Expression  -   java.lang.Character.toString ((char) $V{REPORT_COUNT}+96)
trying to convert A,B,C,D....
while converting error is coming 
Caused by: groovy.lang.MissingMethodException: No signature of method: static java.lang.Character.toString() is applicable for argument types: (java.lang.Integer) values: [97]
Possible solutions: toString(), toString(), toString(), toString(char)