refactor: fixing sonarqube issues in Pattern.java

[rishivijayv]

#2228

This fixes a few sonarqube warnings in the file Pattern.java that were pointed out by the SonarQube for IDE Plugin. Namely, the issues were:

• java:S1905 (Redundant casts should not be used)
• java:S1612 (Lambdas should be replaced with method references)
• java:S1602 (when a lambda expression uses block notation while expression notation could be used)

I believe removing the explicit cast to Map<...,...> also seems to get rid of one of the warnings during compile time, so...yay! ?

[rishivijayv]

@I-Al-Istannen @algomaster99 would appreciate your review of this whenever you guys get the chance! :)

[monperrus]

thanks @rishivijayv