Can't push to the heroku

Question

I was pushing the current git repository into the heroku. That online application was developed using Scala and IntelliJ. And I don't know how to fix this error.

$ git push heroku master
Counting objects: 3, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 531 bytes | 0 bytes/s, done.
Total 3 (delta 0), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: 
remote:  !     No default language could be detected for this app.
remote:             HINT: This occurs when Heroku cannot detect the         buildpack to use for this application automatically.
remote:             See https://devcenter.heroku.com/articles/buildpacks
remote: 
remote:  !     Push failed
remote: Verifying deploy....
remote: 
remote: !   Push rejected to salty-coast-14102.
remote: 
To https://git.heroku.com/salty-coast-14102.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/salty-coast-14102.git'

Answer 1

Read this doc which will explain to you what to do.
https://devcenter.heroku.com/articles/buildpacks

Setting a buildpack on an application

You can change the buildpack used by an application by setting the buildpack value.
When the application is next pushed, the new buildpack will be used.

$ heroku buildpacks:set heroku/php

Buildpack set. Next release on random-app-1234 will use heroku/php.
Run git push heroku master to create a new release using this buildpack.

This is whay its not working for you since you did not set it up.

... When the application is next pushed, the new buildpack will be used.

You may also specify a buildpack during app creation:

$ heroku create myapp --buildpack heroku/python