Programming Grails - Cdn.oreilly.com

or you could just skip the whole for loop and use times:
someCalculation().times {
...
}
or a range with a loop, if you need access to the loop variable:
for (i in 0..someCalculation()-1) {
...
}
Annotations
Annotation values that have array types use a different syntax in Groovy than Java. In
Java, you use { and } to define multivalued attributes:
@Secured({'ROLE_ADMIN', 'ROLE_FINANCE_ADMIN', 'ROLE_SUPERADMIN'})
but because these are used to define closures in Groovy, you must use [ and ] instead:
@Secured(['ROLE_ADMIN', 'ROLE_FINANCE_ADMIN', 'ROLE_SUPERADMIN'])
Groovy Equality
The previous examples will cause compilation errors if you rename a .java class
to .groovy and try to compile it, or copy/paste Java code into an existing Groovy class.
But checking for object equality actually works differently in Groovy.
In Java, == is mostly used for comparing numbers and other primitives, because com‐
paring objects with == just compares object references but not the data in the instances.
We use the equals method to test if two objects are equivalent and can be considered
equal even though they’re not the same instances. But it’s rare to need the == object
comparison, so Groovy overloads it to call equals (or compareTo, if the objects imple‐
ment Comparable). And, if you do need to check that two references are the same object,
use the is method—e.g., foo.is(bar).
Groovy’s == overload is convenient and avoids having to check for null values, but be‐
cause it works differently than the Java operator, you might want to consider not using
it. It’s simple enough to replace x == y with x?.equals(y), which isn’t that many more
characters and is still null-safe. Working with both Java and Groovy will keep you from
introducing subtle bugs in your Java code. (I’m speaking from experience here….)
Multimethod Dispatch
Overloaded method selection is another runtime difference between Java and Groovy.
Java’s type checking is stricter, so it uses the compilation type of a variable to choose
18 | Chapter 1: Introduction to Groovy