How can I use String and Integer variables it together in "Velocity"?
#set ($var1 = "exp"+1)
I tried a few times but I could not.
Any help will be highly appreciated.
If you were trying to do concatenation, it's not supported by Velocity, not even for 2 Strings. Instead, you should use string interpolation. Example:
#set ($string = "exp")
#set ($number = 1)
#set ($interpolatedExample1 = "$string$number")
#set ($interpolatedExample2 = "${string}someStringLiteral$number")
Read more details and examples in the documentation.