- A
The module path order is incorrect, causing a different version of the library to be loaded.
Why wrong: Module path order affects resolution, but the error would typically be a resolution error, not NoClassDefFoundError for a particular class.
- B
The library is not compatible with Java 17.
Why wrong: If the library were incompatible, the error would likely occur during compilation or manifest as a linkage error (e.g., UnsupportedClassVersionError).
- C
The application's module requires the wrong version of the library.
Why wrong: Version requirements would cause a resolution error at startup, not a NoClassDefFoundError for a specific class that exists.
- D
The module com.thirdparty.lib does not export the package containing the required class in its module-info.java.
Even though the module is on the module path, its packages are not accessible without an 'exports' directive.
1Z0-811 What is Java Practice Question
This 1Z0-811 practice question tests your understanding of what is java. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A development team is building a modular Java application using Java 17. They have defined a module named com.myapp with a module-info.java that includes 'requires com.thirdparty.lib;'. The com.thirdparty.lib module is a third-party library packaged as a modular JAR with its own module-info.class. The application compiles successfully using javac with the module path pointing to the directory containing the JAR. However, when starting the application with java --module-path <path> --module com.myapp, a NoClassDefFoundError occurs for a class from com.thirdparty.lib. The error message indicates the class is not found. The team has confirmed that the JAR file is present in the specified module path and that the class exists in the JAR. No other errors or warnings are displayed. The team is puzzled because the code compiles without issues. What is the most likely cause of this runtime error?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The module com.thirdparty.lib does not export the package containing the required class in its module-info.java.
In modular Java, a module must explicitly export a package using the 'exports' directive in its module-info.java for that package to be accessible by other modules. If com.thirdparty.lib does not export the package containing the required class, the class is present in the module but not accessible at runtime, leading to a NoClassDefFoundError even though compilation succeeded. Option D is correct because the missing exports directive causes this issue. Option A is incorrect because module path order affects module resolution, not accessibility of exported packages; if the module is resolved, the correct JAR is used. Option B is incorrect because if the library were incompatible with Java 17, compilation would typically fail or generate different errors (e.g., UnsupportedClassVersionError). Option C is incorrect because version requirements in 'requires' are optional and generally produce compile-time warnings/errors, not a runtime NoClassDefFoundError for a class that exists.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The module path order is incorrect, causing a different version of the library to be loaded.
Why it's wrong here
Module path order affects resolution, but the error would typically be a resolution error, not NoClassDefFoundError for a particular class.
- ✗
The library is not compatible with Java 17.
Why it's wrong here
If the library were incompatible, the error would likely occur during compilation or manifest as a linkage error (e.g., UnsupportedClassVersionError).
- ✗
The application's module requires the wrong version of the library.
Why it's wrong here
Version requirements would cause a resolution error at startup, not a NoClassDefFoundError for a specific class that exists.
- ✓
The module com.thirdparty.lib does not export the package containing the required class in its module-info.java.
Why this is correct
Even though the module is on the module path, its packages are not accessible without an 'exports' directive.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 1Z0-811 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which 1Z0-811 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this 1Z0-811 question test?
What is Java — This question tests What is Java — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The module com.thirdparty.lib does not export the package containing the required class in its module-info.java. — In modular Java, a module must explicitly export a package using the 'exports' directive in its module-info.java for that package to be accessible by other modules. If com.thirdparty.lib does not export the package containing the required class, the class is present in the module but not accessible at runtime, leading to a NoClassDefFoundError even though compilation succeeded. Option D is correct because the missing exports directive causes this issue. Option A is incorrect because module path order affects module resolution, not accessibility of exported packages; if the module is resolved, the correct JAR is used. Option B is incorrect because if the library were incompatible with Java 17, compilation would typically fail or generate different errors (e.g., UnsupportedClassVersionError). Option C is incorrect because version requirements in 'requires' are optional and generally produce compile-time warnings/errors, not a runtime NoClassDefFoundError for a class that exists.
What should I do if I get this 1Z0-811 question wrong?
Identify which 1Z0-811 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 23, 2026
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