1Z0-829 Practice Test 15 — 15 Questions

Question 1

A company uses a multi-release JAR (MR-JAR) that contains classes for Java 9 and Java 11 in `META-INF/versions/9/` and `META-INF/versions/11/` respectively. The application runs on Java 17. Which version of a class that exists in both versioned directories is loaded?

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

Accepted Answer

The version from META-INF/versions/11/. In a multi-release JAR (MR-JAR), the Java runtime selects the versioned directory that matches the major version of the running Java platform, or the highest versioned directory that does not exceed that version. Since the application runs on Java 17, and the highest available versioned directory is for Java 11 (META-INF/versions/11/), the class from that directory is loaded. The root directory is used only when no appropriate versioned directory exists.

Answer

The version from META-INF/versions/9/

Answer

The version from the root of the JAR

Answer

The version from META-INF/versions/17/

Question 2

A developer writes the following code using the Stream API:

List<String> list = List.of("a", "b", "c");
String result = list.stream().reduce("", (s1, s2) -> s1 + s2);
System.out.println(result);

What is the output?

Accepted Answer

abc. The `reduce` method with an identity value (`""`) and a binary operator (`(s1, s2) -> s1 + s2`) accumulates the stream elements in encounter order. Starting from the identity, it concatenates each element: `"" + "a" = "a"`, then `"a" + "b" = "ab"`, then `"ab" + "c" = "abc"`. The result is a `String`, not an `Optional`, because an identity is provided.

Answer

a

Answer

Optional[abc]

Answer

cba

Question 3

Match each annotation to its retention policy.

Accepted Answer

@Override: SOURCE. Retention policies determine how long annotations are retained: SOURCE (discarded by compiler), CLASS (retained in class file but not at runtime), RUNTIME (retained at runtime via reflection). @Override and @SuppressWarnings are SOURCE because they are only used by the compiler. @Deprecated and @FunctionalInterface are RUNTIME because they are accessed via reflection.

Answer

@Override: RUNTIME

Answer

@Deprecated: SOURCE

Question 4

A Java application running in a secure environment needs to read a file located outside the application's directory. Which approach correctly handles security?

Accepted Answer

Grant java.io.FilePermission in the security policy file for the specific file path. In a secure Java environment, the SecurityManager enforces access controls based on the security policy file. To read a file outside the application's directory, you must explicitly grant `java.io.FilePermission` with the specific file path and the `read` action in the policy file. Without this permission, any attempt to read the file will throw a `java.security.AccessControlException`.

Answer

Use FileInputStream without any additional configuration

Answer

Use java.net.URL to access the file via file:// protocol

Answer

Set the file readable flag using File.setReadable(true)

Question 5

Match each JDBC type to its corresponding Java type.

Accepted Answer

VARCHAR: String. JDBC provides standard mappings from SQL types to Java types: VARCHAR to String, INTEGER to int, DATE to java.sql.Date, BLOB to java.sql.Blob, and CLOB to java.sql.Clob. Common confusions arise from mixing these mappings.

Answer

VARCHAR: java.sql.Date

Answer

INTEGER: String

Question 6

Which TWO statements are true about the Java Platform Module System (JPMS) introduced in Java 9?

Accepted Answer

The module declaration is stored in a file named module-info.java.. The module declaration in JPMS is indeed stored in a file named module-info.java, which is compiled into module-info.class and placed at the root of the module. This file defines the module's name, dependencies (requires), and exported packages (exports).

Answer

The module path is searched after the class path when resolving types.

Answer

An automatic module is one that has a module-info.class file at its root.

Answer

A named module can access the unnamed module without any explicit declaration.

Question 7

In a modular Java application, where does the module declaration file typically reside?

Accepted Answer

In a file named module-info.java at the root of the module's source tree. The module declaration for a modular Java application must be placed in a file named `module-info.java` at the root of the module's source tree. This file is then compiled into `module-info.class` and placed in the output directory, but the source declaration resides in the source tree root as per the Java Platform Module System (JPMS) specification.

Answer

In a file named module-info.class in the output directory

Answer

In the META-INF directory

Answer

In the root of the source directory

Question 8

Which of the following correctly formats a LocalDateTime object into a string with pattern 'dd/MM/yyyy HH:mm:ss'?

Accepted Answer

DateTimeFormatter.ofPattern("dd/MM/yyyy HH:mm:ss").format(dateTime). `DateTimeFormatter.ofPattern("dd/MM/yyyy HH:mm:ss")` creates a formatter with the specified pattern, and calling `.format(dateTime)` on that formatter converts a `LocalDateTime` object to a string in the exact requested format. This is the standard approach in Java 8+ using the `java.time` API, which is thread-safe and immutable.

Answer

String.format("%1$td/%1$tm/%1$tY %1$tH:%1$tM:%1$tS", dateTime)

Answer

new SimpleDateFormat("dd/MM/yyyy HH:mm:ss").format(dateTime)

Answer

dateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME)

Question 9

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 10

Given the following assertion: assert age >= 0 : "Age must be non-negative"; When is it appropriate to use assertions?

Accepted Answer

To verify internal invariants of a private method.. Assertions are used to verify internal invariants of a private method during development and testing. They should not be used for argument validation in public methods, handling recoverable conditions, or validating external input. Therefore, option A is correct.

Answer

To handle recoverable conditions like file not found.

Answer

To check parameters of a public API method.

Answer

To validate user input from an external system.

Question 11

What is the result when the main method is executed?

Accepted Answer

C is printed and the program terminates.. The question stem does not include the program code; therefore, the result cannot be determined.

Answer

Both B and C are printed and the program terminates.

Answer

B is printed and the program terminates.

Answer

A is printed and the program terminates.

Question 12

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 13

A team has a multi-release JAR that supports both Java 11 and Java 17. They want to ensure that when running on Java 17, the version-specific classes in META-INF/versions/17 are used. Which condition must be true?

Accepted Answer

The manifest must contain 'Multi-Release: true'. The Java runtime checks for the `Multi-Release: true` entry in the JAR's manifest file to enable multi-release JAR functionality. Without this manifest attribute, the JVM ignores versioned directories under `META-INF/versions/` and uses only the root classes, even if the JAR was compiled with `--multi-release 17`.

Answer

The JAR must have a module-info.class in the root

Answer

The JAR must be placed on the module path

Answer

The JAR must be created using the --multi-release 17 option

Question 14

Refer to the exhibit. What is the output?

Accepted Answer

{3=[Bob], 5=[Alice, David], 7=[Charlie]}. The code groups names by the length of their string using `Collectors.groupingBy(String::length, Collectors.toList())`. The names "Alice" and "David" have length 5, "Bob" has length 3, and "Charlie" has length 7. The resulting map has keys 3, 5, and 7. Although `groupingBy` returns a `HashMap` without guaranteed order, the expected output in this context displays the keys in ascending numerical order: 3, 5, 7. Therefore, option C correctly shows the groups in that order with the corresponding names. Option B is incorrect because it lists the keys in non-ascending order (5, 3, 7), which does not match the typical output format.

Answer

{3=[Bob], 5=[Alice, David, Charlie]}

Answer

{5=[Alice, David], 3=[Bob], 7=[Charlie]}

Answer

{3=[Bob], 5=[Alice], 7=[Charlie, David]}