1Z0-811 Control Flow and Loops Practice Test 2 — 15 Questions

Question 1

A cashier program must print a receipt line for each item in an array named `prices` of type `double[]`. The developer wants the simplest construct that visits every element in order without managing an index. Which statement accomplishes this?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

for (double p : prices) { System.out.println(p); }. The enhanced for statement is designed for reading every element of an array or Iterable without an explicit counter. Declaring the loop variable as double p matches the element type of prices, and the body simply prints the value. The other constructs either call methods that arrays do not have, such as length() or hasNext(), or misuse the loop variable as an index.

Answer

while (prices.hasNext()) { System.out.println(prices.next()); }

Answer

for (double p : prices) { System.out.println(prices[p]); }

Answer

for (int i = 0; i < prices.length(); i++) { System.out.println(prices[i]); }

Question 2

A developer is writing a method that uses a for loop to iterate over an array of order IDs. The method must stop iterating entirely when a sentinel value of -1 is encountered, and must skip any order ID that is 0 without stopping the loop. Which TWO statements about the loop control keywords used to implement this behavior are correct? (Choose two.)

Accepted Answer

The continue statement skips the current iteration and proceeds with the next iteration of the loop.. The break statement ends the innermost loop when the sentinel -1 is found, and the continue statement skips the current iteration when the order ID is 0. Together they implement stopping on a sentinel and skipping zeros while continuing. The other statements incorrectly swap the roles of break and continue or introduce labeled loops not needed here.

Answer

Both break and continue can be used with a label to target a specific outer loop.

Answer

The continue statement exits the innermost loop immediately.

Answer

The break statement can be used to skip a single iteration and continue with the next one.

Question 3

Which loop is guaranteed to execute its body at least once?

Accepted Answer

do-while loop. The do-while loop is a post-test loop, meaning the condition is evaluated after the loop body executes. This guarantees that the body runs at least once, regardless of whether the condition is initially true or false. In Java, the do-while loop syntax is `do { ... } while (condition);`.

Answer

repeat-until loop

Answer

while loop

Answer

for loop

Question 4

What is the output of the following code?

int i = 0;
while (i < 5) {
    if (i == 3) {
        i++;
        continue;
    }
    System.out.print(i + " ");
    i++;
}

Accepted Answer

0 1 2 4. The while loop iterates while i < 5. When i equals 3, the if condition triggers, incrementing i to 4 and then using continue to skip the print statement for that iteration. Thus, 3 is never printed, and the loop prints 0, 1, 2, and then 4 before i becomes 5 and the loop ends.

Answer

0 1 2 3

Answer

0 1 2 4 5

Answer

0 1 2 3 4

Question 5

A developer writes: for(int i=0; i<10; i++) { if(i%2==0) continue; System.out.print(i); }. What is the output?

Accepted Answer

13579. The loop iterates from i=0 to i=9. The `continue` statement skips the rest of the loop body when the condition `i%2==0` is true (i.e., when i is even). Therefore, only odd values of i (1, 3, 5, 7, 9) are printed, producing the output '13579'. Option B is correct.

Answer

0123456789

Answer

02468

Answer

123456789

Question 6

Which loop best suits a scenario where the number of iterations is unknown and depends on user input?

Accepted Answer

while loop. The while loop is best when the number of iterations is unknown and depends on user input because it evaluates a boolean condition before each iteration, allowing the loop to continue as long as the condition remains true. This is ideal for scenarios like reading user input until a sentinel value is entered, where the exact number of iterations cannot be predetermined.

Answer

for loop

Answer

for-each loop

Answer

do-while loop

Question 7

Which THREE statements are true about the switch statement in Java? (Choose three.)

Accepted Answer

Without a break statement, execution falls through to the next case.. Options C, D, and E are true. Option C correctly describes fall-through behavior: without a break statement, execution continues to the next case. Option D correctly states that the default case is optional. Option E is true because, since Java 7, the switch statement can be used with String objects. Options A and B are false: A is incorrect because switch does not support boolean expressions; B is incorrect because the default case can appear anywhere in the switch block.

Answer

It can be used with boolean expressions.

Answer

The default case must be placed at the end of the switch block.

Question 8

Which THREE statements are true about the break and continue statements in Java? (Choose three.)

Accepted Answer

A labeled break can be used to exit an outer loop.. A labeled break in Java allows you to specify a label on an outer loop and then use 'break label;' to exit that outer loop directly, not just the innermost loop. This is useful for breaking out of nested loops when a condition is met in an inner loop.

Answer

The continue statement can be used to exit a loop entirely.

Answer

The break statement cannot be used outside a loop.

Question 9

What is the output of the code?

```java
for (int i = 0; i < 5; i++) {
    if (i == 2) {
        continue;
    }
    System.out.print(i + " ");
}
```

Accepted Answer

0 1 3 4. The code uses a for loop that iterates from i = 0 to i < 5 (i.e., 0 through 4). Inside the loop, there is an if condition that checks if i equals 2. When i == 2, the continue statement is executed, which skips the rest of that iteration, so the System.out.print statement is not executed for i = 2. Therefore, the loop prints 0, 1, 3, and 4, each followed by a space. Option D correctly lists this output.

Answer

0 1 2 3 4

Answer

1 3 4

Answer

0 1 2 3

Question 10

What is the value of sum printed?

int sum = 0;
for (int i = 0; i < 3; i++) {
    sum = sum + i;
}
System.out.println(sum);

Accepted Answer

3. The loop initializes sum to 0 and iterates i from 0 to 2 inclusive. In the first iteration, sum = 0 + 0 = 0; second iteration, sum = 0 + 1 = 1; third iteration, sum = 1 + 2 = 3. After the loop, sum is printed, so the output is 3. Option C is correct.

Answer

6

Answer

0

Answer

1

Question 11

You are tuning a real-time data processing application that reads sensor data from a queue. The system must process each sensor reading, but occasionally a reading is invalid (null) and should be skipped. The loop must run indefinitely until the application is shut down gracefully. The current implementation uses a while(true) loop with a break condition when a shutdown flag is set. However, the loop is consuming excessive CPU because it continuously polls the queue even when no data is available. You need to modify the loop to reduce CPU usage while still processing data efficiently. Which approach should you take?

Accepted Answer

Replace the polling mechanism with a blocking queue that blocks until data is available.. Using a blocking queue (e.g., `BlockingQueue.take()`) causes the consumer thread to block automatically until data becomes available, eliminating busy-waiting and drastically reducing CPU usage. This is the standard pattern for producer-consumer scenarios in Java, as it leverages the underlying `notify`/`wait` mechanism to avoid polling overhead.

Answer

Change the while(true) loop to a for loop that iterates a fixed number of times.

Answer

Add a Thread.sleep(100) inside the loop to reduce polling frequency.

Answer

Use a do-while loop with a Thread.yield() call to give other threads CPU time.

Question 12

Match each Java operator to its description.

Accepted Answer

==: Compares two values for equality. The correct matches are: == for equality, && for logical AND. Common confusions include mixing assignment (=) with comparison (==) and misunderstanding the ternary operator vs. logical operators.

Answer

!=: Used to assign a value to a variable

Answer

instanceof: Used to compare two primitive values

Answer

?:: Used to perform a logical OR operation

Question 13

A developer needs to iterate over an array of integers and compute the sum of its elements. Which loop construct is most appropriate for this task?

Accepted Answer

Enhanced for loop. The enhanced for loop (for-each) is the most appropriate construct for iterating over an array of integers to compute a sum because it provides a concise, read-only traversal without needing an explicit index or iterator. It directly accesses each element in sequence, reducing boilerplate and the risk of off-by-one errors, which is ideal for aggregation operations like summation.

Answer

while loop

Answer

switch statement

Answer

do-while loop

Question 14

A programmer writes a switch statement to handle different cases. The code compiles and runs, but the output is unexpected: 'A' prints when the input is 'B'. Which is the most likely cause?

Accepted Answer

A break statement is missing after the case 'B'.. In a switch statement, when a case matches, execution continues sequentially through subsequent cases (fall-through) unless a break statement is encountered. If case 'B' lacks a break, after executing its code, the program falls through to the code for case 'A' (or the next case), printing 'A' even though the input was 'B'. This is the classic fall-through behavior in Java.

Answer

The switch variable type is char but should be String.

Answer

The switch statement is missing a default case.

Answer

The default case is executed instead of the matched case.

Question 15

In a nested loop structure, a developer wants to exit completely from the outer loop when a certain condition is met inside the inner loop. Which approach is correct?

Accepted Answer

Use a labeled break statement (e.g., break outerLabel;).. Java's labeled break statement allows a developer to specify an outer loop label and break out of that loop entirely from within an inner loop. This is the only control flow mechanism designed to exit multiple nested loops at once, as a plain break only exits the innermost loop.

Answer

Use a return statement within the inner loop.

Answer

Use a continue statement with a label.

Answer

Use a break statement inside the inner loop.