1Z0-829 Java Platform Overview and Packaging Practice Question
This 1Z0-829 practice question tests your understanding of java platform overview and packaging. 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.
Which TWO are characteristics of a multi-release JAR (MR-JAR)?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The root of the JAR contains classes for the oldest supported version.
Option A is correct because in a multi-release JAR (MR-JAR), the root of the JAR contains the classes compiled for the oldest supported Java version. This ensures backward compatibility: when the JAR is run on an older JVM that does not understand the META-INF/versions directory, it will use the classes from the root. The JVM automatically selects the appropriate versioned class from the META-INF/versions/<version>/ directory based on the major version of the running Java runtime.
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 root of the JAR contains classes for the oldest supported version.
Why this is correct
Root provides the base version for platforms that don't support MR-JAR.
Related concept
Read the scenario before looking for a memorised answer.
✗
The version directory must be named with the full version string like "9.0.4".
Why it's wrong here
It uses the major version number only, e.g., 9.
✓
It uses the META-INF/versions/ directory structure.
Why this is correct
Standard structure for versioned classes.
Related concept
Read the scenario before looking for a memorised answer.
✗
It can only contain a single version of each class.
Why it's wrong here
MR-JAR can contain multiple versioned copies of the same class.
✗
It is created using the jlink tool.
Why it's wrong here
jlink creates runtime images, not MR-JARs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the version directory naming convention, assuming it uses a full version string like '9.0.4' instead of the correct major version number (e.g., '9'), or they mistakenly think an MR-JAR can only hold one version of each class.
Detailed technical explanation
How to think about this question
Under the hood, the JVM's class loader checks the META-INF/versions/<major_version>/ directory for a class before falling back to the root. The version directory must match the major version number of the Java release (e.g., 9, 11, 17) as defined by the Java Platform Module System (JPMS). A real-world scenario is a library that uses newer APIs (like java.util.Objects.requireNonNullElse) in Java 9+ while providing a fallback implementation in the root for Java 8, ensuring compatibility without requiring separate JARs.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Java Platform Overview and Packaging — This question tests Java Platform Overview and Packaging — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The root of the JAR contains classes for the oldest supported version. — Option A is correct because in a multi-release JAR (MR-JAR), the root of the JAR contains the classes compiled for the oldest supported Java version. This ensures backward compatibility: when the JAR is run on an older JVM that does not understand the META-INF/versions directory, it will use the classes from the root. The JVM automatically selects the appropriate versioned class from the META-INF/versions/<version>/ directory based on the major version of the running Java runtime.
What should I do if I get this 1Z0-829 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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