How to Group Java Objects by an Attribute Using Collectors.groupingBy()?

How to Group Objects by an Attribute in Java

Grouping objects by a specific attribute is a common operation in programming. To do this, you can use the Collectors.groupingBy() method in Java 8.

Consider the following code, which creates a list of Student objects and stores them in a list:

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

        List<student> studlist = new ArrayList();
        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;
    }
}</student>

To group the Student objects by their location, you can use the following code:

Map<string list>> studlistGrouped =
    studlist.stream().collect(Collectors.groupingBy(w -> w.stud_location));</string>

This code uses the Collectors.groupingBy() method to group the Student objects by their stud_location attribute. The result is a Map that contains the location as the key and a List of Student objects as the value.

This approach provides a clean and concise way to group objects by an attribute in Java 8.

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