Class Interface

A simple inventory example

Posted on by coder 

   

/*
C#: The Complete Reference 
by Herbert Schildt 

Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/

// A simple inventory example. 
 
using System; 
using System.Collections; 
 
class Inventory { 
  string name; 
  double cost; 
  int onhand; 
 
  public Inventory(string n, double c, int h) { 
    name = n; 
    cost = c; 
    onhand = h; 
  } 
 
  public override string ToString() { 
    return 
      String.Format("{0,-10}Cost: {1,6:C}  On hand: {2}", 
                    name, cost, onhand); 
  } 
} 
 
public class InventoryList { 
  public static void Main() { 
    ArrayList inv = new ArrayList(); 
     
    // Add elements to the list 
    inv.Add(new Inventory("Pliers", 5.95, 3)); 
    inv.Add(new Inventory("Wrenches", 8.29, 2));    
    inv.Add(new Inventory("Hammers", 3.50, 4)); 
    inv.Add(new Inventory("Drills", 19.88, 8)); 
 
    Console.WriteLine("Inventory list:"); 
    foreach(Inventory i in inv) { 
      Console.WriteLine("   " + i); 
    } 
  } 
}

Using Initializers

Posted on by coder 
   
 


public class Product {
    public string make = "Ford";
    public string model = "T";
    public string color;  // default value of null
    public int yearBuilt = 1910;

    public void Start() {
        System.Console.WriteLine(model + " started");
    }

    public void Stop() {
        System.Console.WriteLine(model + " stopped");
    }
}

class MainClass {

    public static void Main() {
        Product myProduct = new Product();
        System.Console.WriteLine("myProduct.make = " + myProduct.make);
        System.Console.WriteLine("myProduct.model = " + myProduct.model);
        if (myProduct.color == null) {
            System.Console.WriteLine("myProduct.color is null");
        }
        System.Console.WriteLine("myProduct.yearBuilt = " + myProduct.yearBuilt);
    }
}

simulate a bank account

Posted on by coder

using System;

public class BankAccount {
public static int nNextAccountNumber = 1000;
public int nAccountNumber;
public double dBalance;

public void InitBankAccount() {
nAccountNumber = ++nNextAccountNumber;
dBalance = 0.0;
}

public void Deposit(double dAmount) {
if (dAmount > 0.0) {
dBalance += dAmount;
}
}

public double Withdraw(double dWithdrawal) {
if (dBalance <= dWithdrawal) { dWithdrawal = dBalance; } dBalance -= dWithdrawal; return dWithdrawal; } } [/csharp]

Illustrates the use of various access modifiers

Posted on by coder 

   

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy

Publisher: Sybex;
ISBN: 0782129110
*/

/*
  Example5_10.cs illustrates the use of various
  access modifiers
*/


// declare the Car class
class Car
{

  // declare the fields
  public             string make;
  protected internal string model;
  internal           string color;
  protected          int horsepower = 150;
  private            int yearBuilt;

  // define the methods
  public void SetYearBuilt(int yearBuilt)
  {
    this.yearBuilt = yearBuilt;
  }

  public int GetYearBuilt()
  {
    return yearBuilt;
  }

  public void Start()
  {
    System.Console.WriteLine("Starting car ...");
    TurnStarterMotor();
    System.Console.WriteLine("Car started");
  }

  private void TurnStarterMotor()
  {
    System.Console.WriteLine("Turning starter motor ...");
  }

}


public class Example5_10
{

  public static void Main()
  {

    // create a Car object
    Car myCar = new Car();

    // assign values to the Car object fields
    myCar.make = "Toyota";
    myCar.model = "MR2";
    myCar.color = "black";
    // myCar.horsepower = 200;  // protected field not accessible
    // myCar.yearBuilt = 1995;  // private field not accessible

    // call the SetYearBuilt() method to set the private yearBuilt field
    myCar.SetYearBuilt(1995);

    // display the values for the Car object fields
    System.Console.WriteLine("myCar.make = " + myCar.make);
    System.Console.WriteLine("myCar.model = " + myCar.model);
    System.Console.WriteLine("myCar.color = " + myCar.color);

    // call the GetYearBuilt() method to get the private yearBuilt field
    System.Console.WriteLine("myCar.GetYearBuilt() = " + myCar.GetYearBuilt());

    // call the Start() method
    myCar.Start();
    // myCar.TurnStarterMotor();  // private method not accessible

  }

}

illustrates member hiding

Posted on by coder 

   

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy

Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example7_4.cs illustrates member hiding
*/

using System;


// declare the MotorVehicle class
class MotorVehicle
{

  // declare the fields
  public string make;
  public string model;

  // define a constructor
  public MotorVehicle(string make, string model)
  {
    Console.WriteLine("In MotorVehicle constructor");
    this.make = make;
    this.model = model;
    Console.WriteLine("this.make = " + this.make);
    Console.WriteLine("this.model = " + this.model);
  }

  // define the DisplayModel() method
  public void DisplayModel()
  {
    Console.WriteLine("In MotorVehicle DisplayModel() method");
    Console.WriteLine("model = " + model);
  }

}


// declare the Car class (derived from MotorVehicle)
class Car : MotorVehicle
{

  // hide the base class model field
  public new string model;

  // define a constructor
  public Car(string make, string model) :
  base(make, "Test")
  {
    Console.WriteLine("In Car constructor");
    this.model = model;
    Console.WriteLine("this.model = " + this.model);
  }

  // hide the base class DisplayModel() method
  public new void DisplayModel()
  {
    Console.WriteLine("In Car DisplayModel() method");
    Console.WriteLine("model = " + model);
    base.DisplayModel();  // calls DisplayModel() in the base class
  }

}


public class Example7_4
{

  public static void Main()
  {

    // create a Car object
    Console.WriteLine("Creating a Car object");
    Car myCar = new Car("Toyota", "MR2");

    Console.WriteLine("Back in Main() method");
    Console.WriteLine("myCar.make = " + myCar.make);
    Console.WriteLine("myCar.model = " + myCar.model);

    // call the Car object&#039;s DisplayModel() method
    Console.WriteLine("Calling myCar.DisplayModel()");
    myCar.DisplayModel();

  }

}

illustrates member accessibility

Posted on by coder 

   

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy

Publisher: Sybex;
ISBN: 0782129110
*/

/*
  Example7_3.cs illustrates member accessibility
*/

using System;


// declare the MotorVehicle class
class MotorVehicle
{

  // declare the fields
  private   string make;
  protected string model;

  // define a constructor
  public MotorVehicle(string make, string model)
  {
    this.make = make;
    this.model = model;
  }

  // define the Start() method (may be overridden in a
  // derived class)
  public virtual void Start()
  {
    TurnStarterMotor();
    System.Console.WriteLine("Vehicle started");
  }

  // define the TurnStarterMotor() method
  private void TurnStarterMotor()
  {
    System.Console.WriteLine("Turning starter motor...");
  }

}


// declare the Car class (derived from MotorVehicle)
class Car : MotorVehicle
{

  // define a constructor
  public Car(string make, string model) :
  base(make, model)
  {
    // do nothing
  }

  // override the base class Start() method
  public override void Start()
  {
    Console.WriteLine("Starting " + model);  // model accessible
    base.Start();  // calls the Start() method in the base class
    // Console.WriteLine("make = " + make);  // make is not accessible
  }

}


public class Example7_3
{

  public static void Main()
  {

    // create a Car object and call the object&#039;s Accelerate() method
    Car myCar = new Car("Toyota", "MR2");
    myCar.Start();

    // make and model are not accessible, so the following two lines
    // are commented out
    // Console.WriteLine("myCar.make = " + myCar.make);
    // Console.WriteLine("myCar.model = " + myCar.model);

  }

}

Public vs private access

Posted on by coder 

   

/*
C#: The Complete Reference 
by Herbert Schildt 

Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// Public vs private access. 
 
using System; 
 
class MyClass {  
  private int alpha; // private access explicitly specified 
  int beta;          // private access by default 
  public int gamma;  // public access 
 
  /* Methods to access alpha and beta.  It is OK for a 
     member of a class to access a private member 
     of the same class. 
  */ 
  public void setAlpha(int a) { 
    alpha = a;  
  } 
 
  public int getAlpha() { 
    return alpha; 
  } 
 
  public void setBeta(int a) { 
    beta = a;  
  } 
 
  public int getBeta() { 
    return beta; 
  } 
}  
  
public class AccessDemo {  
  public static void Main() {  
    MyClass ob = new MyClass();  
  
    /* Access to alpha and beta is allowed only 
       through methods. */ 
    ob.setAlpha(-99); 
    ob.setBeta(19); 
    Console.WriteLine("ob.alpha is " + ob.getAlpha()); 
    Console.WriteLine("ob.beta is " + ob.getBeta()); 
 
    // You cannot access alpha or beta like this: 
//  ob.alpha = 10; // Wrong! alpha is private! 
//  ob.beta = 9;   // Wrong! beta is private! 
 
    // It is OK to directly access gamma because it is public. 
    ob.gamma = 99;  
   }  
}