Remove Duplicates from a Java List

Removing duplicates from a Java List can be achieved by utilizing various techniques. This process involves identifying and eliminating duplicate elements, resulting in a list with unique values.

The code examples below show how to remove duplicate elements from a List in Java. These examples illustrate different techniques that can be used to achieve this task:

Example 1:

List<String> list = Arrays.asList("Apple@example.com", "apple@example.com",
                      "tello@example.com", "bello@example.com");

List<String> uniqueList = list.stream().map(String::toLowerCase)
                            .distinct().collect(Collectors.toList());

System.out.println("Unique list: " + uniqueList);

Ouput:

Unique list: [apple@example.com, tello@example.com, bello@example.com]

Example 2:

List<String> list = Arrays.asList("Apple@example.com", "apple@example.com",
                "tello@example.com", "bello@example.com");

ListIterator<String> iterator = list.listIterator();

while (iterator.hasNext()) {
    iterator.set(iterator.next().toLowerCase());
}

Set<String> newSet = new HashSet<>(list);
List<String> uniqueList = new ArrayList<>();
uniqueList.addAll(newSet);

System.out.println("Unique list: " + uniqueList);

Output:

Unique list: [bello@example.com, tello@example.com, apple@example.com]