1Z0-829 Controlling Program Flow Practice Test 4 — 15 Questions

Question 1

Which three of the following are valid case values in a traditional switch statement (non-pattern)?

Accepted Answer

42. In a traditional switch statement (non-pattern), the case values must be compile-time constants of types that are compatible with the switch expression. Integer literals like 42 are valid case values, as they are constant expressions of type int, which is one of the allowed types (byte, short, char, int, their wrapper classes, String, and enum types).

Answer

true

Answer

3.14

Question 2

Which two statements about the do-while loop are true?

Accepted Answer

The do-while loop can be used with a label.. Java allows any loop, including the do-while loop, to be labeled. A label is a valid Java identifier followed by a colon placed immediately before the loop statement, enabling break or continue to transfer control to that labeled point. This is explicitly permitted by the Java Language Specification for all iteration statements.

Answer

The condition is evaluated before the body executes.

Answer

The do-while loop cannot have an initialization statement.

Answer

The do-while loop always executes more times than a while loop with the same condition.

Question 3

```java
int count = 0;
for (int i = 0; i < 5; ++i) {
    if (i == 3) break;
    count++;
}
System.out.println(count);
```
What is the output?

Accepted Answer

3. The code uses a loop that increments a variable count. It breaks when a certain condition (e.g., when a loop index equals 3) is met, after counting three iterations. Therefore, the output is 3.

Answer

4

Answer

5

Answer

Compilation error

Question 4

A developer is designing a loop to iterate through an array of integers and stop processing when the value -1 is encountered. Which loop construct should be used?

Accepted Answer

for(int i : array) { if(i == -1) break; }. The `break` statement immediately terminates the loop when the value -1 is encountered, which is exactly what the requirement specifies. In Java, `break` exits the innermost loop or switch statement, making it the appropriate control flow mechanism for stopping iteration upon a condition.

Answer

for(int i : array) { if(i == -1) exit; }

Answer

for(int i : array) { if(i == -1) return; }

Answer

for(int i : array) { if(i == -1) continue; }

Question 5

Which statement is correct about the following switch expression? String result = switch(day) { case MONDAY, TUESDAY -> "weekday"; case WEDNESDAY -> "midweek"; default -> "other"; };

Accepted Answer

The switch expression must be terminated with a semicolon.. Switch expressions in Java must be terminated with a semicolon, as they produce a value that is assigned to a variable. The given code uses the arrow syntax (->) and assigns the result to a String variable, so a semicolon is required at the end of the entire switch expression.

Answer

The switch expression is not allowed with a colon.

Answer

The default branch is optional.

Answer

The arrow operator requires a yield statement.

Question 6

A developer has a method that contains a try-catch-finally block inside a while loop. The try block throws a checked exception that is caught by the catch block. The catch block throws a new runtime exception. What is the behavior?

Accepted Answer

The loop terminates immediately, and the runtime exception propagates.. When a checked exception is caught and the catch block throws a new runtime exception, the finally block executes before the runtime exception propagates. Since the runtime exception is thrown from within the catch block (inside the while loop), it immediately terminates the loop and propagates up the call stack. Option B is correct because the loop does not continue; the runtime exception is thrown after the finally block completes.

Answer

The loop continues after the finally block, and the runtime exception is thrown after the loop.

Answer

The loop continues after the catch block, and the runtime exception is not propagated.

Answer

The loop continues after the finally block, and the runtime exception is suppressed.

Question 7

Which two of the following statements are true about the continue statement in a loop?

Accepted Answer

continue can be used in a while loop.. The continue statement can be used in any loop construct in Java, including while loops. When executed, continue skips the remaining body of the loop for the current iteration and proceeds to the next iteration's condition check.

Answer

continue cannot be used in a do-while loop.

Answer

continue can be used in a switch statement.

Answer

continue can be used in a try block without a loop.

Question 8

Which two of the following are valid ways to exit a loop in Java?

Accepted Answer

label break. A labeled break statement allows you to exit an outer loop from within a nested loop by specifying the label of the outer loop. This is a valid control flow mechanism in Java, as defined in the Java Language Specification (JLS §14.15).

Answer

continue

Answer

System.exit(0)

Answer

throw new Exception()

Question 9

Which three of the following statements about the switch expression in Java 17 are correct?

Accepted Answer

A switch expression with arrow syntax does not require break.. In a switch expression with arrow syntax (->), each branch is a single expression or block that is automatically terminated, eliminating the need for a break statement. The arrow syntax implicitly prevents fall-through, making the code more concise and less error-prone.

Answer

A switch expression cannot be used with an enum type.

Answer

A switch expression must include a default branch even if all cases are covered.

Question 10

Refer to the exhibit. The exhibit shows a stack trace from a Java application. Which line in the code caused the NullPointerException?

Accepted Answer

Line 8: int len = s.length();. The NullPointerException occurs when invoking the `length()` method on a null reference. In the stack trace, the exception is thrown at line 8, where `s.length()` is called, but `s` has not been assigned a non-null value (it is null by default if declared as a field, or uninitialized locally). The JVM throws NullPointerException when any instance method is called on a null object reference.

Answer

Line 10: System.out.println(len);

Answer

Line 12: String s = "hello";

Answer

Line 5: int x = 10;

Question 11

Refer to the exhibit. The exhibit shows a code snippet. What is the output when the variable day is set to Day.WEDNESDAY?

Accepted Answer

9. (9) because the switch statement on Day.WEDNESDAY (ordinal 2) does not have break statements for cases WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY, causing fall-through. Execution adds values: WEDNESDAY (3), THURSDAY (4), FRIDAY (5), SATURDAY (6), totaling 18. Then the default case subtracts 9, resulting in 9.

Answer

7

Answer

Compilation error

Answer

6

Question 12

In a large enterprise application, a concurrent caching system is implemented using a ConcurrentHashMap that is accessed by multiple threads concurrently. The cache performs atomic operations on individual keys, but some operations require updates on multiple keys. To ensure consistency, the code acquires intrinsic locks on the keys using synchronized blocks. Over time, the system has been experiencing intermittent deadlocks. During post-mortem analysis, it was found that thread A holds a lock on key X and is waiting for key Y, while thread B holds a lock on key Y and is waiting for key X. The development team needs to redesign the locking strategy to eliminate these deadlocks while maintaining high throughput and minimizing code changes. They consider the following proposals: replacing ConcurrentHashMap with Collections.synchronizedMap, using a single ReentrantLock for all cache operations, always acquiring locks on keys in a consistent global order, or using a Lock with tryLock and a timeout and releasing all locks if timeout expires. Based on best practices in concurrent programming and considering the requirements to avoid deadlocks and maintain performance, which approach should they choose?

Accepted Answer

Use a Lock with tryLock and a timeout, and release all locks if timeout expires.. Using tryLock with a timeout allows threads to back off and release all acquired locks if they cannot obtain all required locks within a specified time, which breaks the circular wait condition that causes deadlocks. This approach maintains high throughput by avoiding coarse-grained locking and minimizes code changes by only modifying the lock acquisition logic, not the underlying ConcurrentHashMap structure.

Answer

Use a single ReentrantLock for all cache operations.

Answer

Replace ConcurrentHashMap with Collections.synchronizedMap.

Answer

Always acquire locks on keys in a consistent global order.

Question 13

What is the output of the following code snippet? int x = 5; if(x > 0) { System.out.print('A'); } else if(x > 2) { System.out.print('B'); } else { System.out.print('C'); }

Accepted Answer

A. The condition `x > 0` evaluates to true (x = 5), so the code prints 'A' and then exits the entire if-else-if chain. The subsequent `else if` and `else` blocks are skipped entirely, so only 'A' is output.

Answer

AB

Answer

C

Answer

B