what is association in java with example
In Java, association represents a relationship between two or more classes where objects of one class are related to objects of another class. It defines how objects are related to each other and how they collaborate. There are different types of associations, such as one-to-one, one-to-many, and many-to-many.
Here’s an example to illustrate association in Java using a one-to-many association:
Let’s consider two classes: Department and Employee. A Department can have multiple Employee objects, but an Employee can belong to only one Department.
/*
* Author: Zameer Ali
* */
// Employee class
public class Employee {
private String name;
private int employeeId;
public Employee(String name, int employeeId) {
this.name = name;
this.employeeId = employeeId;
}
// Getters and setters for name and employeeId
// ...
}
// Department class
import java.util.List;
import java.util.ArrayList;
public class Department {
private String departmentName;
private List<Employee> employees;
public Department(String departmentName) {
this.departmentName = departmentName;
this.employees = new ArrayList<>();
}
public void addEmployee(Employee employee) {
employees.add(employee);
}
public List<Employee> getEmployees() {
return employees;
}
// Other methods related to the department
// ...
}
// Association example
public class AssociationExample {
public static void main(String[] args) {
// Creating employees
Employee employee1 = new Employee("John", 1);
Employee employee2 = new Employee("Alice", 2);
// Creating a department
Department department = new Department("Engineering");
// Associating employees with the department
department.addEmployee(employee1);
department.addEmployee(employee2);
// Retrieving employees from the department
List<Employee> employees = department.getEmployees();
// Displaying employees' information
for (Employee employee : employees) {
System.out.println("Employee ID: " + employee.employeeId + ", Name: " + employee.name +
", Department: " + department.departmentName);
}
}
}
In this example, the Department class has a list of Employee objects, representing a one-to-many association. The Department class can associate with multiple Employee objects through the addEmployee() method. The Employee objects, in turn, can belong to only one Department. This relationship represents an association between the Department and Employee classes.