Understanding Groovy's Null-Safe Comparison Operators

It's important to know that Groovy's comparison operators == and != handle nulls gracefully so you don't have to worry about protecting null values in equality or inequality comparisons.

Furthermore, the >, >=, <, and <= operators are also designed to avoid null-related exceptions, however you need to be conscious of how Groovy treats null in these order-dependent comparisons. Effectively, a null value is "less than" any other non-null value in the natural ordering, so for example observe the following comparison results.

Examples of How null Is Less Than Everything

Left-Side Expression	Operator	Right-Side Expression	Comparison Result
'a'	>	null	true
'a'	<	null	false
100	>	null	true
100	<	null	false
-100	>	null	true
-100	<	null	false
now()	>	null	true
now()	<	null	false
now() - 7	>	null	true
now() - 7	<	null	false

If you want a comparison to treat a null-valued field with different semantics — for example, treating a null MaximumOverdraftAmount field as if it were zero (0) like a spreadsheet user might expect — then use the nvl() function as part of your comparison logic as shown in the following example:

// Change default comparison semantics for the MaximumOverdraftAmount custom field in
// case its value is null by using nvl() to treat null like zero (0)
if (nvl(MaximumOverdraftAmount,0) < -2000) {
  // do something for suspiciously large overdraft amount
} 

As illustrated by the table above, without the nvl() function in the comparison any MaximumOverdraftAmount value of null would always be less than -2000 — since by default null is less than everything.