Dynamic
typing means that unlike in Java and other statically-type languages where a
variable has a specific type such as String and only takes values of that type,
Groovy allows you to change the type as well as value of the variable simply by
assigning it a value or object reference of a different type. This is possible
since everything in Groovy is an object, and inherits the java super class
Object.
Being a
scripting language, we need neither a class nor a main method to act as our
entry point to the program. Groovy will simply run any expressions you have in
a file. At this point, I’m assuming you have downloaded and installed groovy as
well as the Java Development Kit (JDK), or its equivalent for your platform.
You can download Groovy for free as well as access its documentation and
installation steps for various platforms at Codehaus.
Declaring Variables
Variables
are declared using the def keyword. For your first example on declaring
variables, start up your favourite text editor or the GroovyConsole and type
this code:
def x=35 //age
println x
Save the
file as age1.groovy. This creates a
groovy script names age1.groovy. Go
to the command-line and navigate to the folder containing your script and type
groovy age1.groovy
Output
35
If you are
using GroovyConsole, you can simply run the script by going to Script > Run
or using the shortcut Ctrl+R without saving the script.
Everything is an Object
Java
programmers are prone to think that x is an int. However, in Groovy, there are
no primitives. The variable x is of type
java.lang.Integer, which is a class, making x an object. (Objects and
Classes will be discussed shortly).
To ascertain
this, add another line to age so it now looks like this:
def x=35 //age
println x
println x.getClass() //print
x’s class
Output
35
class java.lang.Integer
Groovy is Dynamic
As stated
earlier, you can change the type of a variable simply by assigning a value of a
different kind. To illustrate this, modify the script you created earlier as
shown:
def x=35 //age
println x
println x.getClass() //print
x’s class
x="Cabee's
Grovy Mastery Course is Awesome"
println x
println x.getClass()
Output
2
class java.lang.Integer
Cabee's
Grovy Mastery Course is Awesome
class java.lang.String
You can
force a variable to take only values of a given type by explicitly providing
the data type of the variable.
Replace def
with Integer and run the script. It will result in a GroovyCastException after
printing class java.lang.Integer (Groovy is interpreted).
For more on
variables, types, classes, objects and typing, check out the coming tutorials.
Happy coding with Cabee Grovy Mastery
Course!!!
