1Z0-829 Practice Test 9 — 10 Questions

Question 1

Which THREE statements about the SecurityManager and security policies in Java 17 are true? (Choose three.)

Accepted Answer

The SecurityManager class is deprecated in Java 17.. The SecurityManager class is deprecated for removal in Java 17 (JEP 411). This deprecation means that while the class still exists for compatibility, it is no longer recommended for use and may be removed in a future release. The core reasoning is that the SecurityManager architecture is considered legacy and difficult to maintain, so Oracle has deprecated it to encourage developers to adopt alternative security mechanisms.

Answer

System.setProperty("java.security.policy", "policy.url") loads a new policy.

Answer

By default, Java 17 applications run with a SecurityManager installed.

Question 2

A method receives an InputStream and needs to compute its MD5 hash while reading the data. Which approach is most efficient?

Accepted Answer

Use DigestInputStream wrapping the original stream, then read the stream. `DigestInputStream` is a built-in Java class that computes a message digest (e.g., MD5) on the fly as data is read from the underlying stream. This avoids buffering the entire stream into memory, making it both memory-efficient and CPU-efficient for large or streaming data sources.

Answer

Read all bytes into a byte array, then compute hash using MessageDigest

Answer

Use a custom filter that hashes bytes during read

Answer

Use Scanner to read tokens and update hash

Question 3

To generate a cryptographically secure random number for a key generation algorithm, which class should be used?

Accepted Answer

SecureRandom. D is correct because `SecureRandom` is specifically designed to produce cryptographically strong random numbers suitable for key generation, using algorithms like SHA1PRNG or NativePRNG that meet FIPS 140-2 standards. Unlike other random number generators, it ensures unpredictability and resistance to reverse engineering, which is critical for security-sensitive operations.

Answer

ThreadLocalRandom

Answer

Math.random()

Answer

Random

Question 4

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 5

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 6

Which THREE statements about the switch statement in Java are correct?

Accepted Answer

The default case can be placed anywhere within the switch block.. The default case can be placed anywhere within the switch block according to the Java Language Specification. Option D is correct: case labels must be compile-time constant expressions; a final variable assigned a constant expression qualifies as a compile-time constant. Option E is correct: switch works with int, char, String, and enum types. Option B is incorrect because case values must be compile-time constants, not arbitrary runtime expressions. Option C is incorrect because break is not mandatory; it is optional and used to prevent fall-through.

Answer

Case values can be runtime expressions.

Answer

A break statement is mandatory after each case block.

Question 7

Which TWO statements about Java module types are true?

Accepted Answer

An automatic module exports all its packages.. The Java module system automatically exports all packages of an automatic module, making them accessible to other modules without explicit export declarations. This is a key characteristic of automatic modules, which are created from JAR files placed on the module path without a module-info.java file.

Answer

An automatic module can access all packages of named modules without explicit requires.

Answer

The unnamed module can read only the java.base module.

Answer

The unnamed module is a named module.

Question 8

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 $JAVA_HOME/jmods:app --add-modules com.myapp --output myimage. `jlink` with `--add-modules com.myapp` and the module path pointing to both `$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 9

Given the following code snippet: `List list = new ArrayList<>(); list.add(10); list.add(20); list.remove(1); System.out.println(list);` What is the output?

Accepted Answer

[10]. The code creates an ArrayList, adds 10 at index 0 and 20 at index 1. Then `list.remove(1)` removes the element at index 1, which is 20. The list now contains only [10]. Option D is correct because `remove(int index)` removes the element at the specified position, not the value.

Answer

[10, 20]

Answer

[]

Answer

[20]

Question 10

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.