Java8 新特性 list集合利用stream根据对象得某一属性对集合进行分组,附加8之前分组

Java8之后很多新特性，接下来主要讲一下， list集合利用stream根据对象得某一属性对集合进行分组！
话不多说，上代码：
首先准备实体类：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Student {
    private Integer id;private String name;//成绩private Double score;}

然后开始写测试类：

import java.util.*;
import java.util.stream.Collectors;public class GroupByName {
    public static void main(String[] args) {
    //准备要分组得集合List<Student> students = Arrays.asList(new Student(1,"伽罗",99d),new Student(2,"后羿",97d),new Student(3,"鲁班",98d),new Student(4,"后羿",90d),new Student(5,"百里",88d),new Student(6,"狼狗",59d),new Student(7,"艾琳",78d),new Student(8,"伽罗",94d));//jdk8.0新特性来分组,根据学生姓名来进行分组Map<String,List<Student>> result = new HashMap<>();result = students.stream().collect(Collectors.groupingBy(Student::getName));result.forEach((x,y) -> System.out.println(x+"--"+y));System.out.println("华丽分割线"+"------------------------");//jdk1.8之前手写分组Map<String,List<Student>> map = new HashMap<>();for (Student student : students) {
    List<Student> list = map.get(student.getName());if (list == null) {
    list = new ArrayList<>();list.add(student);map.put(student.getName(), list);} else {
    list.add(student);}}map.forEach((x,y) -> System.out.println(x+"--"+y));/*** 结果：* 伽罗--[Student(id=1, name=伽罗, score=99.0), Student(id=8, name=伽罗, score=94.0)]* 百里--[Student(id=5, name=百里, score=88.0)]* 狼狗--[Student(id=6, name=狼狗, score=59.0)]* 艾琳--[Student(id=7, name=艾琳, score=78.0)]* 后羿--[Student(id=2, name=后羿, score=97.0), Student(id=4, name=后羿, score=90.0)]* 鲁班--[Student(id=3, name=鲁班, score=98.0)]*/}
}

到这里新特性分组就介绍完了，列子简单，直接上手简单，谢谢大家支持！！