Java Int Streams

Question

I am a fairly new Java programmer and I am currently learning about streams. I am trying to use a stream to take the salaries from each department and average them. I've been able to add the salaries or average them but I can't figure out how I would do this by department. Here's the code that I have so far.

 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Collectors;


public class AverageSalariesDept {

public static void main(String[] args) {


  Employee[] employees = {
     new Employee("Jason", "Red", 5000, "IT"),
     new Employee("Ashley", "Green", 7600, "IT"),
     new Employee("Matthew", "Indigo", 3587.5, "Sales"),
     new Employee("James", "Indigo", 4700.77, "Marketing"),
     new Employee("Luke", "Indigo", 6200, "IT"),
     new Employee("Jason", "Blue", 3200, "Sales"),
     new Employee("Wendy", "Brown", 4236.4, "Marketing")};


  List<Employee> list = Arrays.asList(employees);

  Function<Employee, String> byDepartment = Employee::getDepartment;
  Function<Employee, Double> bySalary = Employee::getSalary;

  Comparator<Employee> compSalaries = 
  Comparator.comparing(byDepartment).thenComparing(bySalary);

  list.stream()
           .sorted(compSalaries)  
           .forEach(System.out::println);


   System.out.printf("Average of Employees' salaries: %.2f%n",
     list.stream()
         .mapToDouble(Employee::getSalary)
         .average()
         .getAsDouble());



 }
 }

Ravindra Ranwala · Accepted Answer · 2018-09-30 05:03:58Z

4

This is what you need.

Map<String, Double> avgSalByDept = Arrays.stream(employees).
    collect(Collectors.groupingBy(Employee::getDepartment, 
        Collectors.averagingDouble(Employee::getSalary)));

First use the groupingBy collector to group Employees by department. Then use the downstream collector to compute the average salary for each department/group.

edited Sep 30, 2018 at 5:03

answered Sep 30, 2018 at 4:57

Ravindra Ranwala

21.2k7 gold badges50 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Java Int Streams

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related