1Z0-829 Java Platform Overview and Packaging Practice Test 5 — 15 Questions

Question 1

A developer places a non-modular JAR file on the module path. What type of module does this JAR become?

Accepted Answer

Automatic module. When a non-modular JAR is placed on the module path, the Java module system automatically derives a module from it, known as an automatic module. This is because the JAR lacks a module-info.class, so the system infers a module name from the JAR filename (e.g., using the Main-Class attribute or the JAR's name) and exports all packages, giving it access to all other modules. Option C is correct because the JAR becomes an automatic module, not a named or unnamed module.

Answer

Open module

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Named module

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Unnamed module

Question 2

A company wants to distribute a Java desktop application with a bundled JRE for end users who may not have Java installed. Which tool should they use?

Accepted Answer

jpackage. jpackage is the correct tool because it is specifically designed to package a Java application along with a bundled JRE into a native installer (e.g., .exe, .dmg, .deb) for distribution to end users who may not have Java installed. It uses the jlink tool internally to create a custom runtime image and then wraps it with platform-specific packaging tools, ensuring the application runs independently of any pre-installed JRE.

Answer

jlink

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jar

Answer

jmod

Question 3

Given two named modules where module com.example.app requires module com.example.lib, which packages of com.example.lib are readable by com.example.app?

Accepted Answer

Only the packages exported by com.example.lib. In the Java module system, a module can only access packages from another module that are explicitly exported using the `exports` directive in the module's `module-info.java` file. Since `com.example.app` requires `com.example.lib`, only the packages exported by `com.example.lib` are readable; unexported packages remain encapsulated and inaccessible.

Answer

All packages except those explicitly concealed

Answer

All packages of com.example.lib

Answer

Only the packages opened by com.example.lib

Question 4

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?

Accepted Answer

The manifest must contain 'Multi-Release: true'. 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`.

Answer

The JAR must have a module-info.class in the root

Answer

The JAR must be placed on the module path

Answer

The JAR must be created using the --multi-release 17 option

Question 5

A company uses jlink to create a custom runtime image. They want to reduce the image size by removing debug information. Which jlink option or plugin should they use?

Accepted Answer

--strip-debug. The `--strip-debug` option in jlink removes debug information from the custom runtime image, including line numbers, local variable tables, and source file references, which significantly reduces the image size. This is the correct option for stripping debug information, as it directly targets the removal of debugging metadata from the generated image.

Answer

--compress=2

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--no-header-files

Answer

--bind-services

Question 6

Which THREE statements about the jpackage tool are true?

Accepted Answer

jpackage can create native installers for Windows, macOS, and Linux.. The jpackage tool is designed to create native installers for Windows (e.g., .exe/.msi), macOS (e.g., .dmg), and Linux (e.g., .deb/.rpm). This is a core feature of jpackage, which replaces the older Java Packager and allows developers to distribute self-contained applications with platform-specific packaging formats.

Answer

jpackage requires an existing JRE to create a runtime image.

Answer

jpackage uses the Java Packager library.

Question 7

Refer to the exhibit. The resulting image directory includes a 'bin' directory with java launcher. When running the application, a NoClassDefFoundError occurs for a class from module com.example.lib. What is the most likely cause?

Accepted Answer

The com.example.lib module was not added via --add-modules.. When using jlink to create a custom runtime image, only the modules explicitly specified (or their transitive dependencies) are included. If the application depends on com.example.lib but it was not added via --add-modules, the module's classes will be missing from the image, causing a NoClassDefFoundError at runtime. This is the most direct cause among the options.

Answer

The --compress=2 option altered the class.

Answer

The application uses reflection to access the class.

Answer

The --strip-debug option removed the class file.

Question 8

Refer to the exhibit. Which statement is true about the com.example.app.internal package?

Accepted Answer

It is accessible for deep reflection only by com.example.lib.. The exhibit shows that `com.example.app.internal` is declared with `opens com.example.app.internal to com.example.lib`. The `opens` directive grants deep reflection (access to private members) at runtime, but only to the specified module `com.example.lib`. Other modules cannot reflectively access this package unless they are explicitly listed.

Answer

It is accessible for deep reflection by any module.

Answer

It is not accessible for reflection at all.

Answer

It is exported to all modules.

Question 9

Refer to the exhibit. The module path is correctly set to include the JAR containing the module. What is the most likely issue?

Accepted Answer

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

The JAR does not have a module-info.class.

Answer

The module requires a module that is not on the module path.

Answer

The Main class is not in an exported package.

Question 10

An organization has a monolithic Java application built with Java 8 and deployed on a traditional classpath. They are migrating to Java 17 and want to use the module system to improve encapsulation. They have a jar file 'legacy.jar' that contains packages under 'com.legacy' and does not have a module-info.class. Which approach should they take to allow other modules to depend on this jar?

Accepted Answer

Place the jar on the module path; it becomes an automatic module.. When a JAR file without a module-info.class is placed on the module path, Java treats it as an automatic module. This allows other modules to depend on it by name (derived from the JAR filename) and grants it access to all other modules, effectively bridging the gap between the classpath and the module system during migration.

Answer

Add a module-info.class file to the jar using jar tool.

Answer

Place the jar on the classpath; it becomes an unnamed module.

Answer

Use jmod tool to convert the jar into a JMOD file.

Question 11

A team uses 'jlink' to create a custom runtime image for a modular application. They run the following command: 'jlink --module-path $JAVA_HOME/jmods:myapp --add-modules com.example.myapp --output myimage'. The application requires several non-Java native libraries (e.g., .so files) that are loaded via System.loadLibrary(). After creating the image, the application fails with an UnsatisfiedLinkError. What is the most likely cause?

Accepted Answer

The native libraries were not included in the image; they must be manually copied or added using --add-modules and a custom module.. The `jlink` tool creates a runtime image that includes only Java modules and their dependencies, not native libraries (e.g., .so files). Native libraries must be manually placed into the image's library path (e.g., `lib/` or `bin/` directory) or packaged into a custom module that is added via `--add-modules`. The `UnsatisfiedLinkError` occurs because `System.loadLibrary()` cannot find the native library in the image's expected locations.

Answer

The native library loading requires a module that exports the package containing the native method.

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The --add-modules flag omitted transitive dependencies of com.example.myapp.

Answer

The --module-path must also include the directories containing the native libraries.

Question 12

A developer creates a Java application that uses the new 'jpackage' tool to create an installer for Windows. The application is modular and has a main class declared in module-info. Which option is required to specify the main class when using jpackage?

Accepted Answer

--module. For a modular application with a main class declared in module-info, jpackage requires the `--module` option to specify the module name and, optionally, the main class (e.g., `--module com.example/com.example.Main`). This is because jpackage uses the module system to resolve the entry point, not a classpath or JAR-based approach.

Answer

-classpath

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--module-path

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--main-jar

Question 13

A developer runs 'jdeps -s --module-path lib myapp.jar' and gets output: 'myapp.jar -> java.base, myapp.jar -> java.sql, myapp.jar -> notfound'. What does the 'notfound' entry indicate?

Accepted Answer

The application has a dependency on a package that is not provided by any module on the module path.. The 'notfound' entry in the jdeps -s output indicates that the application has a dependency on a package that is not provided by any module on the module path. The -s (summary) flag shows module-level dependencies, and when a required module cannot be located among the specified modules or the JDK's built-in modules, jdeps reports it as 'notfound'. This means the dependency cannot be resolved at analysis time, typically because the required module is missing from the module path.

Answer

The dependency is resolved but its module name is not printed due to a summary flag.

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The jar file is missing or corrupt.

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There is a cyclic dependency among modules.

Question 14

Which TWO statements are true about the Java module system (JPMS) as of Java 17?

Accepted Answer

A named module is defined by a module-info.class file placed in the root of the module.. A named module in JPMS is defined by a module-info.class file (compiled from module-info.java) placed in the root directory of the module. This file declares the module's name, dependencies, and exported packages, making it a fundamental requirement for a named module.

Answer

An automatic module can contain a module-info.class file.

Answer

A jar file placed on the classpath that lacks module-info.class becomes an automatic module.

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A named module can read an unnamed module by default.

Question 15

Which THREE statements are true about the Java Platform editions? (Select three.)

Accepted Answer

Java ME provides a subset of Java SE APIs for embedded devices.. Java ME (Micro Edition) is designed for resource-constrained devices like sensors, mobile phones, and embedded systems. It provides a subset of the Java SE APIs, along with additional APIs tailored for small devices, such as the Connected Limited Device Configuration (CLDC) and the Mobile Information Device Profile (MIDP). This allows developers to write Java applications that run on devices with limited memory, processing power, and display capabilities.

Answer

Java ME (Micro Edition) is the same as Android SDK.

Answer

Java SE includes a full application server for enterprise applications.