This example will show how to sort a map or dictionary by keys in groovy. We will create a map with keys representing candy bar manufactures and values as candy bars. In the snippets below we will use the spread operator *. which is used to invoke the Entry.getKey on each element in the map. This will allow us to easily compare the keys and show them in the unit test. In a comparable example we demonstrate how to order map by keys in java.
Sort map by keys
@Test
void sort_map_by_keys() {
def myMap = ["Toms International":"Yankie Bar", "Mars":"3 Musketeers", "Nestlé": "Yorkie", "Hershey's":"Eat-more"]
assert [
"Hershey's",
"Mars",
"Nestlé",
"Toms International"] == myMap.sort()*.key
}Sort map by key in reverse Java 8
We will pass a java 8 comparator that will be the reverse of the natural ordering of Strings.
@Test
void sort_map_by_key_in_reverse() {
def myMap = ["Toms International" : "Yankie Bar", "Mars" : "3 Musketeers", "Nestlé" : "Yorkie", "Hershey's" : "Eat-more"]
assert [
"Toms International",
"Nestlé",
"Mars",
"Hershey's"
] == myMap.sort(Collections.reverseOrder())*.key
}