list grouping

最新推荐文章于 2024-08-11 02:53:50 发布

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最新推荐文章于 2024-08-11 02:53:50 发布

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分类专栏： JAVA 文章标签： java list分组

本文链接：https://blog.csdn.net/masuwen/article/details/79584669

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本文介绍了一个使用Java实现的学生信息按地理位置进行分组的例子。通过创建一个包含多个学生的列表，并利用HashMap来根据学生的地理位置对学生进行分组，最后输出每个地理位置下的学生信息。

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import java.util.*;

public class Grouping {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        List<Student> studlist = new ArrayList<Student>();
        studlist.add(new Student("1726", "John", "New York"));
        studlist.add(new Student("4321", "Max", "California"));
        studlist.add(new Student("2234", "Andrew", "Los Angeles"));
        studlist.add(new Student("5223", "Michael", "New York"));
        studlist.add(new Student("7765", "Sam", "California"));
        studlist.add(new Student("3442", "Mark", "New York"));

        //Code to group students by location
        /*  Output should be Like below
            ID : 1726   Name : John Location : New York
            ID : 5223   Name : Michael  Location : New York
            ID : 4321   Name : Max  Location : California
            ID : 7765   Name : Sam  Location : California

         */

//        for (Student student : studlist) {
//            System.out.println("ID : "+student.stud_id+"\t"+"Name : "+student.stud_name+"\t"+"Location : "+student.stud_location);
//        }

        Map<String, List<Student>> groupedStudents = new HashMap<String, List<Student>>();
        for (Student student: studlist) {
            String key = student.stud_location;
            if (groupedStudents.get(key) == null) {
                groupedStudents.put(key, new ArrayList<Student>());
            }
            groupedStudents.get(key).add(student);
        }


        Set<String> groupedStudentsKeySet = groupedStudents.keySet();
        for (String location: groupedStudentsKeySet) {
            List<Student> stdnts = groupedStudents.get(location);
            for (Student student : stdnts) {
                System.out.println("ID : "+student.stud_id+"\t"+"Name : "+student.stud_name+"\t"+"Location : "+student.stud_location);
            }
        }

    }
}

public class Student {
    String stud_id;
    String stud_name;
    String stud_location;

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

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

    }
}