1Z0-829 Java Platform Overview and Packaging Practice Test 3 — 15 Questions

Question 1

Which two statements are true about Java module declarations? (Choose two.)

Accepted Answer

A qualified export allows access to the exported package only to specific modules.. A qualified export in a Java module declaration (using the 'exports ... to ...' syntax) restricts access to the exported package only to the specific modules listed after the 'to' keyword. This provides fine-grained control over which other modules can use the exported types, enhancing encapsulation and security.

Answer

The uses directive is used to specify that a module provides a service implementation.

Answer

A module can read another module only if it explicitly requires it.

Answer

The requires directive can be used to specify a module that is optional.

Question 2

A financial trading application is developed using Java 17 and the Java Platform Module System (JPMS). The application consists of 50 named modules, including third-party libraries that are automatic modules. The team uses jlink to create a custom runtime image for deployment on customer servers. They observe that the jlink process takes over 10 minutes and produces an image of 200 MB. They want to reduce both the build time and the image size. Which action would be most effective?

Accepted Answer

Use the --limit-modules option to restrict jlink to only the application's root modules.. The --limit-modules option restricts jlink to only the specified root modules and their transitive dependencies, pruning unnecessary modules from the analysis and image. This directly reduces the number of modules jlink must process, cutting build time, and eliminates unused module classes from the runtime image, shrinking its size. In contrast, options like --strip-java-debug-attributes or --compress=2 only reduce image size after all modules are included, without addressing the root cause of excessive module scanning.

Answer

Replace jlink with jpackage to create a platform-specific installer.

Answer

Use the --strip-java-debug-attributes option to remove debug information.

Answer

Add the --compress=2 option to the jlink command.

Question 3

A developer has a modular Java 17 application whose module descriptor declares: module com.example.app { requires com.example.lib; } The com.example.lib module descriptor declares: module com.example.lib { exports com.example.lib.api; } The developer also adds the line uses com.example.lib.spi.PluginService; to com.example.app's module descriptor. However, com.example.lib.spi.PluginService is not exported by com.example.lib. At compile time, what happens?

Accepted Answer

Compilation fails because the service type com.example.lib.spi.PluginService is not exported by com.example.lib, so com.example.app cannot access it to declare the uses directive.. The uses directive in a module descriptor must reference a service type that is accessible to the module. Accessibility requires that the package containing the service interface be exported by its defining module. Since com.example.lib does not export the package com.example.lib.spi, the type PluginService is not readable, and the compiler rejects the uses clause. This enforces strong encapsulation even for service declarations.

Answer

Compilation succeeds, but a warning is issued because the uses directive is only checked at runtime when ServiceLoader.load() is called.

Answer

Compilation succeeds because com.example.lib is required, and the uses directive implicitly grants access to all packages in the required module.

Answer

Compilation succeeds because the uses directive does not require the service type to be exported; only a provides directive requires the service interface to be accessible.

Question 4

A developer is creating a modular JAR for an application named com.acme.reporting. The module descriptor declares `provides com.acme.spi.ReportFormatter with com.acme.reporting.internal.PdfFormatter;`. The service interface com.acme.spi.ReportFormatter is in a separate named module. To ensure that a service loader in another module can discover and instantiate the provider, which module descriptor declaration is required in com.acme.reporting?

Accepted Answer

requires com.acme.spi;. A provider module must be able to read the module that declares the service interface. The `provides` directive alone does not create readability, so the module descriptor must include `requires com.acme.spi;`. Without that readability edge, the provider class cannot access the service type, and service loading fails even though the provider is declared.

Answer

exports com.acme.reporting.internal;

Answer

uses com.acme.spi.ReportFormatter;

Answer

opens com.acme.reporting.internal to com.acme.spi;

Question 5

A Java 17 application is packaged as a modular JAR named app.jar with a module descriptor for module com.example.app. The JAR also contains a Main-Class attribute in its manifest. A developer runs 'java -jar app.jar'. What is the outcome?

Accepted Answer

The application runs in unnamed module mode, ignoring the module descriptor.. The java -jar command launches a JAR by reading its manifest and placing it on the class path. Even if the JAR contains a module descriptor, the launcher ignores it and loads classes in the unnamed module. Thus, the application runs in unnamed module mode, not as a modular application.

Answer

The application fails to start because a modular JAR cannot be executed with -jar.

Answer

The application runs, but the module com.example.app is resolved and its exports are enforced.

Answer

The application runs as a modular application, using the module path derived from the JAR.

Question 6

A developer is creating a custom Java runtime image for a Java 17 application using jlink. The application only needs basic Java SE functionality and does not use any modules from the java.se module. Which command should the developer use to create a minimal runtime image that includes only the java.base module?

Accepted Answer

jlink --add-modules java.base --output myruntime. The jlink tool creates custom runtime images by resolving a set of root modules and linking them with their dependencies. To include only java.base, the --add-modules option must specify java.base as the root module. The --output option sets the target directory. Other options like --limit-modules or ALL-MODULE-PATH are inappropriate for a minimal image. Thus, the command with --add-modules java.base is correct.

Answer

jlink --limit-modules java.base --output myruntime

Answer

jlink --add-modules ALL-MODULE-PATH --output myruntime

Answer

jlink --module-path $JAVA_HOME/jmods --add-modules java.se --output myruntime

Question 7

A developer is creating a custom runtime image using jlink for a Java 17 application. The application uses the java.sql module. The jlink command includes '--add-modules java.sql'. After creating the image, the developer runs the application and receives a ClassNotFoundException for java.sql.DriverManager. What is the most likely cause?

Accepted Answer

The application module does not declare 'requires java.sql', so the module is not resolved in the custom image.. For an application module to use types from java.sql, it must declare 'requires java.sql' in its module descriptor. Adding java.sql to the image with --add-modules ensures the module is present, but without the requires clause, the application module does not read it, so classes like DriverManager are not accessible.

Answer

The custom image does not include the java.base module because jlink excludes it by default.

Answer

The jlink command must also include '--bind-services' to include the java.sql module's service providers.

Answer

The java.sql module does not export the java.sql package, so DriverManager is not accessible.

Question 8

A team is preparing a Java 17 application for deployment. They want to create a custom runtime image using jlink that includes only the modules required by their application. Which two statements are true about the jlink tool? (Choose two.)

Accepted Answer

jlink can generate a runtime image for a different platform than the one on which it is run, provided the target platform's JMOD files are available.. jlink builds a custom runtime image by resolving a module graph from specified modules and their transitive dependencies. It can also cross-generate images for other platforms if the corresponding JMOD files are provided. Automatic modules cannot be used directly and must be converted to modular JARs or JMODs, and the image does not include the entire JDK by default.

Answer

jlink requires that all modules in the image be modular JARs or JMOD files; automatic modules can be included without conversion.

Answer

jlink can be used to create an image that includes application modules packaged as modular JARs, but it cannot include the application's main class.

Answer

jlink automatically includes all modules from the JDK, so the resulting image is the same size as the full JDK.

Question 9

A build engineer is analyzing a legacy application being migrated to Java 17. The codebase currently relies on several internal JDK APIs, including classes in sun.misc and com.sun.image.codec.jpeg. The team wants to understand which of these dependencies will cause compilation or runtime problems on Java 17. (Choose two.)

Accepted Answer

Classes in com.sun.image.codec.jpeg were removed from the JDK and will fail to compile against Java 17.. Two effects dominate this migration. Packages like com.sun.image.codec.jpeg were removed, so references fail to compile or link. Meanwhile, internal packages such as sun.misc can still be referenced by the compiler with warnings, but strong encapsulation may block reflective access at runtime, yielding InaccessibleObjectException or IllegalAccessError. Recognizing the difference between removal and encapsulation guides correct remediation choices.

Answer

All sun.* packages are still exported by java.base, so no warnings or errors occur when using them.

Answer

The --add-exports option can be used at runtime to grant access to internal packages from the unnamed module.

Answer

sun.misc.Unsafe is fully encapsulated and cannot be accessed at all on Java 17 without a command-line flag.

Question 10

A developer maintains a library JAR `lib.jar` that is not modularized and is placed on the class path. A modular application `com.example.app` on the module path declares `requires lib;`. What is the result when running the application?

Accepted Answer

The application fails to start with a `FindException` or similar error because module `lib` cannot be found on the module path.. A named module can only require another named or automatic module that is observable on the module path. A non-modular JAR on the class path becomes part of the unnamed module, which cannot be named in a `requires` directive. Therefore, the module system cannot resolve `lib`, and the application fails at startup with a resolution error indicating the module was not found.

Answer

The application starts successfully because the class path is merged with the module path for resolution.

Answer

The application starts, and `lib` is treated as an automatic module named after its file name without version.

Answer

The application fails to start because a named module cannot require an automatic module derived from the class path.

Question 11

A Java 17 application is packaged as a non-modular JAR and placed on the classpath. The application uses a library that is also a non-modular JAR. Which statement is true about the unnamed module?

Accepted Answer

The unnamed module reads all named modules on the module path.. The unnamed module is a special module that contains all code on the classpath. It reads every named module that is resolved on the module path, regardless of whether those modules export packages. This automatic readability ensures that classpath code can access modular libraries. However, accessibility still requires that the named module exports the relevant packages. Therefore, the statement that the unnamed module reads all named modules on the module path is correct.

Answer

The unnamed module reads all named modules that are exported.

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Every package in the unnamed module is exported to all other modules.

Answer

The unnamed module can only read named modules that explicitly export packages to it.

Question 12

A Java 17 application is packaged as a modular JAR with a module-info.java that declares 'module com.example.app { requires com.example.lib; }'. The com.example.lib module is a named module that exports package com.example.lib.api. The application also has a non-modular JAR on the classpath that contains a class in package com.example.lib.api. What happens when the application attempts to load a class from com.example.lib.api?

Accepted Answer

The class from the named module com.example.lib is loaded, and the classpath version is ignored.. In the Java Module System, a package cannot be split between a named module and the unnamed module. If a named module exports a package, that package is exclusively owned by that module. Any classpath classes in the same package are ignored when loaded by modules that read the named module. Therefore, the class from com.example.lib is loaded, and the classpath duplicate is not used. This avoids ambiguity and ensures module integrity.

Answer

A ClassNotFoundException is thrown because the package is split between a named module and the unnamed module.

Answer

The class from the non-modular JAR is loaded because classpath takes precedence over module path.

Answer

The class from the non-modular JAR is loaded because the application does not require the unnamed module.

Question 13

A company uses CI/CD to build and package a Java 17 application. They want to produce a single executable JAR that includes all dependencies. Which tool should be used to achieve this?

Accepted Answer

Maven Shade Plugin. The Maven Shade Plugin (B) is the correct choice because it creates an uber-JAR (fat JAR) by merging all project dependencies into a single executable JAR, including transitive dependencies. It also provides a relocation feature to avoid classpath conflicts, which is essential for producing a self-contained artifact for deployment.

Answer

Maven JAR Plugin

Answer

Java jar command

Answer

jlink tool

Question 14

A developer has a module named 'com.example.app' that exports a package 'com.example.api'. Another module 'com.example.client' requires 'com.example.app'. Which directive must be in the module-info.java of 'com.example.client'?

Accepted Answer

requires com.example.app;. The 'requires' directive in a module-info.java file declares a dependency on another module. For 'com.example.client' to access the exported packages of 'com.example.app', it must include 'requires com.example.app;'. This is the standard mechanism for module dependency in the Java Platform Module System (JPMS).

Answer

opens com.example.app;

Answer

uses com.example.api;

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exports com.example.api;

Question 15

A development team wants to ensure that a Java 17 application runs with a specific set of modules. They want to minimize the footprint by including only necessary modules. Which tool should they use?

Accepted Answer

jlink. B is correct because jlink is the Java tool specifically designed to assemble and optimize a custom runtime image containing only the modules explicitly required by an application. It analyzes module dependencies and produces a minimal JRE, reducing footprint by excluding unused modules, which aligns with the team's goal of minimizing size.

Answer

javac

Answer

jmod

Answer

jar