1Z0-829 Multiple Select — 50 Questions

Question 1

Which TWO statements about lambda expressions are true? (Choose two.)
A. A lambda expression can be assigned to a functional interface variable.
B. A lambda expression can access final or effectively final local variables.
C. A lambda expression can throw any checked exception.
D. A lambda expression can be used to create an instance of an abstract class.
E. A lambda expression can be used to implement multiple abstract methods.

Accepted Answer

A lambda expression can be assigned to a functional interface variable.. False: A lambda expression can only throw checked exceptions that are declared in the functional interface's abstract method, not any checked exception. Options B and C are true: a lambda can be assigned to a functional interface variable, and it can access final or effectively final local variables. Option D is false: a lambda can only implement one abstract method (functional interface). Option E is false: lambdas cannot instantiate abstract classes; they only implement functional interfaces.

Answer

A lambda expression can throw any checked exception.

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A lambda expression can be used to implement multiple abstract methods.

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A lambda expression can be used to create an instance of an abstract class.

Question 2

Which THREE of the following are true about the Optional class? (Choose three.)

Accepted Answer

Optional.empty().orElseThrow(IllegalStateException::new) throws IllegalStateException. `Optional.empty().orElseThrow(IllegalStateException::new)` explicitly throws a new `IllegalStateException` when the Optional is empty. The `orElseThrow` method is designed to throw the provided exception supplier's exception if no value is present.

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Optional.of(null) returns an empty Optional

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Optional.get() on empty Optional returns null

Question 3

Which THREE statements are true about loops in Java?

Accepted Answer

The break statement can be used to exit a loop prematurely.. The break statement in Java is used to immediately terminate the execution of a loop (for, while, or do-while) and transfer control to the statement following the loop. This allows premature exit based on a condition, which is a fundamental control flow mechanism in Java.

Answer

A while loop always executes at least once.

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A do-while loop may execute zero times if the condition is false.

Question 4

Which TWO of the following are valid ways to create a LocalDate object in Java 17?

Accepted Answer

LocalDate.of(2023, Month.JANUARY, 15). `LocalDate.of(int year, Month month, int dayOfMonth)` is a standard factory method that creates a `LocalDate` from explicit year, month, and day values. The `Month` enum provides type-safe month constants, making this a valid and commonly used approach.

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LocalDate.from(Instant.now())

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LocalDate.of(2023, 13, 1)

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LocalDate.ofEpochDay("19375")

Question 5

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

Accepted Answer

getValue(). The Map.Entry interface in Java defines the getValue() method, which returns the value associated with the entry's key. This method is part of the core contract for accessing key-value pairs within a Map.

Answer

getHash()

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getValueOrDefault()

Question 6

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.. The primary purpose of the sealed class feature is to explicitly control which other classes or interfaces are permitted to extend or implement it. This is achieved by using the `permits` clause to list the allowed subclasses, thereby restricting the inheritance hierarchy.

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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 7

Which TWO are valid ways to create an immutable List in Java?

Accepted Answer

Collections.unmodifiableList(new ArrayList<>()). `Collections.unmodifiableList()` returns a view of the specified list that cannot be structurally modified; any attempt to add, remove, or set elements will throw an `UnsupportedOperationException`. Option E is correct because `List.of()` (introduced in Java 9) directly creates an immutable list that disallows `null` elements and throws `UnsupportedOperationException` on mutation attempts.

Answer

Stream.of("a").collect(Collectors.toList())

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Arrays.asList("a", "b")

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new ArrayList<>()

Question 8

Which TWO statements are true about the java.time.Duration class? (Choose two.)

Accepted Answer

Duration represents a time-based amount of time, such as hours, minutes, seconds.. The java.time.Duration class models a time-based amount of time in terms of seconds and nanoseconds, which can represent hours, minutes, seconds, and smaller units. It is designed for time-based quantities, not date-based ones like days, months, or years.

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Duration.ofDays(1) returns a Duration that is daylight-saving-safe.

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Duration.between(LocalDate.now(), LocalDate.now().plusDays(1)) returns a Duration of 1 day.

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Duration can represent a period of months.

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 checked exceptions in Java?

Accepted Answer

SQLException. A is correct because `SQLException` is a subclass of `java.lang.Exception` (which is a checked exception class) and does not extend `RuntimeException`. Checked exceptions must be either caught or declared in the method signature; `SQLException` is commonly thrown when database access errors occur, such as connection failures or SQL syntax errors.

Answer

ArithmeticException

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ArrayIndexOutOfBoundsException

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NullPointerException

Question 11

Which two statements are true about the java.util.Comparator and java.lang.Comparable interfaces? (Choose two.)

Accepted Answer

Comparator can be used to sort a list in multiple ways.. The Comparator interface allows you to define multiple different comparison strategies (e.g., by name, by age, by salary) for the same class, enabling sorting of a list in multiple ways. Option D is correct because the Comparable interface is used to define a natural ordering of objects (e.g., String's lexicographic order, Integer's numeric order) by implementing the compareTo method.

Answer

Comparator's compare method returns a boolean.

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A class implementing Comparable must override equals().

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Comparator is in java.lang package.

Question 12

Which three of the following are valid methods in the String class in Java 17? (Choose three.)

Accepted Answer

translateEscapes(). `translateEscapes()` is a valid instance method introduced in Java 14 (and present in Java 17) that translates escape sequences (e.g., `
` to newline) in a string. Option C is correct because `toLowerCase(Locale)` is a standard overloaded method in the String class that converts all characters to lowercase using the specified locale. Option D is correct because `transform(Function<String, String>)` is a valid method added in Java 12 that applies the given function to the string and returns the result.

Answer

substring(int, int, Locale)

Answer

indent(String)

Question 13

Which THREE of the following are valid ways to create a new ArrayList<Integer>? (Select three.)

Accepted Answer

new ArrayList<>(Arrays.asList(1,2,3)). `Arrays.asList(1,2,3)` returns a fixed-size `List`, and passing it to the `ArrayList` constructor creates a new, mutable `ArrayList` containing the same elements. This is a standard way to initialize an `ArrayList` with known values.

Answer

new ArrayList<>(10, 20, 30)

Answer

(ArrayList<Integer>) Arrays.asList(1,2,3)

Question 14

Which two statements about the java.time.Duration class are true? (Choose two.)

Accepted Answer

Duration can be negative.. The java.time.Duration class can represent negative durations, such as when the end instant is before the start instant in a Duration.between() call. Option C is correct because all classes in the java.time package, including Duration, are immutable and thread-safe by design, ensuring safe concurrent access without synchronization.

Answer

Duration supports units like months and years.

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Duration.between(LocalDate.now(), LocalDate.now()) returns a Duration.

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Duration uses a days-based representation.

Question 15

Which TWO statements about Arrays.asList() are true? (Select two.)

Accepted Answer

It returns a fixed-size list backed by the original array.. `Arrays.asList()` returns a fixed-size list backed by the original array, meaning the list's size cannot be changed (no add or remove operations allowed). Option E is correct because any modification to the returned list (e.g., setting an element) directly modifies the underlying array, and vice versa, as the list is a view of the array.

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It supports adding and removing elements.

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It returns a new ArrayList with a copy of the elements.

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It can be used to convert an array to a mutable list if wrapped with new ArrayList<>().

Question 16

Which TWO are valid ways to create an immutable list in Java 17? (Choose two.)

Accepted Answer

Collections.unmodifiableList(new ArrayList<>(List.of("a", "b"))). `Collections.unmodifiableList()` wraps a mutable list in an unmodifiable view, preventing any structural modifications. Option D is correct because `List.copyOf()` creates an immutable list from an existing collection, throwing `NullPointerException` if any element is null. Both produce lists that cannot be modified after creation.

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Arrays.asList("a", "b")

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List.of(List.of("a", "b"))

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new ArrayList<>(List.of("a", "b"))

Question 17

Which THREE statements about the SecurityManager and security policies in Java 17 are true? (Choose three.)

Accepted Answer

The SecurityManager class is deprecated in Java 17.. The SecurityManager class is deprecated for removal in Java 17 (JEP 411). This deprecation means that while the class still exists for compatibility, it is no longer recommended for use and may be removed in a future release. The core reasoning is that the SecurityManager architecture is considered legacy and difficult to maintain, so Oracle has deprecated it to encourage developers to adopt alternative security mechanisms.

Answer

System.setProperty("java.security.policy", "policy.url") loads a new policy.

Answer

By default, Java 17 applications run with a SecurityManager installed.

Question 18

Which THREE statements about the jpackage tool are true?

Accepted Answer

jpackage can create native installers for Windows, macOS, and Linux.. The jpackage tool is designed to create native installers for Windows (e.g., .exe/.msi), macOS (e.g., .dmg), and Linux (e.g., .deb/.rpm). This is a core feature of jpackage, which replaces the older Java Packager and allows developers to distribute self-contained applications with platform-specific packaging formats.

Answer

jpackage requires an existing JRE to create a runtime image.

Answer

jpackage uses the Java Packager library.

Question 19

Which THREE statements about the switch statement in Java are correct?

Accepted Answer

The default case can be placed anywhere within the switch block.. The default case can be placed anywhere within the switch block according to the Java Language Specification. Option D is correct: case labels must be compile-time constant expressions; a final variable assigned a constant expression qualifies as a compile-time constant. Option E is correct: switch works with int, char, String, and enum types. Option B is incorrect because case values must be compile-time constants, not arbitrary runtime expressions. Option C is incorrect because break is not mandatory; it is optional and used to prevent fall-through.

Answer

Case values can be runtime expressions.

Answer

A break statement is mandatory after each case block.

Question 20

Which TWO statements about Java module types are true?

Accepted Answer

An automatic module exports all its packages.. The Java module system automatically exports all packages of an automatic module, making them accessible to other modules without explicit export declarations. This is a key characteristic of automatic modules, which are created from JAR files placed on the module path without a module-info.java file.

Answer

An automatic module can access all packages of named modules without explicit requires.

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The unnamed module can read only the java.base module.

Answer

The unnamed module is a named module.