1Z0-829 Practice Test 12 — 15 Questions

Question 1

Arrange the steps to create a custom exception class in Java in the correct order.

Accepted Answer

1. Define a class that extends Exception or RuntimeException. 2. Add constructors (default, with message, with cause). 3. Optionally override methods like getMessage() or toString().. Custom exceptions extend Exception (checked) or RuntimeException (unchecked). Constructors typically call super(message) or super(cause).

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1. Add constructors (default, with message, with cause). 2. Define a class that extends Exception or RuntimeException. 3. Optionally override methods.

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1. Define a class (without extending Exception or RuntimeException). 2. Add constructors that call super(message). 3. Optionally override methods.

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1. Override methods like getMessage() or toString(). 2. Define a class extending Exception or RuntimeException. 3. Add constructors.

Question 2

Arrange the steps to create and use a generic method in Java.

Accepted Answer

Declare the method with a type parameter in angle brackets before the return type, then use the type parameter for parameters and return type, then implement the method body using the type parameter, then invoke the method either with explicit type argument or type inference.. Generic methods allow type-safe operations on different types. The type parameter is placed before the return type.

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Write the method body first using a specific type, then replace the specific type with a type parameter, then add the type parameter declaration in the method signature, then call the method with the specific type.

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Declare the method with a type parameter after the return type, then use the type parameter in the method body, then call the method with type inference.

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Use a wildcard (?) in the method signature instead of a type parameter, then implement the method body, then call the method with different types.

Question 3

What is the output of the following code?

List<Integer> list = List.of(0, 1, 2, 3);
System.out.println(list.indexOf(0) + " " + list.lastIndexOf(3));

Accepted Answer

0 3. The list is [0, 1, 2, 3]. The indexOf(0) returns 0 because 0 is at index 0. The lastIndexOf(3) returns 3 because 3 is at index 3. The output is "0 3".

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0 2

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1 2

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1 3

Question 4

Refer to the exhibit. What is the output when the program is executed?

Accepted Answer

0 0 0 1 0 2 1 0 1 1. The code uses nested for loops with break labels. The outer loop iterates i from 0 to 2, and the inner loop iterates j from 0 to 2. When i == 1 and j == 1, the break outer; statement exits both loops, so after printing 0 0, 0 1, 0 2, 1 0, 1 1, the program terminates. This matches option C.

Answer

0 0 0 1 0 2 1 0 1 1 1 2

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0 0 0 1 0 2 1 0 1 1 2 0 2 1 2 2

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0 0 0 1 0 2 1 0 1 1 1 2 2 0 2 1 2 2

Question 5

Which TWO statements are true about the sealed class feature in Java 17?

Accepted Answer

A sealed class restricts which other classes or interfaces may extend or implement it.. Option A is correct because the core purpose of the sealed class feature introduced in Java 17 is to restrict which other classes or interfaces may extend or implement it, using the permits clause to name the allowed direct subtypes. Option C is correct because any permitted subclass of a sealed class (or subinterface of a sealed interface) must itself be declared as final, sealed, or non-sealed, ensuring the hierarchy remains controlled and exhaustively known. Option B is wrong because a sealed interface can absolutely use a permits clause to specify its permitted implementing classes or extending interfaces. Option D is wrong because the permits clause lists only the permitted direct subclasses, and it may be omitted entirely when the subclasses are declared in the same source file. Option E is wrong because a sealed class need not be abstract; it can be concrete, and sealing is independent of abstractness.

Answer

A sealed interface cannot use the permits clause.

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The permits clause must list all direct subclasses of a sealed class.

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A sealed class must be declared as abstract.

Question 6

Which statement about java.io and java.nio.file packages is true?

Accepted Answer

The java.nio.file package provides support for symbolic links and file attributes. The java.nio.file package (part of NIO.2) explicitly provides support for symbolic links via methods like Files.createSymbolicLink() and Files.isSymbolicLink(), and it offers comprehensive file attribute access through classes like BasicFileAttributes, DosFileAttributes, and PosixFileAttributes, which are not available in java.io.

Answer

Classes in java.nio.file are thread-safe by default

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The java.io package includes the Path interface

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The java.nio.file package is deprecated in favor of java.io

Question 7

You are developing a microservice that processes order payments. The service uses a custom exception hierarchy: PaymentException (checked), InsufficientFundsException (unchecked, extends RuntimeException), and NetworkException (checked, extends PaymentException). The processPayment method is declared as: public void processPayment(Order order) throws PaymentException. Inside, a call to an external payment gateway may throw InsufficientFundsException or NetworkException. The requirement is to log all payment failures to an audit system, but the service must continue processing other orders. The audit logging method is: public void logFailure(String message) throws Exception. Which approach best handles exceptions while meeting the requirements?

Accepted Answer

Catch InsufficientFundsException and NetworkException in separate catch blocks. Inside each, try to call logFailure; if logFailure throws an exception, catch it and log a generic message to a fallback logger. Then return normally from processPayment without throwing.. It ensures that both checked (NetworkException) and unchecked (InsufficientFundsException) exceptions are caught locally, allowing the service to log the failure via logFailure (which itself throws Exception) without propagating the exception up the call stack. By catching any exception from logFailure and falling back to a generic logger, the method guarantees that processPayment returns normally, meeting the requirement to continue processing other orders. This approach respects the checked exception contract of processPayment (throws PaymentException) while handling all failure scenarios internally.

Answer

Wrap the call to the payment gateway in a try-catch-finally block. In the catch block, log the error using logFailure. In the finally block, return from the method.

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Add a throws clause to processPayment for InsufficientFundsException and NetworkException, and let the caller handle them.

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Catch InsufficientFundsException and NetworkException separately, log the error using logFailure, and then throw a new RuntimeException to indicate failure.

Question 8

A developer uses a stateful lambda in a parallel stream. Which of the following is a potential consequence?

Accepted Answer

Non-deterministic results. Stateful lambdas (e.g., those that modify shared mutable state) in parallel streams break the non-interference and statelessness requirements of the Stream API. Because parallel streams split the source into substreams processed by multiple threads, the lack of synchronization leads to race conditions, producing non-deterministic results that vary between runs.

Answer

ConcurrentModificationException

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All of the above

Answer

Improved performance

Question 9

An organization has a monolithic Java application built with Java 8 and deployed on a traditional classpath. They are migrating to Java 17 and want to use the module system to improve encapsulation. They have a jar file 'legacy.jar' that contains packages under 'com.legacy' and does not have a module-info.class. Which approach should they take to allow other modules to depend on this jar?

Accepted Answer

Place the jar on the module path; it becomes an automatic module.. When a JAR file without a module-info.class is placed on the module path, Java treats it as an automatic module. This allows other modules to depend on it by name (derived from the JAR filename) and grants it access to all other modules, effectively bridging the gap between the classpath and the module system during migration.

Answer

Add a module-info.class file to the jar using jar tool.

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Place the jar on the classpath; it becomes an unnamed module.

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Use jmod tool to convert the jar into a JMOD file.

Question 10

Which THREE statements about exception handling are true? (Choose three.)

Accepted Answer

Multi-catch syntax uses the pipe symbol (|) between exception types.. Option C is correct because Java's multi-catch syntax joins exception types with the pipe symbol, as in catch (IOException | SQLException e), allowing one handler to process several unrelated exception types. Option D is correct because checked exceptions (subclasses of Exception other than RuntimeException and its subclasses) must either be caught with a try/catch or declared in the method's throws clause, otherwise compilation fails. Option E is correct because the finally block is not guaranteed to run if the JVM terminates before reaching it, for example via System.exit() or an abnormal JVM shutdown, since the finally block only executes as part of normal control flow. Option A is not correct because the catch parameter is implicitly final in both single-catch and multi-catch forms, not only in multi-catch syntax. Option B is not correct because try-with-resources does not require a finally block; resources declared in the try-with-resources header are automatically closed, and catch or finally blocks are optional.

Answer

The variable in a catch clause is effectively final only when using multi-catch syntax.

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A finally block is mandatory in a try-with-resources statement.

Question 11

In a try-finally block, what happens to a return statement inside the finally block?

Accepted Answer

The return in the finally block is executed, and the try block return is ignored.. In a try-finally block, the finally block is always executed. If the finally block contains a return statement, that return value overrides any return value from the try block. Therefore, option A is correct. Option B is incorrect because the finally block always executes regardless of a return in try. Option C is incorrect because the finally return overrides the try return. Option D is incorrect because a return in finally is executed even if an exception occurs, overriding the exception.

Answer

The finally block is skipped if there is a return in try.

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The return in the try block takes precedence.

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If the try block throws an exception, the finally block's return is skipped.

Question 12

Match each Java module directive to its description.

Accepted Answer

requires: Specifies a dependency on another module.. Correct matches: requires specifies dependencies, exports grants compile-time access, opens enables reflective access, provides declares service implementations. Common confusion is between exports and opens due to their related but distinct roles.

Answer

exports: Allows reflective access to a package.

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opens: Makes a package accessible to other modules.

Question 13

Which THREE are valid ways to package a Java 17 application for distribution? (Choose three.)

Accepted Answer

JMOD file. A is correct because a JMOD file is a native packaging format introduced in Java 9 (JEP 261) specifically for distributing Java modules. It can include compiled classes, native code, configuration files, and even other JMOD files, making it a valid distribution format for Java 17 applications, especially when using the Java Module System.

Answer

ZIP file containing compiled classes

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Shell script that compiles and runs the application

Question 14

Which two statements about the Stream API are true? (Choose two.)

Accepted Answer

The 'reduce()' operation can produce a result of a different type than the stream elements.. The `reduce()` operation in the Stream API uses a combiner function that can transform the stream elements into an accumulated result of a different type. For example, `stream.reduce(0, (sum, i) -> sum + i, Integer::sum)` returns an `Integer` from an `IntStream`, or you can reduce a `Stream` to a `StringBuilder`. This is explicitly allowed by the `reduce(U identity, BiFunction accumulator, BinaryOperator combiner)` signature.

Answer

The 'flatMap()' operation is a terminal operation.

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The 'collect()' operation is an intermediate operation.

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Streams can be reused after a terminal operation.

Question 15

A developer has a module named 'com.example.app' that exports a package 'com.example.api'. Another module 'com.example.client' requires 'com.example.app'. Which directive must be in the module-info.java of 'com.example.client'?

Accepted Answer

requires com.example.app;. The 'requires' directive in a module-info.java file declares a dependency on another module. For 'com.example.client' to access the exported packages of 'com.example.app', it must include 'requires com.example.app;'. This is the standard mechanism for module dependency in the Java Platform Module System (JPMS).

Answer

opens com.example.app;

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uses com.example.api;

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exports com.example.api;