Java Program To Remove Duplicate Elements From List

Chapter: Miscellaneous Last Updated: 07-10-2023 07:01:17 UTC

Program:

            /* ............... START ............... */
                

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class RemoveDuplicatesFromList {
    public static void main(String[] args) {
        // Create a list with duplicate elements
        List<Integer> listWithDuplicates = new ArrayList<>();
        listWithDuplicates.add(1);
        listWithDuplicates.add(2);
        listWithDuplicates.add(3);
        listWithDuplicates.add(2);
        listWithDuplicates.add(4);
        listWithDuplicates.add(1);

        // Create a Set to store unique elements
        Set<Integer> uniqueSet = new HashSet<>();

        // Iterate through the original list and add elements to the set
        // Duplicate elements will automatically be removed
        for (Integer element : listWithDuplicates) {
            uniqueSet.add(element);
        }

        // Create a new list to store the unique elements
        List<Integer> listWithoutDuplicates = new ArrayList<>(uniqueSet);

        // Print the list without duplicates
        System.out.println("List with duplicates: " + listWithDuplicates);
        System.out.println("List without duplicates: " + listWithoutDuplicates);
    }
}

                /* ............... END ............... */
        

Output

List with duplicates: [1, 2, 3, 2, 4, 1]
List without duplicates: [1, 2, 3, 4]

Notes:

  • First we create a list called listWithDuplicates containing some duplicate elements.
  • In next step create a HashSet called uniqueSet to store the unique elements from the original list. The HashSet automatically removes duplicates because it doesn't allow duplicate elements.
  • Then we iterate through the original list and add each element to the uniqueSet.
  • Finally, we create a new list called listWithoutDuplicates and initialize it with the elements from the uniqueSet. This gives us a list without duplicate elements.
  • When you run this program, you will see that the list listWithoutDuplicates contains the unique elements from the original list, and duplicates are removed.
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