Programming Groovy 2

2.7 Groovy Boolean Evaluation

Boolean evaluation in Groovy is different than in Java. Depending on the context, Groovy will automatically evaluate expressions as ​boolean​.

Let’s see a specific example. The following Java code will not work:

//Java code
String obj = "hello";
int val = 4;
if (obj) {} // ERROR
if(val) {} //ERROR

Java insists that we provide a ​boolean​ expression for the condition part of the ​if​ statement. It wants ​if(obj != null)​ and ​if(val > 0)​ in the previous example, for instance.

Groovy is not that picky. It tries to infer, so we need to know what Groovy is thinking.

If we place an object reference where a ​boolean​ expression is expected, Groovy checks whether the reference is ​null​. It ...