How to use printWhenExpression in JasperReports

Question

Can somebody tell me how to use the printWhenExpression of JasperReports?

Answer 1

The other poster has done a good job of explaining the technical details of how to use it, so I'll try and explain the circumstances in which one might find it useful.

Basically, it allows you to show or hide the contents of a cell based on a boolean expression. For example, you might want to show a person's name only if that person is over 18, then in the name field, using a printwhenexpression like:

$F{age} >= 18