Sex offenders web site - 142 Chapter 6 . When to Use Inheritance
142 Chapter 6 . When to Use Inheritance (continued) //Perform arithmetic for salaried employee break; case 1: //Perform arithmetic for hourly employee break; case 2: //Perform arithmetic for contractor employee break; //and so on if necessary } } And the computePay() method will keep getting longer and longer as different types of employees arise. Any time you find yourself writing classes that do not know what type they are, you probably should rethink your design. With inheritance, all of these issues are avoided. The common features of employees appear in a parent class. Each different type of employee is represented by a child class. When a new type of employee such as a contractor comes along, a new child class is written that extends the parent class. None of the existing code needs to be touched. This benefit is difficult to achieve with procedural programming and also with poorly designed OOP applications. To avoid these situations, constantly test your OOP design against these simple rules: An object has an attribute, and an object does a behavior. In our employee example, if it is not true that an employee has a salary, an Employee class should not have a salary field, and we should redesign our program. The Salary class should have a field to represent the employee s annual salary because a Salaried employee has a salary. The Hourly class should have fields to represent the employee s hourly pay and number of hours worked because these are attributes of an Hourly employee. The following classes demonstrate what the Salary and Hourly classes might look like. Look closely at the attributes and behaviors of these two classes. As with the Employee class, there is something flawed with this design also. public class Salary { public String name; public String address; public int SSN; public int number; public float salary; public void mailCheck() {
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