Group a list of objects by an attribute
grouping, java, list
Solution
This will add the students object to the `HashMap` with `locationID` as key.
HashMap<Integer, List<Student>> hashMap = new HashMap<Integer, List<Student>>();
Iterate over this code and add students to the `HashMap`:
if (!hashMap.containsKey(locationId)) {
List<Student> list = new ArrayList<Student>();
list.add(student);
hashMap.put(locationId, list);
} else {
hashMap.get(locationId).add(student);
}
If you want all the student with particular location details then you can use this:
hashMap.get(locationId);
which will get you all the students with the same the location ID.
Problem
I need to group a list of objects (`Student`) using an attribute (`Location`) of the particular object. The code is like below: ``` public class Grouping { 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")); } } 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; } } ``` Please suggest me a clean way to do it.