1Z0-829 Practice Test 10 — 10 Questions

Question 1

You are developing an online bookstore application. You have a list of Book objects, each with fields: String title, double price, and String genre. You need to generate a report that lists the total price of books in each genre, but only for genres where the average price is greater than $20.00. You are using Java 17 and streams. Which approach correctly accomplishes this task?

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

Accepted Answer

books.stream()
    .collect(Collectors.groupingBy(Book::getGenre,
             Collectors.mapping(Book::getPrice, Collectors.toList())))
    .entrySet().stream()
    .filter(e -> e.getValue().stream().mapToDouble(Double::doubleValue).average().orElse(0) > 20)
    .collect(Collectors.toMap(Map.Entry::getKey,
             e -> e.getValue().stream().mapToDouble(Double::doubleValue).sum()));. It first groups books by genre, collecting prices into lists, then filters entries where the average price exceeds $20 using `mapToDouble` and `average()`, and finally sums the prices for those genres. This two-step process correctly computes the average per genre before filtering, then sums the total per genre.

Answer

books.stream()
    .filter(b -> b.getPrice() > 20)
    .collect(Collectors.groupingBy(Book::getGenre,
             Collectors.summingDouble(Book::getPrice)));

Answer

books.stream()
    .collect(Collectors.groupingBy(Book::getGenre,
             Collectors.averagingDouble(Book::getPrice)))
    .entrySet().stream()
    .filter(e -> e.getValue() > 20)
    .collect(Collectors.toMap(Map.Entry::getKey, e -> {
        return books.stream().filter(b -> b.getGenre().equals(e.getKey())).mapToDouble(Book::getPrice).sum();
    }));

Answer

books.stream()
    .collect(Collectors.groupingBy(Book::getGenre,
             Collectors.summingDouble(Book::getPrice)))
    .entrySet().stream()
    .filter(e -> e.getValue() > 20)
    .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

Question 2

A developer wants to ensure that a block of code always executes regardless of whether an exception occurs or not, and that any exception thrown in the block is not swallowed. Which construct should be used?

Accepted Answer

try-finally. The try-finally construct ensures that the finally block always executes after the try block, regardless of whether an exception occurs, and it does not catch or swallow any exception. This meets the requirement of guaranteed execution without suppressing the exception, as the exception propagates up the call stack.

Answer

try-catch with empty catch block

Answer

try-catch-finally with catch that rethrows the exception

Answer

try-with-resources without catch

Question 3

Consider the following code snippet:

try {
    // some code
} catch (IOException e) {
    // handle
} catch (FileNotFoundException e) { // Line X
    // handle
}

What will be the result?

Accepted Answer

Compilation fails at Line X with an error about an exception already caught.. In Java, when catching exceptions, the more specific exception subclass must be caught before the more general superclass. FileNotFoundException is a subclass of IOException, so catching IOException first makes the catch for FileNotFoundException unreachable, causing a compilation error at Line X.

Answer

The code compiles and runs without issues.

Answer

The code compiles but throws a ClassCastException at runtime.

Answer

The code compiles but the second catch never executes.

Question 4

Given the exhibit showing output from a program that uses try-with-resources, which of the following best describes the program?

Accepted Answer

Both the try block and the close method threw exceptions.. The output shows both a primary exception from the try block and a suppressed exception from the close method. In try-with-resources, if both the try block and the close method throw exceptions, the primary exception from the try block is propagated, and the close method's exception is added as a suppressed exception. The output displays both exceptions, confirming that both occurred.

Answer

The try block threw an exception, but the resource closed successfully.

Answer

Only the close method threw an exception, and the try block did not throw.

Answer

The close method threw an exception, and the try block completed normally.

Question 5

What is the likely cause of this compilation error?
```java
String day = "Monday";
int dayNum = switch (day) {
    case 1 -> 1;
    case 2 -> 2;
    default -> 0;
};
System.out.println(dayNum);
```

Accepted Answer

The switch selector is a String but case labels are int constants.. In a Java switch expression, the selector type and case label types must be compatible. If the selector is a String, the case labels must be String constants; int constants would cause a compilation error due to type mismatch. Options A, B, and C describe syntax issues that are not the primary cause here.

Answer

The switch expression uses arrow syntax but the keys are not unique.

Answer

The switch expression is missing a default case.

Answer

The switch expression is not assigned to a variable.

Question 6

Which THREE statements are true about loops in Java?

Accepted Answer

The break statement can be used to exit a loop prematurely.. The break statement in Java is used to immediately terminate the execution of a loop (for, while, or do-while) and transfer control to the statement following the loop. This allows premature exit based on a condition, which is a fundamental control flow mechanism in Java.

Answer

A while loop always executes at least once.

Answer

A do-while loop may execute zero times if the condition is false.

Question 7

Which TWO of the following are valid ways to create a LocalDate object in Java 17?

Accepted Answer

LocalDate.of(2023, Month.JANUARY, 15). Option B is correct because LocalDate.of(int year, Month month, int dayOfMonth) is a valid static factory method in java.time that accepts a Month enum constant such as Month.JANUARY, producing 2023-01-15. Option D is correct because LocalDate.parse(CharSequence) uses the ISO_LOCAL_DATE formatter by default, and "2023-01-15" matches the required yyyy-MM-dd pattern. Option A is wrong because LocalDate.from(TemporalAccessor) requires a temporal that contains date fields, and Instant only provides an instant on the time-line without a date, so it throws DateTimeException. Option C is wrong because month 13 is outside the valid range of 1-12 and LocalDate.of throws DateTimeException. Option E is wrong because LocalDate.ofEpochDay takes a long primitive, not a String, so passing "19375" does not compile.

Answer

LocalDate.from(Instant.now())

Answer

LocalDate.of(2023, 13, 1)

Answer

LocalDate.ofEpochDay("19375")

Question 8

Which interface is designed for recursively walking a file tree?

Accepted Answer

FileVisitor. The `FileVisitor` interface is designed for recursively walking a file tree, as it provides callback methods (`preVisitDirectory`, `postVisitDirectory`, `visitFile`, `visitFileFailed`) that are invoked during a depth-first traversal of a file tree, typically used with `Files.walkFileTree()`. This allows you to process each file and directory in the tree, including subdirectories, making it the correct choice for recursive file tree walking.

Answer

DirectoryStream

Answer

FilenameFilter

Answer

FileFilter

Question 9

Refer to the exhibit. Which statement is true about the com.example.app.internal package?

Accepted Answer

It is accessible for deep reflection only by com.example.lib.. The exhibit shows that `com.example.app.internal` is declared with `opens com.example.app.internal to com.example.lib`. The `opens` directive grants deep reflection (access to private members) at runtime, but only to the specified module `com.example.lib`. Other modules cannot reflectively access this package unless they are explicitly listed.

Answer

It is accessible for deep reflection by any module.

Answer

It is not accessible for reflection at all.

Answer

It is exported to all modules.

Question 10

A company's Java application processes time-sensitive data from IoT sensors. The system must handle timestamps across multiple time zones. The application runs on a server set to UTC. Developers have been using java.util.Date and SimpleDateFormat for date parsing. Recently, there have been intermittent failures where timestamps from sensors in the America/New_York time zone are parsed incorrectly around daylight saving time transitions. Specifically, during the spring forward (March 12, 2023, at 2:00 AM EST to 3:00 AM EDT), timestamps like "2023-03-12 02:30:00" are being interpreted as times that do not exist, causing DateTimeParseException. The team decides to migrate to the java.time API. They need to parse sensor timestamps that include a time zone offset (e.g., "2023-03-12 02:30:00 -05:00") into an OffsetDateTime. Which course of action correctly parses the timestamp and handles the DST issue?

Accepted Answer

Use DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss XXX") and OffsetDateTime.parse(timestamp, formatter).. The timestamp includes an explicit offset (-05:00), which makes it directly parseable into an OffsetDateTime using a DateTimeFormatter with the XXX pattern for the offset. OffsetDateTime.parse() handles the offset directly without any DST ambiguity, as the offset is explicitly provided in the string, avoiding the nonexistent time issue during spring-forward transitions.

Answer

Use LocalDateTime.parse(timestamp, formatter) and then apply a ZoneOffset.

Answer

Use ZonedDateTime.parse(timestamp, formatter) with a formatter that includes time zone ID, then convert to OffsetDateTime.

Answer

Keep using SimpleDateFormat but set the time zone of the parser to America/New_York.