What do you mean by aggregation?

 In Java, aggregation is a special type of association that represents a "whole-part" relationship between two classes. In an aggregation relationship, one class (the "whole") is composed of multiple instances of the other class (the "parts").

Unlike association, which is implemented using instance variables and methods, aggregation is implemented using constructors and method arguments. For example, consider the following classes:

class Student { // instance variables private String name; private int age; // constructor public Student(String name, int age) { this.name = name; this.age = age; } // getter and setter methods public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } } class Course { // instance variables private String name; private int credits; private List<Student> students; // aggregation relationship with Student class // constructor public Course(String name, int credits, List<Student> students) { this.name = name; this.credits = credits; this.students = students; } // getter and setter methods public String getName() { return name; } public void setName(String name) { this.name = name; } public int getCredits() { return credits; } public void setCredits(int credits) { this.credits = credits; } public List<Student> getStudents() { return students; } }

In this example, the "Course" class has an aggregation relationship with the "Student" class, which means that a "Course" instance is composed of multiple "Student" instances. This relationship is implemented using a constructor argument (List<Student> students) in the "Course" class, which allows you to pass a list of "Student" instances when you create a new "Course" instance.

To create a new "Course" instance with three "Student" instances, you could do the following:

List<Student> students = Arrays.asList( new Student("Alice", 20), new Student("Bob", 21), new Student("Charlie", 22) ); Course course = new Course("Java Programming", 3, students);

I hope this helps! Let me know if you have any other questions.