流式处理

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package test;

import java.util.ArrayList;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Test011 {
    public static void main(String[] args) {
        Student s1 = new Student(1, 11, "111");
        Student s2 = new Student(2, 22, "222");
        Student s3 = new Student(3, 33, "333");
        Student s5 = new Student(5, 55, "555");
        Student s6 = new Student(6, 66, "666");
        Student s7 = new Student(6, 66, "666");

        List<Student> list = new ArrayList<Student>();
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s5);
        list.add(s6);
        list.add(s7);

        // filter
        List<Student> l1 = list.stream().filter(student -> student.mark > 50).collect(Collectors.toList());
        System.out.println(l1);
        // filter
        List<Student> l3 = list.stream().filter(student -> student.mark > 50).limit(1).collect(Collectors.toList());
        System.out.println(l3);

        // distinct
        List<Student> l2 = list.stream().filter(student -> student.mark > 50).distinct().collect(Collectors.toList());
        System.out.println(l2);

        // sort
        List<Student> l4 = list.stream().sorted((t1, t2) -> t2.age - t1.age).distinct().collect(Collectors.toList());
        System.out.println(l4);

        // skip
        List<Student> l5 = list.stream().sorted((t1, t2) -> t2.age - t1.age).distinct().skip(1).collect(Collectors.toList());
        System.out.println(l5);

        // map
        List<String> l6 = list.stream().map(Student::getName).collect(Collectors.toList());
        System.out.println(l6);

        // mapToInt
        int i1 = list.stream().mapToInt(Student::getAge).sum();
        System.out.println(i1);

        // allMatch
        boolean b1 = list.stream().allMatch(student -> student.getAge() > 1);
        System.out.println(b1);

        // IntSummaryStatistics
        IntSummaryStatistics statistics = list.stream().collect(Collectors.summarizingInt(Student::getAge));
        System.out.println(statistics.getMax());

        // groupingBy
        Map<Integer, List<Student>> map = list.stream().collect(Collectors.groupingBy(Student::getMark));
        System.out.println(map);
    }
}

class Student {
    int age;
    int mark;
    String name;

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

    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 getMark() {
        return mark;
    }

    public void setMark(int mark) {
        this.mark = mark;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + mark;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (age != other.age)
            return false;
        if (mark != other.mark)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return this.name + " " + this.age + " " + this.mark;
    }
}

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