1Z0-811 Practice Test 11 — 15 Questions

Question 1

A developer is working on a Java application that processes user input. The application reads an integer from the command line using args[0], converts it to an int, and uses it in a loop. When testing, the application throws a NumberFormatException when the user provides an alphabetic string. The developer needs to handle this exception gracefully by prompting the user to enter a valid number and retrying. However, the developer must avoid infinite loops. The current code uses a while loop with a flag. Which approach ensures the code handles the exception, provides feedback, and terminates if the user enters 'quit'? The environment is a standard Java SE 11 application. The developer wants a robust solution without using external libraries.

Accepted Answer

Use a try-catch inside a loop that continues if exception caught, and breaks if input equals 'quit' or conversion succeeds.. Option B is correct because it catches NumberFormatException, prints a message, and allows retry, but sets the flag to false if user enters 'quit' to exit.

Answer

Catch the exception and ignore it; the loop will naturally terminate.

Answer

Use a do-while loop that never checks for 'quit'; the exception is caught outside the loop.

Answer

Catch the exception in the loop and call System.exit(0) immediately.

Question 2

A junior developer wrote the following code to calculate the sum of an array:

int[] numbers = {1, 2, 3, 4, 5};
int sum = 0;
for (int i = 1; i <= numbers.length; i++) {
    sum += numbers[i];
}
System.out.println("Sum: " + sum);

The developer expects the output to be 15, but the program throws an exception. What is the root cause and the correct fix?

Accepted Answer

Change to: for (int i = 0; i < numbers.length; i++). The loop starts at index 1 instead of 0, and goes up to index numbers.length (which is 5), but valid indices are 0-4. So accessing numbers[5] throws ArrayIndexOutOfBoundsException. The fix is to start at i=0 and continue while i < numbers.length. Option C is correct. Option A is wrong because the condition is still <= causing out-of-bounds. Option B changes step but still wrong start. Option D is for enhanced for loop, but the original is traditional for loop; the fix should maintain traditional loop style.

Answer

Change to enhanced for loop: for (int num : numbers) sum += num;

Answer

Change to: for (int i = 1; i < numbers.length; i += 2)

Answer

Change to: for (int i = 0; i <= numbers.length; i++)

Question 3

A developer implements a loop that processes a list of transactions. The loop must ensure that at least one transaction is processed even if the list is empty. Which loop construct guarantees this?

Accepted Answer

do-while loop. The do-while loop is the correct choice because it guarantees that the loop body executes at least once, regardless of the condition. In Java, the do-while loop evaluates its boolean condition after executing the loop body, so even if the list is empty (e.g., size 0), the transaction processing code inside the loop will run once before the condition is checked.

Answer

while loop

Answer

enhanced for loop

Answer

for loop

Question 4

Which THREE of the following are valid types that can be used as a switch expression in Java (as of Java 8)?

Accepted Answer

String. In Java 8, a switch expression can use `String`, `char`, and `int` as valid types. `String` was added in Java 7, and `char` and `int` are among the original primitive types supported. `long` and `boolean` are not allowed because `long` is a 64-bit type not supported by the switch statement's underlying `tableswitch` or `lookupswitch` bytecode instructions, and `boolean` has only two values, making it unsuitable for switch's multi-branch logic.

Answer

long

Answer

boolean

Question 5

What is the output of the program?

Accepted Answer

4. Option A is correct. The loop runs for i=0,1,2,3,4. When i=2, continue skips the rest of the body, so count is not incremented. For i=0,1,3,4, count increments each time: total 4. Option B is wrong because it incorrectly counts 5. Option C is wrong because it assumes break instead of continue. Option D is wrong because the loop completes normally.

Answer

The loop does not compile.

Answer

5

Answer

2

Question 6

What is printed by the program?

Accepted Answer

0,0 0,1 0,2 1,0. The program uses nested for loops: the outer loop runs with variable `i` from 0 to 1 (inclusive), and the inner loop runs with variable `j` from 0 to 2 (inclusive). For each iteration of the outer loop, the inner loop completes all its iterations, printing `i,j` pairs separated by spaces. This produces the sequence: 0,0 0,1 0,2 1,0. The outer loop stops when `i` becomes 2 (since the condition `i < 2` fails), so only two outer iterations occur.

Answer

0,0 0,1 0,2

Answer

0,0 0,1 0,2 1,0 1,1 1,2 2,0 2,1 2,2

Answer

0,0 0,1 0,2 1,0 1,1

Question 7

A team is implementing a search algorithm that iterates over an array of integers. The loop should stop as soon as the target value is found. Which loop construct is most appropriate?

Accepted Answer

For loop with break. Option C is correct because a for loop with a break statement allows early termination after finding the target. Option A (enhanced for loop) cannot easily break when conditions are met? Actually enhanced for can use break, but it's less common? The best practice is a traditional for loop with index. Option B (while loop) is also possible but less concise. Option D (do-while) is not ideal because it guarantees at least one iteration.

Answer

While loop with a flag variable

Answer

Enhanced for loop with continue

Answer

Do-while loop

Question 8

Consider a method that processes a two-dimensional array (matrix). It uses nested for loops. The inner loop uses a label 'outer' to break out of the outer loop. Under what condition is this label beneficial?

Accepted Answer

When you need to exit the outer loop from inside the inner loop. Option D is correct because a labeled break is used when you need to exit an outer loop from within an inner loop based on a condition. Option A is wrong because it's not about continuing the outer loop. Option B is wrong because you can also use a flag variable. Option C is wrong because it's specifically for nested loops, not single loops.

Answer

When you want to skip the current iteration of the outer loop

Answer

When you have a single loop and need to break to a specific point

Answer

When you want to exit the inner loop only

Question 9

A developer writes a loop that iterates over an array of integers. The loop should stop when it encounters a negative number. Which control flow construct best achieves this?

Accepted Answer

for loop with break inside if condition. Option A is correct because break exits the loop when condition met. Option B is wrong because continue skips to next iteration, doesn't stop loop. Option C is wrong because do-while executes at least once but doesn't provide early exit without additional logic. Option D is wrong because return exits the method, which may not be desired.

Answer

do-while loop

Answer

enhanced for loop with return

Answer

while loop with continue

Question 10

A developer receives a ticket that a batch processing job is running indefinitely. The job reads records from a database and processes them in a loop. The code uses a while(true) loop with a break condition when a sentinel value is encountered. However, due to a data anomaly, the sentinel value is never reached, causing the loop to run forever. The developer needs to fix the loop to prevent infinite execution while still allowing processing of all records until the sentinel is reached. Which approach is most appropriate?

Accepted Answer

Add a counter variable and break after a maximum number of iterations. Option A is correct because adding a counter and breaking after a maximum number of iterations provides a safeguard against infinite loops. Option B is wrong because the exact number of records may not be known in advance. Option C is wrong because a do-while loop does not solve the fundamental issue of missing sentinel. Option D is wrong because throwing an exception is not a graceful handling and would disrupt the batch job.

Answer

Use a do-while loop that checks the condition at the end

Answer

Change the loop to a for loop with a fixed range based on the expected number of records

Answer

Throw an exception when the loop runs too long

Question 11

A developer writes a switch statement that checks the day of the week. The code uses fall-through to handle weekdays. What happens if a case does not end with a break?

Accepted Answer

Execution continues to the next case. Option A is correct. In a traditional switch, without break, execution continues into the next case (fall-through). Option B is wrong because compile error occurs only if there is syntax issue. Option C is wrong because no runtime exception. Option D is wrong because it does not skip.

Answer

The default case is executed

Answer

Compilation error

Answer

Runtime exception is thrown

Question 12

A company's application uses a switch statement to handle different user roles. The code currently has a bug where after processing one role, it unintentionally executes the next role's logic. Which concept is being misused?

Accepted Answer

Missing break statements causing fall-through. Option B is correct because without break, execution falls through to the next case. Option A is wrong because default handles unmatched cases, not fall-through. Option C is wrong because using String in switch is valid. Option D is wrong because using enum in switch is valid.

Answer

Incorrect default case

Answer

Using enum in switch

Answer

Using string in switch (Java 7+)

Question 13

A developer writes the following code: for (int i = 0; i < 5; i++) { for (int j = i; j < 5; j++) { System.out.print(j); } } How many times does the inner loop execute in total?

Accepted Answer

15. Option D is correct. Outer loop i=0: inner j=0-4 (5 times); i=1: j=1-4 (4); i=2: 3; i=3: 2; i=4: 1; total = 5+4+3+2+1 = 15. Option A (5) is only the outer iterations. Option B (10) is incorrect. Option C (20) would be if both loops ran 5 times each.

Answer

5

Answer

10

Answer

20

Question 14

In a Java method, a developer needs to skip the current iteration and move to the next when a certain condition is met inside a for loop. Which statement should be used?

Accepted Answer

continue;. Option D is correct because continue skips the rest of the loop body for the current iteration. Option A is wrong because return exits the method. Option B is wrong because break exits the loop. Option C is wrong because exit is not a Java keyword.

Answer

return;

Answer

exit;

Answer

break;

Question 15

A novice developer wrote a condition: if (x = 10) { ... } What is the result?

Accepted Answer

Compilation error. Option A is correct. In Java, assignment inside if is allowed only if the type is boolean, but x=10 returns int, which is not boolean, so compilation fails. Option B (uses assignment) is wrong because it doesn't compile. Option C (runtime error) wrong. Option D (true) wrong.

Answer

The condition always evaluates to true

Answer

It executes the block if x equals 10

Answer

Runtime exception thrown