1. Introduction

In Java, a List can contain duplicate elements. There are several ways to remove duplicates from a List, one common way is by using a Set. A Set is a Collection that does not allow duplicate elements. In this tutorial, we will demonstrate how to remove duplicate elements from a List using a Set.

2. Program Steps

1. Import the necessary classes.

2. Create a List with some duplicate elements.

3. Convert the List to a Set to remove the duplicate elements.

4. Convert the Set back to a List.

5. Print the original and the modified List.

3. Code Program

// Step 1: Importing necessary classes
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class RemoveDuplicates {

    public static void main(String[] args) {

        // Step 2: Creating a List with some duplicate elements
        List<String> listWithDuplicates = new ArrayList<>();
        listWithDuplicates.add("Apple");
        listWithDuplicates.add("Banana");
        listWithDuplicates.add("Cherry");
        listWithDuplicates.add("Apple");
        listWithDuplicates.add("Banana");

        // Printing the original list
        System.out.println("Original List: " + listWithDuplicates);

        // Step 3: Converting the List to a Set to remove the duplicate elements
        Set<String> setWithoutDuplicates = new HashSet<>(listWithDuplicates);

        // Step 4: Converting the Set back to a List
        List<String> listWithoutDuplicates = new ArrayList<>(setWithoutDuplicates);

        // Printing the modified list
        System.out.println("List Without Duplicates: " + listWithoutDuplicates);
    }
}

Output:

Original List: [Apple, Banana, Cherry, Apple, Banana]
List Without Duplicates: [Banana, Cherry, Apple]

4. Step By Step Explanation

Step 1: Import the necessary classes. In this case, we import ArrayList, HashSet, List, and Set.

Step 2: Create a List named listWithDuplicates and add some elements to it, including duplicates.

Step 3: Create a Set named setWithoutDuplicates and initialize it with the elements of listWithDuplicates. Since a Set does not allow duplicate elements, this will effectively remove any duplicates from the List.

Step 4: Convert setWithoutDuplicates back to a List named listWithoutDuplicates.

Finally, print the original listWithDuplicates and the listWithoutDuplicates to observe the removal of duplicate elements.