1Z0-811 Exception Handling and Development Tools Practice Question
You are a Java developer at a financial firm. The application processes transactions from a queue. The team recently migrated from Java 8 to Java 11. After the migration, the application intermittently throws an exception: 'java.lang.reflect.InaccessibleObjectException: Unable to make field private final byte[] java.lang.String.value accessible: module java.base does not 'opens java.lang' to unnamed module'. This error occurs when the application tries to use reflection to access private fields of String objects for serialization. The application runs on a server where you cannot modify the JVM startup scripts. However, you can modify the application code and the module-info.java file. You need to resolve the exception without breaking existing functionality. Which approach should you take?
⚠ Common exam trap
Oracle often tests the misconception that you can fix module-access errors by adding 'opens' directives in your own module-info.java, but you cannot open packages belonging to other modules (like java.base) from your module descriptor.
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
✓
Refactor the code to use public APIs instead of reflecting on String's internal fields.
The root cause is that the application uses reflection to access private fields of java.lang.String, which is prohibited in Java 9+ by default due to module system encapsulation. Refactoring to use public APIs (e.g., String.getBytes(), String.charAt()) eliminates the need for reflection entirely, resolving the InaccessibleObjectException without requiring JVM flags or module declarations, and preserves compatibility with Java 11.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Refactor the code to use public APIs instead of reflecting on String's internal fields.
Why this is correct
This avoids the module access issue entirely.
- ✗
Add --add-opens java.base/java.lang=ALL-UNNAMED to the JVM command line.
Why it's wrong here
You cannot modify JVM startup scripts per the scenario.
- ✗
Use sun.misc.Unsafe to access the String field directly.
Why it's wrong here
Unsafe still requires reflection and is not a solution.
- ✗
Add 'opens java.lang;' to the module-info.java file.
Why it's wrong here
You cannot open java.lang from your module; it's a system module.
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