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

Question 1

Which TWO statements are true about Java modules in Java 17? (Choose two.)

Accepted Answer

A module can export a package only to specific modules using 'exports ... to ...'. The 'exports ... to ...' directive in module-info.java restricts the exported package to only the specified target modules, providing fine-grained access control. This is a key feature of the Java module system introduced in Java 9, allowing a module to expose its packages only to trusted modules rather than all other modules.

Answer

All packages in a module are automatically exported.

Answer

The jdeps tool can be used to create a module graph.

Answer

The jlink tool creates a JAR file containing the module.

Question 2

Which THREE are valid ways to package a Java 17 application for distribution? (Choose three.)

Accepted Answer

JMOD file. A is correct because a JMOD file is a native packaging format introduced in Java 9 (JEP 261) specifically for distributing Java modules. It can include compiled classes, native code, configuration files, and even other JMOD files, making it a valid distribution format for Java 17 applications, especially when using the Java Module System.

Answer

ZIP file containing compiled classes

Answer

Shell script that compiles and runs the application

Question 3

A developer runs 'java --list-modules' and sees the output above. Which command can be used to create a custom runtime image containing only the 'java.base' module?

Accepted Answer

jlink --add-modules java.base --output myimage. The `jlink` tool is used to assemble and optimize a set of modules and their dependencies into a custom runtime image. The `--add-modules` option specifies which modules to include, and `--output` specifies the target directory. Option D correctly uses `jlink --add-modules java.base --output myimage` to create a runtime image containing only the `java.base` module.

Answer

jar --create --file myimage --module java.base

Answer

jimage --add-modules java.base --output myimage

Answer

jlink --modules java.base --output myimage

Question 4

Which TWO statements about the Java Platform Module System (JPMS) are true? (Choose two.)

Accepted Answer

JPMS provides reliable configuration through explicit module dependencies.. Option B is correct because JPMS achieves reliable configuration by requiring each module to declare its dependencies explicitly in module-info.java (via requires), so the module graph is resolved at startup and missing modules are detected before execution rather than at runtime. Option E is correct because JPMS enforces strong encapsulation: a module exports only the packages listed in its exports directives, and all other packages are inaccessible to other modules even via reflection (unless opened with opens). Option A is wrong because classes on the classpath are loaded into the unnamed module, not automatically into the boot layer; only the java.base and other root modules form the boot layer. Option C is wrong because the module declaration source file is module-info.java, which is compiled to module-info.class; the declaration itself is not authored in a .class file. Option D is wrong because the classpath does not add modules to the module graph; automatic modules come from the module path, and classpath content is treated as the unnamed module.

Answer

All classes on the classpath are automatically placed in the boot layer.

Answer

A module declaration is placed in a file named module-info.class.

Answer

JPMS allows the use of the classpath to add modules to the module graph.

Question 5

Arrange the steps to read a file using NIO.2 Files.lines() in Java.

Accepted Answer

1. Create a Path object using Paths.get("file.txt"). 2. Call Files.lines(path) to obtain a Stream<String>. 3. Process the stream using stream operations like forEach, filter, etc. 4. Close the stream by calling close() or using try-with-resources.. Files.lines() returns a Stream that must be closed to release file handles. The stream is lazily populated.

Answer

1. Call Files.lines("file.txt") directly with a string. 2. Create a Path object. 3. Process the stream. 4. Close the stream.

Answer

1. Create a Path object. 2. Process the stream (e.g., apply operations). 3. Call Files.lines(path) to get the stream. 4. Close the stream.

Answer

1. Create a Path object. 2. Call Files.lines(path) to get the stream. 3. Close the stream. 4. Process the stream.

Question 6

A developer has written a Java class that uses external libraries packaged as JAR files. The application runs correctly when launched from an IDE but fails with a ClassNotFoundException when run from the command line using `java -cp`. What is the most likely cause?

Accepted Answer

The JAR files are not listed in the classpath argument.. When running a Java application from the command line with `java -cp`, the classpath must explicitly include all JAR files and directories containing the required classes. If the external library JARs are not listed in the `-cp` argument, the class loader cannot find them, resulting in a `ClassNotFoundException`. IDEs typically manage the classpath automatically, which is why the application works there but fails from the command line.

Answer

The classpath is missing the directory containing the class files.

Answer

The JAR files are not in the module path.

Answer

The Java command should use java -jar instead.

Question 7

A team is migrating a large monolithic Java 8 application to Java 17 using modules. They want to ensure that only the required packages are exported. Which tool should they use to analyze current dependencies and generate module descriptors?

Accepted Answer

jdeps. jdeps is the correct tool because it is specifically designed to analyze class dependencies in Java applications and can generate module descriptor (module-info.java) suggestions. It shows which packages are used and which are not, enabling the team to export only the required packages when migrating to Java modules.

Answer

jlink

Answer

javap

Answer

jar

Question 8

A developer creates a module `com.example.app` that requires `java.sql` and `com.example.util`. The module is compiled and packaged into a JAR. When launching the application with `java --module-path app.jar:lib --module com.example.app`, it fails with `java.lang.module.ResolutionException: Module com.example.util not found`. What is the most likely cause?

Accepted Answer

The module `com.example.util` is not in the module path.. The error `Module com.example.util not found` indicates that the module system cannot locate `com.example.util` on the module path. Since the command specifies `--module-path app.jar:lib`, the JAR for `com.example.util` must be present in the `lib` directory (or another directory on that path). If it is missing or not in the correct location, the module resolution fails. Option B correctly identifies that the module is simply not on the module path.

Answer

The module `com.example.util` is an automatic module and requires specific flags.

Answer

The module `com.example.util` is a named module but not exported.

Answer

The module `com.example.util` is on the classpath and not visible to module system.

Question 9

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?

Accepted Answer

The version from META-INF/versions/11/. 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.

Answer

The version from META-INF/versions/9/

Answer

The version from the root of the JAR

Answer

The version from META-INF/versions/17/

Question 10

Which command creates a custom runtime image containing only the modules needed by an application, reducing the size of the JRE?

Accepted Answer

jlink. The `jlink` tool is specifically designed to create a custom runtime image that contains only the modules required by a given application, along with their transitive dependencies. This reduces the JRE size by eliminating unused modules, which is a key feature of Java's module system (Project Jigsaw). Option C is correct because `jlink` is the only command among the choices that performs this modular runtime image assembly.

Answer

jmod

Answer

jar

Answer

jdeps

Question 11

An application uses `--add-opens java.base/java.lang=ALL-UNNAMED` to allow reflective access to `java.lang` internals from the classpath. After migrating to a module, the flag is changed to `--add-opens java.base/java.lang=com.example.app`. Yet reflective access still fails with `InaccessibleObjectException`. What is the most likely reason?

Accepted Answer

The reflective call is made from a different module than com.example.app.. `--add-opens` specifies which module's package is opened to which target module. When the flag is changed from `ALL-UNNAMED` to `com.example.app`, only code in the `com.example.app` module is granted reflective access. If the reflective call originates from a different module (e.g., a third-party library or another application module), the `InaccessibleObjectException` will still be thrown because that module is not listed as the target.

Answer

The class performing reflection is in an unnamed module.

Answer

The module does not read the module java.base.

Answer

The module name in --add-opens is misspelled.

Question 12

Which TWO statements are true about the Java module system?

Accepted Answer

The --add-exports flag can be used to export a package from one module to a specific target module.. The --add-exports command-line flag allows you to export a package from one module to a specific target module at runtime, overriding the module system's encapsulation. This is useful for modules that do not export a package by default but need to be accessed by a specific module during development or testing.

Answer

The --add-exports command-line flag opens a package for deep reflection.

Answer

The jlink tool can generate module-info.java files for automatic modules.

Answer

The exports directive can be used to export a specific class to another module.

Question 13

A developer runs `java --list-modules` and sees the above output on a standard JDK installation. What does this output represent?

Accepted Answer

The set of modules available in the current JDK.. The `java --list-modules` command outputs the names of all observable modules that are part of the current JDK installation. This includes all platform modules (e.g., `java.base`, `java.sql`, `jdk.compiler`) that are available for use, regardless of whether they are currently required or loaded by an application. Option C correctly identifies this as the set of modules available in the current JDK.

Answer

The modules that are part of the java.base module.

Answer

The modules that are required by the current application.

Answer

The modules that are currently loaded by the JVM.

Question 14

A developer has created a modular Java application. They want to distribute a minimal runtime image containing only the required 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 minimal runtime image containing only the modules explicitly required by the application and its transitive dependencies. It links the specified modules and their dependencies into a custom JRE that excludes unused modules, reducing footprint for distribution.

Answer

javac

Answer

jar

Answer

jpackage

Question 15

In a modular Java application, where does the module declaration file typically reside?

Accepted Answer

In a file named module-info.java at the root of the module's source tree. The module declaration for a modular Java application must be placed in a file named `module-info.java` at the root of the module's source tree. This file is then compiled into `module-info.class` and placed in the output directory, but the source declaration resides in the source tree root as per the Java Platform Module System (JPMS) specification.

Answer

In a file named module-info.class in the output directory

Answer

In the META-INF directory

Answer

In the root of the source directory