summarizing集合统计

• 作⽤：可以⼀个⽅法把统计相关的基本上都完成

• 分类

summarizingInt
summarizingLong
summarizingDouble

• 案例

# 统计学⽣的各个年龄信息

public class Main {

    public static void main(String[] args) throws Exception {
        List<Student> students = Arrays.asList(
                new Student("广东", 23),
                new Student("广东", 24),
                new Student("广东", 23),
                new Student("北京", 22),
                new Student("北京", 20),
                new Student("北京", 20),
                new Student("海南", 25));

        IntSummaryStatistics summaryStatistics = students.stream().collect(Collectors.summarizingInt(Student::getAge));

        System.out.println("平均值"+summaryStatistics.getAverage());
        System.out.println("人数"+summaryStatistics.getCount());
        System.out.println("最大值"+summaryStatistics.getMax());
        System.out.println("最小值"+summaryStatistics.getMin());
        System.out.println("总和"+summaryStatistics.getSum());
    }

}

// 内部类
class Student {

    private int age;

    private String province;

    public Student(String province, int age) {
        this.province = province;
        this.age = age;
    }

    public Student() {
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }
}