Java 整数流

Question

我是一名相当新的 Java 程序员，目前正在学习流。我正在尝试使用流来获取每个部门的工资并对其进行平均。我已经能够添加工资或平均工资，但我不知道如何按部门执行此操作。 这是我到目前为止所拥有的代码。

 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());



 }
 }

Answer 1

这就是您所需要的。

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

首先使用groupingBy收集器按部门对Employees进行分组。然后使用下游collector计算每个部门/组的平均工资。