Exercise 1. (Modified GradeBook Class) Modify class Gradebook (fig. 3.10) as follows:
Include a String instance variable that represents the name of the course's instructor.
Provide a set method to change the instructor's name and a get method to retrieve it.
Modify the constructor to specify 2 parameters-one for the course name and 1 for the instructor's name.
Modify method displayMessage to output the welcome message and course name, followed by "This course is presented by:" and the instructor's name.
Exercise 2. JHTP (Employee Class) Create a class called Employee that includes 3 instance variables-a first name (type String), a last name (type String), and a monthly salary (double). Provide a constructor that initializes the 3 instance variables. Provide a set and a get method for each instance variable. If the monthly salary is not positive, do not set its value. Write a test application named EmployeeTest that demonstrates class Employee's capabilities. Create 2 Employee objects and display each object's yearly salary. Then give each Employee a 10% raise and display each Employee's yearly salary again.
Exercise 3. JHTP (Date Class) Create a class called Date that includes 3 instance variables-a month (type int), a day (type int), and a year (type int). Provide a constructor that initializes the 3 instance variables and assumes the values provided are correct. Provide a set and a get method for each instance variable. Provide a method displayDate that displays the month, day, and year separated by forward slashes(/). Write a test application named DateTest that demonstrates class Date's capabilities.