improve code quality

Description

collection of code quality improvements containing:
-organize imports
-make code reusable or reduce complexity
-better javadoc
-codacy fixes
-update code header copyright/license statement
and other not bug/feature related code improvements

Environment

None

Assignee

Matthias Eichner

Reporter

Matthias Eichner

Labels

None

URL

None

External issue ID

None

Fix versions

Priority

Medium
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