How to group stream of Map to Map<String, Map<String, String>>? - groovy

Question

I have stream of Map [name:name1, type:type1, desc:desc1, ordinal:1]. How to convert/group (with Groovy) to Map>: Map(type1: Map (neme:name1, desc:desc1, ordinal:1)).
Stream of Map
[name:productName, type:IN, ordinal:1, description:desc]
[name:productName1, type:IN, ordinal:2, description:desc]
[name:productName2, type:OUT, ordinal:3, description:desc]
and I have get: Map:
IN: Map[
[name:productName, type:IN, ordinal:1, description:desc.],
[name:productName1, type:IN, ordinal:2, description:desc.]]
OUT: Map[
[name:productName2, type:OUT, ordinal:3, description:desc.]]

Answer 1

You can use Stream.collect() method with Collectors.groupingBy { it.type } to collect all elements as map of type key and value of list of elements. Consider the following example:
import java.util.stream.Collectors
import java.util.stream.Stream
def input = Stream.of(
[name: 'productName', type: 'IN', ordinal: 1, description: 'desc'],
[name: 'productName1', type: 'IN', ordinal: 2, description: 'desc'],
[name: 'productName2', type: 'OUT', ordinal: 3, description: 'desc'],
)
def result = input.collect(Collectors.groupingBy { it.type })
result.each { println it }
Output:
IN=[{name=productName, type=IN, ordinal=1, description=desc}, {name=productName1, type=IN, ordinal=2, description=desc}]
OUT=[{name=productName2, type=OUT, ordinal=3, description=desc}]
Alternatively, if your input is not a Stream but a List, you could use good old Groovy Collection.groupBy() that does the same effect:
def input2 = [[name: 'productName', type: 'IN', ordinal: 1, description: 'desc'],
[name: 'productName1', type: 'IN', ordinal: 2, description: 'desc'],
[name: 'productName2', type: 'OUT', ordinal: 3, description: 'desc']]
def result2 = input2.groupBy { it.type }
result2.each { println it }