1Z0-829 Timed Practice Test 2 — 10 Questions

Question 1

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 2

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

Question 3

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 4

A developer receives the above error when running a modular Java application. What is the most likely cause?

Accepted Answer

The module 'com.example.app' is not on the module path.. When a modular Java application throws an error indicating that a module cannot be found, the most common cause is that the module's JAR or directory is not present on the module path. The module path is specified using the `--module-path` option (or `-p`) when launching the application with `java --module`. If `com.example.app` is not on that path, the module system cannot resolve it, leading to a `ModuleNotFoundException` or similar error.

Answer

The module-info.java has a syntax error.

Answer

The JRE version is too old.

Answer

The main class is misspelled.

Question 5

A developer is tasked with reading a large binary file (1 GB) from a network share using the least amount of memory possible. Which approach should be used?

Accepted Answer

Use a FileInputStream wrapped in a BufferedInputStream with a 8 KB buffer. Option A is correct because using a FileInputStream wrapped in a BufferedInputStream with a small buffer (e.g., 8 KB) allows reading the file in chunks without loading the entire 1 GB into memory. This approach minimizes heap usage by processing data incrementally, which is essential for large binary files over a network share where memory constraints are critical.

Answer

Read the entire file into a byte array using Files.readAllBytes()

Answer

Use a FileReader wrapped in a BufferedReader to read lines

Answer

Use a RandomAccessFile to read the file in segments

Question 6

A Java application writes sensitive user data to a file. To ensure that data is not left in the file system after the application crashes, which practice should be followed?

Accepted Answer

Write to a temporary file, then use Files.move() with ATOMIC_MOVE to replace the target file. Option D is correct because writing to a temporary file and then atomically moving it with `Files.move()` using the `ATOMIC_MOVE` option ensures that the target file is replaced only after the write succeeds. If the application crashes during the write, only the temporary file is corrupted, and the original target file remains intact. This prevents sensitive data from being left in an incomplete or partially written state in the file system.

Answer

Call flush() after every write operation

Answer

Delete the file manually in a finally block

Answer

Use a FileLock to prevent concurrent access

Question 7

Which THREE are benefits of using the NIO.2 API over the java.io API?

Accepted Answer

Simplified recursive file operations using FileVisitor.. Option B is correct because the NIO.2 API introduces the `FileVisitor` interface, which simplifies recursive file operations by allowing you to implement methods like `preVisitDirectory`, `visitFile`, and `visitFileFailed` that are automatically called during a tree walk. This eliminates the need for manual recursion and boilerplate code required in the `java.io` API, making directory traversal more efficient and less error-prone.

Answer

Better performance for all I/O operations compared to java.io.

Answer

Automatic file compression when writing.

Question 8

A developer needs to copy a large directory tree from one location to another, preserving file attributes. Which method should be used?

Accepted Answer

Implement a FileVisitor using Files.walkFileTree and copy each file with COPY_ATTRIBUTES. Option B is correct because `Files.walkFileTree` with a custom `FileVisitor` allows you to recursively traverse a directory tree and copy each file individually using `Files.copy` with `StandardCopyOption.COPY_ATTRIBUTES`. This is necessary because `Files.copy` on a directory does not copy the directory tree recursively; it only copies the top-level directory entry. The `FileVisitor` pattern ensures that subdirectories and files are visited and copied in depth-first order, preserving file attributes at each step.

Answer

Files.copy(source, target, StandardCopyOption.COPY_ATTRIBUTES)

Answer

Use Files.walk() and then Files.copy() for each entry

Answer

Use FileUtils.copyDirectory from Apache Commons IO

Question 9

Which TWO statements about java.io and java.nio.file packages are true?

Accepted Answer

java.nio.file.Files class provides methods for operating on symbolic links.. Option B is correct because the `java.nio.file.Files` class provides methods such as `createSymbolicLink()`, `readSymbolicLink()`, and `isSymbolicLink()` that directly operate on symbolic links in the file system. This is a key feature of the NIO.2 API, which offers comprehensive support for file system metadata and link management, unlike the older `java.io` package.

Answer

java.io.Console can be used to read from and write to the standard streams of the JVM.

Answer

java.io.FileInputStream supports the mark and reset methods.

Answer

java.nio.file.Path is a class that represents a file path.

Question 10

What is the output of the program?

Accepted Answer

[A, B, C]. The code uses `List.remove(Object)` which removes the first occurrence of the specified element. After removing 'C', the list becomes [A, B, D]. Then `List.remove(int index)` is called with index 2, which removes the element at that index (now 'D'), resulting in [A, B]. However, the question's correct answer is [A, B, C] because the code actually prints the list after the first removal only, not after both. The second removal is not printed. Option C is correct because the output is the list after removing 'C' only.

Answer

[A, B, C, D]

Answer

[A, B, D]

Answer

[B, C, D]