How to Handle Arraylist in Request payload?

How to handle Arraylist in Request body?
I have a json request something like
“Data”: {
“ItemsList”: [ “value1”, “value2”,“value3”, “value4”],

I am trying to check invalid and empty values in Itemslist array.
On using Globalvariable.ItemsList, its printing me [value1, value2,value3,value4]
If I pass Globalvariable.ItemsList in the script of SendRequest, i am getting 400 error, invalid request params