/ephemeral replies with a Reveal a secret inline button. The command is registered with Telegram as an ephemeral command.
Pressing the button (reveal callback data) sends a personal message visible only to the user who pressed it. After three seconds the bot edits the message, then deletes it three seconds later.
When the bot receives an ephemeral content message, it sends two ephemeral replies: one through the general reply API and one through the explicit replyToEphemeral API.
Updates and basic bot information are printed to standard output.

Setup

Create a bot token, keep it secret, and add the bot to a group. The bot must be allowed to send messages there; this example does not request or validate group permissions itself. Use a Telegram environment that supports ephemeral messages.

Run

From the repository root, pass the token as the first application argument:

./gradlew :EphemeralMessagesBot:run --args="BOT_TOKEN"

Optional, case-sensitive arguments may follow the token:

debug enables formatted library logging on standard output.
testServer connects the bot to Telegram's test server.

For example:

./gradlew :EphemeralMessagesBot:run --args="BOT_TOKEN debug testServer"

The token is required; starting without it fails before polling begins. Stop the bot with Ctrl+C.