if request input parameter “customerID” is part of comma delimited property string e.g.: “A,B,C,D” then perform block of code .
Like testing for few customers first in production if all goes well, then execute the same block of code for all customers.

e.g. 
String[] arr = "A,B,C,D".split(",");
String inputCustomerId="A";


if( Arrays.asList(arr).contains(inputCustomerId))
{
//execute block of code
}

**Scenario **:

after certain time if I want to execute the same block of code present above to all the incoming customer ID’s . i,e **E **or **F **or **G **which are not part of property string arr

Question:

Is it achievable to write code which can accomplish both scenarios at the same time with out code changes or releases .
I know if I remove if condition it executes for all customers. But I am trying to see if I can achieve it with out code changes.