java NVL function

NVL is a function in Oracle PL/SQL that is more or less this:

NVL(a,b) ==> (a == null)?b:a

And that's all well and good. The only problem occurs when the value of a either has side effects or either a or b are long and complex. You could write


foo a = ... long complicated code with possible side effects ...
foo b = ...yadda yadda yadda...
a = (a==null)?b:a;


But wouldn't it be easier to read as



a=nvl(... long complicated code with possible side effects ..., ... yadda yadda yadda ...)

?

Well, nvl() is easy to write, except that Java wants the arguments to be strongly typed.

Or does it?

You can declare the arguments are return as Object, but then you have to cast the return, and the compiler will not protect you from type mismatches.

The solution is generics. Write nvl like this:


public <T> T nvl(T a, T b) {
return (a == null)?b:a;
}


Mischief managed. The compiler will guarantee that there can be no type clashes, and so long as the same type is used for the two args and return, you're good to go.