OCP Java 21 Certification Exam Experience

We at Enthuware took the new OCP Java 21 Certification exam and the following is our feedback about this exam.

The number of questions in the 1Z0-830 exam is 50, which is the same as the older OCP Java 17 exam but the new exam gives you 120 minutes instead of 90 minutes. Now, it may seem like an extra 30 minutes has made the exam easier but some of the questions on this exam are framed in a style that is quite different from the older exam, and the extra time is definitely required to answer such questions. More about that later. First the basics.

What topics does the OCP Java 21 exam cover?

Just like the OCP 17 exam, the the exam objectives for OCP 21 cover a lot of topics. They range from basic, such as variable declarations, classes, loops, conditionals, overloading, and overriding) to really advanced, such as concurrency, streams, Date API, and NIO. Notably though, JDBC has been removed from OCP Java 21. Such a wide range of topics means that you may not get a question on all the topic in the exam. But believe it or not, this is a very good thing. In the past, it was easy to cheat on the exam by using exam dumps (which is just a euphemism for real exam questions). This reduced the integrity of the exam and reduced the value of the certification for those who study using genuine study material. But now, it will now be very difficult to pass the exam just by studying dumps. No two candidates will get the same questions. So, even if one studies from exam dumps, they may get a totally different set of questions.

Our content experts got questions on the following topics, and as explained above, since the number of questions were so less (only 50), some topics were completely left out. Of course, this doesn't mean that the exam doesn't have questions on these topics. Another candidate may get a different set of questions, which may include questions on these topics.

Feedback on the content of OCP Java 21 Certification Exam

1. Java Language updates:

   • Basic questions on records and sealed classes.

   • Questions on instanceof and switch with pattern matching. Must know "flow scope" as well as record deconstruction.

   • Some questions used the new multiline strings (text blocks) in their problem statement, but only a couple of questions were specifically about this feature.

   • Some questions used the new switch expressions even though the question was not really about case expression as such.

   • Theoretical questions on Virtual threads, thread states, and locks.

   • No question on less commonly used interfaces/methods of the Collection API such as Spliterator.

   • No question requiring knowledge of classes in the atomic package (such as AtomicInteger)

2. Localization: Questions on various API methods such as NumberFormat.getCurrencyInstance.

3. Modules:

   1. A few questions on Modules including advanced topics such as services including questions on command line options such as -classpath and --module-path.

   2. Surprisingly, we got questions on JImage.

4. Questions requiring thorough knowledge of the java.time package (the new Date API), including time zones and Daylight savings time.

5. Multithreading/Locking:

   1. Question on Lock, ReadWriteLock, ReentrantReadWriteLock, and its methods (tryLock(), lock(), and unlock())

   2. No question on ExecutorService

   3. There were a few questions that required a thorough understanding of thread states and wait and notify.

6. File I/O:

   1. Questions requiring thorough knowledge of Files and Path classes.

   2. For some reason, exam designers are crazy about serialization because the exam had really tough questions on this topic. One of the questions even expected the candidate to know a bit about customizing serialization by implementing readObject/writeObject methods.

7. Arrays/Collection/Stream: Several questions

8. Overloading: Complicated questions on method resolution when using ambiguous arguments involving int/float/long/double.

9. Advanced questions on Enum. Must know about methods such as valueOf() and ordinal().

10. Moderately tough questions on exceptions.

11. No question requiring knowledge of Annotations, Logging, or Math.random().

12. A few moderately tough questions on streams.

13. Many questions had errors - grammatical as well as technical.

General Feedback about the OCP Java 21 Certification Exam

• Most questions have 5 to 6 options but some of them had 7 or 8 options as well.

• Unlike OCP 17, this new OCP 21 exam has many questions that are very lengthy to read. This is because some questions (definitely not all) were styled differently. Instead of asking, "what will be the output of the following code", they asked, "Which of the following code snippets will produce this output?". This style of questioning puts multiple code fragments in options and that makes the question really lengthy to answer. You really need to act smart by eliminating obviously wrong options to arrive at the right answer for such questions. Some questions had long code in the problem statement as well. Which is why the extra 30 minutes is not really a favor.
  Another thing that makes this exam tougher than the previous version is that many questions required thorough knowledge of multiple topics. There weren't many such questions on OCP Java 17.

• Time is NOT enough even if you know the material well. Besides memorizing a lot to stuff, you must practice solving questions thoroughly if you want to pass this exam.

Overall, the test was very hard (harder than OCP 17) in terms of breadth of topics and depth of understanding required. You can't just read a topic cursorily and expect to answer exam questions on it. For example, the questions on enums required that you know the complete ins and outs of how they work. The exam also requires a lot of memorization. Questions on Date, Localization, I/O, threading, and the Collections/Stream API require you to know a wide range of methods that are provided by the Java library.

Conclusion

We have observed that Oracle starts administering the exam with low quality questions because OCP 17 also had the same issues initially (ambiguous questions, mistakes, long code snippets, 8+ options). Oracle then updates the questions based on the candidates feedback and/or performance. So, if you can, just avoid taking this exam just yet. Let it stabilize for a few months. If you are in a hurry to get certified, take OCP 17.

How to prepare for 1Z0-830 exam

1. Books: Fortunately, OCP Java 17 and 21 Exam Fundamentals Study Guide for 1Z0-829/1Z0-830 book written by Hanumant Deshmukh has been released. It covers all of the topics required for this exam.

2. Mock Exams: Enthuware will be coming up with a set of mock exams for OCP Java 21 soon.