The answer is that the manifest must contain 'Multi-Release: true'. This is the essential condition because the Java runtime explicitly checks for this manifest attribute to enable version selection from the `META-INF/versions/` directory; without it, the JVM ignores all versioned directories and falls back to the root classes, even if the JAR was compiled with `--multi-release 17`. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this concept tests your understanding of the multi-release JAR manifest requirement as a gatekeeper for modular versioning—a common trap is assuming that merely placing classes in versioned folders is enough, when in fact the runtime only reads them if the manifest flag is present. A reliable memory tip is to think of the manifest as a "key" that unlocks the versioned directories: no `Multi-Release: true`, no version-specific class loading.
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.
A team has a multi-release JAR that supports both Java 11 and Java 17. They want to ensure that when running on Java 17, the version-specific classes in META-INF/versions/17 are used. Which condition must be true?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The manifest must contain 'Multi-Release: true'
Option D is correct because the Java runtime checks for the `Multi-Release: true` entry in the JAR's manifest file to enable multi-release JAR functionality. Without this manifest attribute, the JVM ignores versioned directories under `META-INF/versions/` and uses only the root classes, even if the JAR was compiled with `--multi-release 17`.
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 JAR must have a module-info.class in the root
Why it's wrong here
A module-info.class is not required for multi-release JARs.
✗
The JAR must be placed on the module path
Why it's wrong here
The JAR can be on classpath or module path; the manifest is key.
✗
The JAR must be created using the --multi-release 17 option
Why it's wrong here
The --multi-release option adds versioned directories but the manifest entry is still needed at runtime.
✓
The manifest must contain 'Multi-Release: true'
Why this is correct
The manifest entry is required to activate multi-release behavior.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the misconception that the `--multi-release` compiler or jar tool option alone enables version selection at runtime, when in fact the manifest entry `Multi-Release: true` is the sole runtime trigger.
Detailed technical explanation
How to think about this question
The multi-release JAR mechanism is defined by JEP 238 and relies on the `Multi-Release` manifest attribute as a runtime switch. When the JVM loads a class, it checks the manifest; if `Multi-Release: true` is present and the runtime Java version matches a directory under `META-INF/versions/`, the class loader uses the versioned class instead of the root class. A subtle behavior is that the root directory must still contain a base version of every class, as the runtime falls back to the root if no versioned directory matches the current Java version.
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 manifest must contain 'Multi-Release: true' — Option D is correct because the Java runtime checks for the `Multi-Release: true` entry in the JAR's manifest file to enable multi-release JAR functionality. Without this manifest attribute, the JVM ignores versioned directories under `META-INF/versions/` and uses only the root classes, even if the JAR was compiled with `--multi-release 17`.
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.
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. Which TWO are characteristics of a multi-release JAR (MR-JAR)?
easy
✓ A.The root of the JAR contains classes for the oldest supported version.
B.The version directory must be named with the full version string like "9.0.4".
✓ C.It uses the META-INF/versions/ directory structure.
D.It can only contain a single version of each class.
E.It is created using the jlink tool.
Why A: 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.
Variation 2. A company uses a multi-release JAR (MR-JAR) that contains classes for Java 9 and Java 11 in `META-INF/versions/9/` and `META-INF/versions/11/` respectively. The application runs on Java 17. Which version of a class that exists in both versioned directories is loaded?
hard
A.The version from META-INF/versions/9/
B.The version from the root of the JAR
✓ C.The version from META-INF/versions/11/
D.The version from META-INF/versions/17/
Why C: Option C is correct because in a multi-release JAR (MR-JAR), the Java runtime selects the versioned directory that matches the major version of the running Java platform, or the highest versioned directory that does not exceed that version. Since the application runs on Java 17, and the highest available versioned directory is for Java 11 (META-INF/versions/11/), the class from that directory is loaded. The root directory is used only when no appropriate versioned directory exists.
Last reviewed: Jun 30, 2026
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