1Z0-829 Handling Exceptions Practice Test 3 — 15 Questions

Question 1

Which of the following is a best practice when designing custom exception classes?

Accepted Answer

Extend an existing exception class and provide constructors that call the superclass constructor.. The Java best practice for custom exceptions is to extend an existing exception class (e.g., Exception or RuntimeException) and provide constructors that call the superclass constructor. This ensures the custom exception inherits the standard exception mechanism, including proper chaining, stack trace handling, and compatibility with try-catch blocks, without reinventing the wheel.

Answer

Define a custom exception with a single constructor that takes an int error code.

Answer

Extend the Throwable class directly to create a new exception type.

Answer

Use a generic Exception class with a string message to indicate the type of error.

Question 2

Given the following code snippet inside a method:

try {
    // risky code
} catch (IOException | SQLException e) {
    // handle
}

What is the implicit type of the exception variable 'e' in the catch block?

Accepted Answer

It is of type Exception.. In Java, when a multi-catch clause catches multiple exception types (e.g., IOException | SQLException), the compiler infers the catch parameter's type as the closest common superclass that is not Object or Throwable. Since IOException and SQLException both extend Exception directly, the implicit type of 'e' is Exception. This allows the catch block to handle both exception types polymorphically.

Answer

It is of type Object.

Answer

It is of type Throwable.

Answer

It is either IOException or SQLException.

Question 3

What happens when a finally block throws an exception?

Accepted Answer

The exception from the try block is suppressed and the finally exception is reported.. When a finally block throws an exception, the JVM suppresses the exception that was thrown from the try block (if any) and propagates the exception thrown from the finally block. This behavior is defined in the Java Language Specification (JLS §14.20.2) and ensures that the finally block's exception takes precedence, as the finally block is executed after the try block completes abruptly.

Answer

The JVM logs both exceptions and then terminates the thread.

Answer

The exception from the try block is propagated and the finally exception is ignored.

Answer

Both exceptions are reported as suppressed exceptions of a new exception.

Question 4

Consider try-with-resources where resource1 is opened first, then resource2. During closing, both throw exceptions. Which exception is propagated to the caller?

Accepted Answer

The exception from resource2 (closed first) with resource1's exception as suppressed.. In try-with-resources, resources are closed in the reverse order of their declaration. Resource2 (declared second) is closed first, and resource1 (declared first) is closed last. If both throw exceptions during closing, the exception from the first resource closed (resource2) is propagated to the caller, and the exception from the second resource closed (resource1) is added as a suppressed exception. This matches option B.

Answer

The exception from resource1 (closed last) with resource2's exception as suppressed.

Answer

Only the exception from the resource declared first is propagated.

Answer

Both exceptions are wrapped in a new exception.

Question 5

A developer wants to ensure that a block of code always executes regardless of whether an exception occurs or not, and that any exception thrown in the block is not swallowed. Which construct should be used?

Accepted Answer

try-finally. The try-finally construct ensures that the finally block always executes after the try block, regardless of whether an exception occurs, and it does not catch or swallow any exception. This meets the requirement of guaranteed execution without suppressing the exception, as the exception propagates up the call stack.

Answer

try-catch with empty catch block

Answer

try-catch-finally with catch that rethrows the exception

Answer

try-with-resources without catch

Question 6

Which of the following is a checked exception in Java?

Accepted Answer

IOException. IOException is a checked exception in Java. Checked exceptions are subclasses of Exception (excluding RuntimeException and its subclasses), and the compiler enforces that they are either caught or declared in the method's throws clause. IOException directly extends Exception, making it a checked exception that must be handled at compile time.

Answer

NullPointerException

Answer

ArithmeticException

Answer

IllegalArgumentException

Question 7

Given a method that throws IOException, SQLException, and TimeoutException, a developer writes a catch block that rethrows the exception. Using Java 17, which exception types can the catch block declare in its throws clause if the rethrown exception is not modified?

Accepted Answer

Any single exception type that covers all caught exceptions.. In Java, when a catch block catches multiple exception types and rethrows the exception without modification, the compiler uses precise rethrow. This allows the throws clause to declare any exception type that is a supertype of all the caught exceptions, such as Exception (which is a common supertype of IOException, SQLException, and TimeoutException). Therefore, the developer does not need to list each checked exception individually; a single covering type is sufficient. Option D correctly states that any single exception type covering all caught exceptions can be declared.

Answer

The method must declare all checked exceptions individually.

Answer

Only the common superclass of the exceptions (Exception).

Answer

No throws clause is needed if the catch block logs and returns.

Question 8

Which TWO statements about try-with-resources are correct? (Choose two.)

Accepted Answer

Resources are closed in the reverse order of their declaration.. The Java Language Specification (JLS §14.20.3) mandates that resources declared in a try-with-resources statement are closed in the reverse order of their declaration. This ensures that if a resource depends on another declared earlier, the dependent resource is closed first, preventing resource leaks or inconsistent states.

Answer

Resources are closed in the same order as their declaration.

Answer

Resources declared in try-with-resources must implement the Closeable interface.

Answer

Resources declared earlier in the try clause are closed first.

Question 9

Which THREE practices are recommended for effective exception handling? (Choose three.)

Accepted Answer

Throw exceptions early, catch them late, but handle them at the appropriate level.. Effective exception handling in Java recommends throwing exceptions as soon as an error is detected (fail-fast), catching them at a level where the error can be meaningfully handled (not too early), and handling them at the appropriate layer of abstraction. This prevents swallowing exceptions or losing context, and aligns with the principle of separation of concerns.

Answer

Define custom exceptions without providing any additional context.

Answer

Catch exceptions at the highest level of the application and log them generically.

Question 10

Which TWO of the following are unchecked exceptions? (Choose two.)

Accepted Answer

NullPointerException. NullPointerException (option C) is an unchecked exception because it extends RuntimeException, which means it is not checked at compile time. The Java compiler does not require you to handle or declare NullPointerException, making it an unchecked exception.

Answer

SQLException

Answer

Exception

Answer

IOException

Question 11

In the following try-with-resources block, resources are declared as: try (FileInputStream fis = new FileInputStream("data.txt"); BufferedInputStream bis = new BufferedInputStream(fis)) { ... } If an IOException occurs during the closing of both resources, which resource's close exception is returned by e.getSuppressed()?

Accepted Answer

Only the exception from FileInputStream close is in the suppressed array.. In a try-with-resources statement, resources are closed in the reverse order of their declaration. Here, FileInputStream is declared first and BufferedInputStream second, so BufferedInputStream is closed first. If both resources throw an IOException during closing, the exception from BufferedInputStream (the first to close) becomes the primary exception, and the exception from FileInputStream (the second to close) is suppressed. The primary exception is thrown from the try block, while the suppressed exception is accessible via the getSuppressed() method. Therefore, e.getSuppressed() returns an array containing the exception from FileInputStream. Option B is correct because only the FileInputStream's close exception is in the suppressed array.

Answer

The suppressed array contains both exceptions.

Answer

The suppressed array contains the exception from FileInputStream.

Answer

Only the exception from BufferedInputStream close is in the suppressed array.

Question 12

What is the result of executing the code in the exhibit?

Accepted Answer

The code does not compile because methodA does not declare that it throws Exception.. The code does not compile because methodA explicitly throws an IOException, but the catch block in main catches Exception (a broader type). However, the compiler performs improved rethrow analysis only when the exception parameter is effectively final and the catch block is multi-catch or rethrows a checked exception that is declared in the method signature. Here, methodA does not declare that it throws Exception, and the catch block catches Exception, which is not a declared exception in methodA's throws clause, causing a compilation error.

Answer

The code compiles and prints 'Caught in main: IOException' because the compiler uses improved rethrow analysis.

Answer

Prints: Caught in main: Exception

Answer

Prints: Caught in main: IOException

Question 13

Your team manages a high-throughput financial transaction system running on Java 17. Recently, the application experiences intermittent slowdowns and increased CPU usage during peak hours. Monitoring reveals that exception handling code is invoked frequently due to validation errors in incoming data. The system uses a central exception handler that logs every exception and throws a custom ApplicationException. In many places, the code catches generic Exception and rethrows the custom exception after logging. Additionally, method signatures include throws Exception. The team wants to improve performance and maintainability without changing the external behavior significantly. Which course of action best addresses the performance and maintainability issues?

Accepted Answer

Define specific custom checked exception classes for each validation error and catch them precisely, avoiding generic Exception catches.. Catching generic `Exception` forces the JVM to build a full stack trace for every validation error, which is expensive in a high-throughput system. By defining specific custom checked exception classes and catching them precisely, the team reduces unnecessary stack trace generation and makes the code more maintainable by clearly documenting which errors are expected. This approach aligns with Java best practices for exception handling, improving both performance and code clarity without altering external behavior.

Answer

Change all catch blocks to catch Throwable and ignore irrecoverable errors to reduce logging.

Answer

Add a try-catch block around every method call that might throw an exception to handle locally.

Answer

Wrap all exceptions in a single custom unchecked exception to simplify exception handling.

Question 14

A Java application uses a custom resource class implementing AutoCloseable. The close() method throws a checked exception. In a try-with-resources block, if both the try block and the close() method throw exceptions, which exception is propagated to the caller? Assume the resource is declared in try-with-resources.

Accepted Answer

The exception from the try block is the primary exception, and the close() exception is added as a suppressed exception.. In a try-with-resources block, when both the try block and the close() method throw exceptions, the exception from the try block is the primary exception propagated to the caller. The exception thrown by close() is added to the primary exception's suppressed exception list, as defined by the Java Language Specification (JLS §14.20.3.2). This ensures that the most relevant exception (the one from the application logic) is not masked by a resource-closing failure.

Answer

The exception from close() is always the primary exception.

Answer

Both exceptions are thrown simultaneously as a multi-catch exception.

Answer

The exception from the try block is always suppressed.

Question 15

Which TWO are valid multi-catch statements in Java 17? (Choose two.)

Accepted Answer

catch (SQLException | IOException e). Java 17 allows a multi-catch clause to handle multiple exception types in a single catch block, provided the exception types are unrelated in the class hierarchy. SQLException and IOException are both checked exceptions that do not inherit from each other, so they can be caught together in a multi-catch statement.

Answer

catch (Exception | RuntimeException e)

Answer

catch (SQLException | Exception e)

Answer

catch (IOException | FileNotFoundException e)