1Z0-829 Practice Test 3 — 10 Questions

Question 1

A developer is designing a method that processes a stream of Employee objects. The method needs to group employees by department and then, within each department, sort by salary in descending order, and collect the top 3 highest-paid employees per department into a list. Which approach correctly accomplishes this using streams?

Accepted Answer

stream.collect(Collectors.groupingBy(Employee::getDepartment, Collectors.collectingAndThen(Collectors.toList(), list -> list.stream().sorted(Comparator.comparing(Employee::getSalary).reversed()).limit(3).collect(Collectors.toList())))). Option A is correct because it uses `Collectors.groupingBy` to partition employees by department, then applies `Collectors.collectingAndThen` to post-process each department's list. Inside, it sorts the list by salary in descending order, limits to the top 3, and collects them into a new list. This ensures each department's result is independently sorted and truncated.

Answer

stream.collect(Collectors.toMap(Employee::getDepartment, e -> { List l = new ArrayList<>(); l.add(e); return l; }, (l1, l2) -> { l1.addAll(l2); l1.sort(Comparator.comparing(Employee::getSalary).reversed()); return l1.subList(0, Math.min(3, l1.size())); }))

Answer

stream.sorted(Comparator.comparing(Employee::getSalary).reversed()).collect(Collectors.groupingBy(Employee::getDepartment, Collectors.toList())).values().stream().map(l -> l.subList(0, Math.min(3, l.size()))).collect(Collectors.toList())

Answer

stream.collect(Collectors.groupingBy(Employee::getDepartment, Collectors.toList())).entrySet().stream().flatMap(e -> e.getValue().stream().sorted(Comparator.comparing(Employee::getSalary).reversed()).limit(3)).collect(Collectors.toList())

Question 2

Which TWO are correct about parallel streams in Java? (Choose TWO.)

Accepted Answer

Parallel streams use the common ForkJoinPool by default.. Option D is correct because parallel streams in Java, by default, use the common ForkJoinPool (ForkJoinPool.commonPool()), which is a shared thread pool designed for parallel task execution. This pool is lazily initialized and has a default parallelism level equal to the number of available processors minus one, as per the ForkJoinPool implementation.

Answer

Parallel streams always improve performance over sequential streams.

Answer

Any lambda expression is safe to use in a parallel stream.

Answer

Using parallel streams guarantees the order of elements in the result.

Question 3

Which of the following correctly formats a NumberFormat instance to display a currency value for the US locale with exactly two decimal places, rounding half-up?

Accepted Answer

NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.US);. Option D is correct because `NumberFormat.getCurrencyInstance(Locale.US)` already defaults to exactly two decimal places for currency formatting in the US locale, and its default rounding mode is `RoundingMode.HALF_EVEN`. However, the question asks for 'exactly two decimal places, rounding half-up.' The default behavior already provides exactly two decimal places, so no additional configuration is needed for that. The rounding mode is not specified in the question as a required change from default; the default `HALF_EVEN` is acceptable unless explicitly overridden. Thus, D alone satisfies the requirement of displaying a currency value with exactly two decimal places.

Answer

NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.US); nf.setRoundingMode(RoundingMode.HALF_UP);

Answer

NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.US); nf.setMinimumFractionDigits(2);

Answer

NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.US); nf.setMaximumFractionDigits(2);

Question 4

Which THREE statements are true about the Boolean class? (Choose three.)

Accepted Answer

The parseBoolean(String) method returns false if the string is null or not equal to "true" (case-insensitive).. Option A is correct because the `Boolean.parseBoolean(String)` method returns `false` for any input that is not exactly equal to `"true"` (case-insensitive), including `null`. This is specified in the Java API documentation and is a common way to safely parse boolean strings without throwing a NullPointerException.

Answer

The Boolean constructor is the preferred way to create a Boolean object.

Answer

Boolean has three possible values: true, false, and null.

Question 5

A developer needs to parse the string "2023-12-31T23:59:60Z" (a leap second) into a java.time.Instant. Which statement is true?

Accepted Answer

It returns an Instant representing 2023-12-31T23:59:59Z with an added nanosecond.. Option B is correct because java.time.Instant.parse() handles leap seconds by converting them to the last valid second of the minute (23:59:59) and then adding a nanosecond to account for the extra second. This behavior is specified by the ISO-8601 standard and the Java Time API, which does not support a true 60th second but represents it as an Instant with a fractional second adjustment.

Answer

It returns an Instant representing 2023-12-31T23:59:59Z, ignoring the leap second.

Answer

It throws a DateTimeParseException because 60 seconds is invalid.

Answer

It returns null because the string is invalid.

Question 6

Given the exhibit, what is the output?

Accepted Answer

12.50%. The correct answer is B (12.50%) because the code uses `NumberFormat.getPercentInstance()` which formats a decimal value as a percentage by multiplying it by 100 and appending a '%' sign. The input value 0.125 is formatted as '12.50%' with two decimal places by default.

Answer

0.125

Answer

%12.50

Answer

12.5%

Question 7

Which of the following correctly uses DateTimeFormatter to parse the date "2023-01-15" into a LocalDate?

Accepted Answer

LocalDate.parse("2023-01-15", DateTimeFormatter.ofPattern("yyyy-MM-dd")). Option A is correct because `LocalDate.parse()` uses the `DateTimeFormatter` with the pattern `"yyyy-MM-dd"` which matches the ISO 8601 date format of the input string "2023-01-15". The uppercase `MM` correctly represents the month, and the pattern exactly matches the input, allowing successful parsing into a `LocalDate`.

Answer

LocalDate.parse("2023-01-15", DateTimeFormatter.ofPattern("yyyy-mm-dd"))

Answer

MonthDay.parse("2023-01-15")

Answer

LocalDate.parse("2023-01-15", DateTimeFormatter.ISO_LOCAL_DATE)

Question 8

A developer writes code to iterate over a list of strings and print each element. The code uses an enhanced for loop. Which statement is true about the enhanced for loop?

Accepted Answer

It can be used with arrays and any object that implements Iterable.. The enhanced for loop (for-each) in Java can iterate over arrays and any object that implements the Iterable interface, which includes all Collection classes (e.g., List, Set, Queue). This is because the for-each loop internally uses an iterator for Iterable objects or array indexing for arrays, making it a versatile construct for traversing elements without needing an explicit counter.

Answer

It can only be used with arrays.

Answer

It requires an explicit counter variable.

Answer

It allows removing elements from the collection during iteration without ConcurrentModificationException.

Question 9

Given the code snippet:
int x = 10;
if (x > 5) {
    System.out.print("A");
} else if (x > 7) {
    System.out.print("B");
} else {
    System.out.print("C");
}
What is the output?

Accepted Answer

A. The if-else chain evaluates conditions sequentially. Since x=10 satisfies x > 5, the first block executes and prints 'A'. The else if and else branches are skipped entirely because the first condition was true. Thus, only 'A' is output.

Answer

C

Answer

ABC

Answer

B