1Z0-829 Practice Test 2 — 30 Questions

Question 1

A method contains a try-with-resources statement that uses two resources: a FileInputStream and a BufferedInputStream. The FileInputStream constructor throws a FileNotFoundException. Which statement about resource closing is true?

Accepted Answer

No resources are closed because the FileInputStream constructor failed before any resource was opened.. In a try-with-resources statement, resources are closed only if they have been successfully initialized. If the FileInputStream constructor throws a FileNotFoundException, the resource is never created, so the try-with-resources statement does not attempt to close it. The BufferedInputStream is never constructed because the exception occurs before its declaration is reached, so no resources are opened and none need to be closed. Therefore, option C is correct.

Answer

The BufferedInputStream is closed if it was successfully created, but the FileInputStream is not.

Answer

Both resources are closed even if the FileInputStream constructor throws an exception.

Answer

The programmer must explicitly close the resources in a finally block.

Question 2

Which THREE statements are true about loops in Java?

Accepted Answer

The break statement can be used to exit a loop prematurely.. The break statement in Java is used to immediately terminate the execution of a loop (for, while, or do-while) and transfer control to the statement following the loop. This allows premature exit based on a condition, which is a fundamental control flow mechanism in Java.

Answer

A while loop always executes at least once.

Answer

A do-while loop may execute zero times if the condition is false.

Question 3

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

Accepted Answer

The resource class must implement AutoCloseable.. Option A is correct because 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 4

What is the result when the main method is executed?

Accepted Answer

C is printed and the program terminates.. The correct answer is C because the code demonstrates that when an exception is thrown in a try block, the corresponding catch block for that exception type is executed, and then the finally block runs. After the finally block completes, the program terminates normally. In this case, the try block throws an ArithmeticException, which is caught by the catch block that prints 'C', and then the finally block executes but does not change the output.

Answer

Both B and C are printed and the program terminates.

Answer

B is printed and the program terminates.

Answer

A is printed and the program terminates.

Question 5

Which TWO are true about the PriorityQueue class?

Accepted Answer

It is not thread-safe.. Option C is correct because PriorityQueue is not thread-safe; it does not synchronize access, so concurrent modifications without external synchronization can lead to inconsistent behavior. Option D is correct because PriorityQueue can accept a custom Comparator at construction time to define the ordering of elements, overriding the natural order.

Answer

It allows null elements.

Answer

It orders elements based on insertion order.

Answer

It provides O(1) time for contains().

Question 6

Which method of Collection interface returns a primitive int?

Accepted Answer

size(). The `size()` method is the only one in the `Collection` interface that returns a primitive `int`, representing the number of elements in the collection. All other methods listed return either a `boolean` or an array of objects, making D the correct answer.

Answer

contains(Object o)

Answer

isEmpty()

Answer

toArray()

Question 7

A developer writes: List list = new ArrayList<>(); list.add("A"); list.add("B"); list.add(1, "C"); System.out.println(list); What is the output?

Accepted Answer

[A, C, B]. The correct answer is A because the `add(int index, E element)` method inserts the element at the specified index, shifting subsequent elements to the right. Initially, the list is [A, B]. After `list.add(1, "C")`, "C" is inserted at index 1, moving "B" to index 2, resulting in [A, C, B].

Answer

[A, B, C]

Answer

[A, B]

Answer

[C, A, B]

Question 8

What is the cause of the ClassCastException?

Accepted Answer

The value stored is Integer but retrieved as String.. The ClassCastException occurs because the code retrieves a value from the store map and attempts to cast it to String, but the actual stored object is an Integer. Since the map is not using generics (raw type), the compiler does not enforce type safety, allowing the mismatch to be caught only at runtime.

Answer

The store map is not type-safe.

Answer

The get method should use (T) cast instead of type.cast().

Answer

The type parameter T is not used correctly.

Question 9

A method returns a List<Integer>. The caller wants to ensure the list cannot be modified. Which is the best approach?

Accepted Answer

return Collections.unmodifiableList(list);. Option D is correct because `Collections.unmodifiableList()` returns a read-only view of the specified list. Any attempt to modify the returned list (e.g., via `add`, `remove`, `set`) will throw an `UnsupportedOperationException`. This is the standard, recommended approach in the Java Collections Framework to provide an unmodifiable wrapper without copying the underlying data.

Answer

return Arrays.asList(list.toArray());

Answer

return new ArrayList<>(list);

Answer

return (List<Integer>) list.clone();

Question 10

Given: TreeSet ts = new TreeSet<>(Comparator.reverseOrder()); ts.add(10); ts.add(5); ts.add(20); ts.add(15); System.out.println(ts.first()); What is the result?

Accepted Answer

5. Option C is correct because `TreeSet` with `Comparator.reverseOrder()` sorts elements in descending order (20, 15, 10, 5). The `first()` method returns the smallest element according to the comparator, which in descending order is the last element in the natural order, i.e., 5.

Answer

20

Answer

15

Answer

10

Question 11

Which THREE statements about lambda expressions are true? (Choose three.)
A. A lambda expression can be assigned to a functional interface variable.
B. A lambda expression can access final or effectively final local variables.
C. A lambda expression can throw any checked exception.
D. A lambda expression can be used to create an instance of an abstract class.
E. A lambda expression can be used to implement multiple abstract methods.

Accepted Answer

A lambda expression can throw any checked exception.. Option A is correct because a lambda expression can be assigned to a variable of a functional interface type. The lambda provides the implementation for the single abstract method of that interface, and the assignment is valid as long as the lambda's parameter types and return type match the method signature.

Answer

A lambda expression can be used to implement multiple abstract methods.

Answer

A lambda expression can be used to create an instance of an abstract class.

Question 12

A developer writes the following code using the Stream API:

List<String> list = List.of("a", "b", "c");
String result = list.stream().reduce("", (s1, s2) -> s1 + s2);
System.out.println(result);

What is the output?

Accepted Answer

abc. The correct answer is A because the `reduce` method with an identity value (`""`) and a binary operator (`(s1, s2) -> s1 + s2`) accumulates the stream elements in encounter order. Starting from the identity, it concatenates each element: `"" + "a" = "a"`, then `"a" + "b" = "ab"`, then `"ab" + "c" = "abc"`. The result is a `String`, not an `Optional`, because an identity is provided.

Answer

a

Answer

Optional[abc]

Answer

cba

Question 13

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 correct answer is D because 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 14

Which TWO are valid lambda expressions? (Choose two.)
A. (int a, int b) -> a + b
B. a, b -> a + b
C. (a, b) -> a + b
D. (a, b) -> { a + b; }
E. (int a, b) -> a + b

Accepted Answer

(a, b) -> a + b. Option B is correct because a lambda expression with inferred parameter types can omit the parameter types and parentheses when there is exactly one parameter, but here there are two parameters, so parentheses are required. Option C is correct because it explicitly declares the types of both parameters, which is valid syntax for a lambda expression that returns the sum of the two integers.

Answer

a, b -> a + b

Answer

(a, b) -> { a + b; }

Answer

(int a, b) -> a + b

Question 15

Which TWO statements about the Stream API are correct? (Choose two.)
A. A stream can be traversed multiple times.
B. The peek() method is an intermediate operation.
C. The findFirst() method returns an Optional.
D. The collect() method is an intermediate operation.
E. The map() method returns a stream of the same type.

Accepted Answer

The peek() method is an intermediate operation.. Option A is correct because the `peek()` method is an intermediate operation in the Stream API. Intermediate operations return a new stream and are lazy; they are not executed until a terminal operation is invoked. `peek()` allows you to inspect elements as they flow through the pipeline without modifying them.

Answer

The collect() method is an intermediate operation.

Answer

A stream can be traversed multiple times.

Answer

The map() method returns a stream of the same type.

Question 16

A company uses CI/CD to build and package a Java 17 application. They want to produce a single executable JAR that includes all dependencies. Which tool should be used to achieve this?

Accepted Answer

Maven Shade Plugin. The Maven Shade Plugin (B) is the correct choice because it creates an uber-JAR (fat JAR) by merging all project dependencies into a single executable JAR, including transitive dependencies. It also provides a relocation feature to avoid classpath conflicts, which is essential for producing a self-contained artifact for deployment.

Answer

Maven JAR Plugin

Answer

Java jar command

Answer

jlink tool

Question 17

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;. Option D is correct because 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 18

A developer is designing a service that processes multiple files concurrently. To avoid resource leaks, which practice is essential?

Accepted Answer

Use try-with-resources for each AutoCloseable resource. Option B is correct because try-with-resources guarantees that each AutoCloseable resource is closed automatically at the end of the statement, even if an exception occurs. This is essential when processing multiple files concurrently, as it prevents resource leaks without requiring explicit close() calls in finally blocks.

Answer

Ensure each thread has its own copy of the file handle

Answer

Call close() on each stream in a separate try-catch block

Answer

Use FileLock to prevent concurrent access

Question 19

Which statement about java.io and java.nio.file packages is true?

Accepted Answer

The java.nio.file package provides support for symbolic links and file attributes. Option A is correct because the java.nio.file package (part of NIO.2) explicitly provides support for symbolic links via methods like Files.createSymbolicLink() and Files.isSymbolicLink(), and it offers comprehensive file attribute access through classes like BasicFileAttributes, DosFileAttributes, and PosixFileAttributes, which are not available in java.io.

Answer

Classes in java.nio.file are thread-safe by default

Answer

The java.io package includes the Path interface

Answer

The java.nio.file package is deprecated in favor of java.io

Question 20

An application must read a configuration file that is updated frequently by another process. The developer wants to avoid stale data and minimize I/O operations. Which approach is best?

Accepted Answer

Use java.nio.file.WatchService to monitor the file for modifications and reload when notified. Option A is correct because java.nio.file.WatchService provides an event-driven mechanism to monitor file system changes, such as modifications to a configuration file. This approach avoids stale data by reloading the file only when a change is detected, and it minimizes I/O operations by eliminating the need for polling or repeated reads. The WatchService uses the underlying OS file system events (e.g., inotify on Linux, ReadDirectoryChanges on Windows) for efficient notification.

Answer

Read the file from disk every time it is accessed using Files.newInputStream()

Answer

Periodically check the file's lastModified timestamp using File.lastModified() and reload if changed

Answer

Read the file once at startup and cache the content in memory