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Well, there you go then. There's nothing which calls that method so you shouldn't be surprised that it never gets run and never prints anything. (Not that it would print anything even if it did get run.)
Perhaps there's something else that you didn't tell us about? Some framework which somebody else is going to use to run your code, perhaps?
I haven't replicated the code but I think that the method is not using custArray properly, please have a look at this code, it is using custArray;
On the other hand, you need to have a class called Customer with a member "ID". Then in order to call the method "searchCustomerByID" maybe the best is to write a run method as explained on this https://coderanch.com/wiki/660020/Main-Pain post.
I prefer to focus on the impossible, because about the possible we already know too much.
Code without tests simply doesn’t exist!
Code is how we tell our colleagues how we feel about them.