Java - Understanding static

Understanding static

There will be times when you will want to define a class member that will be used independently of any object of that class. Normally, a class member must be accessed only in conjunction with an object of its class. However, it is possible to create a member that can be used by itself, without reference to a specific instance. To create such a member, precede its declaration with the keyword static.

Instance variables declared as static are, essentially, global variables.

Methods declared as static have several restrictions:

• They can only call other static methods.

• They must only access static data.

• They cannot refer to this or super in any way.

//  when the member is static it can be accessed //before any object can be created

public class supercla {

static int a=3; static int b;

/*static method access only static variable

*  call ststic method.

*  cant be used by this & super keyword*/ static void meth(int x){

System.out.println("X=" +x); System.out.println("a="+a); System.out.println("b="+b);

}

//Static block loaded exactly once when the //class is first loaded

static{

System.out.println("Static block"); b=a*10;

}

public static void main(String args[]){ meth(50);

}

}

Inheritance Basics

To inherit a class, you simply incorporate the definition of one class into another by using the extends keyword.