Spaceship Operator

Basic usage

the spaceship operator returns -1 when the left operator is smaller, 0 when the operators are equal and 1 otherwise:

assert 10 <=> 20 == -1
assert 10 <=> 10 == 0
assert 30 <=> 10 == 1

assert 'a' <=> 'b' == -1
assert 'a' <=> 'a'== 0
assert 'b' <=> 'a' == 1

It is equivalent to the Comparable.compareTo method:

assert 10.compareTo(20) == (10 <=> 20)
assert 'a'.compareTo('b') == ('a' <=> 'b')

Spaceship operator for custom sortings

class User {
  String name
  int age
}

def users = [
  new User(name: "Bob", age: 20),
  new User(name: "Tom", age: 50),
  new User(name: "Bill", age: 45)
]

// sort by age
users.sort { a, b -> a.age <=> b.age }

Usage with Comparator and SortedSet

Comparator cmp = [ compare:{ a, b -> a <=> b } ] as Comparator
def col = [ 'aa', 'aa', 'nn', '00' ]
SortedSet sorted = new TreeSet( cmp )
sorted.addAll col
assert '[00, aa, nn]' == sorted.toString()