/* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852 */ // Use a static constructor. using System; class Cons { public static int alpha; public int beta; // static constructor static Cons() { alpha = 99; Console.WriteLine("Inside static constructor."); } // instance constructor public Cons() { beta = 100; Console.WriteLine("Inside instance constructor."); } } public class ConsDemo { public static void Main() { Cons ob = new Cons(); Console.WriteLine("Cons.alpha: " + Cons.alpha); Console.WriteLine("ob.beta: " + ob.beta); } }
Month: February 2011
Use a static class factory
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// Use a static class factory.
using System;
class MyClass {
int a, b;
// Create a class factory for MyClass.
static public MyClass factory(int i, int j) {
MyClass t = new MyClass();
t.a = i;
t.b = j;
return t; // return an object
}
public void show() {
Console.WriteLine(“a and b: ” + a + ” ” + b);
}
}
public class MakeObjects1 {
public static void Main() {
int i, j;
// generate objects using the factory
for(i=0, j=10; i < 10; i++, j--) {
MyClass ob = MyClass.factory(i, j); // get an object
ob.show();
}
Console.WriteLine();
}
}
[/csharp]
Use a static field to count instances
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// Use a static field to count instances.
using System;
class CountInst {
static int count = 0;
// increment count when object is created
public CountInst() {
count++;
}
// decrement count when object is destroyed
~CountInst() {
count–;
}
public static int getcount() {
return count;
}
}
public class CountDemo {
public static void Main() {
CountInst ob;
for(int i=0; i < 10; i++) { ob = new CountInst(); Console.WriteLine("Current count: " + CountInst.getcount()); } } } [/csharp]
Can call a non-static method through an object reference from within a static method
/* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852 */ using System; public class MyClass { // non-static method. void nonStaticMeth() { Console.WriteLine("Inside nonStaticMeth()."); } /* Can call a non-static method through an object reference from within a static method. */ public static void staticMeth(MyClass ob) { ob.nonStaticMeth(); // this is OK } }
Error using static
/* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852 */ using System; public class AnotherStaticError { // non-static method. void nonStaticMeth() { Console.WriteLine("Inside nonStaticMeth()."); } /* Error! Can't directly call a non-static method from within a static method. */ static void staticMeth() { nonStaticMeth(); // won't compile } }
Static members are frequently used as counters.
using System; public class Starter { public static void Main() { MyClass<int> obj1 = new MyClass<int>(); MyClass<double> obj2 = new MyClass<double>(); MyClass<double> obj3 = new MyClass<double>(); MyClass<int>.Count(obj1); MyClass<double>.Count(obj2); } } public class MyClass<T> { public MyClass() { ++counter; } public static void Count(MyClass<T> _this) { Console.WriteLine("{0} : {1}", _this.GetType().ToString(), counter.ToString()); } private static int counter = 0; }
Use static
/* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852 */ // Use static. using System; class StaticDemo { // a static variable public static int val = 100; // a static method public static int valDiv2() { return val/2; } } public class SDemo { public static void Main() { Console.WriteLine("Initial value of StaticDemo.val is " + StaticDemo.val); StaticDemo.val = 8; Console.WriteLine("StaticDemo.val is " + StaticDemo.val); Console.WriteLine("StaticDemo.valDiv2(): " + StaticDemo.valDiv2()); } }