Java 8 Program to Remove Duplicates from LinkedList

Learn how to remove duplicates from LinkedList in Java using Java 8 Stream API and distinct() method with examples. LinkedList is one of the most commonly used collection classes in Java. Sometimes a LinkedList may contain duplicate elements that need to be removed before further processing.

Code Explanation (Step-by-Step)

  • Convert the array elements into a List using the Arrays.asList() method.
  • Create a LinkedList object and pass the list to its constructor.
  • Convert the LinkedList into a stream using the stream() method.
  • Use the distinct() method to remove duplicate elements from the stream .
  • Use Collectors.toList() to collect the unique elements into a new list.
  • Print the list containing the unique elements.
				
					import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;

public class RemoveDuplicates {

    public static void main(String[] args) {

        List<Integer> list = Arrays.asList(1, 2, 3, 5, 6, 1, 2, 3);

        LinkedList<Integer> linkedList = new LinkedList<>(list);

        List<Integer> number = linkedList.stream()
                                         .distinct()
                                         .collect(Collectors.toList());

        System.out.println("Number List: " + number);
    }
}

Output :-
Number List :- [1, 2, 3, 5, 6]

How distinct() Method Works

The distinct() method is a convenient way to remove duplicate elements from a stream. It processes each element, keeps only the first occurrence, and returns a stream containing unique values while preserving the original order.
Syntax : stream.distinct()

Can distinct() be used with parallel streams?

distinct() method can be used with parallel streams. it will remove duplicate elements across multiple threads. Since distinct() is a stateful intermediate operation, maintaining uniqueness and encounter order can reduce some of the performance benefits of parallel processing.

				
					import java.util.Arrays;
import java.util.List;

public class DistinctParallelStream {

    public static void main(String[] args) {

        List<Integer> numbers = Arrays.asList(1, 2, 3, 2, 4, 1, 5, 3);

        numbers.parallelStream()
               .distinct()
               .forEach(System.out::println);
    }
}

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