员工名单

import java.util.Comparator; // 比较器接口
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

public class ReducingDemo {
public static void main(String[] args) {
List<Employee> list = Employee.getEmpList(); // 获取测试数据

    long count = list.stream().count(); // 获取总人数
    // 下行代码也能实现获取总人数效果
    // count = stream.collect(Collectors.counting());
    System.out.println("公司总人数为：" + count);

    // 通过Comparator比较接口，比较员工年龄,再通过Collectors的maxBy()方法取出年龄最大的员工的Optional对象
    Optional<Employee> ageMax = list.stream().collect(Collectors.maxBy(Comparator.comparing(Employee::getAge)));
    Employee older = ageMax.get();// 获取员工对象
    System.out.println("公司年龄最大的员工是：\n    " + older);

    // 通过Comparator比较接口，比较员工年龄,再通过Collectors的minBy()方法取出年龄最小的员工的Optional对象
    Optional<Employee> ageMin = list.stream().collect(Collectors.minBy(Comparator.comparing(Employee::getAge)));
    Employee younger = ageMin.get();// 获取员工对象
    System.out.println("公司年龄最小的员工是：\n    " + younger);

    // 统计公司员工薪资总和
    double salarySum = list.stream().collect(Collectors.summingDouble(Employee::getSalary));
    System.out.println("公司的薪资总和为：" + salarySum); // 输出结果

    // 统计公司薪资平均数
    double salaryAvg = list.stream().collect(Collectors.averagingDouble(Employee::getSalary));
    // 使用格式化输出，保留2位小数
    System.out.printf("公司的平均薪资为：%.2f\n", salaryAvg);

    // 创建统计对象，利用summarizingDouble()方法获取员工薪资各方面的统计数据
    java.util.DoubleSummaryStatistics s = list.stream().collect(Collectors.summarizingDouble(Employee::getSalary));
    System.out.print("统计：拿薪资的人数=" + s.getCount() + ", ");
    System.out.print("薪资总数=" + s.getSum() + ", ");
    System.out.print("平均薪资=" + s.getAverage() + ", ");
    System.out.print("最大薪资=" + s.getMax() + ", ");
    System.out.print("最小薪资=" + s.getMin() + "\n");

    // 将公司员工姓名拼成一个字符串，用逗号分隔
    String nameList = list.stream().map(Employee::getName).collect(Collectors.joining(", "));
    System.out.println("公司员工名单如下：\n    " + nameList);
}

}