Java Reference
In-Depth Information
Figure 4.3. Groovy operators are implemented as methods, so if the Java class contains the right methods, Groovy
scripts can use the associated operators on their instances.
To demonstrate this I'll create a Java class that wraps a map. A
Department
contains
a collection of
Employee
instances and will have a
hire
method to add them and a
layOff
method to remove them (hopefully not very often). I'll implement operator over-
loading through three methods:
plus
,
minus
, and
leftShift
. Intuitively,
plus
will
add a new employee,
minus
will remove an existing employee, and
leftShift
will be
an alternative way to add. All three methods will allow chaining, meaning that they'll re-
turn the modified
Department
instance.
Here's the
Employee
class, which is just the
Person
POJO by another name:
public class Employee {
private int id;
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getId() { return id; }
public void setId(int id) { this.id = id; }
}
Now for the
Department
class, shown in the following listing, which maintains the em-
ployee collection in a
Map
keyed to the employee
id
values.
