1Z0-829 Controlling Program Flow Practice Test 5 — 15 Questions

Question 1

Given nested loops with labels, which statement correctly breaks out of the outer loop?

Accepted Answer

break outer;. The labeled break statement 'break outer;' terminates the outer loop when executed inside the inner loop. In Java, a label (e.g., 'outer:') placed before a loop allows a break or continue to target that specific loop, overriding the default behavior of breaking only the innermost loop. The other options do not break out of the outer loop: 'continue outer;' would skip the current iteration of the outer loop but not break it, 'return;' would exit the method entirely, and 'break inner;' would break the inner loop but not the outer.

Answer

continue outer;

Answer

return;

Answer

break inner;

Question 2

A resource is declared in a try-with-resources statement. The try block throws an exception. The close method throws a different exception. What exception is thrown by the try-with-resources statement?

Accepted Answer

The exception from the try block.. In a try-with-resources statement, if both the try block and the close() method throw exceptions, the exception from the try block is the one thrown by the statement. The exception from close() is suppressed and added to the thrown exception's suppressed exception list (via Throwable.addSuppressed()). This is specified by JLS §14.20.3.2 and ensures the primary failure (the try block exception) is not masked.

Answer

The exception from the close method.

Answer

A compilation error occurs.

Answer

Both exceptions are thrown simultaneously.

Question 3

How many times does the following loop execute? int i=0; while(i<5) { System.out.println(i); i++; }

Accepted Answer

5. The loop starts with i=0, checks the condition i<5 (true), prints i, then increments i. This repeats until i becomes 5, at which point i<5 is false and the loop terminates. Thus, the loop executes exactly 5 times (i=0,1,2,3,4).

Answer

0

Answer

6

Answer

4

Question 4

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 5

Given the following switch expression with colon syntax, what is the result when code equals 2? int val = switch(code) { case 1: yield 10; case 2: yield 20; default: yield 30; };

Accepted Answer

20. When code equals 2, the switch expression matches case 2: and executes the yield 20; statement, which returns 20 as the value assigned to val. The colon syntax with yield is valid in Java 14+ switch expressions, and each case must yield a value.

Answer

10

Answer

30

Answer

Compilation error

Question 6

A developer is implementing a method that processes a collection of objects. The objects are instances of various classes that implement a common interface. The developer wants to use a switch expression to perform different actions based on the runtime type of each object. Which approach is correct?

Accepted Answer

Use a switch expression with pattern matching without a default case if all possible types are covered.. Java 17+ switch expressions with pattern matching allow exhaustive type coverage without a default case when all possible subtypes of the sealed interface or hierarchy are explicitly listed. This ensures compile-time safety and eliminates the need for a default branch, aligning with the principle of exhaustive pattern matching.

Answer

Use a series of if-else statements with instanceof.

Answer

Use a switch expression with pattern matching and a default case.

Answer

Use a traditional switch statement with instanceof checks and casting.

Question 7

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 8

Which TWO statements about the break and continue statements in Java are correct?

Accepted Answer

The break statement without a label always terminates the innermost enclosing loop or switch.. The break statement without a label, when executed inside a loop or switch, immediately terminates the innermost enclosing loop or switch construct. This is defined by the Java Language Specification (JLS §14.15), which states that an unlabeled break statement transfers control to the immediately enclosing statement of the break target.

Answer

The continue statement can be used inside a switch statement to skip the rest of the switch body.

Answer

The break statement can be used only inside loops and switch statements.

Answer

The continue statement without a label skips the current iteration and proceeds to the next iteration without reevaluating the loop condition.

Question 9

A junior developer writes a method that uses a switch statement to handle different types of user input. The input is an integer representing an operation code. The developer uses a traditional switch statement with break statements. However, when operation code 2 is entered, the program also executes the code for operation 3. What is the most likely cause?

Accepted Answer

The break statement is missing after the operation 2 case.. In a traditional Java switch statement, execution continues into the next case block unless a break statement is encountered. If operation code 2 executes the code for operation 3, it indicates that the break statement is missing after the case for operation 2, causing fall-through to the next case.

Answer

The operation codes are not mutually exclusive.

Answer

The variable is being modified inside the switch.

Answer

The switch statement uses fall-through by design.

Question 10

A developer is implementing a batch processing application that reads records from a list and processes them. The method uses a for loop with an index variable. Inside the loop, if a record is null, the developer wants to skip that iteration and continue with the next index. The developer writes: for (int i = 0; i < records.size(); i++) { if (records.get(i) == null) continue; process(records.get(i)); updateCounter(); } However, the counter is not updated correctly. The developer expects the counter to reflect the number of processed (non-null) records. What is the problem?

Accepted Answer

The continue statement skips the rest of the loop body, including the counter update.. The `continue` statement immediately jumps to the next iteration of the loop, skipping any remaining code in the current iteration. In this case, `updateCounter()` is placed after the `continue` in the loop body, so when a null record is encountered, the counter update is never executed, causing the counter to not reflect the number of processed (non-null) records.

Answer

The continue statement is only valid inside a while loop.

Answer

The continue statement should be replaced with a break.

Answer

The counter variable should be declared as volatile.

Question 11

A financial trading system uses a Java application to process market data. The core algorithm uses nested loops to compare price arrays. The developer uses a labeled continue statement to skip certain combinations. After a code review, the team suspects the algorithm has a bug that causes incorrect results. The developer writes a unit test and discovers that the labeled continue sometimes skips more iterations than intended. The code is: outer: for (int i = 0; i < prices1.length; i++) { for (int j = 0; j < prices2.length; j++) { if (prices1[i] < prices2[j]) continue outer; // process combination } } The developer intended that if any price in prices1 is less than a price in prices2, the entire row (i) should be skipped. However, the algorithm skips rows even when the condition is not met for all j. What is the most likely cause?

Accepted Answer

The condition for continuing is not correctly evaluated.. The developer intended to skip the i-th row only if for every j, prices1[i] < prices2[j]. However, the condition currently uses an inequality that triggers on any j, causing rows to be skipped prematurely. The bug is that the condition is not correctly evaluating the intended logic; it should check that the condition holds for all j, not just one. Therefore, the correct answer is C.

Answer

A break statement is missing after processing a combination.

Answer

The label outer is placed on the inner loop, not the outer loop.

Answer

The continue outer statement should be a break outer.

Question 12

A developer writes a method that uses a for loop to iterate over a list of strings and remove elements that match a specific pattern using the list's remove(int index) method. The developer uses an index variable that increments normally. However, after running the method, some elements that should have been removed are still present, and some elements are skipped. The list initially contains [A, B, C, D, E] and the developer expects to remove B and D. After the loop, the list is [A, C, E] as expected? Actually, the developer observes that after the loop, the list contains [A, C, D, E] (D was not removed). What is the most likely cause?

Accepted Answer

The for loop uses an index that becomes invalid after removal.. When using a for loop with an index variable that increments normally, removing an element via `remove(int index)` causes all subsequent elements to shift left. This means the loop effectively skips the element that moves into the current index after a removal. In this scenario, after removing B at index 1, element C moves to index 1, but the loop increments i to 2, so C is never checked. Then at i=2, the loop sees D (originally at index 3). If the removal condition for D is checked at this point and matches, D would be removed, yielding [A, C, E]. However, the observed result is [A, C, D, E], indicating D was not removed. This can happen if the loop's condition uses a fixed bound (e.g., original size) causing an `IndexOutOfBoundsException` (not shown) or if the removal pattern is based on original indices that become invalid after the first removal. The most likely cause is that the index variable becomes stale after removal, leading to skipped elements or missed removals.

Answer

The list is unmodifiable, so remove throws UnsupportedOperationException.

Answer

The remove method is called with the wrong index.

Answer

The for loop uses an iterator that throws ConcurrentModificationException.

Question 13

A developer needs to iterate over a List<String> and remove elements that are null. Which approach guarantees correct behavior without throwing a ConcurrentModificationException?

Accepted Answer

Use an Iterator explicitly and call its remove() method. Iterator.remove() is the safe and recommended way to remove elements during iteration, avoiding ConcurrentModificationException. Option A is incorrect because using list.remove() inside a for-each loop modifies the list directly while iterating, causing ConcurrentModificationException. Option B is incorrect because Stream.filter() does not modify the original list; it creates a new list, which may not meet the requirement to remove elements from the original. Option C is incorrect because although a decrementing for loop may work, it is error-prone and not the guaranteed approach; it is not the idiomatic Java solution.

Answer

Use a for-each loop and call list.remove() on the current element

Answer

Use a Stream's filter() method and collect the results

Answer

Use a traditional for loop with an index that decrements

Question 14

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 15

Which two statements about the enhanced for-each loop in Java are true? (Choose two.)

Accepted Answer

It requires the target to implement the Iterable interface, except for arrays.. The enhanced for-each loop requires the target to implement the Iterable interface, except for arrays, which are handled natively by the compiler using index-based iteration. This is specified in the Java Language Specification (JLS §14.14.2), where arrays are a special case that does not require Iterable.

Answer

It can safely modify the underlying collection during iteration.

Answer

It can be used to iterate directly over a Stream object.

Answer

It provides an implicit counter variable that can be accessed.