1Z0-829 Java Platform Overview and Packaging Practice Question
Exhibit
Error: Could not find or load main class com.example.Main
Refer to the exhibit. The module path is correctly set to include the JAR containing the module. What is the most likely issue?
⚠ Common exam trap
Oracle often tests the distinction between module-path requirements for `java -jar` versus `java --module`, where candidates mistakenly think the main class must be exported or that a missing `module-info.class` is the issue, but the real trap is the missing main-class declaration in either the module descriptor or manifest.
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 Main class is not specified as the main class in the module descriptor or manifest.
When launching a modular JAR with `java -jar`, the JVM requires the main class to be explicitly declared either in the module descriptor (`module-info.java` with a `main-class` directive) or in the JAR's `MANIFEST.MF` (`Main-Class` attribute). Without this declaration, the JVM cannot determine the entry point, resulting in a 'Main class not found' error. Option A correctly identifies this missing declaration as the most likely issue.
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 Main class is not specified as the main class in the module descriptor or manifest.
Why this is correct
The JVM needs the main class specified via --main-class or manifest.
- ✗
The JAR does not have a module-info.class.
Why it's wrong here
A module-info.class is not required; the JAR could be an automatic module.
- ✗
The module requires a module that is not on the module path.
Why it's wrong here
That would cause a different error like 'module not found'.
- ✗
The Main class is not in an exported package.
Why it's wrong here
The main class can be in a non-exported package; the JVM can still launch it.
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