square - okhttp - OkHttpClient cannot be resolved
Try Removing your import, and just go to this line
OkHttpClient client = new OkHttpClient();
move your cursor to OkHttpClient
and press Alt+Enter, you will see 2 classes to choose import from as you can see in this image:
So basically there are two types of imports available
1). import com.squareup.okhttp.OkHttpClient;
2). import okhttp3.OkHttpClient;
and yours is matching none of them, Please try to import the correct one, depending upon your requirements.