1Z0-829 Practice Test 27 — 15 Questions

Question 1

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

Accepted Answer

JPMS provides reliable configuration through explicit module dependencies.. JPMS enforces reliable configuration by requiring modules to explicitly declare their dependencies using the 'requires' directive in the module descriptor. This eliminates the classpath's silent dependency resolution, where missing or conflicting JARs often cause runtime errors like ClassNotFoundException.

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 2

You are a Java developer at a logistics company. Your team is maintaining a legacy Java 8 application that uses dozens of jars on the classpath. The company has decided to migrate to Java 17 and adopt the module system. As a first step, you are analyzing the application's dependencies using jdeps. You run 'jdeps -s -dotoutput /tmp/deps' on all jars. The output shows many dependencies labeled 'not found' for internal packages that belong to other jars in the application. The packages are correctly exported by the respective jars (which are on the classpath). You suspect that because the jars are on the classpath, jdeps cannot resolve inter-jar dependencies as modules. To get accurate dependency information, what should you do?

Accepted Answer

Place all the jars on the module path and remove them from the classpath when running jdeps.. When jars are on the classpath, jdeps treats them as unnamed modules and cannot resolve inter-jar dependencies as module-level relationships, leading to 'not found' labels. Placing all jars on the module path (Option B) forces jdeps to treat each jar as a module (if it has a module-info.class) or as an automatic module (if it does not), enabling accurate dependency resolution. This is the correct approach because the module path is designed for module-aware analysis, while the classpath is a legacy flat namespace.

Answer

Use jlink to create a custom runtime image that includes all the jars.

Answer

Run jdeps with the --module-path option pointing to the directory containing all jars, and keep the jars on the classpath.

Answer

Convert each jar into a named module by adding module-info.java to each jar and recompiling.

Question 3

Refer to the exhibit. Which algorithm was used to generate the certificate fingerprint shown?

Accepted Answer

MD5. The certificate fingerprint shown is a 32-character hexadecimal string, which corresponds to a 128-bit hash. MD5 produces a 128-bit (16-byte) hash, displayed as 32 hex digits. This matches the fingerprint format exactly, confirming that MD5 was used.

Answer

SHA-1

Answer

SHA-384

Answer

SHA-256

Question 4

A developer creates an unmodifiable list via Collections.unmodifiableList(originalList). Later, originalList is modified by adding an element. Which statement is true?

Accepted Answer

The unmodifiable list reflects the addition. D is correct because `Collections.unmodifiableList()` returns a view-backed unmodifiable list that reflects any changes made to the original list. The unmodifiable list does not create a snapshot; it wraps the original list, so modifications to the original are visible through the unmodifiable wrapper.

Answer

The unmodifiable list remains unchanged

Answer

The unmodifiable list becomes inconsistent

Answer

An UnsupportedOperationException is thrown

Question 5

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. 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 6

A developer wants to collect elements from a stream into an immutable List. Which collector should be used?

Accepted Answer

Collectors.toUnmodifiableList(). `Collectors.toUnmodifiableList()` directly returns a collector that accumulates elements into an immutable `List`. This was introduced in Java 10 and guarantees that the resulting list cannot be modified, throwing `UnsupportedOperationException` on any mutation attempt.

Answer

Collectors.toList()

Answer

Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList)

Answer

Collectors.toList().stream().collect(Collectors.toUnmodifiableList())

Question 7

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. 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 8

Given the following switch expression with colon syntax, what is the result when code equals 2? int val = switch(code) { case 1: yield 10; case 2: yield 20; default: yield 30; };

Accepted Answer

20. When code equals 2, the switch expression matches case 2: and executes the yield 20; statement, which returns 20 as the value assigned to val. The colon syntax with yield is valid in Java 14+ switch expressions, and each case must yield a value.

Answer

10

Answer

30

Answer

Compilation error

Question 9

Which TWO statements about the try-with-resources statement are correct? (Choose two.)

Accepted Answer

The resource class must implement AutoCloseable.. The try-with-resources statement requires that each resource implements the AutoCloseable interface (or its subinterface Closeable). This interface defines the close() method, which is automatically invoked by the JVM when the try block completes, ensuring proper resource management without explicit finally blocks.

Answer

The resource variable must be declared as final.

Answer

A try-with-resources statement cannot have a finally block.

Answer

Resources are closed before the try block executes.

Question 10

Which TWO statements about creating custom exceptions are correct? (Choose two.)

Accepted Answer

It is good practice to provide a constructor that takes a String message and a Throwable cause.. It is a well-established best practice in Java to provide a constructor that accepts both a String message and a Throwable cause, enabling precise error reporting and chaining of exceptions. This allows developers to pass a human-readable description along with the underlying cause, which is essential for debugging and logging.

Answer

Custom exceptions should extend Error to indicate fatal errors.

Answer

Custom exception classes should be declared final to prevent subclassing.

Answer

Custom exceptions must implement the Exception interface.

Question 11

Which TWO are valid multi-catch statements in Java 17? (Choose two.)

Accepted Answer

catch (SQLException | IOException e). Java 17 allows a multi-catch clause to handle multiple exception types in a single catch block, provided the exception types are unrelated in the class hierarchy. SQLException and IOException are both checked exceptions that do not inherit from each other, so they can be caught together in a multi-catch statement.

Answer

catch (Exception | RuntimeException e)

Answer

catch (SQLException | Exception e)

Answer

catch (IOException | FileNotFoundException e)

Question 12

Which three actions help secure a Java application that uses serialization? (Select three.)

Accepted Answer

Overriding resolveClass() in ObjectInputStream to validate class names.. Overriding `resolveClass()` in `ObjectInputStream` allows you to validate the class name before it is deserialized. This prevents deserialization attacks where an attacker sends a malicious class that could execute arbitrary code. By checking the class name against a whitelist, you can block untrusted classes from being loaded.

Answer

Using SecureRandom to generate serialVersionUID.

Answer

Declaring serialVersionUID explicitly as a long constant.

Question 13

What is the result of executing this code?

Accepted Answer

Runtime exception. The code uses `Collectors.toUnmodifiableList()` which returns an unmodifiable list. Attempting to add an element to this list throws an `UnsupportedOperationException` at runtime. Therefore, option C (Runtime exception) is correct.

Answer

Compilation error

Answer

[b]

Answer

[b, d]

Question 14

Which TWO statements are true regarding reading files with the NIO.2 API?

Accepted Answer

Files.newBufferedReader() provides buffered character input.. `Files.newBufferedReader()` returns a `BufferedReader` that wraps a `FileReader` (or underlying `FileChannel`), providing efficient buffered character input. This method is designed for reading text files line-by-line with reduced I/O operations, making it suitable for large or stream-oriented text processing.

Answer

Files.readAllLines() is memory efficient for large files.

Answer

Files.newInputStream() wraps a FileChannel for high performance.

Answer

Files.readAllBytes() is the best choice for large binary files.

Question 15

In a JAAS login module, after the login() method returns true, which method must be called to commit the authentication and add principals to the Subject?

Accepted Answer

commit(). In a JAAS login module, after the `login()` method returns `true`, the `commit()` method must be called to associate the authenticated principals and credentials with the `Subject`. The `commit()` method is responsible for adding the successfully authenticated principals to the Subject, making them available for subsequent authorization checks. This is part of the two-phase authentication protocol defined by the `javax.security.auth.spi.LoginModule` interface.

Answer

login()

Answer

initialize()

Answer

abort()