My Experience Taking the Java SE 21 Exam (1Z0-830)

Oct 12, 2025

The Java SE 21 certification is currently the latest available exam, and let me tell you: it’s tough, but not impossible. In this post, I want to share my personal experience preparing for and passing the exam, and hopefully give you some insights if you’re planning to take it too.

From Java 8 to Java 21

My previous certification was for Java 8, and it took me about two months to prepare. Java 21, on the other hand, felt like an entirely different challenge. The scope of content has expanded significantly, and the questions are far more complex.

Even though I was already familiar with many of the new Java 21 features, it still took me around five months of preparation to feel ready for the exam.

How I Prepared

I started with the OCP Oracle Certified Professional Java SE 21 Developer Study Guide by Jeanne Boyarsky and Scott Selikoff, over 1,000 pages of material!

After finishing the book, I moved on to practice:

I used Enthuware mock exams, completing all the 1,000+ questions.
My goal was to score at least 75% on every mock test before moving on.

This strategy paid off. When the real exam day came, I was able to finish in about 90 minutes and scored 82%.

Exam Details

⏱️ Time limit: 120 minutes
❓ Number of questions: 50
✅ Passing score: 68% (34 correct answers)

Extra Notes & Tips

The exam can only be taken online, so make sure you have a stable internet connection.
You cannot use paper to take notes, you need to use a notepad from the Oracle exam, it can a little annoying.
Using a big monitor helps, since some questions are long and require scrolling.
Compared to previous versions, the questions are bigger and more complex, so be ready to focus.