create a variable In subreport  say returnValue

variable class type --> whatever u want

calculation type --> nothing

reset type and increment type -->none

variable expression --> value you want to return

In main report create variable with same name as returnValue

variable class type --> same as return type

calculation type --> nothing

reset type and increment type -->none

variable expression --> blank

In main report  Subreport --> properties -->Subreport(other)-->subreport return values-->add

Subreport variable--> variable name as returnValue(u want to return) 

local destination variable --> main report variable (returnValue)

calculation type --> nothing

and use that variable wherever u want .

10_jasper return value from the subreport to main report