How to evaluate a blank string "" in an expression

[dprogrammer]

I have a parameter1 that may be blank in some cases. So I have another parameter2 which wants to check if the parameter1 is blank, then it will say 'All' else parameter1. I have tried following but its not evaluating correctly.

$P{parameter1}.equals("")? 'ALL':$P{parameter1}

$P{parameter1}==""? 'ALL':$P{parameter1}

$P{parameter1}==null? 'ALL':$P{parameter1}

Any ideas please?

[dprogrammer]

nevermind, I found function IsEmpty() which works fine in my case. Thanks