C# Program with "base - keyword".

class aaa
{
public void sam()
{
System.Console.WriteLine("Hello");
}
}
class bbb:aaa
{
public void sam()
{
System.Console.WriteLine("Great");
}
public void lion()
{
sam();
base.sam();
}
}
class psp
{
public static void Main()
{
bbb b=new bbb();
b.lion();
}
}

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C# Program with "as - keyword".

//C# Program with "as - keyword".


class aaa
{
public void sam()
{
System.Console.WriteLine("Hello");
}
}
class bbb
{
public void accept(object k)
{
aaa a=k as aaa;  // Null will be assigned if not castable
//aaa a=(aaa)k; //Would generate an exception if the material is not castable
if(a!=null)
{
a.sam();
}
}
}
class ccc
{
public void tom()
{
System.Console.WriteLine("good");
}
}
class psp
{
public static void Main()
{
aaa a=new aaa();
bbb b=new bbb();
b.accept(a);
ccc c=new ccc();
b.accept(c);
}
}

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C# Program with "abstract keyword".

C# Program with "abstract keyword".

abstract class aaa

{

abstract public void sam();

}

/* class bbb:aaa                   // wrong

{

}  */

abstract class ccc:aaa         //Correct

{

}

class ddd:aaa

{

public override void sam()

{

System.Console.WriteLine("Hello");

}

}

class psp

{

public static void Main()

{

//aaa a;                              //Correct

//a=new aaa();               // Wrong , Because can't create instance or object of an abstract class . 

ddd d =new ddd();

d.sam();

}

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A Java program using static variables, methods and blocks.

Demonstrate  
    
                   "static variables, methods, and blocks".                       

class UseStatic

{ 
static int a = 3; 
static int b; 
static void meth(int x)

{ 
System.out.println("x = " + x); 
System.out.println("a = " + a); 
System.out.println("b = " + b); 
} 
static

 { 
System.out.println("Static block initialized."); 
b = a * 4; 
} 
public static void main(String args[])

 { 
meth(42); 
} 
}

---------------------------------x----------------------

class StaticDemo { 
static int a = 42; 
static int b = 99; 
static void callme() { 
System.out.println("a = " + a); 
} 
} 
class StaticByName { 
public static void main(String args[]) { 
StaticDemo.callme(); 
System.out.println("b = " + StaticDemo.b); 
} 
} 

Here is the output of this program: 
a = 42 
b = 99

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A Java program using abstarct keyword

A Simple demonstration of ........ abstract keyword ..........

abstract class A

 { 
abstract void callme(); 
// concrete methods are still allowed in abstract classes 
void callmetoo()

 { 
System.out.println("This is a concrete method."); 
} 
}

class B extends A

 { 
void callme()

 { 
System.out.println("B's implementation of callme."); 
} 
}

class AbstractDemo

 { 
public static void main(String args[])

 { 
B b = new B(); 
b.callme(); 
b.callmetoo(); 
} 
}

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Java Program using this keyword

"A java program to demonstrate the use of this keyword "

class ThisDemo1

{

int a = 0;

int b = 0;

ThisDemo1(int x, int y)

{

this.a = x;

this.b = y;

}

public static void main(String [] args)

{

ThisDemo1 td = new ThisDemo1(10,12);

ThisDemo1 td1 = new ThisDemo1(100,23);

System.out.println(td.a); // prints 10

System.out.println(td.B); // prints 12

System.out.println(td1.a);// prints 100

System.out.println(td1.B);// prints 23

}

}

when we compile and run the program we get the output as:-

C:\Java\Concepts\DeclarationAndAccessControl>java ThisDemo1
10
12
100
23

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