1Z0-829 Practice Test 3 — 25 Questions

Question 1

A reporting module formats durations for a dashboard. The developer writes:

Duration d = Duration.ofMinutes(90);
System.out.println(d.toMinutes() + ":" + d.toMinutesPart());

What is printed?

Accepted Answer

90:30. Duration exposes both total-unit accessors and component accessors. toMinutes() returns the entire duration expressed in whole minutes, giving 90 for a 90-minute duration, while toMinutesPart() returns only the minutes left after whole hours are removed, giving 30. Concatenating them yields 90:30.

Answer

90:90

Answer

1:30

Answer

A DateTimeException is thrown because Duration has no hour component.

Question 2

What is the output of the following code?

```java
int i = 5;
while (i > 0) {
    System.out.print(i + " ");
    i--;
}
```

Accepted Answer

5 4 3 2 1. The while loop runs as long as i > 0. Starting with i = 5, each iteration prints the current value of i followed by a space, then decrements i by 1. The loop stops when i becomes 0, so the output is '5 4 3 2 1 '.

Answer

The code does not compile because i is not declared final.

Answer

5 4 3 2

Answer

4 3 2 1

Question 3

Given a list of strings, which of the following will produce a Map<String, Long> counting the occurrences of each string?

Accepted Answer

.collect(Collectors.groupingBy(Function.identity(), Collectors.counting())). `Collectors.groupingBy(Function.identity(), Collectors.counting())` groups each string by itself (using `Function.identity()` as the classifier) and then applies a downstream collector `Collectors.counting()` that counts the number of elements in each group, producing a `Map<String, Long>` where each key is a unique string and the value is its frequency.

Answer

.collect(Collectors.toMap(Function.identity(), String::length))

Answer

.collect(Collectors.groupingBy(Function.identity(), Collectors.summingInt(e->1)))

Answer

.collect(Collectors.toMap(Function.identity(), v->1))

Question 4

Which TWO are terminal operations on the Stream interface? (Choose two.)

Accepted Answer

count(). Option A, count(), is a terminal operation because it triggers the stream pipeline to execute and returns a long result (the number of elements), consuming the stream so it cannot be reused. Option B, forEach(), is also terminal: it accepts a Consumer and performs an action on each element, causing the pipeline to run and rendering the stream consumed. By contrast, filter(), map(), and sorted() are intermediate operations—they return a new Stream (or a specialized stream) and are lazy, merely building up the pipeline until a terminal operation is invoked. Therefore C, D, and E do not belong among the terminal operations.

Answer

filter()

Answer

map()

Answer

sorted()

Question 5

A Java application running on a server reads configuration from a file 'config.properties' located in the same directory as the JAR. The application uses java.util.Properties.load(InputStream) to read the file. Recently, the file was modified by an unauthorized user, and the application started throwing runtime exceptions due to corrupted property values. The security team requires that the file be protected from unauthorized modifications while still being readable by the application. Which action should be taken to ensure the integrity of the configuration file?

Accepted Answer

Digitally sign the file and verify the signature before loading properties.. Digital signing provides both integrity and authenticity. By signing the file with a private key and verifying the signature with a public key before calling Properties.load(InputStream), the application can detect any unauthorized modification. This directly addresses the security requirement without relying on encryption (which protects confidentiality, not integrity) or file permissions (which can be bypassed by a privileged attacker).

Answer

Encrypt the file using AES and decrypt it in the application.

Answer

Set the file permissions to read-only for the application user.

Answer

Store the file in a ZIP archive with a checksum.

Question 6

A resource is declared in a try-with-resources statement. The try block throws an exception. The close method throws a different exception. What exception is thrown by the try-with-resources statement?

Accepted Answer

The exception from the try block.. In a try-with-resources statement, if both the try block and the close() method throw exceptions, the exception from the try block is the one thrown by the statement. The exception from close() is suppressed and added to the thrown exception's suppressed exception list (via Throwable.addSuppressed()). This is specified by JLS §14.20.3.2 and ensures the primary failure (the try block exception) is not masked.

Answer

The exception from the close method.

Answer

A compilation error occurs.

Answer

Both exceptions are thrown simultaneously.

Question 7

A development team wants to ensure that a Java 17 application runs with a specific set of modules. They want to minimize the footprint by including only necessary modules. Which tool should they use?

Accepted Answer

jlink. B is correct because jlink is the Java tool specifically designed to assemble and optimize a custom runtime image containing only the modules explicitly required by an application. It analyzes module dependencies and produces a minimal JRE, reducing footprint by excluding unused modules, which aligns with the team's goal of minimizing size.

Answer

javac

Answer

jmod

Answer

jar

Question 8

Which THREE statements about the jpackage tool are true?

Accepted Answer

jpackage can create native installers for Windows, macOS, and Linux.. The jpackage tool is designed to create native installers for Windows (e.g., .exe/.msi), macOS (e.g., .dmg), and Linux (e.g., .deb/.rpm). This is a core feature of jpackage, which replaces the older Java Packager and allows developers to distribute self-contained applications with platform-specific packaging formats.

Answer

jpackage requires an existing JRE to create a runtime image.

Answer

jpackage uses the Java Packager library.

Question 9

What is the output when this code is executed?

```java
int x = 2;
switch (x) {
    case 1:
        System.out.print("One ");
    case 2:
        System.out.print("Two ");
    case 3:
        System.out.print("Three ");
        break;
    default:
        System.out.print("Default");
}
```

Accepted Answer

Two Three. The switch statement matches the value 2, so it executes the case 'Two' block, which prints 'Two ' and then falls through to the next case because there is no break statement. The case 'Three' block prints 'Three ' and then breaks, exiting the switch. The default case is skipped because a matching case was found and the break in case 'Three' prevents further fall-through. Thus, the output is 'Two Three '.

Answer

Two

Answer

Two Three Default

Answer

One Two Three

Question 10

Refer to the exhibit. What is the output?

```java
import java.util.stream.IntStream;

public class Example {
    public static void main(String[] args) {
        int sum = IntStream.rangeClosed(0, 5)
                .filter(i -> i >= 0)
                .sum();
        System.out.println(sum);
    }
}
```

Accepted Answer

15. The stream pipeline starts with `IntStream.rangeClosed(0, 5)` producing the integers 0, 1, 2, 3, 4, 5. The filter passes all these values, and the map is an identity function (or absent). The reduction sums them: 0+1+2+3+4+5 = 15. Therefore, the output is 15.

Answer

0

Answer

10

Answer

5

Question 11

Which of the following lambda expressions is syntactically invalid?

Accepted Answer

(a, b) -> return a + b;. Syntactically invalid because in a lambda expression, the `return` keyword is only allowed inside a block body (with braces). When using an expression body (no braces), the `return` keyword must be omitted, and the expression itself is implicitly returned. Option C incorrectly uses `return` without braces, which is a syntax error.

Answer

() -> {return 42;}

Answer

(a, b) -> a + b

Answer

(int a, int b) -> a + b

Answer

(a) -> a * 2

Question 12

A developer creates an unmodifiable list via Collections.unmodifiableList(originalList). Later, originalList is modified by adding an element. Which statement is true?

Accepted Answer

The unmodifiable list reflects the addition. D is correct because `Collections.unmodifiableList()` returns a view-backed unmodifiable list that reflects any changes made to the original list. The unmodifiable list does not create a snapshot; it wraps the original list, so modifications to the original are visible through the unmodifiable wrapper.

Answer

The unmodifiable list remains unchanged

Answer

The unmodifiable list becomes inconsistent

Answer

An UnsupportedOperationException is thrown

Question 13

Which two statements about the java.time.Duration class are true? (Choose two.)

Accepted Answer

Duration can be negative.. Option B is correct because java.time.Duration models an amount of time in terms of seconds and nanoseconds, and both components may carry a negative sign, so a Duration can represent a negative span (e.g., Duration.ofSeconds(-5) or the result of between() when the end is before the start). Option C is correct because Duration is a final, immutable value-based class: all its fields are final and every mutating-looking method such as plus() or withSeconds() returns a new instance, which makes instances safe to share across threads without synchronization. Option A is wrong because Duration only supports time-based units (days treated as exactly 24 hours, hours, minutes, seconds, nanos); months and years are date-based and are handled by java.time.Period. Option D is wrong because Duration.between() requires two Temporal objects that support time-based fields, and LocalDate is date-only, so passing LocalDate arguments throws an UnsupportedTemporalTypeException (or fails to compile against the Temporal signature). Option E is wrong because Duration's internal representation is seconds plus a nanosecond adjustment, not a days-based representation; the days-based model belongs to Period.

Answer

Duration supports units like months and years.

Answer

Duration.between(LocalDate.now(), LocalDate.now()) returns a Duration.

Answer

Duration uses a days-based representation.

Question 14

A web application allows users to specify filenames for uploaded documents. The application saves files to a directory using the provided name. Which secure programming practice should be applied to prevent path traversal attacks?

Accepted Answer

Use File.getCanonicalPath() to resolve the path and check it starts with the intended directory.. `File.getCanonicalPath()` resolves all symbolic links, `.` and `..` sequences, and platform-specific path conventions to produce an absolute, unique path. By then verifying that this canonical path starts with the intended base directory (e.g., `/var/uploads/`), the application can definitively reject any path that escapes outside the allowed directory, even if the user-supplied filename contains encoded or obfuscated traversal sequences.

Answer

Validate that the filename contains only alphanumeric characters.

Answer

Generate a random UUID for each file, ignoring the user-provided filename.

Answer

Replace all occurrences of ".." and "/" with an empty string.

Question 15

Which of the following is a terminal operation of the Stream API?

Accepted Answer

forEach(). (forEach()) is correct because it is a terminal operation in the Stream API. Terminal operations produce a result or side effect and close the stream, meaning no further operations can be performed on the same stream. forEach() consumes each element of the stream and returns void, making it a terminal operation.

Answer

map()

Answer

filter()

Answer

peek()

Question 16

A team uses a TreeSet with a custom Comparable that returns 0 for objects that are not logically equal (e.g., based on one field but objects differ in another). What is the likely outcome when adding such objects?

Accepted Answer

The second object is not added because TreeSet considers it a duplicate. TreeSet uses the compareTo() method of the Comparable interface (or Comparator) to determine ordering and equality. When compareTo() returns 0 for two objects that are not logically equal (e.g., they share the same field used in comparison but differ in other fields), TreeSet treats them as duplicates and does not add the second object. This is because TreeSet relies on the comparison result, not the equals() method, for uniqueness.

Answer

The second object replaces the first

Answer

A ClassCastException is thrown

Answer

Both objects are added and insertion order is preserved

Question 17

Which of the following correctly uses try-with-resources to ensure a FileInputStream is closed after use?

Accepted Answer

try (FileInputStream fis = new FileInputStream("file.txt")) { ... }. It uses the try-with-resources syntax (try (resource declaration) { ... }), which automatically closes the FileInputStream when the block exits, regardless of exceptions. This ensures the resource is closed without requiring an explicit finally block, as mandated by the AutoCloseable interface.

Answer

FileInputStream fis = new FileInputStream("file.txt"); try { ... } finally { fis.close(); }

Answer

try { FileInputStream fis = new FileInputStream("file.txt"); ... } finally { fis.close(); }

Answer

try (fis = new FileInputStream("file.txt")) { ... }

Question 18

You are developing a microservice that processes financial transactions. The service reads transaction data from a message queue, validates it, and writes results to a database. The code uses a try-with-resources statement to manage database connections. During testing, you notice that when a transaction fails validation, the service throws an IllegalStateException before closing the database connection, causing a resource leak. You need to ensure that the database connection is always closed properly, even if an exception is thrown during validation. The current code structure is:

try (Connection conn = DriverManager.getConnection(url, user, pass)) {
    // read from queue
    // validate transaction
    // if invalid, throw new IllegalStateException("Invalid transaction");
    // write to database
}

Which course of action would you recommend?

Accepted Answer

No change is needed; the try-with-resources ensures the connection is closed.. Try-with-resources automatically closes any resource that implements AutoCloseable (including Connection) when the try block exits, whether normally or via an exception. The IllegalStateException thrown during validation does not prevent the connection from being closed; the close() method is called as part of the implicit finally block generated by the compiler.

Answer

Move the connection creation outside the try-with-resources to manually manage it.

Answer

Replace the try-with-resources with a try-catch-finally block and close the connection in the finally block.

Answer

Add a catch block to catch the IllegalStateException and close the connection.

Question 19

A junior developer writes a method that uses a switch statement to handle different types of user input. The input is an integer representing an operation code. The developer uses a traditional switch statement with break statements. However, when operation code 2 is entered, the program also executes the code for operation 3. What is the most likely cause?

Accepted Answer

The break statement is missing after the operation 2 case.. In a traditional Java switch statement, execution continues into the next case block unless a break statement is encountered. If operation code 2 executes the code for operation 3, it indicates that the break statement is missing after the case for operation 2, causing fall-through to the next case.

Answer

The operation codes are not mutually exclusive.

Answer

The variable is being modified inside the switch.

Answer

The switch statement uses fall-through by design.

Question 20

Which method of Collection interface returns a primitive int?

Accepted Answer

size(). The `size()` method is the only one in the `Collection` interface that returns a primitive `int`, representing the number of elements in the collection. All other methods listed return either a `boolean` or an array of objects, making D the correct answer.

Answer

contains(Object o)

Answer

isEmpty()

Answer

toArray()