How to find session variable present or not

Question

How i can find values is set to variable in session or not?

if(session.getAttribute("tot_demand"))//need to change

  //if value is already set then do this.

else

  //if not set then do this.

Please answer what i need to write for above code.

Thanks in advance.

Answer 1

Compare to null:

if (session.getAttribute("tot_demand") != null) {
   // already set
} else {
   // not yet set
}