Using Classes and Objects, pretty hard stuff!

Question

I am pretty stumbled on this one just like on any other homeworks i get.............

Vulpes · Answer

It's not as difficult as it might seem. However, the tax system seems very unfair - you get to 30,000 and have to pay an extra 13% on all your income! Best to stay on 29,999: using System; class TaxPayer : IComparable { private string ssn; private double grossIncome; private double taxOwed; public string SSN { get { return ssn; } set { ssn = value; } } public double GrossIncome { get { return grossIncome; } set { grossIncome = value; if (grossIncome taxOwed = 0.15 * grossIncome; else taxOwed = 0.28 * grossIncome; } } public double TaxOwed { get{ return taxOwed; } } public TaxPayer(string ssn, double grossIncome) { this.ssn = ssn; GrossIncome = grossIncome; // need to set the property here, not the field directly } public override string ToString() { return String.Format("SSN = {0}, Income = {1,11:C}, Tax Owed = {2,10:C}", ssn, grossIncome, taxOwed); } public int CompareTo(TaxPayer other) { return this.taxOwed.CompareTo(other.taxOwed); } } class TaxPayerDemo { static void Main() { TaxPayer[] taxPayers = new TaxPayer[10]; string ssn; double grossIncome; Console.WriteLine("Please enter details for 10 taxpayers
"); for(int i = 0; i { Console.WriteLine("Details for taxpayer #{0}", i + 1); Console.Write(" Enter Social Security Number : "); ssn = Console.ReadLine().Replace("-", ""); // get rid of any dashes Console.Write(" Enter Yearly Gross Income : "); grossIncome = Convert.ToDouble(Console.ReadLine()); taxPayers[i] = new TaxPayer(ssn, grossIncome); Console.WriteLine(); } Console.WriteLine("The taxpayers and their details are
"); for(int i = 0; i Array.Sort(taxPayers); // sorts the taxpayers in order of tax owed Console.WriteLine(); Console.WriteLine("The taxpayers in order of tax owed are
"); for(int i = 0; i Console.ReadKey(); } }

Vulpes · Answer

The code in green tells you that the TaxPayer class implements the generic interface IComparable . In order to implement this interface, TaxPayer must have a CompareTo method (the code in red) which takes another TaxPayer object as an argument and returns an int. This int indicates how TaxPayer objects are to be ordered by default when you sort them. Here, we make use of double's CompareTo method which sorts the doubles (namely taxOwed) in increasing order of magnitude. When Array.Sort is called the code inside it does the sorting by applying the Taxpayer.CompareTo method which it knows exists because TaxPayer implements IComparable . For more about this interface, check this MSDN link: http://msdn.microsoft.com/en-us/library/4d7sx9hd.aspx

Prime b · Answer

Vulpes I have few questions highlighted in red color, whats that? and what do you use it for? highlighted in green color, same thing, whats that, and what do you use if for? using System; class TaxPayer : IComparable { private string ssn; private double grossIncome; private double taxOwed; public string SSN { get { return ssn; } set { ssn = value; } } public double GrossIncome { get { return grossIncome; } set { grossIncome = value; if (grossIncome taxOwed = 0.15 * grossIncome; else taxOwed = 0.28 * grossIncome; } } public double TaxOwed { get{ return taxOwed; } } public TaxPayer(string ssn, double grossIncome) { this.ssn = ssn; GrossIncome = grossIncome; // need to set the property here, not the field directly } public override string ToString() { return String.Format("SSN = {0}, Income = {1,11:C}, Tax Owed = {2,10:C}", ssn, grossIncome, taxOwed); } public int CompareTo(TaxPayer other) { return this.taxOwed.CompareTo(other.taxOwed); } } class TaxPayerDemo { static void Main() { TaxPayer[] taxPayers = new TaxPayer[10]; string ssn; double grossIncome; Console.WriteLine("Please enter details for 10 taxpayers
"); for(int i = 0; i { Console.WriteLine("Details for taxpayer #{0}", i + 1); Console.Write(" Enter Social Security Number : "); ssn = Console.ReadLine().Replace("-", ""); // get rid of any dashes Console.Write(" Enter Yearly Gross Income : "); grossIncome = Convert.ToDouble(Console.ReadLine()); taxPayers[i] = new TaxPayer(ssn, grossIncome); Console.WriteLine(); } Console.WriteLine("The taxpayers and their details are
"); for(int i = 0; i Array.Sort(taxPayers); // sorts the taxpayers in order of tax owed Console.WriteLine(); Console.WriteLine("The taxpayers in order of tax owed are
"); for(int i = 0; i Console.ReadKey(); } }