Java - remove duplicates from ArrayList

In this article, we would like to show you how to remove duplicates from ArrayList in Java.

In the following example, to remove duplicates from letters ArrayList, we create a new ArrayList (filtered) and add the first appearance of each element from letters using contains() method. As a result, we receive a new ArrayList without duplicates.

Practical example:

import java.util.*;

public class Example {

    public static void main(String[] args) {
        List<String> letters = new ArrayList<>();

        letters.add("A");
        letters.add("A");
        letters.add("B");
        letters.add("B");
        letters.add("C");
        letters.add("C");

        List<String> filtered = new ArrayList<>();

        for (String letter : letters) {
            if (!filtered.contains(letter)) {
                filtered.add(letter);
            }
        }

        System.out.println("Original ArrayList: " + letters);
        System.out.println("Without duplicates: " + filtered);
    }
}

Output:

Original ArrayList: [A, A, B, B, C, C]
Without duplicates: [A, B, C]