Object-Oriented Programming (From Problem Solving to JAVA) (Charles River Media Programming)
7.3 The Salary Problem with Selection
This is an extension of the salary problem presented earlier. A company is to give salary increases to its employees. The salary increase is 4.5% of the salary—but only for those employees with a salary greater than $45,000.00; otherwise, the salary increase is 5%. The solution should calculate the salary increase for the employees and the updated salary.
7.3.1 Preliminary Design
To describe the transformation on the data, a selection structure is needed in the algorithm. Figure 7.3 shows the selection structure applied to this problem.
The flow of control in the sequence of instructions takes alternate routes depending on the condition: salary greater than 45,000. The left path is followed when the condition is true (salary is greater than 45,000), the right path is followed when the condition is not true.
The first level of detail for the algorithm description in informal pseudocode is:
get the salary for an employee if salary is greater than $45,000.00 then calculate increase with 4.5% else calculate increase with 5% endif update salary show increase and updated salary for this employee
Note that the flowchart shown for the salary problem is not complete, the start and the end symbols are not shown. The flowchart is only slightly more complicated than the one for the previous version of the salary problem.
7.3.2 Final Design and Implementation
The following class definition implements part of the solution for the salary problem. The most relevant part of the solution for this problem is found in function sal_increase of class Employee_m.
description This program computes the salary increase for an employee. If his/her salary is greater than $45,000, the salary increase is 4.5%; otherwise, the salary increase is 5%. This is the class for employees. The main attributes are salary, age, and name. */ class Employee_m is private variables // variable data declarations real salary integer age string obj_name real increase // salary increase public // description This is the constructor, it initializes an object on creation. */ function initializer parameters string iname, real isalary, integer iage is begin set salary = isalary set age = iage set obj_name = iname endfun initializer // description This function gets the salary of the employee object. */ function get_salary of type real is begin return salary endfun get_salary // description This function returns the name of the employee object. */ function get_name of type string is begin return obj_name endfun get_name // description This function changes the salary of the Employee object by adding the change to current salary. */ function change_sal parameters real change is begin add change to salary endfun change_sal // description This function computes the salary increase and updates the salary of an employee. */ function sal_increase is constants real percent1 = 0.045 // percent real percent2 = 0.05 begin // body starts here if salary > 45000 then set increase = salary * percent1 else set increase = salary * percent2 endif add increase to salary // update salary endfun sal_increase // description This function returns the salary increase for the object. */ function get_increase of type real is begin return increase endfun get_increase endclass Employee_m
| On the CD | The code of the KJP implementation for this class is stored in the file |
The following class, Comp_salary_m includes the function main, which creates and manipulates objects of class Employee_m.
description This program computes the salary increase for an employee. If his/her salary is greater than $45,000, the salary increase is 4.5%; otherwise, the salary increase is 5%. This class creates and manipulates the objects of class Employee_m. */ class Comp_salary_m is public description This is the main function of the appli- cation. */ function main is variables real increase real salary integer age string oname objects object emp_obj of class Employee_m begin display "Enter salary: " read salary display "Enter age: " read age display "Enter name: " read oname create emp_obj of class Employee_m using salary, age, oname set increase = call sal_increase of emp_obj // get updated salary set salary = get_salary() of emp_obj print "Employee name: ", oname print "increase: ", increase, " new salary: ", salary endfun main endclass Comp_salary_m
| On the CD | The code for the KJP implementation is stored in the file |
The following is the code for the Java implementation of class Employee_m.
// KJP v 1.1 File: Employee_m.java, Thu Dec 12 20:09:35 2002 /** This program computes the salary increase for an employee. If his/her salary is greater than $45,000, the salary increase is 4.5%; otherwise, the salary increase is 5%. This is the class for employees. The main attributes are salary, age, and name. */ public class Employee_m { // variable data declarations private float salary; private int age; private String obj_name; private // salary increase float increase; /** This is the initializer function (constructor), it initializes an object on creation. */ public Employee_m(String iname, float isalary, int iage) { salary = isalary; age = iage; obj_name = iname; } // end constructor /** This function gets the salary of the employee object. */ public float get_salary() { return salary; } // end get_salary /** This function returns the name of the employee object. */ public String get_name() { return obj_name; } // end get_name /** This function computes the salary increase and updates the salary of an employee. */ public void sal_increase() { // constant data declarations final float percent1 = 0.045F; // increase final float percent2 = 0.05F; // body of function starts here if ( salary > 45000) { increase = (salary) * (percent1); } else { increase = (salary) * (percent2); } // endif salary += increase; // update salary } // end sal_increase /** This function returns the salary increase for the object. */ public float get_increase() { return increase; } // end get_increase } // end Employee_m
| On the CD | The implementation of class Employee_m is stored in the file |
The output of the execution of this program is shown in Figure 7.4. This program uses class Comp_salary_m as the main class that includes the two classes. Two runs are shown, the first with a salary less than $45,000.00, and the second with a salary higher than $45,000.00.
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