如何使用流在Java 8中按值范围分组

以下代码将为您提供所需的内容。关键是“ Collectors”类，它支持分组。

Map<Double,Integer> ageGroup= employees.stream().collect(Collectors.groupingBy(e->Math.ceil(e.age/10.0),Collectors.summingInt(e->e.salary)));

假设工资为整数但易于转换为两倍的插图

完整的程序看起来像

public static void main(String[] args) {    // TODO Auto-generated method stub    List<Employee> employees = new ArrayList<>();    employees.add(new Employee("a",20,100));    employees.add(new Employee("a",21,100));    employees.add(new Employee("a",35,100));    employees.add(new Employee("a",32,100));    Map<Double,Integer> ageGroup= employees.stream().collect(Collectors.groupingBy(e->Math.ceil(e.age/10.0),Collectors.summingInt(e->e.salary)));    System.out.println(ageGroup);}public static class Employee {    public Employee(String name, int age, int salary) {        super();        this.name = name;        this.age = age;        this.salary = salary;    }    public String name;    public int age;    public int salary;}

输出是

{4.0=200, 2.0=100, 3.0=100}