How to check whether a int is not null or empty?

int variables can't be null

If a null is to be converted to int, then it is the converter which decides whether to set 0, throw exception, or set another value (like Integer.MIN_VALUE). Try to plug your own converter.

if your int variable is declared as a class level variable (instance variable) it would be defaulted to 0. But that does not indicate if the value sent from the client was 0 or a null. may be you could have a setter method which could be called to initialize/set the value sent by the client. then you can define your indicator value , may be a some negative value to indicate the null..

I think you are asking about code like this.

int  count = (request.getParameter("counter") == null) ? 0 : Integer.parseInt(request.getParameter("counter"));

I think you can initialize the variables a value like -1, because if the int type variables is not initialized it can't be used. When you want to check if it is not the value you want you can check if it is -1.