如何验证KeyCloak userModel中是否存在用户

import org.keycloak.admin.client.Keycloak;
import org.keycloak.admin.client.KeycloakBuilder;
import org.keycloak.representations.idm.UserRepresentation;

public class KeyCloakUserValidation {
    public static void main(String[] args) {
        // KeyCloak服务器的URL、Realm、Client ID等信息
        String serverUrl = "http://localhost:8080/auth";
        String realm = "your_realm";
        String clientId = "your_client_id";
        String username = "your_username";

        // KeyCloak管理员的用户名和密码
        String adminUsername = "admin";
        String adminPassword = "admin_password";

        // 创建Keycloak实例
        Keycloak keycloak = KeycloakBuilder.builder()
                .serverUrl(serverUrl)
                .realm(realm)
                .clientId(clientId)
                .username(adminUsername)
                .password(adminPassword)
                .build();

        // 获取用户模型中的用户列表
        List<UserRepresentation> users = keycloak.realm(realm).users().list();

        // 遍历用户列表，查找指定用户名的用户
        boolean userExists = false;
        for (UserRepresentation user : users) {
            if (user.getUsername().equals(username)) {
                userExists = true;
                break;
            }
        }

        // 打印验证结果
        if (userExists) {
            System.out.println("用户存在");
        } else {
            System.out.println("用户不存在");
        }
    }
}