Java 8 FAQ: Top Questions

The distinct() method in Java 8 Streams is used to remove duplicate elements from a stream. It uses the equals() method of objects to determine uniqueness and works on both object and primitive streams.

🗺️ Step-by-Step Instructions:

1. Call distinct() on a stream to filter out duplicates.
2. It uses equals() and hashCode() for comparison.
3. Follow it with a terminal operation like collect() or forEach().

📥 Example Input:

List words = Arrays.asList("apple", "banana", "apple", "orange", "banana");

🏆 Expected Output:

[apple, banana, orange]

✅ Java 8 Solution:

import java.util.*;
import java.util.stream.*;

public class DistinctExample {
  public static void main(String[] args) {
    List words = Arrays.asList("apple", "banana", "apple", "orange", "banana");

    List uniqueWords = words.stream()
                                    .distinct()
                                    .collect(Collectors.toList());

    System.out.println(uniqueWords);
  }
}

📘 Detailed Explanation:

• distinct(): Filters out duplicate elements using equals().
• Only works properly if the objects implement equals() and hashCode() correctly.
• Maintains the encounter order of the stream.

🛠️ Use Cases:

• Removing duplicates from a collection during stream processing.
• Pre-cleaning lists for further transformation or aggregation.
• Extracting unique records for reporting or display.