Saturday, June 6, 2009

uCertify PrepKit for SCJP 5.0

Recently, I got an exciting opportunity to review the uCertify Prepkit for SCJP 5.0 certification.

SCJP stands for Sun Certified Java Professional and is one of the many certifications offered by Sun Microsystems that makes you stand out in the crowd. In the times like these, who would not want that. :-)
If you want to know more about SCJP, you can look at the Sun's site here or you check this to see some related FAQ's.

Coming back to uCertify Preparation Kit, I actually found it pretty useful overall, for it gives you a broad spectrum of features for a relatively smaller price. The preparation engine provides you with
  • Study Notes & Helpful Articles
  • 7 Mock Tests, each with 75 questions
  • Study & Learn Module
  • Ability to Bookmark and Tag Questions
The Study & Learn Module provides a presentation (thus not really boring) based on each Examination Objective of SCJP 5.0. Going through them before the exam could be the fastest way to revise the entire syllabus. This is so because SCJP has well-defined objectives (rules & syntax of the language) that it tests. There is no need to go beyond these objectives if you want to clear the exam.

You can also attach your own notes with Study Notes and Articles, thus making a note of some exceptional condition or some related fact. These makes life really easy when you go through them again.

The practice exams give you a real feel of the actual certification exam as it contains both multiple choice questions (MCQ's) and few drag-and-drop questions. Also the level of the questions are neither too high nor too low. On a personal level, when I took the first practice exam without really preparing for it, I faltered on questions related to in-built classes like Locale, Date, NumberFormat and use of native modifier and Enumerations.

According to me, the best feature is certainly the way the answers are explained once your test is over and you see the results. You can review all the answers whether correct or not, and find out the reason for the same.
The answers are explained in length, touching the concept involved and focussing on why other options are wrong. This gives you a proper insight of what's going on.

On the downside, I would have preferred a highlighting feature that enables me to highlight important facts in the study notes and articles, so that next time I read only that part, which is important to me. Also, I would have loved had they allowed me to copy the code and paste it to test it but I understand that they probably can't do it for piracy issues and misuse.

Although it is an excellent kit to give you a proper feel of the actual exam; it is equipped with some easy ones and some tough(read tricky) questions as well just as the actual paper would. But, do not think that you need just this PrepKit to clear the paper!!
What you also need is a javac(Java compiler) to practice and code. I strongly recommend understanding the involved concepts and coding by hand (not by IDE), then take these useful tests to gain confidence as the actual exam looks almost the same.

For more information about the other preparation kits that uCertify provides you, please visit there site here.

Monday, June 1, 2009

ByteCode Back to Java Source Code !!

I have always thought about the title of this blog entry, ever since I started learning Java. But, until recently, I had no idea about the same. I didn't knew that something magical existed that would perform this conversion. But now since I know a bit, I thought I better share it.

Java Decompiler
As you would have guessed by now, a Java Decompiler is a computer program capable of reversing the work done by a Compiler. In essence, it can convert back the Bytecode (the .class file) into the source code (the .java file).
There are many decompilers that exist today, but we will talk about the most widely used JD - Java Decompiler, which is available both as a stand-alone GUI program and as an Eclipse-plugin.

To install and use these tools are a breeze and would not take you more than a few minutes to get accustomed to it. Hence, I would not repeat the process that's already mentioned on their site.

One thing that we must note here is that the process of conversion might NOT result into 100% exact code, i.e. the generated Java file might not match the actual Java code character by character. However, most of the code would be replicated but things like variable & function names or some other minor details may differ.

Lets have a look at the JD-GUI, stand-alone tool, written in C++;making it pretty fast to execute(decompile) and display the result. Also, it is independent of the the Java Runtime Environment and thus no setup is required to install it.

Lets test the tool now.

Example Java Code:
public class test{
public static void main(String[] args){
System.out.println("Hello world");

Compile it: javac
so that we have ByteCode (test.class file) with us now.

Decompile it using any one of the following ways:
  1. Execute the following on the command line: jdi-gui.exe test.class
  2. Select 'Open File' from the menu, browse to get to the test.class file and open it
  3. Drag and Drop the test.class file into the JD-GUI tool
All of the above situations result in generating the following Java Code, have a look:


public class test
public static void main(String[] paramArrayOfString)
System.out.println("Hello world");

Well just by seeing JD perform really well on this simple example, we cannot decide how efficient is this tool. But, still it is a tool that every Java Developer must be aware of. Because, in case you have accidently deleted your Java files and are left with only the .class files, this is the tool that can save your neck. :-)