1. What is the output of this code?

Stream.of("a", "b", "c")

    .map(String::toUpperCase)

    .forEach(System.out::print);

 

  1. abc
     B. ABC
     C. a b c
     D. Compilation Error

✅ Answer: B. ABC

2. Which of the following is a valid functional interface in Java 8?

  1. An interface with two abstract methods
     B. An interface with one abstract method and multiple default methods
     C. An interface with no methods
     D. A class with one method

✅ Answer: B

3. What does Optional.empty() return?

  1. Null
     B. Optional with null value
     C. An Optional instance with no value present
     D. Compilation error

✅ Answer: C

4. Which interface does Function<T, R> belong to?

  1. java.lang
     B. java.io
     C. java.util
     D. java.util.function

✅ Answer: D

5. What is the purpose of Collectors.toList()?

  1. It converts a stream to a set
     B. It terminates the stream
     C. It collects stream elements into a list
     D. It sorts a list

✅ Answer: C