The correct answer is to recompile the library with the -g flag and redeploy. This works because the -g flag instructs the Java compiler to include full debug information—specifically line numbers, local variable names, and source file details—directly into the compiled class files. Without this debug metadata, the JVM cannot map bytecode instructions back to specific source lines, resulting in a stack trace that shows only method names and not the exact line where the NullPointerException occurred. On the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of how the compiler’s debug options affect runtime diagnostics; a common trap is assuming you can fix the exception by changing the code logic rather than by enabling debug symbols. Remember the mnemonic: “No -g, no line—trace is blind, fix the compile, find the line.”
1Z0-811 Exception Handling and Development Tools Practice Question
This 1Z0-811 practice question tests your understanding of exception handling and development tools. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Consider a Java application that throws a NullPointerException deep inside a library method. The stack trace does not include the caller's line numbers because the library was compiled without debug information. Which approach would best help identify the root cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Recompile the library with -g flag and redeploy.
Option B is correct because recompiling the library with the `-g` flag includes debug information (such as line numbers and local variable names) in the class files. This allows the JVM to produce a stack trace with precise line numbers, enabling you to trace the NullPointerException back to the exact source line in the library code, even though the library was originally compiled without debug info.
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.
✗
Use a debugger to set breakpoints in the library.
Why it's wrong here
This requires source code and knowledge of where to break, which may not be available.
✓
Recompile the library with -g flag and redeploy.
Why this is correct
The -g flag generates debugging information including line numbers, making stack traces more informative.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use logging statements in the application code before and after the call.
Why it's wrong here
This can help but is less direct and may not pinpoint the exact location in the library.
✗
Add a try-catch around the library call and print the stack trace.
Why it's wrong here
The stack trace still lacks line numbers, so this does not provide additional information.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the misconception that adding a try-catch or logging around the call site can reveal the internal cause of an exception, when in fact only the library's own debug information (or recompilation with `-g`) can provide the line-level detail needed to trace the root cause.
Detailed technical explanation
How to think about this question
The `-g` flag in javac generates a `LineNumberTable` and `LocalVariableTable` in the class file's attribute section, which the JVM uses to map bytecode offsets to source line numbers. Without these attributes, the stack trace shows only method names and class names, but no line numbers, making debugging of third-party or precompiled libraries extremely difficult. In real-world scenarios, this is common when using closed-source libraries or when build pipelines strip debug info to reduce artifact size, and recompiling with `-g` is the standard fix.
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.
TExam Day Tips
→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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Exception Handling and Development Tools — This question tests Exception Handling and Development Tools — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Recompile the library with -g flag and redeploy. — Option B is correct because recompiling the library with the `-g` flag includes debug information (such as line numbers and local variable names) in the class files. This allows the JVM to produce a stack trace with precise line numbers, enabling you to trace the NullPointerException back to the exact source line in the library code, even though the library was originally compiled without debug info.
What should I do if I get this 1Z0-811 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A developer is debugging a Java application that throws a NullPointerException. Which two actions help identify the source of the exception? (Choose two.)
medium
A.Use System.out.println statements
✓ B.Use a debugger to step through code
✓ C.Examine the stack trace
D.Recompile with -g flag
E.Catch the exception and print its message
Why B: Examining the stack trace (option A) shows the exact line number where the exception occurred, and using a debugger (option D) allows stepping through code to see variable states. While System.out.println (B) and catching the exception (C) can be helpful, they are less efficient and don't provide the precise location as directly. Recompiling with -g (E) adds debug info but is not an action to identify the source; it's a prerequisite for better stack traces.
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Question Discussion
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