Requirements
------------

OkHttp works on Android 5.0+ (API level 21+) and Java 8+.

On Android, OkHttp uses [AndroidX Startup][androidx_startup]. If you disable the initializer in the manifest,
then apps are responsible for calling `OkHttp.initialize(applicationContext)` in `Application.onCreate`.

import okhttp3.WebSocket;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.WebSocketListener;
import okio.ByteString;

/**
 * API access to the <a href="https://api.slack.com/apps">Slack API</a> as an application. One
 * instance of this class may operate without a user, or on behalf of many users. Use the Slack API
 * dashboard to create a client ID and secret for this application.
 *

              .addTrustedCertificate((X509Certificate) isgCertificate)
              // Uncomment to allow connection to any site generally, but will cause
              // noticeable memory pressure in Android apps.
//              .addPlatformTrustedCertificates()
              .build();

      builder.sslSocketFactory(certificates.sslSocketFactory(), certificates.trustManager());
    }

    // the behaviour of the non-GWT implementation of newConcurrentHashSet().
    // On the other hand HashSet might be better for code size if apps aren't
    // already using Collections.newSetFromMap and ConcurrentHashMap.
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }