for java

. . . . Problem 1: 60% 1) Define the class Publication that contains The private properties title of type String, year of type int, authors of type String, and publisher of type String An empty no-arg constructor A constructor that takes four parameters and sets the instance variables accordingly A getter and setter methods for each instance variable The instance method toString that does not take any parameter and returns a string. The returned string is a string representation of the four instance variables. The format is of your choice. 2) Define the class Conference that extends the class Publication and contains The private properties name of type String, pages of type String, location of type String, and fee of type double. An empty no-arg constructor A constructor that takes four parameters and sets the instance variables of the class Conference accordingly A constructor that takes eight parameters and sets the instance variables of the class Conference and the class Publication accordingly. You may use the setter methods to set the values of the private instance variables of the class Publication. A setter and getter methods for each instance variable The instance method toString that does not take any parameter and returns a string. The returned string is a string representation of the eight instance variables (four defined in Conference and four defined in Publication). The format is of your choice