A tuple is an ordered, immutable list of elements. Groovy supported tuples with one or two elements before Groovy 2.5.0. Since Groovy 2.5.0 we can use tuples with maximal nine items. Groovy added the classes Tuple3 up to Tuple9. The bonus we get compared to an unmodifiable list with elements is that we can use properties like first, second, third, fourth, fifth, sixth, seventh, eighth, ninth to get items at the specified position.

In the following example we use different Tuple classes:

// We can define the types of the elements when we
// construct a tuple.
def tuple3 = new Tuple3('add', 2, 40.0)

// We can use first, second, third properties
// to get values from the tuple.
assert tuple3.first == 'add'
assert tuple3.second == 2
assert tuple3.third == 40.0

// We can use the [index] syntax to get element.
assert tuple3[0] == 'add'

// Fully typed tuple.
Tuple4 tuple4 =
    new Tuple4<>('subtract', 100, 55.0, 3)

assert tuple4.first == 'subtract'
assert tuple4.second == 100
assert tuple4.third == 55.0
assert tuple4.fourth == 3
assert tuple4[-1] == 3

// With subTuple we can get subsequent
// values from the tuple as a new tuple.
assert tuple4.subTuple(2, tuple4.size()) == new Tuple2(55.0, 3)

// We can imagine how to work with Tuple4..Tuple8 :-)
// ...

// Finally a tuple with 9 items.
def tuple9 = new Tuple9('Groovy', 'rocks', 'and', 'is', 'fun', 'to', 'use', 'as', 'language')

assert tuple9.fifth == 'fun'
assert tuple9.sixth == 'to'
assert tuple9.seventh == 'use'
assert tuple9.eighth == 'as'
assert tuple9.ninth == 'language'

// Tuple extends AbstractList, so we can
// use all methods from List as well.
assert tuple9.join(' ') == 'Groovy rocks and is fun to use as language'

Written with Groovy 2.5.0.

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