1Z0-829 Practice Test 26 — 15 Questions

Question 1

Match each Java module directive to its description.

Accepted Answer

requires: Specifies a dependency on another module.. Correct matches: requires specifies dependencies, exports grants compile-time access, opens enables reflective access, provides declares service implementations. Common confusion is between exports and opens due to their related but distinct roles.

Answer

exports: Allows reflective access to a package.

Answer

opens: Makes a package accessible to other modules.

Question 2

What does the following code print?

List<Integer> list = List.of(1, 2, 3, 4, 5);
list.stream().filter(i -> i % 2 == 0).forEach(System.out::print);

Accepted Answer

24. The stream filters only even numbers (i % 2 == 0) from the list, producing 2 and 4, which are then printed sequentially via forEach. The filter operation retains elements where the predicate is true, so only 2 and 4 satisfy the condition.

Answer

No output

Answer

12345

Answer

135

Question 3

Which TWO statements are true about the switch statement in Java?

Accepted Answer

It can be used with String objects.. Java's switch statement supports String objects since Java 7, allowing comparison based on the string's hashCode() and equals() methods. Option D is correct because switch can be used as an expression (e.g., with the arrow syntax) that yields a value, which can be assigned to a variable or returned.

Answer

Case values can be variables that are not final.

Answer

It requires a default case.

Answer

Each case must have a unique code block.

Question 4

Which two statements about the Stream API are true? (Choose two.)

Accepted Answer

The 'reduce()' operation can produce a result of a different type than the stream elements.. The `reduce()` operation in the Stream API uses a combiner function that can transform the stream elements into an accumulated result of a different type. For example, `stream.reduce(0, (sum, i) -> sum + i, Integer::sum)` returns an `Integer` from an `IntStream`, or you can reduce a `Stream` to a `StringBuilder`. This is explicitly allowed by the `reduce(U identity, BiFunction accumulator, BinaryOperator combiner)` signature.

Answer

The 'flatMap()' operation is a terminal operation.

Answer

The 'collect()' operation is an intermediate operation.

Answer

Streams can be reused after a terminal operation.

Question 5

Which TWO of the following statements about the Collections framework are true?

Accepted Answer

Collections.unmodifiableList returns an unmodifiable view of the list.. `Collections.unmodifiableList()` returns a view of the specified list that cannot be modified. Any attempt to modify the returned list (e.g., add, remove, set) will throw an `UnsupportedOperationException`. This is a standard method in the Java Collections Framework to provide read-only access to a list.

Answer

Collections.checkedList performs type checking at compile time.

Answer

List.of returns a mutable list.

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Arrays.asList returns a mutable list of variable size.

Question 6

Which statement about TreeSet is true when using a custom Comparator that does not define equals() consistently with compare()?

Accepted Answer

TreeSet considers two elements equal if the comparator returns 0.. TreeSet uses the compare() method of the provided Comparator (or the natural ordering's compareTo()) to determine element equality. When a custom Comparator returns 0 for two elements, TreeSet treats them as duplicates and does not add the second element, regardless of what equals() returns. This is specified in the Java Collections Framework documentation and is critical for maintaining the Set contract.

Answer

TreeSet uses equals() to determine duplicates.

Answer

TreeSet uses hashCode() for ordering.

Answer

TreeSet throws IllegalArgumentException if equals() is inconsistent.

Question 7

A developer has a module named 'com.example.app' that exports a package 'com.example.api'. Another module 'com.example.client' requires 'com.example.app'. Which directive must be in the module-info.java of 'com.example.client'?

Accepted Answer

requires com.example.app;. The 'requires' directive in a module-info.java file declares a dependency on another module. For 'com.example.client' to access the exported packages of 'com.example.app', it must include 'requires com.example.app;'. This is the standard mechanism for module dependency in the Java Platform Module System (JPMS).

Answer

opens com.example.app;

Answer

uses com.example.api;

Answer

exports com.example.api;

Question 8

Which TWO statements about Java serialization are true?

Accepted Answer

During deserialization, the constructor of the serialized class is not invoked.. During deserialization, Java does not invoke the constructor of the class being deserialized. Instead, the object is reconstructed from the serialized stream data using the no-arg constructor of the first non-serializable superclass (if any), and the serialized class's fields are populated via reflection or readObject() methods. This avoids re-executing initialization logic that may have side effects or depend on runtime state.

Answer

The serialVersionUID must be explicitly declared in every serializable class.

Answer

A class that implements Externalizable does not need to implement Serializable.

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Fields marked as transient are serialized by default.

Question 9

Refer to the exhibit. What is the most direct way to fix the compilation error without changing the access modifier of the field?

Accepted Answer

Change line 14 to System.out.println(emp.getName());. The compilation error is caused by attempting to access a private field `name` directly via `emp.name` from a different class. The most direct fix without changing the access modifier is to use the public getter method `getName()`, which provides controlled access to the private field. This adheres to encapsulation principles and resolves the visibility issue.

Answer

Move the main method to another class in the same package.

Answer

Import the class in the same file and create a subclass.

Answer

Change line 14 to System.out.println(emp.name); and make the field protected.

Question 10

A team uses 'jlink' to create a custom runtime image for a modular application. They run the following command: 'jlink --module-path $JAVA_HOME/jmods:myapp --add-modules com.example.myapp --output myimage'. The application requires several non-Java native libraries (e.g., .so files) that are loaded via System.loadLibrary(). After creating the image, the application fails with an UnsatisfiedLinkError. What is the most likely cause?

Accepted Answer

The native libraries were not included in the image; they must be manually copied or added using --add-modules and a custom module.. The `jlink` tool creates a runtime image that includes only Java modules and their dependencies, not native libraries (e.g., .so files). Native libraries must be manually placed into the image's library path (e.g., `lib/` or `bin/` directory) or packaged into a custom module that is added via `--add-modules`. The `UnsatisfiedLinkError` occurs because `System.loadLibrary()` cannot find the native library in the image's expected locations.

Answer

The native library loading requires a module that exports the package containing the native method.

Answer

The --add-modules flag omitted transitive dependencies of com.example.myapp.

Answer

The --module-path must also include the directories containing the native libraries.

Question 11

What is the output when the code is executed?

Accepted Answer

Arithmetic
Finally
[stack trace]. The code throws an ArithmeticException (division by zero) inside the try block, which is caught by the first catch block (ArithmeticException). The finally block always executes after the catch block, printing 'Finally'. The stack trace is printed because the exception is re-thrown in the catch block (implicitly or explicitly) and not handled, causing the program to terminate with an uncaught exception. The output shows 'Arithmetic', then 'Finally', followed by the stack trace.

Answer

Arithmetic
Finally

Answer

Arithmetic
Exception
Finally

Answer

Exception
Finally

Question 12

Given: var list = List.of("A", "B", "C"); list.set(0, "Z"); What is the result?

Accepted Answer

An UnsupportedOperationException is thrown. The `List.of()` method returns an immutable list, meaning its elements cannot be added, removed, or replaced. Calling `set()` on an immutable list throws an `UnsupportedOperationException` at runtime, which is why option B is correct.

Answer

An ArrayIndexOutOfBoundsException is thrown

Answer

The code does not compile because var cannot be used with List.of

Answer

The list is modified to [Z, B, C]

Question 13

Refer to the exhibit. What is the output?

Accepted Answer

12. (12). The exhibit shows a stream reduction with identity value 1 and elements 2, 3, 2. The reduce operation multiplies each element with the accumulated result: 1 * 2 = 2, 2 * 3 = 6, 6 * 2 = 12. The identity is the starting accumulator, not a stream element.

Answer

30

Answer

0

Answer

20

Question 14

Which interface should be implemented to create a custom filter for deserialization in Java?

Accepted Answer

ObjectInputFilter. The `ObjectInputFilter` interface (introduced in Java 9) allows you to define a custom filter that validates classes and data being deserialized from an `ObjectInputStream`. By implementing this interface, you can reject potentially malicious or unexpected classes during deserialization, which is a key security measure against deserialization attacks.

Answer

Serializable

Answer

ObjectOutput

Answer

FilterOutputStream

Question 15

Refer to the exhibit. A developer runs a keytool command and sees the output above. Which command produced this output?

Accepted Answer

keytool -list -v -alias mykey -keystore keystore.jks. The `keytool -list -v -alias mykey -keystore keystore.jks` command displays detailed certificate information (including owner, issuer, serial number, validity, and fingerprint) for the specified alias in the JKS keystore. The `-v` flag produces verbose output, which matches the exhibit's detailed certificate listing.

Answer

keytool -exportcert -alias mykey -keystore keystore.jks -file cert.cer

Answer

keytool -importcert -alias mykey -keystore keystore.jks -file cert.cer

Answer

keytool -printcert -file cert.cer