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Four Basic Topics Not on the OCJP

 
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In conversation with Campbell I had mentioned four areas I care about as part of Core Java that aren't on the OCJP, so I am paying a bit less attention to them while the exam is in scope for me.

I mentioned:

1. BigDecimal/BigInteger which came up today in this forum and reminded me to write this post.

2. Regex, very important in real life, often the best way to do interview problems, not in scope for the OCJP except maybe in .split()

3. Reflection, I think very important in Real Life, almost out of scope for the OCJP (they do use class literals for multiply-applied annotations, but nothing else from Reflection).

4. LocalDate/LocalTime I occasionally still see Date on mock exams, but not in any way that we see or are tested on the nasty details, these were on the Java 8 certs, but not the 11.  Still, don't leave home without 'em.

No action item here, they just came up as important stuff I am semi-ignoring in favor of stuff in scope for the exam, so I tend to be quiet about them...
 
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Yes, BigDecimal is an important part of basic Java®, as far as I am concerned. But how do you write multiple choice questions about it? You can't ask about operator precedence or anything like that. The most you can do is ask about methods:-

What is the output of the following code:-a: No output: throws an exception
b: 123
c: 321
d: 444
e: No output: fails to compile

That sort of question will simply add noise to the exam and little value.
 
Jesse Silverman
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And the question in Beginning Java reminds me of another one I forgot:

Scanner!!

Scanner is out-of-scope for the OCJP despite being very widely used and also a little tricky.

Console is in-scope for the OCJP despite being much less commonly used than Scanner.

 
Campbell Ritchie
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Weird. Once you start moving from apps run from the command line/terminal, you can use neither. In fact then System.console() will return null, and any attempt to use the console will cause an exception to be thrown.
Maybe it is because once people get more experienced they move away from the command line/terminal? No, it can't be, because they have other questions requiring a command line/terminal.
 
Jesse Silverman
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One more note on Reflection.

In the Sybex 815 book by Scott and Jeanne, they briefly introduce the fact that a module-info.java file can have lines like:

opens myModule.myPackage1 to myModule2,myModule3;

Which allows something called Reflection, which is out of scope for the 819 exam.

I thought it might get revisited in the Chapter on Modules from the 816 book, but it is never mentioned again.

It seems unlikely to find questions on it on the 819, but hey, if we do see one, it was mentioned in the 815 book.

Unsure if their mock tests or the Enthuware mock tests for the 819 include any questions at all on the opens directive or the open descriptor for a module.
 
Jesse Silverman
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And another thing...

Jeanne has indicated here that --module-source-path option for javac is not in scope for the 819 exam.

The only problem is, I find most materials of any quality discussing how modules actually work in JPMS make heavy use of it.

So, you kind of need to know it anyway to understand modules reasonably well, it just gets used a lot in good tutorials.

But apparently, it is out-of-scope for the 819.
 
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