Java8 flatMap demo 代码直接可以运行

参考自:http://www.cnblogs.com/shenlanzhizun/p/6027042.html

package com.by.interfaces;import java.util.ArrayList;import java.util.Arrays;import java.util.List;import java.util.stream.Collectors;class Student {    public Student(long id, String name, int age, int grade, String major, String school) {        this.id = id;        this.name = name;        this.age = age;        this.grade = grade;        this.major = major;        this.school = school;    }    public Student(String name) {        this.name = name;    }    public Student() {    }    private List<String> attributes = Arrays.asList("111", "222", "333");    /**     * 学号     */    private long id;    private String name;    private int age;    /**     * 年级     */    private int grade;    /**     * 专业     */    private String major;    /**     * 学校     */    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 List<String> getAttributes() {        return attributes;    }    public void setAttributes(List<String> attributes) {        this.attributes = attributes;    }}public class Main {    public static void main(String[] args) {        List<Student> students = new ArrayList<Student>();        students.add(new Student(20160001, "孔明4", 20, 1, "土木工程", "武汉大学"));        students.add(new Student(20160002, "伯约", 21, 2, "信息安全", "武汉大学"));        students.add(new Student(20160003, "玄德", 22, 3, "经济管理", "武汉大学"));        students.add(new Student(20160004, "云长", 21, 2, "信息安全", "武汉大学"));        students.add(new Student(20161001, "翼德", 21, 2, "机械与自动化", "华中科技大学"));        students.add(new Student(20161002, "元直", 23, 4, "土木工程", "华中科技大学"));        students.add(new Student(20161003, "奉孝", 23, 4, "计算机科学", "华中科技大学"));        students.add(new Student(20162001, "仲谋", 22, 3, "土木工程", "浙江大学"));        students.add(new Student(20162002, "鲁肃", 23, 4, "计算机科学", "浙江大学"));        students.add(new Student(20163001, "丁奉", 24, 5, "土木工程", "南京大学"));        //mapToLong的使用demo        double value = students.stream().filter(student -> "计算机科学".equals(student.getMajor())).mapToLong(aaa -> aaa.getId()).sum();        String[] strs = {"java8", "is", "easy", "to", "use"};        List<String[]> distinctStrs = Arrays.stream(strs)                .map(str -> str.split(""))  // 映射成为Stream<String[]>                .distinct()                .collect(Collectors.toList());        distinctStrs.forEach(strings -> Arrays.stream(strings).forEach(s -> System.out.println(s)));        System.out.println("==================================map方式");        List<String> distinctStrsByFlatMap = Arrays.stream(strs)                .map(str -> str.split(""))  // 映射成为Stream<String[]>                .flatMap(Arrays::stream)  // 扁平化为Stream<String>                .distinct()                .collect(Collectors.toList());        distinctStrsByFlatMap.forEach(s -> System.out.println(s));        System.out.println("==================================flatMap的方式");        List<List<Student>> studentss = new ArrayList<>();        studentss.add(students);        studentss.add(students);        System.out.println(studentss.size());        System.out.println("经过了flatmap处理后的stream查看下尺寸是多少" + studentss.stream().flatMap(students1 -> students1.stream()).count());        System.out.println(studentss.stream().flatMap(students1 -> students1.stream()).max((o1, o2) -> (o1.getName().length() - o2.getName().length())).get().getName());        System.out.println("经过了flatMap进行了彻底的流处理查看下有多少流" + studentss.stream().flatMap(students1 -> students1.stream()).flatMap(student -> student.getAttributes().stream()).count());        studentss.stream().flatMap(students1 -> students1.stream()).flatMap(student -> student.getAttributes().stream()).forEach(s -> System.out.println(s));            }}