sdk-for-kotlin/docs/examples/java/sites/update-variable.md

import io.appwrite.Client;
import io.appwrite.coroutines.CoroutineCallback;
import io.appwrite.services.Sites;

Client client = new Client()
    .setEndpoint("https://<REGION>.cloud.appwrite.io/v1") // Your API Endpoint
    .setProject("<YOUR_PROJECT_ID>") // Your project ID
    .setKey("<YOUR_API_KEY>"); // Your secret API key

Sites sites = new Sites(client);

sites.updateVariable(
    "<SITE_ID>", // siteId
    "<VARIABLE_ID>", // variableId
    "<KEY>", // key
    "<VALUE>", // value (optional)
    false, // secret (optional)
    new CoroutineCallback<>((result, error) -> {
        if (error != null) {
            error.printStackTrace();
            return;
        }

        System.out.println(result);
    })
);