This article shows how to use regex + code to validate a date format, support single and leading zero month and day format (1 or 01), check for the 30 or 31 days of the month, and leap year validation. Below are the requirements for a valid date. Year format, 1900, 2099 regex Month format, […]
Time in 24-Hour Format Regular Expression Pattern ([01]?[0-9]|2[0-3]):[0-5][0-9] Description ( #start of group #1 [01]?[0-9] # start with 0-9,1-9,00-09,10-19 | # or 2[0-3] # start with 20-23 ) #end of group #1 : # follow by a semi colon (:) [0-5][0-9] # follw by 0..5 and 0..9, which means 00 to 59 The 24-hour clock […]
Time in 12-Hour Format Regular Expression Pattern (1[012]|[1-9]):[0-5][0-9](\\s)?(?i)(am|pm) Description ( #start of group #1 1[012] # start with 10, 11, 12 | # or [1-9] # start with 1,2,…9 ) #end of group #1 : # follow by a semi colon (:) [0-5][0-9] # follw by 0..5 and 0..9, which means 00 to 59 (\\s)? […]
This article focus on how to validate an IP address (IPv4) using regex and Apache Commons Validator. Here is the summary. IPv4 regex explanation. Java IPv4 validator, using regex. Java IPv4 validator, using commons-validator-1.7 JUnit 5 unit tests for the above IPv4 validators. IPv4 regex final version. ^(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(\.(?!$)|$)){4}$ # Explanation ( [0-9] # 0-9 | […]
Image File Extension Regular Expression Pattern ([^\s]+(\.(?i)(jpg|png|gif|bmp))$) Description ( #Start of the group #1 [^\s]+ # must contains one or more anything (except white space) ( # start of the group #2 \. # follow by a dot "." (?i) # ignore the case sensive checking for the following characters ( # start of the […]
This article shows how to use regex to validate a username in Java. Username requirements Username consists of alphanumeric characters (a-zA-Z0-9), lowercase, or uppercase. Username allowed of the dot (.), underscore (_), and hyphen (-). The dot (.), underscore (_), or hyphen (-) must not be the first or last character. The dot (.), underscore […]
This article shows how to use regex to validate a password in Java. Secure Password requirements Password must contain at least one digit [0-9]. Password must contain at least one lowercase Latin character [a-z]. Password must contain at least one uppercase Latin character [A-Z]. Password must contain at least one special character like ! @ […]
The format of an email address is local-part@domain. Look at this email address [email protected] local-part = mkyong @ = @ domain = example.com The formal definitions of an email address are in RFC 5322 and RFC 3696. However, this article will not follow the above RFC for email validation. The official email "local-part" is too […]
Java2HTML is a tool to converts Java source code into a colorized and browsable HTML page, and the steps are quite straight forward. Steps to convert it 1) Download Java2HTML – http://www.java2html.com/download.html 2) Unzip it , e.g “D:\Java2HTML” 3) Edit the “j2h.bat” file and modify the CLASSPATH variable. Make sure it point to the correct […]
This article shows how to use regex to validate a hex color code. Regex for hex color code. ^#([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$ Regex explanation ^ # start of the line # # start with a number sign `#` ( # start of (group 1) [a-fA-F0-9]{6} # support z-f, A-F and 0-9, with a length of 6 | # […]
If you are running Linux system, high chance Apache is already installed by default. In case, you can use the following commands to determining whether Apache is already installed. In RPM system like Fedora Core Issue httpd -v or /usr/sbin/httpd -v [root@snake init.d]# httpd -v Server version: Apache/2.2.11 (Unix) Server built: Mar 6 2009 09:12:25 […]
I hit the Apache server error (13)Permission denied: make_sock in my console, while i try to start the Apache http server with the ./apache2 start script under init.d folder. mkyong@mkyong-desktop:/etc/init.d$ ./apache2 start * Starting web server apache2 apache2: Could not reliably determine the server fully qualified domain name, using 127.0.0.1 for ServerName (13)Permission denied: make_sock: […]
Often times, as server administrator, have to telnet or SSH to their server to restart the Apache Http services. The Apache http services are usually located at the following location, 1) init.d start script folder. issue “./apache restart” to restart it debian:/etc/init.d# ./apache restart Forcing reload of web server (apache)… waiting . debian:/etc/init.d# 2) usr/local/apache/bin […]
Installing Apache Http server in Windows is more easier than Linux. See my following posts for installing Apache http server in Linux system 1) How to install Apache Http server in Fedora Core 2) How to install Apache Http server in Ubuntu The steps are quite straight forward, download the binary installation and install it. […]
There are two ways to install Apache Http server in Fedora Core, either with yum command to install automatically and manual install it by compiling the source. Steps to install automatically 1) Search Apache package with yum search command yum search httpd P.S Apache http server in fedora is called httpd 2) Get the Apache […]
There is two ways to install Apache Http server on Ubuntu : Use apt command to install it automatically. Configure and build the source code, and install it manually. 1. Install it automatically 1. Search Apache package with “apt-cache search” command apt-cache search apache 2. Get Apache package name “apache2”, issue the “apt-get” install command. […]
It is very easy to encrypt a text file in Linux, VIM text editor can be used to achieve it.. vim -x [file name] mkyong@snake ~]$ vim -x mkyong.txt This will prompt us to enter encryption key (password) Enter encryption key : ****** Enter same key again: ****** After that, key in the text data […]
In this article, we will show you how to use a SHA-256 and MD5 algorithm to generate a checksum for a file. MessageDigest.getInstance(“algorithm”) Apache Commons Codec 1. MessageDigest d:\server.log hello world 1.1 Generate a file checksum with a SHA256 algorithm. FileCheckSumSHA.java package com.mkyong.hashing; import java.io.FileInputStream; import java.io.IOException; import java.security.DigestInputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class […]
This article shows two ways to resize an image (create a thumbnail) in Java. 1. Original Image, 544×184 Below is a Google logo image, width, height 544×184, and file size 14k. Later, we will resize the below image to a new width and height 300×150. 2. Resize an image or create a thumbnail. This Java […]
This article shows how to convert a byte[] to a BufferedImage in Java. InputStream is = new ByteArrayInputStream(bytes); BufferedImage bi = ImageIO.read(is); The idea is puts the byte[] into an ByteArrayInputStream object, and we can use ImageIO.read to convert it to a BufferedImage. 1. Convert byte[] to BufferedImage. The below example shows how to convert […]
This article shows how to convert a BufferedImage to a byte array or byte[]. BufferedImage bi = ImageIO.read(new File("c:\\image\\mypic.jpg")); ByteArrayOutputStream baos = new ByteArrayOutputStream(); ImageIO.write(bi, "jpg", baos); byte[] bytes = baos.toByteArray(); The idea is uses the ImageIO.write to write the BufferedImage object into a ByteArrayOutputStream object, and we can get the byte[] from the ByteArrayOutputStream. […]
Today, i received an email, subject as “Account Review Department” from PayPal ([email protected]). This email said my Paypal account is limited access due to some fault credit card cases, request download the attached form and open in my browser to restore my Paypal password. It’s just a funny email, how can i trust an email […]
Eclipse IDE, press CTRL + T or F4 to view the Java class hierarchy, no need to search the JavaDoc API online. Note For Mac OS X, press Command + T Steps to show class hierarchy 1. Clicks on a class, press CTRL + T to view the subtype hierarchy. 2. Press CTRL + T […]
Adsense Daemon is a WordPress plugin that is used to integrate “Google Adsense” into blog content easily. I had used few Google Adsense WordPress plugins, and found out many of those will hijack and replace my Google Adsense code with theirs. This inspired me to create this simplest solution to integrate Google Adsense into blog […]
Here is an email example written in Python module “smtplib”. It will connect to the GMail SMTP server and do the authentication with username and password given (hardcoded in program), and use the GMail SMTP server to send email to the recipient. import smtplib to = ‘[email protected]’ gmail_user = ‘[email protected]’ gmail_pwd = ‘yourpassword’ smtpserver = […]
As simple, HTML documents are simply a text file made up of many HTML elements. These HTML elements are always between a start tag and end tag. Where the element appears is determined by the order in which the tags appear. HTML Elements An HTML element is everything from the start tag to the end […]
Windows store all the documents , images or files you have recently opened in “Recent Documents Folder” . Sometime it’s a handy function to access your recent document, but it also raise out a serious privacy issue, because anyone who has access to your computer can know what files you’ve opened recently. How to clear […]
Regular Expression is a very powerful tools for programming language like java, .NET, PHP , Perl…or even PostgreSQL. Here i write some basic examples to show how to use regular expression in PostgreSQL. 1) isdigit function – This function is missing in PostgreSQL, as this is a built-in function in others database. This is a […]
Many users are cracked because of their poor password structure, here i summarize 5 of the strongest password that i know. Hope this help. 5. Combine partial unrelated words together Combine partial 2 or 3 or even 4 unrelated words together (mix uppercase and lowercase), for example, combine these words together like “Diamond”, “Blog”,”Security” to […]
I had encountered following error message while starting my Tomcat server. [2009-01-16 11:22:19] [1343 prunsrv.c] [debug] Procrun log initialized [2009-01-16 11:22:19] [info] Procrun (2.0.4.0) started [2009-01-16 11:22:19] [info] Running Service… [2009-01-16 11:22:19] [1166 prunsrv.c] [debug] Inside ServiceMain… [2009-01-16 11:22:19] [info] Starting service… … [error] The specified module could not be found. [2009-01-16 11:22:19] [994 prunsrv.c] […]
Example UUID is the fastest and easiest way to generate unique ID in Java. import java.util.UUID; public class UniqueIDTest { public static void main(String[] args) { UUID uniqueKey = UUID.randomUUID(); System.out.println (uniqueKey); } } Result 0a6a3de7-b974-42d0-af9e-9c23473b09b9
As i know, there are two ways to calculate MySQL database size. 1. SQL script Sum up the data_length + index_length is equal to the total table size. data_length – store the real data. index_length – store the table index. Here’s the SQL script to list out the entire databases size SELECT table_schema "Data Base […]
While i using my little fancy program to simulate millions of data in MySQL database for volumn testing, my program straight hit the following error after execute few seconds. Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: User ‘mkyong’ has exceeded the ‘max_questions’ resource (current value: 1000) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.Util.getInstance(Util.java:381) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3536) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3468) at […]
Often times, the following error is happened. This is due to the MySQL resource monitor feature, the “max_questions” means “Number of queries the user can execute within one hour”. MySQL Error – exceeded the ‘max_questions’ resource (current value: 1000) Here i will demonstrate how to update or modify the ‘max_questions’ value in MySQL. 1) Log […]
Here i provide a simple user guide to find out where does MySQL database stored the data in our hard disk, both in Windows and Linux. Windows 1) Locate the my.ini, which store in the MySQL installation folder. For Example, C:\Program Files\MySQL\MySQL Server 5.1\my.ini 2) Open the “my.ini” with our favor text editor. #Path to […]
A JDBC example to show you how to connect to a MySQL database with a JDBC driver. Tested with: Java 8 MySQL 5.7 MySQL JDBC driver mysql-connector-java:8.0.16 1. Download MySQL JDBC Driver Visit https://dev.mysql.com/downloads/connector/j/ to download the latest MySQL JDBC Driver. 2. JDBC Connection 2.1 Make a connection to the MySQL database. JDBCExample.java import java.sql.Connection; […]
Problem Runing the following Hibernate’s annotation sequence generator with PostgreSQL database. @Id @Column(name="user_id", nullable=false) @GeneratedValue(strategy = GenerationType.SEQUENCE ,generator="account_user_id_seq") private Integer userId; Hits the following Unknown Id.generator exception. Caused by: org.hibernate.AnnotationException: Unknown Id.generator: account_user_id_seq at org.hibernate.cfg.BinderHelper.makeIdGenerator(BinderHelper.java:413) at org.hibernate.cfg.AnnotationBinder.bindId(AnnotationBinder.java:1795) at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1229) at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:733) The sequence “account_user_id_seq” is created in PostgreSQL database, what caused the above exception? Solution […]
Problem While accessing the PHP file, it display as “application/x-httpd-php” downloading instead of interpreted properly by Apache. See figure below : Solution The PHP downloading issue is caused by the Apache didn’t load the PHP module properly. 1. Find and edit Apache configuration file, which should be able to find at $APACHE_PATH/conf/httpd.conf. 2. Make sure […]
Often times, Eclipse IDE may need access to the Internet for some plugins install and update. If your computer is behind a proxy server, most company do, Eclipse will keep hanging and take very long time to process and failed at the end. You have to configure the proxy settings in Eclipse in order to […]
The wget is a useful command to download a website in Linux. For example , wget [url]. [mkyong@snake ~]$ wget -r -p -k -E http://www.google.com –2009-07-19 14:07:27– http://www.google.com/ Resolving www.google.com… 64.233.189.104 Connecting to www.google.com|64.233.189.104|:80… connected. HTTP request sent, awaiting response… 302 Found Location: http://www.google.com.my/ [following] –2009-07-19 14:07:27– http://www.google.com.my/ Resolving www.google.com.my… 64.233.189.147 Connecting to www.google.com.my|64.233.189.147|:80… connected. […]
