels and perform corresponding operations when any of the channels are ready. This article will summarize the common uses of the select statement and provide some considerations when using it. Basic syntax The basic syntax of the select statement is as follows: select { case <-channel1: // when channel1 has data to ...
When will resizing be triggered in Java HashMap?
HashMap is one of the most frequently used collection types in Java, it stores key-value pairs. Ideally it expects to use hash table which expects the data access time complexity to be O(1), however, due to hash conflicts, in reality, it uses linked list or red-black tree to store data which makes the worst case time complexity to be O(logn). Although collections are using data structures like arrays and linked lists, unlike arrays, they will dynamically resize when there is not enough spa...
Change password of postgres account in Postgres
When installing Postgres on Windows, there is some default account created for user to login. One of them is postgres, but we often don;t know what's the password for this account when we first login using this account. We need to change the password for this account. How to change it? Step 1. Modify the pg_hba.conffile Go to the /data/ and open the pg_hba.conf. # TYPE DATABASE USER ...
Postgres,password, user account 2013-03-04 01:51:02
Are You a Good Programmer?
If someone asks you to recommend a good programmer, who comes to mind? Do you consider yourself a good programmer? What criteria do you use to judge? In thinking about this, I realized that there are different ways that a programmer can be good. So I present to you The Four Kinds of Good Programmers. And in celebration of Whyday, I include quirky Why-styled illustrations* for your viewing pleasure! The Philosopher The PhilosopherThe philosopher loves to write well-defined, well-structured...
Programmer,Inventor,Philosopher,Conquero 2011-08-23 07:56:26
Samsung will build its own mobile browser
According to the Korean IT News, Samsung is developing its own brand mobile browser based on WebKit, make its the default browser for future Gaxlaxy products.Samsung has posted recruitment advertisements for recruiting Webkit developers in its Advanced Software Platform Lab located in the Silicon Valley. Webkit is an open-source browser engine, Apple's Safari and Google's Chrome are based on this open source engine.For many users, the phone's built-in default browser is still the most used, so S...
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