Herokuを使ってGitHub連携でデプロイするときにエラーが発生します。

ローカルPC：Windows10

javaで簡単なアプリケーションを作ったので試しにデプロイしてみようと思ったのでいろいろ試していたところ、いくつかエラーが出てしまい、下記サイトを参考に色々試しました。

https://qiita.com/ShandyGaffLover/items/0dad6ebf48d649aab761

このサイトの　②「pom.xmlが見つからない」と言われてビルドされない　を解決したあと、再度デプロイを試してみると下記のようなエラーが出たのですが、これはなにでエラーが出ているのでしょうか？
エラー内容の説明と、解決方法をご協力をお願いしたいです。

-----> Java app detected
-----> Installing JDK 1.8... done
-----> Installing Maven 3.6.2... done
-----> Executing Maven
       $ mvn -DskipTests clean dependency:list install
       [INFO] Scanning for projects...
       [INFO] 
       [INFO] ------------------< com.example:java-getting-started >------------------
       [INFO] Building java-getting-started 1.0
       [INFO] --------------------------------[ jar ]---------------------------------
       [INFO] 
       [INFO] --- maven-clean-plugin:3.1.0:clean (default-clean) @ java-getting-started ---
       [INFO] 
       [INFO] --- maven-dependency-plugin:3.1.2:list (default-cli) @ java-getting-started ---
       [INFO] 
       [INFO] --- spring-boot-maven-plugin:2.3.0.RELEASE:build-info (default) @ java-getting-started ---
       [INFO] 
       [INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ java-getting-started ---
       [INFO] Using 'UTF-8' encoding to copy filtered resources.
       [INFO] skip non existing resourceDirectory /tmp/build_41245e83_/src/main/resources
       [INFO] skip non existing resourceDirectory /tmp/build_41245e83_/src/main/resources
       [INFO] 
       [INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ java-getting-started ---
       [INFO] No sources to compile
       [INFO] 
       [INFO] --- maven-resources-plugin:3.1.0:testResources (default-testResources) @ java-getting-started ---
       [INFO] Using 'UTF-8' encoding to copy filtered resources.
       [INFO] skip non existing resourceDirectory /tmp/build_41245e83_/src/test/resources
       [INFO] 
       [INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-testCompile) @ java-getting-started ---
       [INFO] No sources to compile
       [INFO] 
       [INFO] --- maven-surefire-plugin:2.22.2:test (default-test) @ java-getting-started ---
       [INFO] Tests are skipped.
       [INFO] 
       [INFO] --- maven-jar-plugin:3.2.0:jar (default-jar) @ java-getting-started ---
       [INFO] Building jar: /tmp/build_41245e83_/target/java-getting-started-1.0.jar
       [INFO] 
       [INFO] --- spring-boot-maven-plugin:2.3.0.RELEASE:repackage (repackage) @ java-getting-started ---
       [INFO] ------------------------------------------------------------------------
       [INFO] BUILD FAILURE
       [INFO] ------------------------------------------------------------------------
       [INFO] Total time:  3.990 s
       [INFO] Finished at: 2020-08-13T17:34:22Z
       [INFO] ------------------------------------------------------------------------
       [ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.3.0.RELEASE:repackage (repackage) on project java-getting-started: Execution repackage of goal org.springframework.boot:spring-boot-maven-plugin:2.3.0.RELEASE:repackage failed: Unable to find main class -> [Help 1]
       [ERROR] 
       [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
       [ERROR] Re-run Maven using the -X switch to enable full debug logging.
       [ERROR] 
       [ERROR] For more information about the errors and possible solutions, please read the following articles:
       [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
 !     ERROR: Failed to build app with Maven
       We're sorry this build is failing! If you can't find the issue in application code,
       please submit a ticket so we can help: https://help.heroku.com/
 !     Push rejected, failed to compile Java app.
 !     Push failed