1Z0-829 Timed Practice Test 4 — 10 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