What is the difference between Hacking and programming? One opinion I have heard expressed is that a hacker can put a lot of code together in a hurry but if a change is needed the code has to be completely rewritten. A programmer may take a little longer but if changes are needed they are more quickly and easily installed without the need for a complete rewrite. One source I heard attributed an observation like this to Maggie Johnson of Google. It rings true to me though. Hacking is usually described as “quick and dirty.” You though a bunch of code together and make it up as you go...

In previous post, we have introduced the use of Certificate and how to generate self signed certificate using Java. In this post, we will show you how to generate a certificate chain. Sometimes we may only have a certificate request or we don't have a trusted certificate which can be used for business. Now we need to have a trusted CA to sign our certificate so that it can be used on SSL communications.To generate a certificate chain, we may first have our own certificate(A), then we may use other certificate(B) and its associated private key to sign the certificate we have, then we will use a...

Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them.ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHashMap uses segmentation to lock the data, it uses concurrent locks operations for thread safety inste...

In Java, we can create modal dialog so that the main JFrame cannot be operated on until the modal dialog is closed. To achieve this, we need to use one class in Java--JDialog. This class can be used to create an modal dialog.Example code :import javax.swing.JDialog;import javax.swing.JLabel;import javax.swing.JPanel;public class Dialog extends JDialog{ public Dialog(){ super(); JPanel panel=new JPanel(); panel.add(new JLabel("Hello dialog")); this.getContentPane().add(panel); } public Dialog(MainFrame mf,String title,boolean modal){ super(mf,title...

There is a question asked on Stackoverflow : Divide a number by 3 without using *,/,+,-,% operators. This question is an Oracle interview question. Some people give excellent answers. You can go there and take a look. Usually we need to use bitwise operators to do this kind of implementations. Here I want to show you ways to implement +,-,*,/ with bitwise operators.A bitwise operation operates on one or more bit patterns or binary numerals at the level of their individual bits. It is a fast, primitive action directly supported by the processor, and is used to manipulate values for comparisons ...

Macros are small but very powerful VBA programs in Microsoft Office software. They can help us complete some repeated tasks automatically. Today, I will show you one macro example which is to change the text color conditionally. The excel file has a work sheet which contains some records of request. I want to check the status of each request, if the status of a request is approved, the text color of the status should be green; if the status of a request is rejected, the text color of the status should be red; otherwise the text color of the status should be black. Here is the code for the mac...

Most enterprises today are application centric. But the problem with the application is that their database schemas, user interfaces, programming interfaces and object models are tightly coupled and difficult to change. If you want to add a new field to a database table and you’re lucky, the change will reflect through the entire system. But often the change needs to be replicated manually across the entire system. And as applications are difficult to change, adding business rules or process to the application does not facilitate business agility. This is where layered architecture comes...

The popular online publishing platform Medium has adopted an impressive image loading mechanism -- pure color - blur image loading - real image loading.Since images on Medium usually have high definition, it takes much time to load an image and hence brings a bad user experience if rendering the image after it's completely downloaded. The solution Medium comes out is to preload an small image when the real image is being loaded. On Medium, the HTML code will have below pattern for every page.<figure name="512a" id="512a" class="graf--figure graf--layoutCroppedHe...