Java8 streams : Transpose map with values as list

Question

I have map with key as String and value as List. List can have 10 unique values. I need to convert this map with key as Integer and value as List. Example as below :

Answer 1

You can Achieve in this way

Let suppose I have Person class with Gender and Age . I want to get it in this form

Map> 

I would write simply

Map> map =  personList.stream()

                           .collect(Collectors.groupingBy(Person::getGender));

it will get me something like below (one key against multiple values )

key:MALE
age31sexMALE
age28sexMALE

key:FEMALE
age40sexFEMALE
age44sexFEMALE