1Z0-829 Practice Test 7 — 10 Questions

Question 1

What is the output of the following code? int i=5; do { System.out.print(i); i--; } while(i>0);

Accepted Answer

54321. The do-while loop executes the body first, printing the current value of i (5), then decrements i to 4. The loop continues while i > 0, so it prints 5, 4, 3, 2, 1, and stops when i becomes 0, as the condition i > 0 is false. This results in the output "54321".

Answer

Compilation error

Answer

543210

Answer

5432

Question 2

A Java application uses FileChannel to copy a file to a remote network drive. The developer wants to ensure atomic file replacement on the destination. Which approach is correct?

Accepted Answer

Use Files.move() with StandardCopyOption.ATOMIC_MOVE.. `Files.move()` with `StandardCopyOption.ATOMIC_MOVE` guarantees that the file replacement on the destination file system is atomic — either the entire move succeeds or the original state remains intact. This is essential for remote network drives where partial writes or concurrent access could leave the destination in an inconsistent state. The `ATOMIC_MOVE` option leverages file system–level atomic rename operations (e.g., NFS or SMB support) to ensure no intermediate state is visible.

Answer

Delete the destination file, then rename the temporary file.

Answer

Use FileChannel.transferTo() to write directly.

Answer

Use Files.copy() with REPLACE_EXISTING option.

Question 3

A developer creates a Java application that uses the new 'jpackage' tool to create an installer for Windows. The application is modular and has a main class declared in module-info. Which option is required to specify the main class when using jpackage?

Accepted Answer

--module. For a modular application with a main class declared in module-info, jpackage requires the `--module` option to specify the module name and, optionally, the main class (e.g., `--module com.example/com.example.Main`). This is because jpackage uses the module system to resolve the entry point, not a classpath or JAR-based approach.

Answer

-classpath

Answer

--module-path

Answer

--main-jar

Question 4

Which of the following correctly sorts an array of integers (int[] arr) in descending order?

Accepted Answer

Integer[] boxed = Arrays.stream(arr).boxed().toArray(Integer[]::new); Arrays.sort(boxed, Collections.reverseOrder()); arr = Arrays.stream(boxed).mapToInt(i->i).toArray();. It demonstrates the proper technique for sorting a primitive int array in descending order. The `Arrays.sort()` method does not accept a `Comparator` for primitive arrays, so the array must first be boxed into an `Integer[]` using `Arrays.stream(arr).boxed().toArray(Integer[]::new)`. After sorting with `Collections.reverseOrder()`, the result is unboxed back to `int[]` via `mapToInt(i->i).toArray()`. This approach correctly leverages the `Comparator` interface, which only works with object types.

Answer

Arrays.sort(arr, Collections.reverseOrder());

Answer

None of the above, because primitive arrays cannot be sorted in descending order.

Answer

Arrays.sort(arr, (a,b) -> b - a);

Answer

Arrays.parallelSort(arr, (a,b) -> b - a);

Question 5

Which of the following correctly describes the behavior of the following code? List list = new ArrayList<>(); list.add("A"); list.add("B"); for (String s : list) { if (s.equals("A")) { list.remove(s); } } System.out.println(list);

Accepted Answer

ConcurrentModificationException is thrown. The code uses an enhanced for-each loop to iterate over an ArrayList while calling `list.remove(s)` when the element equals "A". This modifies the list structurally during iteration, which causes the iterator (used internally by the for-each loop) to detect the concurrent modification and throw a `ConcurrentModificationException` at runtime. The exception is thrown because the iterator's `modCount` check fails when the list is modified outside of the iterator's own `remove` method.

Answer

Compilation error

Answer

[B]

Answer

[A, B] unchanged

Question 6

Which is true about CopyOnWriteArrayList?

Accepted Answer

Modifications are expensive as they create a new array.. CopyOnWriteArrayList is a thread-safe variant of ArrayList where all mutative operations (add, set, remove, etc.) are implemented by making a fresh copy of the underlying array. This design makes modifications expensive because each modification requires copying the entire array, but it provides safe iteration without locking. Option C correctly identifies that modifications are expensive due to the array copy.

Answer

It is not thread-safe.

Answer

Iterators reflect concurrent modifications.

Answer

It is optimized for frequent modifications.

Question 7

Given an enum Direction { NORTH, SOUTH, EAST, WEST } and a variable d of type Direction, which code snippet correctly uses a switch expression to map each direction to an abbreviation (N, S, E, W) without using a default branch?

Accepted Answer

switch (d) { case NORTH -> "N"; case SOUTH -> "S"; case EAST -> "E"; case WEST -> "W"; }. It uses the arrow syntax in a switch expression, which requires that all possible enum values are covered without a default branch. Since Direction has exactly four constants and each is mapped to a yield value via the arrow, the switch is exhaustive and compiles successfully.

Answer

switch (d) { case NORTH: yield "N"; case SOUTH: yield "S"; case EAST: yield "E"; case WEST: yield "W"; }

Answer

switch (d) { case NORTH -> "N"; case SOUTH -> "S"; case EAST -> "E"; }

Answer

switch (d) { case NORTH: yield "N"; case SOUTH: yield "S"; case EAST: yield "E"; default: yield "W"; }

Question 8

Which three of the following are valid methods in the String class in Java 17? (Choose three.)

Accepted Answer

translateEscapes(). `translateEscapes()` is a valid instance method introduced in Java 14 (and present in Java 17) that translates escape sequences (e.g., `
` to newline) in a string. Option C is correct because `toLowerCase(Locale)` is a standard overloaded method in the String class that converts all characters to lowercase using the specified locale. Option D is correct because `transform(Function<String, String>)` is a valid method added in Java 12 that applies the given function to the string and returns the result.

Answer

substring(int, int, Locale)

Answer

indent(String)

Question 9

Which THREE of the following are valid ways to create a new ArrayList<Integer>? (Select three.)

Accepted Answer

new ArrayList<>(Arrays.asList(1,2,3)). `Arrays.asList(1,2,3)` returns a fixed-size `List`, and passing it to the `ArrayList` constructor creates a new, mutable `ArrayList` containing the same elements. This is a standard way to initialize an `ArrayList` with known values.

Answer

new ArrayList<>(10, 20, 30)

Answer

(ArrayList<Integer>) Arrays.asList(1,2,3)