**Course Title:** Comprehensive Java Programming: From Basics to Advanced Concepts **Section Title:** Inheritance and Polymorphism in Java **Topic:** Create a class hierarchy to demonstrate inheritance and polymorphism.(Lab topic) **Objective:** By the end of this lab, students will be able to design and implement a class hierarchy using inheritance and polymorphism in Java. They will understand the benefits and limitations of inheritance and learn how to apply these concepts in real-world scenarios. **Lab Exercise:** Create a class hierarchy to demonstrate inheritance and polymorphism. Consider a scenario of a University with different types of employees, such as Professors, Administrators, and Researchers. **Step 1: Create the superclass "Employee"** The "Employee" class will contain common attributes and methods that will be inherited by other employee types. Create a new Java class called "Employee" with the following attributes: * `name` * `age` * `salary` * `department` ```java public class Employee { private String name; private int age; private double salary; private String department; public Employee(String name, int age, double salary, String department) { this.name = name; this.age = age; this.salary = salary; this.department = department; } 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; } public double getSalary() { return salary; } public void setSalary(double salary) { this.salary = salary; } public String getDepartment() { return department; } public void setDepartment(String department) { this.department = department; } public void displayInfo() { System.out.println("Name: " + name); System.out.println("Age: " + age); System.out.println("Salary: " + salary); System.out.println("Department: " + department); } } ``` **Step 2: Create subclasses "Professor" and "Administrator"** The "Professor" and "Administrator" classes will extend the "Employee" class and contain additional attributes and methods specific to each type. Create a new Java class called "Professor" that extends "Employee": ```java public class Professor extends Employee { private String specialization; private int yearsOfExperience; public Professor(String name, int age, double salary, String department, String specialization, int yearsOfExperience) { super(name, age, salary, department); this.specialization = specialization; this.yearsOfExperience = yearsOfExperience; } public String getSpecialization() { return specialization; } public void setSpecialization(String specialization) { this.specialization = specialization; } public int getYearsOfExperience() { return yearsOfExperience; } public void setYearsOfExperience(int yearsOfExperience) { this.yearsOfExperience = yearsOfExperience; } public void displayInfo() { super.displayInfo(); System.out.println("Specialization: " + specialization); System.out.println("Years of Experience: " + yearsOfExperience); } } ``` Create a new Java class called "Administrator" that extends "Employee": ```java public class Administrator extends Employee { private String responsibility; public Administrator(String name, int age, double salary, String department, String responsibility) { super(name, age, salary, department); this.responsibility = responsibility; } public String getResponsibility() { return responsibility; } public void setResponsibility(String responsibility) { this.responsibility = responsibility; } public void displayInfo() { super.displayInfo(); System.out.println("Responsibility: " + responsibility); } } ``` **Step 3: Demonstrate polymorphism** Create a new Java class called "University" that contains a method to display information of all employees: ```java public class University { public static void displayEmployees(Employee[] employees) { for (Employee employee : employees) { employee.displayInfo(); System.out.println(); } } public static void main(String[] args) { Employee[] employees = new Employee[3]; employees[0] = new Professor("John Doe", 35, 60000.0, "Mathematics", "Algebra", 5); employees[1] = new Administrator("Jane Smith", 30, 50000.0, "Administration", "HR"); employees[2] = new Professor("Bob Johnson", 40, 70000.0, "Computer Science", "Programming", 10); displayEmployees(employees); } } ``` **Conclusion:** In this lab exercise, we created a class hierarchy using inheritance and polymorphism to demonstrate the relationships between different employee types in a university setting. The "Employee" class served as the superclass, containing common attributes and methods, while the "Professor" and "Administrator" classes extended the "Employee" class to include additional attributes and methods specific to each type. **Key Concepts:** * Inheritance: Creating a new class that inherits attributes and methods from an existing class. * Polymorphism: Ability of an object to take on multiple forms, depending on the context. * Subclasses: Classes that extend a superclass, inheriting its attributes and methods. **Practical Takeaways:** * Use inheritance to create a class hierarchy that models real-world relationships between objects. * Use polymorphism to write more flexible and reusable code. * Use the `extends` keyword to create a subclass that inherits from a superclass. For more information on inheritance and polymorphism in Java, refer to the official Oracle Java Tutorials: [Inheritance](https://docs.oracle.com/javase/tutorial/java/concepts/inheritance.html) and [Polymorphism](https://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html). Please leave a comment or ask for help if you have any questions or need further clarification on any of the concepts covered in this lab exercise.