Groovy uses a similar syntax to Java although in Groovy semicolons are optional. This saves a little typing but also makes code look much cleaner (surprisingly so for such a minor change). So normally if one statement is on each line you can ommit semicolons altogether - though its no problem to use them if you want to. If you want to put multiple statements on a line use a semicolon to separate the statements.

x = [1, 2, 3]
println(x)
y = 5; x = y + 7
println(x)
assert x == 12

If the end of the line is reached and the current statement is not yet complete it can be spanned across multiple lines. So for things like method parameters or creating lists or for complex if expressions you can span multiple lines.

x = [1, 2, 3,
	4, 5, 6]
println(
	x
)
if (x != null && 
	x.size() > 5) {
	println("Works!")
}
else {
	assert false: "should never happen ${x}"
}

Method calling syntax is similar to Java where methods can be called on an object (using dot) or a method on the current class can be called. Static and instance methods are supported.

class Foo {
	calculatePrice() {
		1.23
	}

static void main(args) { foo = new Foo() p = foo.calculatePrice() assert p > 0

println "Found price: " + p } }

Notice that the return statement is optional at the end of methods. Also you don't need to specify a return type (it will default to Object in the bytecode if none is specified).

Method calls in Groovy can ommit the parenthesis if there is at least one parameter and there is no ambiguity.

println "Hello world"
System.out.println "Nice cheese Gromit!"

When calling a method you can pass in named parameters. Parameter names and values are separated by a colon (like the Map syntax) though the parameter names are identifiers rather than Strings.

Currently this kind of method passing is only implemented for calling methods which take a Map or for constructing JavaBeans.

bean = new Expando(name:"James", location:"London", id:123)
println "Hey " + bean.name
assert bean.id == 123

Please refer to GroovyMarkup for more examples

Closures are described in more detail here. Closures can be passed into methods like any other object

closure = { param | param + 1 }
answer = [1, 2].collect(closure)
assert answer == [2, 3]

Though there is some syntax sugar to make calling methods which take a closure easier. Instead of specifying parenthesis, you can just specify a closure. e.g.

answer = [1, 2].collect { param | param + 1 }
assert answer == [2, 3]

The above code is equivalent to the previous code, just a little more groovy. If a method takes parameters you can leave the closure outside of the parenthesis (provided that the closure parameter is the last parameter on the underlying method).

value = [1, 2, 3].inject(0) { count, item | count + item }
assert value == 6

The above code is equivlanent to the following (but just neater)

value = [1, 2, 3].inject(0, { count, item | count + item })
assert value == 6

1.1. Important Note Note that when using the neater syntax for specifying closures either without parenthesis or by specifying the closure after the parenthesis, the closure must start on the same line. i.e. the { symbol must be on the same line as the method call statement. Otherwise the parser interprets the { as a start of a block.

If a variable is not constrained by a type then dynamic method dispatch is used. This is often referred to as dynamic typing whereas Java uses static typing by default.

You can mix and match both dynamic and static typing in your code by just adding or removing types. e.g.

dynamicObject = "hello world".replaceAll("world", "Gromit")
dynamicObject += "!"
assert dynamicObject == "hello Gromit!"

String staticObject = "hello there" staticObject += "!" assert staticObject == "hello there!"

These are described in more detail in the {link:GroovyBeans|beans.html} section.

To access properties you use dot with the property name. e.g.

bean = new Expando(name:"James", location:"London", id:123)
name = bean.name
println("Hey ${name}")
bean.location = "Vegas"
println bean.name + " is now in " + bean.location
assert bean.location == "Vegas"

If you are walking a complex object graph and don't want to have NullPointerExceptions thrown you can use the -> operator rather than . to perform your navigation.

foo = null
bar = foo->something->myMethod()
assert bar == null