Question

This function will receive a list of elements with duplicate elements, this function should remove the duplicate elements in the list and return a list without duplicate elements. The elements in the returned list must be in the same order that they were found in the list the function received. A duplicate element is an element found more than one time in the specified list.

JAVA

Answer 1

If you have any problem with the code feel free to comment.

Program

import java.util.ArrayList;
import java.util.function.Predicate;

public class Test {
        public static void main(String[] args) {
                ArrayList<Integer> list = new ArrayList<>();
                list.add(1);
                list.add(2);
                list.add(1);
                list.add(5);
                list.add(2);
                list.add(4);
                list.add(2);
                System.out.println("Duplicate list: " + list);
                System.out.println("Non duplicate list: " + removeDuplicates(list));
        }

        public static <T> ArrayList<T> removeDuplicates(ArrayList<T> list) {
                ArrayList<T> newList = new ArrayList<>(list);

                // replacing the duplicate items with null
                for (T item : newList) {
                        if (item == null)
                                continue;
                        int count = 0;
                        for (int i = 0; i < newList.size(); i++) {
                                if (item.equals(newList.get(i)))
                                        count++;
                                if (item.equals(newList.get(i)) && count > 1) {
                                        newList.set(i, null);
                                }
                        }
                }

                // removing all null values from the list
                newList.removeIf((Predicate<T>) ((t) -> t == null));

                return newList;
        }

}

Output