implemented login and findByEmail

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

@@ -1,16 +1,14 @@
 package mate.academy.service;
 
+import mate.academy.model.User;
+
 public class AuthenticationService {
-    /**
-     * 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 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.
-     */
+
+    private final UserService userService = new UserService();
+
     public boolean login(String email, String password) {
-        return false;
+        UserService userService = new UserService();
+        User user = userService.findByEmail(email);
+        return user == null ? false : user.getPassword().equals(password);
     }
 }

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

@@ -15,6 +15,11 @@ public class UserService {
      * 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;
     }
 }