I have a List<Employee> e which I want to convert into Map<String, Map<String,Emp>> where the outer string should be "Name" and the inner string should be "Domain".
Name Id Domain
e(0) - Emp1, 1, Insurance
e(1) - Emp1, 2, Sales
e(2) - Emp2, 3, Sales
e(3) - Emp4, 4, Marketing
I am tried the following-
e.stream().collect(Collectors.groupingBy(
Employee::getName,
toMap(Employee::getDomain,Emp)));
So the expected output map should look like
<Emp1>
<Insurance, e(0)>
<Sales, e(1)>
<Emp2>
<Sales, e(2)>
<Emp4>
<Marketing, e(3)>
But I get only unique values, actual output-
<Emp1>
<Insurance, e(0)>
<Emp2>
<Sales, e(2)>
<Emp4>
<Marketing, e(3)>
Can someone tell the best way to do it?
What you are mostly looking for is nested grouping such as :
Map<String, Map<String, List<Employee>>> groupedMap = employees.stream()
.collect(Collectors.groupingBy(Employee::getName,
Collectors.groupingBy(Employee::getDomain, Collectors.toList())));
Note - The values are List<Employee> which are the employees grouped by name and then by domain. (Both same clubbed into a List.)
If you were to stricly adhere to getting a single employee corresponding to the specified grouping, the code pretty much works for me with a small modification:
Map<String, Map<String, Employee>> groupedReducedMap = employees.stream()
.collect(Collectors.groupingBy(Employee::getName,
Collectors.toMap(Employee::getDomain,
Function.identity(), // value as the employee instance
(a, b) -> a))); // choose first instance for similar 'domain'
Collected from the Internet
Please contact [email protected] to delete if infringement.
Comments