Fix java language level issues

[sigee]

What changes were proposed in this pull request?

• Replace String.indexOf() calls with String.contains() method for improved readability
• Remove unnecessary explicit type parameters
• Replace try-finally statement with try-with-resources
• Replace Anonymous types with lambda

[github-actions]

This pull request has been automatically marked as stale because it has had no activity for at least 3 months. If you are still working on this change or plan to move it forward, please leave a comment or push a new commit so we know to keep it open. Otherwise, this PR will be closed automatically in about one month. Thank you for your contribution to Apache Livy!