1Z0-829 Practice Test 3 — 10 Questions

Question 1

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 2

A stream pipeline uses the peek method for debugging. Which statement about peek is correct?

Accepted Answer

peek is an intermediate operation used for debugging; it is not suitable for production side effects.. The `peek` method is an intermediate operation in the Stream API, designed primarily for debugging to observe elements as they flow through the pipeline. It is not intended for production side effects because its execution is not guaranteed for every element (e.g., due to short-circuiting or optimization), and relying on it for stateful operations can lead to unpredictable behavior.

Answer

peek is a terminal operation that prints elements.

Answer

peek can only be used with parallel streams.

Answer

peek is an intermediate operation, and it is guaranteed to be executed for each element.

Question 3

Which THREE of the following are true about the Optional class? (Choose three.)

Accepted Answer

Optional.empty().orElseThrow(IllegalStateException::new) throws IllegalStateException. Option A is correct: Optional.empty() creates an empty Optional, and orElseThrow(IllegalStateException::new) invokes the supplied exception supplier when no value is present, so it throws a new IllegalStateException. Option C is correct: Optional.ofNullable(null) explicitly returns an empty Optional because ofNullable is designed to accept null and map it to Optional.empty(). Option E is correct: ifPresent executes the given Consumer only when a value is present, so on an empty Optional the lambda is skipped and nothing is printed. Option B is wrong because Optional.of(null) throws NullPointerException rather than returning an empty Optional. Option D is wrong because Optional.get() on an empty Optional throws NoSuchElementException, not null.

Answer

Optional.of(null) returns an empty Optional

Answer

Optional.get() on empty Optional returns null

Question 4

A developer wrote a method that uses a for-each loop to iterate over a list of strings and remove elements that match a certain condition. However, the method throws a ConcurrentModificationException at runtime. What is the most likely cause?

Accepted Answer

The loop modifies the list by calling remove() on the list itself.. A for-each loop internally uses an Iterator to traverse the list. If the list is structurally modified (e.g., by calling remove() directly on the list) during iteration, the iterator's expected modCount will differ from the actual modCount, triggering a ConcurrentModificationException. This is a fail-fast behavior of the ArrayList and other Collection implementations.

Answer

The loop uses a for-each loop with an array instead of a list.

Answer

The loop uses an iterator that is not properly initialized.

Answer

The list is unmodifiable.

Question 5

Order the steps to handle checked exceptions in a method that throws IOException.

Accepted Answer

1. Locate the code that throws IOException. 2. Enclose the code in a try block. 3. Add a catch block for IOException. 4. Provide exception handling code in the catch block.. Checked exceptions must be either caught or declared in the method signature. Unhandled checked exceptions cause compilation errors.

Answer

1. Locate the code that throws IOException. 2. Add a catch block for IOException. 3. Enclose the code in a try block. 4. Add a finally block.

Answer

1. Locate the code that throws IOException. 2. Add a finally block. 3. Add a try block. 4. Add a catch block.

Answer

1. Locate the code that throws IOException. 2. Continue writing code without any exception handling. 3. Assume the program will not throw IOException. 4. Compile and ignore errors.

Question 6

A developer is designing a loop to iterate through an array of integers and stop processing when the value -1 is encountered. Which loop construct should be used?

Accepted Answer

for(int i : array) { if(i == -1) break; }. The `break` statement immediately terminates the loop when the value -1 is encountered, which is exactly what the requirement specifies. In Java, `break` exits the innermost loop or switch statement, making it the appropriate control flow mechanism for stopping iteration upon a condition.

Answer

for(int i : array) { if(i == -1) exit; }

Answer

for(int i : array) { if(i == -1) return; }

Answer

for(int i : array) { if(i == -1) continue; }

Question 7

A team is migrating a large legacy application from Java 8 to Java 17. The application consists of multiple JAR files that are placed on the classpath. Some of these JAR files have been updated to include module-info.class files, making them named modules. After migration, the application throws `IllegalAccessError` for several deep reflection calls that used to work in Java 8. The team has added `--add-opens` JVM flags to open the required packages, but the error persists. The application also uses a third-party library that is not modularized and is placed on the classpath. The team notices that the `--add-opens` flags are being ignored for packages in the modularized JARs. What is the most likely reason?

Accepted Answer

The modularized JARs are being loaded from the classpath, so they become unnamed modules, and `--add-opens` does not apply to unnamed modules.. When a JAR file containing a module-info.class is placed on the classpath instead of the module path, it is treated as an unnamed module. The `--add-opens` JVM flag only applies to named modules (those on the module path) and has no effect on unnamed modules. Since the modularized JARs are loaded from the classpath, they become unnamed modules, and the `--add-opens` flags are ignored, causing the `IllegalAccessError` to persist.

Answer

The `--add-opens` flags are being overridden by other JVM flags.

Answer

The application does not have a module-info.java file for its own code.

Answer

The classpath is deprecated and ignored in Java 17, so all JARs are treated as modules.

Question 8

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 9

A company wants to distribute a Java desktop application with a bundled JRE for end users who may not have Java installed. Which tool should they use?

Accepted Answer

jpackage. jpackage is the correct tool because it is specifically designed to package a Java application along with a bundled JRE into a native installer (e.g., .exe, .dmg, .deb) for distribution to end users who may not have Java installed. It uses the jlink tool internally to create a custom runtime image and then wraps it with platform-specific packaging tools, ensuring the application runs independently of any pre-installed JRE.

Answer

jlink

Answer

jar

Answer

jmod

Question 10

Refer to the exhibit. What is the output?

Accepted Answer

{3=[Bob], 5=[Alice, David], 7=[Charlie]}. The code groups names by the length of their string using `Collectors.groupingBy(String::length, Collectors.toList())`. The names "Alice" and "David" have length 5, "Bob" has length 3, and "Charlie" has length 7. The resulting map has keys 3, 5, and 7. Although `groupingBy` returns a `HashMap` without guaranteed order, the expected output in this context displays the keys in ascending numerical order: 3, 5, 7. Therefore, option C correctly shows the groups in that order with the corresponding names. Option B is incorrect because it lists the keys in non-ascending order (5, 3, 7), which does not match the typical output format.

Answer

{3=[Bob], 5=[Alice, David, Charlie]}

Answer

{5=[Alice, David], 3=[Bob], 7=[Charlie]}

Answer

{3=[Bob], 5=[Alice], 7=[Charlie, David]}