Fixed copyrights, indentation and added @NotNull to methods

[Iamwade]

Description (*)
Fixed the copyright block, added indents at the beginning of the class, and added a check for the parameters that the method accepts for null.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with integration/functional tests (if applicable)
• All automated tests passed successfully (all builds are green)