1Z0-829 Practice Test 9 — 10 Questions

Question 1

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.

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

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.

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

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The exception from the try block is always suppressed.

Question 2

A developer writes: List list = List.of(1, 2, 3); Optional opt = list.stream().reduce((a, b) -> a + b); System.out.println(opt.get()); What is the result?

Accepted Answer

6. The `reduce` method with a single argument (a `BinaryOperator`) returns an `Optional` because the stream might be empty. Here, the stream contains three integers, so the reduction computes `1 + 2 = 3`, then `3 + 3 = 6`, yielding `Optional[6]`. Calling `get()` on a non-empty `Optional` returns the contained value `6`, which is printed.

Answer

Optional[6]

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Optional.empty

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NoSuchElementException

Question 3

What does the Map.merge() method do if the specified key is absent?

Accepted Answer

Associates the key with the given value. When the specified key is absent in the map, the `Map.merge()` method associates the key with the given value without invoking the remapping function. This is specified in the Java API documentation: if the key is not present (or maps to null), the key is associated with the given non-null value.

Answer

Calls the remapping function with null and the value

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Throws NullPointerException

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Removes the key if present

Question 4

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.

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

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

Question 5

Given a try-with-resources statement where both the try block and the close method of the resource throw exceptions, which of the following is true about exception handling?

Accepted Answer

The try block exception is the primary exception; the close exception is suppressed.. In a try-with-resources statement, if both the try block and the resource's close() method throw exceptions, the exception from the try block is the primary exception, and any exception thrown by close() is added as a suppressed exception. This is defined by Java's try-with-resources semantics (JLS §14.20.3.2), ensuring the primary exception is not masked by resource cleanup failures.

Answer

The exception from the close method is the primary exception.

Answer

Both exceptions are thrown simultaneously, causing a multi-catch.

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The close method exception is ignored if the try block succeeds.

Question 6

Which two statements about multi-catch blocks are correct?

Accepted Answer

A multi-catch block can be used with a finally block.. Option B is correct because a multi-catch block is simply an alternative form of a catch clause, so it can be freely combined with a finally block (and with other catch clauses) in the same try statement, e.g. try { ... } catch (IOException | SQLException e) { ... } finally { ... }. Option E is correct because the exception parameter types listed in a multi-catch must be disjoint — the compiler rejects alternatives where one type is a subclass of another (e.g. catch (IOException | FileNotFoundException e) fails), since the parameter is implicitly final and typed as the least upper bound of the alternatives. Option A is wrong because a multi-catch may combine checked and unchecked exception types, such as catch (IOException | IllegalArgumentException e), as long as the alternatives are disjoint. Option C is wrong because the multi-catch parameter is implicitly final, which is exactly why it cannot be reassigned inside the handler. Option D is wrong because multi-catch is independent of try-with-resources; it works with any try statement, with or without resources.

Answer

A multi-catch block cannot catch both checked and unchecked exceptions.

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The variable in a multi-catch block is not implicitly final.

Answer

A multi-catch block can only be used with try-with-resources.

Question 7

To generate a cryptographically secure random number for a key generation algorithm, which class should be used?

Accepted Answer

SecureRandom. D is correct because `SecureRandom` is specifically designed to produce cryptographically strong random numbers suitable for key generation, using algorithms like SHA1PRNG or NativePRNG that meet FIPS 140-2 standards. Unlike other random number generators, it ensures unpredictability and resistance to reverse engineering, which is critical for security-sensitive operations.

Answer

ThreadLocalRandom

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Math.random()

Answer

Random

Question 8

Which THREE are methods of the Map.Entry interface? (Java 17)

Accepted Answer

getValue(). The java.util.Map.Entry interface defines getKey() (option C), which returns the key corresponding to the entry, and getValue() (option A), which returns the value corresponding to the entry; both are core accessors used when iterating a map's entrySet(). It also defines setValue(V value) (option D), which replaces the value for this entry and returns the previous value, enabling in-place modification during iteration. Option B, getHash(), does not exist on Map.Entry (hashing is handled by hashCode() inherited from Object), and option E, getValueOrDefault(), is not a Map.Entry method — it is a default method on the Map interface (getOrDefault(Object key, V defaultValue)), so neither belongs here.

Answer

getHash()

Answer

getValueOrDefault()

Question 9

Which statement about Collection interface remove methods is correct?

Accepted Answer

Collection.remove(Object) removes the first occurrence and returns boolean.. The Collection interface's remove(Object) method removes the first occurrence of the specified element from the collection, if present, and returns true if the collection was modified (i.e., the element was found and removed). This behavior is defined in the Java Collections Framework and applies to all implementations of Collection, such as ArrayList and HashSet.

Answer

List.remove(int) removes element at index and returns the removed element.

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Collection.remove(Object) removes all occurrences of the element.

Answer

Both B and C

Question 10

You are developing a Java application that processes sensitive user data. The application runs on a server with strict security policies. You need to read configuration properties from a file located at /etc/app/config.properties. The application uses a SecurityManager. During testing, you get a security exception: java.security.AccessControlException: access denied (java.io.FilePermission /etc/app/config.properties read). You have already added a file permission grant in the policy file for the application codebase. However, the exception persists. What is the most likely cause?

Accepted Answer

A library or caller on the execution stack does not have the required FilePermission.. Even if the application's own codebase has the required FilePermission, any library or caller on the execution stack that does not have the permission will cause an AccessControlException. The SecurityManager performs stack inspection: every class on the call stack must have the required permission. If a library or framework method invoked by your code lacks the grant, the check fails.

Answer

The application codebase URL in the policy file is incorrect.

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The file path is relative and needs to be resolved against user.dir.

Answer

The policy file is not being loaded because the JVM was not started with -Djava.security.policy.