Done

src/main/java/mate/academy/service/AuthenticationService.java

@@ -1,16 +1,25 @@
 package mate.academy.service;
 
+import mate.academy.model.User;
+
 public class AuthenticationService {
+    private final UserService userService = new UserService();
+
     /**
      * Imagine that some user wants to login to your site.
      * You should check if user credentials (login and password) are valid or not.
      * All users are stored in <code>UserService</code> class.
-     * @param email - user's email
+     *
+     * @param email    - user's email
      * @param password - user's password
      * @return true if user by email exists and passed password is equal to user's password.
      * Return false in any other cases.
      */
     public boolean login(String email, String password) {
+        User loginUser = userService.findByEmail(email);
+        if (loginUser != null && loginUser.getPassword().equals(password)) {
+            return true;
+        }
         return false;
     }
 }

src/main/java/mate/academy/service/UserService.java

@@ -3,18 +3,25 @@
 import mate.academy.model.User;
 
 public class UserService {
-    private static final User[] users = new User[] {
+    private static final User[] users = new User[]{
             new User("[email protected]", "1234"),
             new User("[email protected]", "1234")
     };
 
     /**
      * Find user by email. All users are stored in <code>private static final User[] users</code>
+     *
      * @param email - the input parameter
      * @return - user if his email is equal to passed email.
      * Return <code>null</code> if there is no suitable user
      */
     public User findByEmail(String email) {
+        for (User user : users) {
+            if (user.getEmail().equals(email)) {
+                return user;
+            }
+
+        }
         return null;
     }
 }