Skip to content

added a select all that apply multiple choice based question to section9.3 #416

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
pearcej merged 1 commit into from
Aug 12, 2026
Merged

added a select all that apply multiple choice based question to section9.3 #416

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
50 changes: 50 additions & 0 deletions source/ch9_commonmistakes.ptx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,56 @@
<p>
The 'cannot find symbol' error for the variable <c>count</c> on line 6 indicates that <c>count</c> was used before it was declared within the <c>Histo</c> class. In Java, all variables must be explicitly declared with a data type (e.g., <c>int</c>, <c>String</c>, <c>ArrayList&lt;Integer&gt;</c>) before they can be assigned a value or referenced in any way. The arrow in the error message points to where the undeclared variable <c>count</c> was first encountered. To resolve this, <c>count</c> needs to be declared with its appropriate type (e.g., <c>ArrayList&lt;Integer&gt; count;</c>) before any attempt to initialize or use it.
</p>
<exercise label="java-declare-variable-checkpoint">
<statement>
<p>
Based on <xref ref="undeclared-variable" text="type-global"/>, select all of the
statements that are true about declaring variables in Java.
</p>
</statement>
<choices>
<choice correct="yes">
<statement>
<p>Every variable must be declared with a data type before it is used.</p>
</statement>
<feedback>
<p>Correct! Java requires a variable to be declared with its type before it can be assigned or referenced.</p>
</feedback>
</choice>
<choice correct="yes">
<statement>
<p>The "cannot find symbol" error happens because <c>count</c> was used before being declared.</p>
</statement>
<feedback>
<p>Correct! That error means the compiler reached a variable it has no declaration for.</p>
</feedback>
</choice>
<choice correct="yes">
<statement>
<p>Writing <c>ArrayList&lt;Integer&gt; count;</c> before using <c>count</c> would fix the "cannot find symbol" error.</p>
</statement>
<feedback>
<p>Correct! Declaring <c>count</c> with its type resolves the error.</p>
</feedback>
</choice>
<choice>
<statement>
<p>Java lets you use a variable without declaring it first, just like Python.</p>
</statement>
<feedback>
<p>Incorrect. Unlike Python, Java requires all variables to be declared before use.</p>
</feedback>
</choice>
<choice>
<statement>
<p>The error can be fixed by adding an import statement.</p>
</statement>
<feedback>
<p>Incorrect. The import is already present; the problem is the missing variable declaration, not a missing import.</p>
</feedback>
</choice>
</choices>
</exercise>

</section>

Expand Down