Jump into our engaging blog post for a quiz on Java Streams. It’s the perfect chance to test your skills and learn more about handling data in Java!
Java Streams are a feature that helps you process collections of data declaratively. They allow you to perform complex operations on data sets easily, such as filtering, sorting, and searching, without the need for complicated loops and conditionals. Understanding streams is crucial for writing clean, efficient Java code that handles data processing.
Tackle our MCQs to sharpen your understanding of Java Streams. Whether you’re a seasoned programmer or new to Java, this quiz is a great way to challenge yourself and enhance your coding capabilities. Ready to stream through some questions? Let’s get started!
1. What is a Stream in the context of the Java 8 Stream API?
Answer:
Explanation:
In the Java 8 Stream API, a Stream represents a sequence of data elements that can be processed in parallel or sequentially. It allows for efficient and functional-style operations on collections of data. Streams provide a way to perform operations on a collection of elements, such as filtering, mapping, and reducing. They enable concise and expressive code for data manipulation tasks.
2. Which interface represents a sequence of elements on which one or more operations can be performed?
Answer:
Explanation:
The Stream interface represents a sequence of objects, allowing various operations to be performed.
3. Which of the following is not a terminal operation in the Stream API?
Answer:
Explanation:
map is an intermediate operation that transforms the elements of the stream.
4. Which method is used to create a Stream from a collection in Java 8?
Answer:
Explanation:
The stream() method is used to create a Stream from a collection in Java 8. It is available on any collection object and returns a sequential Stream.
5. What is the purpose of the filter() operation in the Stream API?
Answer:
Explanation:
The filter() operation is used to filter elements based on a condition in the Stream API. It takes a Predicate as an argument and returns a new Stream containing only the elements that satisfy the given condition.
6. What is the purpose of the map() operation in the Stream API?
Answer:
Explanation:
map is an intermediate operation that transforms the elements of the stream.
7. What is the difference between intermediate and terminal operations in the Stream API?
Answer:
Explanation:
Intermediate operations in the Stream API return a new Stream that can be further processed, while terminal operations produce a final result or perform a side effect.
8. What is the output of the following Stream operation?
Stream.of(1, 2, 3, 4).map(i -> i * 2).collect(Collectors.toList())
Answer:
Explanation:
The map() operation multiplies each element of the Stream by 2, resulting in the output [2, 4, 6, 8].
9. What is the purpose of the collect() method in the Stream API?
Answer:
Explanation:
The collect() method is used to accumulate the elements of a Stream into a collection or a summary result.
10. Which of the following can turn a Stream into a Stream>?
Answer:
Explanation:
Using map with a function that returns a Stream would result in a Stream
11. Which method will return a stream without any duplicates?
Answer:
Explanation:
The distinct method returns a stream consisting of the distinct elements.
12. Which of the following operations is stateful?
Answer:
Explanation:
A stateful operation, such as sorted, may incorporate state from previously seen elements when processing new elements.
13. Which method can produce a Stream from an array?
Answer:
Explanation:
Arrays.stream() method provides a way to obtain a stream from an array.
14. What will the following code return?
Stream<String> stream = Stream.of("a", "b", "c");
Optional<String> result = stream.filter(s -> s.equals("d")).findFirst();
Answer:
Explanation:
Since there’s no “d” in the stream, findFirst() will return Optional.empty.
15. Which operation can transform a Stream into a Stream representing the length of each string?
Answer:
Explanation:
The map operation can transform the type of elements in a stream. For instance, using map(s -> s.length()) will achieve the transformation in the question.
16. Which method in the Stream API can be used to obtain the average of IntStream?
Answer:
Explanation:
The average() method is specifically available for IntStream, LongStream, and DoubleStream and it returns an OptionalDouble representing the average of the elements.