Hướng dẫn cách dùng

The NetTradeX language supports inheritance from a single base class. When your derived class inherits from a base class, it implements all the methods and properties of the base class, at the same time it may override methods of the base class.

When implementing a derived class, constructor calling the base class constructor may be needed, this can be accomplished by using the keyword super . If the derived class does not call the base class constructor, the compiler will automatically call the default base class constructor.

Example of the class inheritance procedure:

class Base
{
	int a;
	Base(int a)
	{
		this.a=a;
		System.Print("Base conscructor is evoked");
	}
}
class Derived: Base
{
	int b;
	Derived(int a,int b)
	{
	    super(a);
	    this.b=b;   
	    System.Print("Derived conscructor is evoked");
	}
}
int Run()
{
    Derived x(5,10);
    System.Print("a="+x.a+" b="+x.b);
  	return(0);
}

Output:

Base constructor is evoked
Derived constructor is evoked
a=5 b=10

Converting an instance of a derived class object into an instance of the base class object can be done as follows:

class Base
{
	int a;
	Base(int a)
	{
		this.a=a;
		System.Print("Base conscructor is evoked");
	}
}
class Derived: Base
{
	int b;
	Derived(int a,int b)
	{
	    super(a);
	    this.b=b;   
	    System.Print("Derived conscructor is evoked");
	}
}
int Run()
{   
    Derived x(11,22);
    Base @bObj=x;
    System.Print("bObj.a="+bObj.a);
    return(0);
}

The class can be specified with the keyword final before class , in which case the class cannot be inherited. Also final can be specified before any class method that will lead to a ban of overriding this method in a derived class.

final class A
{
}
//This inheritance is forbidden
//class B: A
//{
//}
class C
{
	void D() final 
	{
	}
	void E()
	{
	}
}
class F: C
{
	// Can redefine the E method
	void E()
	{
	}
	
	//This override is prohibited
	//void D()
	//{
	//}	
}
int Run()
{
  return(0);
}