1Z0-829 Practice Test 13 — 15 Questions

Question 1

Given two named modules where module com.example.app requires module com.example.lib, which packages of com.example.lib are readable by com.example.app?

Accepted Answer

Only the packages exported by com.example.lib. In the Java module system, a module can only access packages from another module that are explicitly exported using the `exports` directive in the module's `module-info.java` file. Since `com.example.app` requires `com.example.lib`, only the packages exported by `com.example.lib` are readable; unexported packages remain encapsulated and inaccessible.

Answer

All packages except those explicitly concealed

Answer

All packages of com.example.lib

Answer

Only the packages opened by com.example.lib

Question 2

Given the module descriptor for com.example.payment:

module com.example.payment {
    exports com.example.payment;
    // does not require com.example.store
}

And the Main class is in the unnamed module (on the classpath). The invocation is:

java --add-modules com.example.store --module-path mods -cp classes com.example.Main

What will happen?

Accepted Answer

The application runs successfully because com.example.store is added with --add-modules, and its exported packages are available.. The `--add-modules com.example.store` directive explicitly adds the module `com.example.store` to the set of root modules at startup, making its exported packages available to the unnamed module (or to modules that do not otherwise require it). Since the `Main` class is in the unnamed module (not in a named module), it can access the exported packages of `com.example.store` without a `requires` clause. This is the intended behavior of `--add-modules` for resolving modules that are not automatically resolved.

Answer

The application throws NoClassDefFoundError because the Main class is in a different module.

Answer

The application runs successfully because com.example.store is on the module path.

Answer

The application throws ModuleNotFoundException because com.example.store is not required by com.example.payment.

Question 3

Match each exception class to its category (checked/unchecked).

Accepted Answer

IOException: Checked. Checked exceptions must be handled or declared; unchecked extend RuntimeException.

Answer

ArrayIndexOutOfBoundsException: Checked

Answer

IllegalArgumentException: Checked

Question 4

You are a software architect at a financial firm. Your team is developing a modular Java 17 application that comprises several modules: 'com.bank.core' (provides core banking services), 'com.bank.web' (REST API), and 'com.bank.persistence' (database access). The application uses the 'java.sql' module for JDBC and 'java.logging' for logging. The team uses Maven for dependency management. The application has an external dependency on the 'com.fasterxml.jackson.databind' library (Jackson) for JSON processing, which is provided as a non-modular jar. The Jackson jar is placed on the module path. The application modules are all named modules with module-info files. At runtime, the 'com.bank.web' module requires 'com.bank.core' and 'com.fasterxml.jackson.databind' (the automatic module). The 'com.bank.core' module requires 'java.sql' and 'java.logging'. When the application runs, it throws an 'IllegalAccessError' indicating that the module 'com.bank.core' tries to access a class from 'com.fasterxml.jackson.databind' but the module does not read it. Yet, 'com.bank.web' is the only module that explicitly requires Jackson. What is the most likely cause and the correct resolution?

Accepted Answer

Add 'requires com.fasterxml.jackson.databind' to the module-info.java of 'com.bank.core' because it uses Jackson classes directly.. The error indicates that 'com.bank.core' directly uses classes from 'com.fasterxml.jackson.databind', but its module-info.java does not include a 'requires com.fasterxml.jackson.databind' directive. In the Java module system, a module can only access types from another module if it explicitly reads that module. Since 'com.bank.core' needs Jackson classes at runtime, it must declare the dependency itself, even if another module ('com.bank.web') also requires it.

Answer

Convert all application modules to unnamed modules by removing module-info files.

Answer

Place the Jackson jar on the classpath instead of the module path.

Answer

Use jlink to create a custom runtime image including all modules and the Jackson jar.

Question 5

Which code correctly reads a line of text from the console using System.console()?

Accepted Answer

Console cons = System.console(); String line = cons.readLine();. `System.console()` returns a `Console` object that provides a direct, secure method for reading text from the console without buffering issues. The `readLine()` method reads a line of text as a `String`, which is the intended approach when using the console API.

Answer

Scanner sc = new Scanner(System.in); String line = sc.nextLine();

Answer

DataInputStream dis = new DataInputStream(System.in); String line = dis.readLine();

Answer

BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String line = br.readLine();

Question 6

Which TWO of the following will sort a List<String> in natural (ascending) order?

Accepted Answer

list.sort(Comparator.naturalOrder());. `Comparator.naturalOrder()` returns a comparator that imposes the natural (ascending) ordering on `String` objects, which is lexicographic order based on Unicode values. The `List.sort()` method accepts this comparator and sorts the list in place, making it a concise and idiomatic way to sort a list in ascending order.

Answer

list.sort((a,b) -> b.compareTo(a));

Answer

Collections.sort(list, Collections.reverseOrder());

Answer

Arrays.sort(list);

Question 7

Given the code in the exhibit, which of the following is true about this custom exception?

Accepted Answer

It is an unchecked exception.. The custom exception extends RuntimeException, which makes it an unchecked exception. Unchecked exceptions do not require handling or declaration in the method signature, and they can be used in multi-catch blocks.

Answer

It cannot be used with multi-catch because it is unchecked.

Answer

It must be caught or declared in the method signature.

Answer

It must implement the Serializable interface.

Question 8

Given: int x=0; do { x++; } while(x<5); How many times does the loop body execute?

Accepted Answer

5. The do-while loop executes the body first, then checks the condition. The variable x starts at 0, so initially the body executes with x=0, then x increments to 1. The loop continues as long as x < 5. The body executes for x = 0, 1, 2, 3, 4 — a total of 5 times. When x becomes 5, the condition x < 5 is false, so the loop stops.

Answer

4

Answer

6

Answer

0

Question 9

Given: TreeSet ts = new TreeSet<>(Comparator.reverseOrder()); ts.add(10); ts.add(5); ts.add(20); ts.add(15); System.out.println(ts.first()); What is the result?

Accepted Answer

5. `TreeSet` with `Comparator.reverseOrder()` sorts elements in descending order (20, 15, 10, 5). The `first()` method returns the smallest element according to the comparator, which in descending order is the last element in the natural order, i.e., 5.

Answer

20

Answer

15

Answer

10

Question 10

A method reads a file and throws IOException. Which of the following is the correct way to declare the method?

Accepted Answer

public void readFile() throws IOException { ... }. The method explicitly declares that it throws IOException, which is a checked exception. In Java, if a method can throw a checked exception like IOException, it must either handle it with a try-catch block or declare it in the throws clause. This allows the caller to handle the exception appropriately.

Answer

public void readFile() throws RuntimeException { ... }

Answer

public void readFile() throws Exception { ... }

Answer

public void readFile() { ... } // assumes try-catch inside

Question 11

Which TWO statements are true about the Stream API and lambda expressions in Java 17?

Accepted Answer

The Stream API does not modify the original data source.. The Stream API is designed to work on a view of the data, not the data itself. Operations like filter, map, and collect produce new streams or results without altering the original collection, array, or I/O source. This non-interference guarantee is a core principle of the Stream API, ensuring safe parallel execution and functional programming style.

Answer

A stream can be consumed by multiple terminal operations sequentially.

Answer

Intermediate operations on a stream are executed eagerly.

Answer

Lambda expressions introduce a new level of scope, similar to an anonymous inner class.

Question 12

A method catches multiple exceptions using a multi-catch clause. Which statement about the exceptions in a multi-catch clause is correct?

Accepted Answer

The exceptions must be disjoint; if one is a subclass of another, the code will not compile.. Java requires that exception types in a multi-catch clause be disjoint (i.e., not in a subclass/superclass relationship). If one exception is a subclass of another, the code will not compile because the catch block would be unreachable for the subclass exception, violating the rule that catch blocks must be ordered from most specific to most general. This ensures that the multi-catch clause is unambiguous and that each exception type is distinct.

Answer

All exceptions in a multi-catch must be unchecked exceptions.

Answer

The multi-catch clause can have up to three exception types.

Answer

The exceptions can be in any order, and the first matching catch handles the exception.

Question 13

Which TWO statements about java.io and java.nio.file packages are true?

Accepted Answer

java.nio.file.Files class provides methods for operating on symbolic links.. The `java.nio.file.Files` class provides methods such as `createSymbolicLink()`, `readSymbolicLink()`, and `isSymbolicLink()` that directly operate on symbolic links in the file system. This is a key feature of the NIO.2 API, which offers comprehensive support for file system metadata and link management, unlike the older `java.io` package.

Answer

java.io.Console can be used to read from and write to the standard streams of the JVM.

Answer

java.io.FileInputStream supports the mark and reset methods.

Answer

java.nio.file.Path is a class that represents a file path.

Question 14

Refer to the exhibit. Which concept does this error relate to?

Accepted Answer

Leap seconds. The error relates to leap seconds because the exhibit (not shown here) likely involves a date-time calculation or parsing failure caused by the extra second (23:59:60) that is occasionally inserted into UTC to keep atomic time in sync with astronomical time. Java's `java.time` API, such as `LocalTime.parse()`, does not handle the 60th second, throwing a `DateTimeException` when encountering a leap second value.

Answer

ISO week date

Answer

Time zone offsets

Answer

Daylight Saving Time

Question 15

A financial services company runs a Java 17 application on a server with 8 GB RAM. The application reads daily transaction files in CSV format (each file is about 500 MB). It processes each line, validates it against a SQL database, and writes results to an output file. Recently, after processing about 60% of a file, the application crashes with an OutOfMemoryError: Java heap space. The heap size is set to 2 GB. The code uses Files.readAllLines() to load the entire file into a List<String>, then iterates. The team is evaluating solutions to avoid memory issues. Which approach is the best course of action?

Accepted Answer

Replace Files.readAllLines() with Files.lines() and process the stream line by line.. Files.readAllLines() loads the entire 500 MB CSV file into memory as a List, which causes the OutOfMemoryError when combined with other heap usage. Replacing it with Files.lines() returns a Stream that reads lines lazily, processing each line one at a time without holding the entire file in memory. This directly solves the heap space issue without requiring additional hardware or manual file splitting.

Answer

Increase the JVM heap size to 4 GB.

Answer

Enable class data sharing to reduce memory footprint.

Answer

Split the file into 100 MB chunks and process each chunk sequentially.