Missed Demo for the Japanese Students I Gave Speech to

I had an opportunity to give a speech to students who are looking to become engineers in Japan last Friday. It was great to meet them though it was online. They seemed eager to learn what takes to be engineers. I was honored to give speech to them. They were also learning English, so this may be good for them.

Due to my unpreparedness on my side, I missed one demo. I was basically compiling Java code and decomplie it with IntelliJ. I would like to show how it can be done here in this blog for their view.

First, create a text file (helloworld.java) with the following code. It’s just a simple hello world program in Java.

public class helloworld {
    public static void main(String args[])
        System.out.println("Hello World");

Once you have the file, compile it like the following from your terminal (command line).

javac helloworld.java

The javac (Java compiler) compiles the text file to Java byte code (helloworld.class). You can execute the hello world program like the following.

java helloworld


Hello World

When you open helloworld.class file with IntelliJ, you can decompile it.

Decompilation is not really a useful technique anymore because of the current trend of open source but if the source code is closed but you want to learn how the Java program works, it’s still an interesting technique to use especially while you are learning how program works.

I believe JetBrain provides students with free license so you may be able to use the IDEs for free.

The reason why I could not find the helloworld.class file at the time of demo was because I was using WSL 2 on Windows. I had the file on the Linux side of the OS but I had forgotten to copy the file on the Windows side. I’m so sorry about it.

There was so much more I wanted to talk to everyone about but our time was limited. I wish all of you successful careers and bright future. 🙂

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