Post a Tweet with twitter4j
From this response below, I think you are using this API.
401:Authentication credentials (https://dev.twitter.com/pages/auth) were missing or incorrect. Ensure that you have set valid consumer key/secret, access token/secret, and the system clock is in sync.
{"request":"\/1.1\/media\/upload.json","error":"Read-only application cannot POST."}
As there is an error message like below you need to create a Twitter application with Read & Write permissions. For more details about error messages, check this.
Read-only application cannot POST.
Here is the official developer document about app permissions.
Change this:
to this:
I hope, this is clear enough.