Resident treatment calculation JavaFunction.sub problem

Background requirements:

If the household registration period in this city reaches 8 years, the basic pension standard is different. But the parameter 5 or 8 is passed in, and the returned results are all results that meet the 8-year period?? Look at the corresponding algorithm configuration

 

Just look at the algorithm configuration, there is no problem. Test it in Java code.

JavaFunction.sub(5,8), code comments are subtraction. But tm's returned 0 for me? ?

String rhn = JavaFunction.caseWhen(JavaFunction.compare(JavaFunction.sub(5,8),0,"lt"),7,8);

 

So JavaFunction.compare( JavaFunction.sub(5,8) ,0,"lt") always returns false, and the basic pension standard of 8 is always obtained.