Monday, October 28, 2013

How to use multiple JQuery UI Date Picker or Datepicker in HTML or JSP page

We often needs to use multiple JQuery date picker in one HTML or JSP page, classical example is online flight booking for return trips, where you need to pick departure date and arrival date from two separate datepickers. While designing HTML forms either statically or dynamically using JSP, you may want to associate date picker with multiple input text field, paragraph or any other HTML elements. By using JQuery UI and some help from CSS ID and class selector, we can easily use multiple datepicker in one HTML page. All you need to do is, declare a CSS class say .datepicker and apply that class to all HTML elements which needs date picker, for example we have associated date picker with 4 input text fields, which has .datepicker class. By using a class, it becomes extremely easy to select all those elmeent using JQuery class selector, and once you got all those element, you can just call datepicker() methos. This method does all the hard-work and associate a date picker object with selected items, that's it. Now you are ready to use multiple date picker in your HTML or JSP page, let's see the complete code. By the way if you are just starting with jQuery than I highly recommend Head First Query, it’s easy to read  and contain some non trivial example to learn jQuery quickly.

Friday, October 4, 2013

Database Website to Run and Practice SQL Query Online for FREE - SQLFiddle

Other day, I was looking for a website to execute SQL query online, since I have uninstalled Microsoft SQL Server because of memory and CPU constraint and I don't want to install it again, just for executing another query. Also, installing database is pain, it takes time and eats up lots of resources e.g. RAM memory, CPU etc; Given so many database to work with e.g. Oracle, MySQL, Sybase, PostgreSQL and SQLLite, it's not really possible to have all of them in your poor laptop. Fortunately my search leads be to this wonderful site called SQLFiddle, this is what exactly I wanted. This site offers support for lot of popular databases, allows you to build your database schema online and execute SQL query on the fly. I couldn't have asked more, It's a great resource to learn and practice SQL queries online. Apart from many sweet feature, it also allows you to share your problem with community. If you are writing a complex query and stuck in middle, looking for help, you can create your schema on SQLFiddle and can share with your query to any forum or question answer website like StackOverFlow or any forum. Having a collection of online database, just makes running SQL query a fun. You can understand, how happy I am to know about this site, which let me to run and practice my SQL queries online, that I am sharing with you guys. To be frank, there is not many online site, where you can practice SQL query in your favorite database. I was looking for online website to test SQL query from long time, but couldn't find anything like SQL Fiddle, May be I am not aware if couple of them like SQLFiddle already exists, but this  a site every programmer, database administrator, SQL beginners and SQL Experts must bookmark, a great tool in SQL developer and any programmers armory.

Wednesday, October 2, 2013

What is PriorityQueue or priority queue data structure in Java with Example - Tutorial

PriorityQueue is an unbounded Queue implementation in Java, which is based on priority heap. PriorityQueue allows you to keep elements in a particular order, according to there natural order or custom order defined by Comparator interface in Java. Head of priority queue data structure will always contain least element with respect to specified ordering. For example, in this post, we will create a PriorityQueue of Items, which are ordered based upon there price, this will allow us to process Items, starting from lowest price. Priority queue is also very useful in implementing Dijkstra algorithm in Java. You can use to PriorityQueue to keep unsettled nodes for processing. One of the key thing to remember about PriorityQueue in Java is that it's Iterator doesn't guarantee any order, if you want to traverse in ordered fashion, better use Arrays.sort(pq.toArray()) method. PriorityQueue is also not synchronized, which means can not be shared safely between multiple threads, instead it's concurrent counterpart PriorityBlockingQueue is thread-safe and should be used in multithreaded environment. Priority queue provides O(log(n)) time performance for common enqueing and dequeing methods e.g. offer(), poll() and add(), but constant time for retrieval methods e.g. peek() and element().