package domain;

import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Users {
    private final List<User> usersList = new ArrayList<>();

    public Users() {
        super();
    }

    public Users(User... user) {
        usersList.addAll(Arrays.asList(user));
    }

    public Users(Users users) {
        usersList.addAll(users.usersList);
    }

    public boolean contains(User user) {
        return usersList.contains(user);
    }

    public void add(User user) {
        usersList.add(user);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }

        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        Users users = (Users) o;

        return new EqualsBuilder()
                .append(usersList, users.usersList)
                .isEquals();
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder(17, 37)
                .append(usersList)
                .toHashCode();
    }
}

@@ -145,20 +145,17 @@
 il.Array
-List
+s
 ;%0Aimport
@@ -157,38 +157,39 @@
 mport java.util.
-Arrays
+HashSet
 ;%0Aimport java.ut
@@ -191,19 +191,18 @@
 va.util.
-Lis
+Se
 t;%0A%0Apubl
@@ -236,19 +236,18 @@
 e final 
-Lis
+Se
 t%3CUser%3E 
@@ -247,16 +247,22 @@
 %3CUser%3E u
+niqueU
 sersList
@@ -272,16 +272,14 @@
 new 
-ArrayLis
+HashSe
 t%3C%3E(
@@ -361,32 +361,38 @@
 ser) %7B%0A        u
+niqueU
 sersList.addAll(
@@ -453,32 +453,38 @@
 ers) %7B%0A        u
+niqueU
 sersList.addAll(
@@ -486,24 +486,30 @@
 dAll(users.u
+niqueU
 sersList);%0A 
@@ -571,16 +571,22 @@
 return u
+niqueU
 sersList
@@ -651,16 +651,22 @@
        u
+niqueU
 sersList
@@ -975,32 +975,38 @@
        .append(u
+niqueU
 sersList, users.
@@ -1006,16 +1006,22 @@
  users.u
+niqueU
 sersList
@@ -1168,16 +1168,22 @@
 append(u
+niqueU
 sersList

Change Users internal implementation for unique list of users from List to Set, also renamed usersList to uniqueUsersList