1Z0-829 Java Platform Overview and Packaging Practice Test 4 — 15 Questions

Question 1

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 2

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.. Option A is correct because 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 3

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 4

A Java application is developed using Java SE 17. It uses only standard Java APIs and no external libraries. The application runs without errors in the development environment. When deploying to a production server, which minimal Java environment is sufficient?

Accepted Answer

Java Runtime Environment (JRE). The correct answer is D because a Java application compiled into bytecode (`.class` files) requires only the Java Runtime Environment (JRE) to execute. The JRE includes the Java Virtual Machine (JVM), core libraries, and supporting files, but not development tools like the compiler. Since the application is already compiled and uses only standard APIs, no additional tools are needed at runtime.

Answer

Java compiler (javac)

Answer

Java Virtual Machine (JVM) only

Answer

Java Development Kit (JDK)

Question 5

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.. Option B is correct because 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 6

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.. Option C is correct because 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.

Answer

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 7

A Java 17 application is packaged as a modular jar and deployed on a system with the full JDK. The application uses the java.sql module. The system administrator wants to minimize the footprint by creating a custom runtime image using jlink. Which command would create an image with only the necessary modules?

Accepted Answer

jlink --module-path $JAVA_HOME/jmods:app --add-modules com.myapp --output myimage. Option A is correct because `jlink` with `--add-modules com.myapp` and the module path pointing to both `$JAVA_HOME/jmods` and the application JAR automatically resolves all transitive dependencies, including `java.sql`, and creates a minimal runtime image containing only the required modules. The `--output myimage` specifies the target directory for the custom image.

Answer

jlink --module-path $JAVA_HOME/jmods:app --add-modules com.myapp --bind-services --output myimage

Answer

jlink --module-path $JAVA_HOME/jmods:app --add-modules java.sql --output myimage

Answer

jlink --module-path $JAVA_HOME/jmods:app --add-modules ALL-MODULE-PATH --output myimage

Question 8

A Java 17 application uses the Java Platform Module System (JPMS). The module 'com.example.service' exports 'com.example.service.api' and requires 'java.logging'. Another module 'com.example.client' requires 'com.example.service'. The client module cannot access the 'com.example.service.api' package. What is the most likely reason?

Accepted Answer

The 'com.example.client' module does not contain a 'requires com.example.service' directive.. Option C is correct because the question states that the client module 'requires com.example.service', so the client module does contain the required directive. The most likely reason the client cannot access 'com.example.service.api' is that the 'com.example.service' module does not export that package. According to JPMS, a package must be explicitly exported via the 'exports' directive in the module-info.java of the owning module for other modules to access its public types. Without that export, even with a 'requires' directive, the package remains inaccessible.

Answer

The 'com.example.service' module does not use 'requires transitive' for 'java.logging'.

Answer

The 'com.example.service.api' package is not exported by 'com.example.service'.

Answer

The 'java.logging' module does not export its packages to 'com.example.service'.

Question 9

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

Answer

--module-path

Answer

--main-jar

Question 10

A company deploys a Java 17 application on a server with a custom runtime image created by jlink. The application uses the Java logging API (java.util.logging). The server administrator notices that the image size is approximately 45 MB. They need to reduce it further. Which jlink option would help exclude unnecessary locale data?

Accepted Answer

--include-locales en_US. Option A is correct because the `--include-locales` option in jlink allows you to specify which locale data to include in the custom runtime image. By default, jlink includes all locale data, which can significantly increase image size. Using `--include-locales en_US` restricts the image to only US English locale data, reducing unnecessary bloat for applications that do not require multiple locales.

Answer

--compress=2

Answer

--strip-debug

Answer

--no-header-files

Question 11

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.

Answer

The jar file is missing or corrupt.

Answer

There is a cyclic dependency among modules.

Question 12

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.. Option A is correct because 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.

Answer

A named module can read an unnamed module by default.

Question 13

Which TWO are valid uses of the 'jmod' tool in Java 17?

Accepted Answer

Listing the contents of a JMOD file.. The 'jmod' tool is primarily used for creating and inspecting JMOD files, which are a packaging format for Java modules that can include native libraries, configuration files, and other resources beyond what a modular JAR can hold. Option B is correct because 'jmod list' lists the contents of a JMOD file, showing its entries such as classes, native code, and legal notices. Option C is correct because 'jmod create' can create a JMOD file from a modular JAR and additional native libraries using the --libs option.

Answer

Creating a custom runtime image.

Answer

Executing a JMOD file as an application.

Answer

Identifying module dependencies of a jar.

Question 14

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.

Question 15

You are a software architect at a financial firm. Your team is developing a modular Java 17 application that comprises several modules: 'com.bank.core' (provides core banking services), 'com.bank.web' (REST API), and 'com.bank.persistence' (database access). The application uses the 'java.sql' module for JDBC and 'java.logging' for logging. The team uses Maven for dependency management. The application has an external dependency on the 'com.fasterxml.jackson.databind' library (Jackson) for JSON processing, which is provided as a non-modular jar. The Jackson jar is placed on the module path. The application modules are all named modules with module-info files. At runtime, the 'com.bank.web' module requires 'com.bank.core' and 'com.fasterxml.jackson.databind' (the automatic module). The 'com.bank.core' module requires 'java.sql' and 'java.logging'. When the application runs, it throws an 'IllegalAccessError' indicating that the module 'com.bank.core' tries to access a class from 'com.fasterxml.jackson.databind' but the module does not read it. Yet, 'com.bank.web' is the only module that explicitly requires Jackson. What is the most likely cause and the correct resolution?

Accepted Answer

Add 'requires com.fasterxml.jackson.databind' to the module-info.java of 'com.bank.core' because it uses Jackson classes directly.. Option B is correct because the error indicates that 'com.bank.core' directly uses classes from 'com.fasterxml.jackson.databind', but its module-info.java does not include a 'requires com.fasterxml.jackson.databind' directive. In the Java module system, a module can only access types from another module if it explicitly reads that module. Since 'com.bank.core' needs Jackson classes at runtime, it must declare the dependency itself, even if another module ('com.bank.web') also requires it.

Answer

Convert all application modules to unnamed modules by removing module-info files.

Answer

Place the Jackson jar on the classpath instead of the module path.

Answer

Use jlink to create a custom runtime image including all modules and the Jackson jar.