Optional Class in Java - Multiple-Choice Questions (MCQs) with Answers

Java Optional Class Quiz

1: What is the purpose of the `Optional` class in Java?

a) To represent an optional value that may or may not be present.
b) To replace the `null` value with an empty string.
c) To create immutable objects.

2: Which method is used to create an `Optional` with a non-null value?

a) Optional.create()
b) Optional.ofNullable()
c) Optional.of()

3: Which method is used to access the value if present or return a default value?

a) getValue()
b) orElse()
c) obtain()

4: What does the method isPresent() check in the Optional class?

a) Checks if the value is non-null.
b) Checks if the value is present or empty.
c) Checks if the Optional object is initialized.

5: Which method is used to apply a mapping function to the value if it is present?

a) map()
b) transform()
c) apply()

6: What does the orElseThrow() method do?

a) Returns the value if present; otherwise, returns null.
b) Returns the value if present; otherwise, throws an exception.
c) Returns the value if present or an empty Optional.

7: What is the purpose of the filter() method in the Optional class?

a) To filter out null values.
b) To filter elements based on a predicate.
c) To filter out empty Optionals.

8: How does the ifPresent() method differ from orElseGet()?

a) ifPresent() returns a value; orElseGet() returns an empty Optional.
b) ifPresent() takes a Supplier; orElseGet() takes a Consumer.
c) ifPresent() takes a Consumer; orElseGet() takes a Supplier.

9: What is the purpose of the flatMap() method in the Optional class?

a) To flatten a nested Optional structure.
b) To map a value using a provided function.
c) To filter elements based on a predicate.

10: Which method is used to perform an action based on the presence or absence of a value, without returning any result?

a) ifPresentOrElse(Consumer action, Runnable emptyAction)
b) ifPresent(Consumer consumer)
c) perform(Consumer action)

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