1Z0-829 Practice Test 30 — 15 Questions

Question 1

A Java 17 application uses the Java Platform Module System (JPMS). The module 'com.example.service' exports 'com.example.service.api' and requires 'java.logging'. Another module 'com.example.client' requires 'com.example.service'. The client module cannot access the 'com.example.service.api' package. What is the most likely reason?

Accepted Answer

The 'com.example.client' module does not contain a 'requires com.example.service' directive.. Option C is correct because the question states that the client module 'requires com.example.service', so the client module does contain the required directive. The most likely reason the client cannot access 'com.example.service.api' is that the 'com.example.service' module does not export that package. According to JPMS, a package must be explicitly exported via the 'exports' directive in the module-info.java of the owning module for other modules to access its public types. Without that export, even with a 'requires' directive, the package remains inaccessible.

Answer

The 'com.example.service' module does not use 'requires transitive' for 'java.logging'.

Answer

The 'com.example.service.api' package is not exported by 'com.example.service'.

Answer

The 'java.logging' module does not export its packages to 'com.example.service'.

Question 2

A team uses 'jlink' to create a custom runtime image for a modular application. They run the following command: 'jlink --module-path $JAVA_HOME/jmods:myapp --add-modules com.example.myapp --output myimage'. The application requires several non-Java native libraries (e.g., .so files) that are loaded via System.loadLibrary(). After creating the image, the application fails with an UnsatisfiedLinkError. What is the most likely cause?

Accepted Answer

The native libraries were not included in the image; they must be manually copied or added using --add-modules and a custom module.. Option C is correct because the `jlink` tool creates a runtime image that includes only Java modules and their dependencies, not native libraries (e.g., .so files). Native libraries must be manually placed into the image's library path (e.g., `lib/` or `bin/` directory) or packaged into a custom module that is added via `--add-modules`. The `UnsatisfiedLinkError` occurs because `System.loadLibrary()` cannot find the native library in the image's expected locations.

Answer

The native library loading requires a module that exports the package containing the native method.

Answer

The --add-modules flag omitted transitive dependencies of com.example.myapp.

Answer

The --module-path must also include the directories containing the native libraries.

Question 3

Refer to the exhibit. The module path is correctly set to include the JAR containing the module. What is the most likely issue?

Accepted Answer

The Main class is not specified as the main class in the module descriptor or manifest.. When launching a modular JAR with `java -jar`, the JVM requires the main class to be explicitly declared either in the module descriptor (`module-info.java` with a `main-class` directive) or in the JAR's `MANIFEST.MF` (`Main-Class` attribute). Without this declaration, the JVM cannot determine the entry point, resulting in a 'Main class not found' error. Option A correctly identifies this missing declaration as the most likely issue.

Answer

The JAR does not have a module-info.class.

Answer

The module requires a module that is not on the module path.

Answer

The Main class is not in an exported package.

Question 4

A company deploys a Java 17 application on a server with a custom runtime image created by jlink. The application uses the Java logging API (java.util.logging). The server administrator notices that the image size is approximately 45 MB. They need to reduce it further. Which jlink option would help exclude unnecessary locale data?

Accepted Answer

--include-locales en_US. Option A is correct because the `--include-locales` option in jlink allows you to specify which locale data to include in the custom runtime image. By default, jlink includes all locale data, which can significantly increase image size. Using `--include-locales en_US` restricts the image to only US English locale data, reducing unnecessary bloat for applications that do not require multiple locales.

Answer

--compress=2

Answer

--strip-debug

Answer

--no-header-files

Question 5

A developer runs 'jdeps -s --module-path lib myapp.jar' and gets output: 'myapp.jar -> java.base, myapp.jar -> java.sql, myapp.jar -> notfound'. What does the 'notfound' entry indicate?

Accepted Answer

The application has a dependency on a package that is not provided by any module on the module path.. The 'notfound' entry in the jdeps -s output indicates that the application has a dependency on a package that is not provided by any module on the module path. The -s (summary) flag shows module-level dependencies, and when a required module cannot be located among the specified modules or the JDK's built-in modules, jdeps reports it as 'notfound'. This means the dependency cannot be resolved at analysis time, typically because the required module is missing from the module path.

Answer

The dependency is resolved but its module name is not printed due to a summary flag.

Answer

The jar file is missing or corrupt.

Answer

There is a cyclic dependency among modules.

Question 6

Which THREE statements are true about the Java Platform editions? (Select three.)

Accepted Answer

Java ME provides a subset of Java SE APIs for embedded devices.. Java ME (Micro Edition) is designed for resource-constrained devices like sensors, mobile phones, and embedded systems. It provides a subset of the Java SE APIs, along with additional APIs tailored for small devices, such as the Connected Limited Device Configuration (CLDC) and the Mobile Information Device Profile (MIDP). This allows developers to write Java applications that run on devices with limited memory, processing power, and display capabilities.

Answer

Java ME (Micro Edition) is the same as Android SDK.

Answer

Java SE includes a full application server for enterprise applications.

Question 7

Refer to the exhibit. The resulting image directory includes a 'bin' directory with java launcher. When running the application, a NoClassDefFoundError occurs for a class from module com.example.lib. What is the most likely cause?

Accepted Answer

The com.example.lib module was not added via --add-modules.. When using jlink to create a custom runtime image, only the modules explicitly specified (or their transitive dependencies) are included. If the application depends on com.example.lib but it was not added via --add-modules, the module's classes will be missing from the image, causing a NoClassDefFoundError at runtime. This is the most direct cause among the options.

Answer

The --compress=2 option altered the class.

Answer

The application uses reflection to access the class.

Answer

The --strip-debug option removed the class file.

Question 8

Which TWO are valid uses of the 'jmod' tool in Java 17?

Accepted Answer

Listing the contents of a JMOD file.. The 'jmod' tool is primarily used for creating and inspecting JMOD files, which are a packaging format for Java modules that can include native libraries, configuration files, and other resources beyond what a modular JAR can hold. Option B is correct because 'jmod list' lists the contents of a JMOD file, showing its entries such as classes, native code, and legal notices. Option C is correct because 'jmod create' can create a JMOD file from a modular JAR and additional native libraries using the --libs option.

Answer

Creating a custom runtime image.

Answer

Executing a JMOD file as an application.

Answer

Identifying module dependencies of a jar.

Question 9

A developer writes a method that processes a grade and returns a message using a switch expression. The code is:

```java
public static String getMessage(int grade) {
    return switch (grade) {
        case 90, 80 -> "Excellent";
        case 70, 60 -> "Good";
        case 50 -> "Pass";
        default -> "Fail";
    };
}
```

Which statement is correct about this code?

Accepted Answer

The code compiles and runs correctly, returning the appropriate message.. Option C is correct because the switch expression uses the arrow form with a list of constants per case, which is valid syntax in Java 14+. The arrow form does not require a 'yield' statement when the right side is a single expression or block; here, each case yields a string literal directly. The 'default' clause is mandatory in a switch expression to cover all possible values, and it is correctly included.

Answer

The code does not compile because the switch expression must be enclosed in parentheses.

Answer

The code does not compile because the arrow form requires a 'yield' statement.

Answer

The code does not compile because 'default' is not allowed in a switch expression.

Question 10

Which THREE statements are true about the enhanced for loop in Java?

Accepted Answer

The enhanced for loop internally uses an iterator for collections.. Option B is correct because the enhanced for loop (for-each) over a collection internally uses an Iterator obtained from the collection's iterator() method. This is specified in the Java Language Specification (JLS 14.14.2) and is the mechanism that allows sequential access to each element without exposing the iterator directly.

Answer

If the underlying collection is modified during iteration, the loop will continue without error.

Answer

The loop variable must be declared final in the loop header.

Question 11

Given the following code snippet:

```java
outer:
for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        if (i == 1 && j == 1) {
            break outer;
        }
        System.out.print(i + "-" + j + " ");
    }
}
```

What is the output?

Accepted Answer

0-0 0-1 0-2 1-0. The correct answer is B because the labeled `break outer;` statement exits the outer loop entirely when `i == 1` and `j == 1`. Before that condition is met, the inner loop prints pairs for `i=0` (all j values 0,1,2) and for `i=1` with `j=0`. When `i=1` and `j=1`, the break occurs, so `1-1` is never printed, and the outer loop stops, preventing any further iterations.

Answer

0-0 0-1 0-2 1-0 1-1 1-2

Answer

0-0 0-1 0-2 1-0 2-0 2-1 2-2

Answer

0-0 0-1 0-2 1-0 1-1

Question 12

Which TWO of the following are valid forms of the switch statement/expression in Java?

Accepted Answer

switch(x) { case 1: System.out.println("one"); break; }. Option B is correct because it uses the traditional switch statement syntax with a colon after the case label, a statement to execute, and a break statement to prevent fall-through. This is a valid and long-standing form of the switch statement in Java.

Answer

switch(x) { case 1 -> "one"; }

Answer

String r = switch(x) { case 1: break "one"; };

Answer

switch(x) { case 1: yield "one"; }

Question 13

Consider the following code:

```java
boolean a = true, b = false, c = false;
if (a && b || c) {
    System.out.println("True");
} else {
    System.out.println("False");
}
```

What is the output?

Accepted Answer

False. The expression `a && b || c` evaluates as `(a && b) || c` due to operator precedence (`&&` has higher precedence than `||`). With `a=true`, `b=false`, `c=false`, `(true && false)` is `false`, then `false || false` is `false`, so the `else` branch prints "False". Option B is correct.

Answer

The code does not compile because of invalid boolean expression.

Answer

The output cannot be determined without runtime values.

Answer

True

Question 14

What is the output when this code is executed?

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 15

Given: for(int i=0; i<3; i++) { for(int j=0; j<3; j++) { if(i==1 && j==1) break; } } What is the value of i after the outer loop completes?

Accepted Answer

3. The outer loop variable `i` increments from 0 to 2. When `i` is 1 and `j` is 1, the `break` statement exits only the inner `for` loop, not the outer loop. The outer loop continues to its next iteration, incrementing `i` to 2, then to 3. When `i` becomes 3, the outer loop condition `i < 3` fails, so the loop terminates. Thus, after the outer loop completes, `i` is 3.

Answer

1

Answer

2

Answer

4