[#873] Fixed Checkstyle Issues In HIRS_STRUCTS

[ThatSilentCoder]

Description

Checkstyle is used for meeting best practices for java code styling. All classes in HIRS_Structs should be updated to pass checkstyle tests being run by gradle.

Test Instructions:

1. Follow steps 1 - 3 in this previous pull request: https://github.com/nsacyber/HIRS/pull/846to confirm you can save and apply checkstyle recommended styling changes to your code in your favorite IDE.
2. Run the command below to confirm that all the checkstyle errors for the HIRS_STRUCTS module have been fixed:
   ./gradlew clean HIRS_Structs:check --rerun-tasks
3. .Run the command below to confirm that there are no issues building or running tests for the entire application:
   ./gradlew clean build --rerun-tasks
4. If you were able to run all the commands without running into any issues, you have successfully verified that the checkstyles guidelines have been applied to the these HIRS_Structs module successfully.

Issues this PR addresses:

Closes issue #873