JAVA 8按某些属性分组
例如下面的先按名字再按地方进行分组

class Student {

    String stud_id;
    String stud_name;
    String stud_location;

    public String getStud_id() {
        return stud_id;
    }

    public String getStud_name() {
        return stud_name;
    }

    public String getStud_location() {
        return stud_location;
    }



    Student(String sid, String sname, String slocation) {

        this.stud_id = sid;
        this.stud_name = sname;
        this.stud_location = slocation;

    }
}

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

        Stream<Student> studs =
                Stream.of(new Student("1726", "小红", "上海"),
                        new Student("4321", "小米", "北京"),
                        new Student("2234", "小明", "深圳"),
                        new Student("7765", "小胡", "北京"),
                        new Student("1726", "小胡", "上海"));
        Map<String, Map<Object, List<Student>>> map= studs.collect(Collectors.groupingBy(Student::getStud_name,Collectors.groupingBy(Student::getStud_location)));
        System.out.println(map);//print by name and then location
    }

}

结果