code and setup

src/main/java/models/User.java

@@ -0,0 +1,42 @@
+package models;
+
+public abstract class User {
+    protected String username;
+    protected String password;  // ساده نگه می‌داریم برای سطح مقدماتی
+
+    public User(String username, String password) {
+        this.username = username;
+        this.password = password;
+    }
+
+    public String getUsername() { return username; }
+
+    public boolean checkPassword(String password) {
+        return this.password.equals(password);
+    }
+
+    public static String validateUsername(String username) {
+        if (username == null || username.trim().isEmpty()) {
+            return "Username cannot be empty!";
+        }
+        if (username.length() < 3) {
+            return "Username must be at least 3 characters!";
+        }
+        return null;
+    }
+
+    public static String validatePassword(String password) {
+        if (password == null || password.length() < 4) {
+            return "Password must be at least 4 characters!";
+        }
+        return null;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null || getClass() != obj.getClass()) return false;
+        User user = (User) obj;
+        return username.equalsIgnoreCase(user.username);
+    }
+}