closure in groovy code example

Example 1: groovy3 closure

def listener = { e -> println "Clicked on $e.source" }      (1)
assert listener instanceof Closure
Closure callback = { println 'Done!' }                      (2)
Closure<Boolean> isTextFile = {
    File it -> it.name.endsWith('.txt')                     (3)
}

Example 2: groovy3 closure

{ [closureParameters -> ] statements }

Example 3: groovy3 closure

{ item++ }                                          (1)

{ -> item++ }                                       (2)

{ println it }                                      (3)

{ it -> println it }                                (4)

{ name -> println name }                            (5)

{ String x, int y ->                                (6)
    println "hey ${x} the value is ${y}"
}

{ reader ->                                         (7)
    def line = reader.readLine()
    line.trim()
}