java8-10.1-IntSummaryStatistics 類的使用

public class Student {

    /** 學號 */
    private long id;

    private String name;

    private int age;

    /** 年級 */
    private int grade;

    /** 專業 */
    private String major;

    /** 學校 */
    private String school;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    public int getGrade() {
        return grade;
    }

    public void setGrade(int grade) {
        this.grade = grade;
    }

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }

    public String getSchool() {
        return school;
    }

    public void setSchool(String school) {
        this.school = school;
    }

    public Student(long id, String name, int age, int grade, String major, String school) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.grade = grade;
        this.major = major;
        this.school = school;
    }

    
}

public class Test {
    public static void main(String[] args) {

        List<Student> students = Arrays.asList(
    
                new Student(200123,"蘇明",20,1,"土木工程","蘇州大學"),
                new Student(200456,"張阿凡",21,2,"機械工程","杭州師范大學"),
                new Student(200789,"范總",20,3,"計算機工程","蘇州工業大學"),
                new Student(201123,"劉飛",22,1,"考古","上海大學"),
                new Student(202123,"萬三",17,3,"歷史","復旦大學"),
                new Student(203123,"克里",25,2,"數學","上海外國語大學")
                
                );
        
        //第一種  集合有6條數據
        System.out.println(students.size());
        
        //第二種  集合有6條數據
        long count = students.stream().count();
        System.out.println(count);
        
        //第三種  集合有6條數據
        Long count2 = students.stream().collect(Collectors.counting());
        System.out.println(count2);
       

        //第一種 年齡總和
        Integer sumAge = students.stream().collect(Collectors.summingInt(Student::getAge));
        System.out.println(sumAge);
        
        //第二種 年齡總和
        long sum = students.stream().collect(Collectors.summarizingInt(Student::getAge)).getSum();
        System.out.println(sum);
        
       //IntSummaryStatistics  一次性得到元素個數、總和、均值、最大值、最小值
       IntSummaryStatistics summaryStatistics = students.stream()
                                                        .collect(Collectors.summarizingInt(Student::getAge));
       
        System.out.println(summaryStatistics.getCount());
        System.out.println(summaryStatistics.getSum());
        System.out.println(summaryStatistics.getAverage());
        System.out.println(summaryStatistics.getMax());
        System.out.println(summaryStatistics.getMin());
        
        //純數字的計算
        List<Integer> integers = Arrays.asList(1,2,3,4,5,6,7,8,9,25);
        IntSummaryStatistics summary = integers.stream().mapToInt(T -> T).summaryStatistics();
        System.out.println(summary.getAverage());
        System.out.println(summary.getCount());
        System.out.println(summary.getMax());
        System.out.println(summary.getMin());
        System.out.println(summary.getSum());

    }
}