make some changes

jv-oop-lesson-01/src/main/java/mate/academy/service/AuthenticationService.java

@@ -21,13 +21,8 @@ public class AuthenticationService  {
      * Return false in any other cases.
      */
     public boolean login(String email, String password) {
-        boolean a = true;
-        for (int i = 0; i < users.length; i++) {
-            if (email.equals(users[i].getEmail()) && password.equals(users[i].getPassword())) {
-                a = true;
-            }
-            else a = false;
-        }
-        return a;
+        UserService userService = new UserService();
+        User user = userService.findByEmail(email);
+        return user != null && user.getPassword().equal(password);
     }
-}
+}

jv-oop-lesson-01/src/main/java/mate/academy/service/UserService.java

@@ -15,12 +15,12 @@ public class UserService {
      * @return - user if his email is equal to passed email.
      * Return <code>null</code> if there is no suitable user
      */
-    public String findByEmail(String email) {
-        String a = null;
-        for (int i = 0; i < users.length; i++)
-            if (email.equals(users[i].getEmail())) {
-                a = String.valueOf(users[i]);
+    public User findByEmail(String email) {
+        for (User user : users) {
+            if (user.getEmail().equals(email)) {
+                return user;
             }
-        return a;
+        }
+        return null;
     }
-}
+}