Correlation function for discrete variable correlation (#7326)

* Correlation function for discrete variable correlation

* Add unit tests for Correlation class

Added unit tests for the Correlation class to validate correlation calculations under various scenarios, including linear dependence and constant values.

* Added missing bracket

* Refactor variable initialization in correlation method

* Remove unused imports and clean up CorrelationTest

* Fix formatting of variable declarations in correlation method

* Update Correlation.java

* Fix formatting in CorrelationTest.java

* Enhance comments in correlation function

Added detailed comments to the correlation function for better understanding.

* Add correlation tests for various scenarios

* Format comments for clarity in correlation method

* Fix formatting and comments in correlation method