Question

I have a logical error. I provided the following as input:

• the salary is 30000
• the child n° is 9

So the the net salary will be:

• the family bonus + salary – tax

   (750)       + (30000) - (3000) 

• but my program count them as

    (1500)    + (30000) + (6000) 

My program doubled (accumulated) the family bonus and the tax. Can anyone explain why?

class Program {     static void Main(string[] args)     {         Employee e = new Employee();         e.ReadEmployee();         e.PrintEmployee();     } }  class Employee {     private string n;     private int byear;     private double sal;     private bool gen;     private bool mar;     private int child;     public static double tax = 0;     public static double familybonus = 0;     public string Ename     {         get { return this.n; }         set         {             this.n = value;          }     }     public int Birthyear     {         get { return this.byear; }         set         {             if (value >= 1970 && value <= 1990) this.byear = value;             else this.byear = 0;         }     }     public double Salary     {         get { return this.sal; }         set         {             if (value >= 5000 && value <= 50000) this.sal = value;             else this.sal = 0;         }     }      public bool Gender     {         get { return this.gen; }         set { this.gen = value; }     }     public bool Married     {         get { return this.mar; }         set { this.mar = value; }     }     public int NChildren     {         get { return this.child; }         set         {             if (value >= 0 && value <= 12) this.child = value;             else this.child = 0;         }     }      public double getAge()     {         return 2008 - this.Birthyear;     }     public double getNet()     {         double net = getFamilyBonus() + this.Salary - getTax();         return net;     }      public double getFamilyBonus()     {          if (this.Married == true)             familybonus += 300;         if (this.NChildren == 1) familybonus += 200;         else if (this.NChildren == 2) familybonus += 350;         else if (this.NChildren >= 3) familybonus += 450;         return familybonus;     }      public double getTax()     {         if (Salary < 10000)             tax = 0;         if (Salary <= 10000 && Salary >= 20000)             tax += Salary * 0.05;         else tax += Salary * 0.1;         return tax;      }      public void ReadEmployee()     {         Console.Write('Enter Employee Name: ');         Ename = Console.ReadLine();         Console.Write('Enter Employee birth date: ');         Birthyear = int.Parse(Console.ReadLine());          while (Birthyear < 1970 || Birthyear > 1990)         {             Console.WriteLine('Invalid Birthyear!');             Console.Write('Enter Employee Birth date: ');              Birthyear = int.Parse(Console.ReadLine());         }         string g = null;         while (g != 'M' && g != 'm' && g != 'F' && g != 'f')         {             Console.Write('Enter Employee Gender (M/F)');             g = Convert.ToString(Console.ReadLine());         }          if (g == 'M' || g == 'm')             Gender = true;         else             Gender = false;         Console.Write('Enter Employee Salary: ');         Salary = Double.Parse(Console.ReadLine());         while (Salary < 5000 || Salary > 50000)         {             Console.WriteLine('Invalid Salary!');             Console.Write('Enter Employee Salary: ');             Salary = int.Parse(Console.ReadLine());         }         string m = null;         while (m != 'true' && m != 'True' && m != 'false' && m != 'False')         {             Console.Write('Married (true/false)');             m = Console.ReadLine();          }         if (m == 'true')             this.Married = true;         else             this.Married = false;          Console.Write('Enter Employee Children count: ');         NChildren = int.Parse(Console.ReadLine());          while (NChildren < 0 || NChildren > 12)         {             Console.WriteLine('Invalid NChildren!');             Console.Write('Enter Employee Children count: ');              NChildren = int.Parse(Console.ReadLine());         }      }     public void PrintEmployee()     {         Console.Write('Hello ');         {             if (Gender == true)                 Console.Write('Mr. ');             else                 Console.Write('Mrs. ');             Console.WriteLine(Ename);         }         Console.WriteLine('You are {0} years old', getAge());         Console.WriteLine('Salary= {0}', Salary);         Console.WriteLine('Tax= {0}', getTax());         Console.WriteLine('Family bonus= {0}', getFamilyBonus());         Console.WriteLine('Net= {0}', getNet());     } } 

Answer 1

I took the existing code, and hard-wired the inputs (rather than using Console.ReadLine()), I get:

You are 28 years old Salary= 30000 Tax= 3000 Family bonus= 750 Net= 25500

The main problem seems to be not initializing values – i.e. treating fields as variables:

public double getTax() {     if (Salary < 10000)         tax = 0;     if (Salary <= 10000 && Salary >= 20000)         tax += Salary * 0.05;     else tax += Salary * 0.1;     return tax; } 

OK – and what does tax start at if Salary >= 10000, etc. Likewise familyBouns in getFamilyBonus. By the way, how can Salary be both <= 10000 and >= 20000?

To illustrate, I’ve changed the output to:

    Console.WriteLine('Tax= {0}', getTax());     Console.WriteLine('Tax= {0}', getTax());     Console.WriteLine('Tax= {0}', getTax()); 

Which shows:

Tax= 3000 Tax= 6000 Tax= 9000

My advice would be: don’t store calculated values unless you know the math is so complex that it is worth it. Just calculate them as needed (no field at all).