Quiz for Optional, Method References

Q1: What does the Optional class help with in Java 8?

A. Handling exceptions B. Avoiding null pointer exceptions C. Creating threads D. Parsing dates

Q2: How do you create an empty Optional?

A. Optional.empty() B. Optional.of(null) C. new Optional() D. Optional.get()

Q3: Which method is used to get the value inside Optional if present?

A. fetch() B. value() C. get() D. obtain()

Q4: What is the purpose of Optional.ofNullable()?

A. It creates an empty Optional B. It creates an Optional that can hold a null value C. It forces a non-null value D. It throws NullPointerException

Q5: Which method reference is valid syntax?

A. String.length B. System::out C. System.out::println D. new String::valueOf

Q6: Which functional interface is commonly used with method references?

A. Runnable B. Comparable C. Function D. Map

Q7: What does Optional.orElse() do?

A. Throws exception if value is null B. Returns value if present, otherwise a default C. Returns null D. Always returns default value

Q8: Which is not a method of Optional?

A. ifPresent() B. map() C. filter() D. sort()

Q9: Which type of method reference is used for static methods?

A. ClassName::staticMethodName B. object::instanceMethod C. ClassName::new D. objectName::staticMethodName

Q10: Which method will throw NoSuchElementException if value not present?

A. orElse() B. get() C. orElseGet() D. isPresent()

Q11: What is the output of Optional.of(null)?

A. null B. empty Optional C. NullPointerException D. Compile error

Q12: What type does Optional<T> represent?

A. A thread-safe object B. A container that may hold a non-null value C. A generic collection D. A stream of values

Q13: Which method reference syntax creates a new object?

A. ClassName::new B. new::ClassName C. Object::new D. Class.new()

Q14: Optional.map() is used to:

A. Get a value directly B. Transform the value if present C. Create new Optional D. Print the value

Q15: Optional.ifPresent() accepts:

A. Consumer B. Function C. Supplier D. Runnable

Q16: What is the purpose of orElseGet()?

A. Returns fallback value only when needed B. Always returns fallback value C. Throws exception D. Clears the value

Q17: Which is a benefit of method references?

A. Avoids null values B. More readable and concise code C. Improves performance significantly D. Disables exceptions

Q18: What does Optional.filter() do?

A. Filters a collection B. Returns same Optional if predicate true C. Removes null values D. Deletes Optional value

Q19: Which interface works with constructor references?

A. Runnable B. Supplier C. Function D. Predicate

Q20: Optional is part of which package?

A. java.optional B. java.util C. java.util.function D. java.core